WO2023176791A1 - Iron casting and method for producing same - Google Patents

Iron casting and method for producing same Download PDF

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Publication number
WO2023176791A1
WO2023176791A1 PCT/JP2023/009691 JP2023009691W WO2023176791A1 WO 2023176791 A1 WO2023176791 A1 WO 2023176791A1 JP 2023009691 W JP2023009691 W JP 2023009691W WO 2023176791 A1 WO2023176791 A1 WO 2023176791A1
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Prior art keywords
mass
cooling
less
heat treatment
holding
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PCT/JP2023/009691
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French (fr)
Japanese (ja)
Inventor
拓郎 梅谷
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日之出水道機器株式会社
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Publication of WO2023176791A1 publication Critical patent/WO2023176791A1/en

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D5/00—Heat treatments of cast-iron
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C37/00—Cast-iron alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C37/00—Cast-iron alloys
    • C22C37/04—Cast-iron alloys containing spheroidal graphite
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/10—Ferrous alloys, e.g. steel alloys containing cobalt

Definitions

  • the present invention relates to iron castings and methods of manufacturing them.
  • Patent Document 1 provides a method for easily manufacturing a cast iron material that has good castability and workability similar to general cast iron materials, and has even better low thermal expansion characteristics. It is stated that.
  • the summary of Patent Document 1 states that a casting having a cast iron composition containing 2.5% by mass or less of carbon and 25% by mass or more and 40% by mass or less of nickel obtained by casting is heated to 550°C. After holding the casting at a temperature of 700°C or higher for 3 hours or more, annealing is performed by naturally cooling it by furnace cooling to at least 200°C, and then the annealed casting is heated to a temperature of 600°C or higher and 1150°C.
  • the coefficient of thermal expansion in the temperature range of 50°C to 200°C is 4x. It is described that a cast iron material with a low thermal expansion of 10 -6 /°C or less is produced.
  • a method according to one aspect of the present invention is a method for manufacturing an iron casting by heat-treating a heat-treated object cast using an austenitic casting material.
  • the casting material contains Ni of 26.0% by mass or more and 50.0% by mass or less, C of 0.1% by mass or more and 3.5% by mass or less, and 0.1% by mass or more and 3.5% by mass or less. of Si, 0 mass% to 8.0 mass% Co, 0 mass% to 3.0 mass% Mn, and 0 mass% to 0.2 mass% Mg, with the balance being Fe and inevitable elements.
  • the heat treatment includes a first holding step in which the heat treatment target is held at a first holding temperature of 850°C or higher and 1250°C or lower, and after the first holding step, the heat treatment target is held at a temperature of -150°C or higher and 150°C or higher. and a first cooling step of cooling to a first cooling end temperature of .degree. C. or lower.
  • the first holding step includes holding the heat treatment object for a first holding time of 0.25 hours or more and 100 hours or less.
  • the heat-treated object in the first holding step, is held at a first holding temperature (850° C. or more and 1250° C. or less) and a first holding time (0.25 hours or more and 100 hours or less). Then, in a first cooling step after the first holding step, the heat treatment target is cooled to a first cooling end temperature (-150° C. or higher and 150° C. or lower).
  • a first holding step it is possible to reduce the solidification segregation of solute elements in the heat-treated object and to reduce the relative difference in crystal orientation (crystal orientation difference) inside each crystal grain constituting the austenite phase. can. This makes it possible to arrange the crystal lattice in the austenite phase. As a result, the coefficient of linear expansion of the iron casting can be reduced.
  • the first cooling step includes cooling the object to be heat treated at a first cooling rate of 0.01° C./min or more and 300° C./min or less.
  • the first cooling rate is preferably 0.01°C/min or more and 20°C/min or less.
  • the first holding time is preferably 2.5 hours or more and 25 hours or less.
  • the first cooling end temperature is preferably 0°C or more and 100°C or less.
  • the first cooling step includes a primary cooling step in which the heat treatment target is cooled at a primary cooling rate, and after the primary cooling step, the heat treatment target is subjected to secondary cooling at a rate higher than the primary cooling rate.
  • the secondary cooling step includes cooling the heat treatment object to a primary cooling end temperature of 250° C. or more and 950° C. or less, and the secondary cooling step includes Preferably, the method includes cooling the object to the first cooling end temperature.
  • the first cooling step after the first holding step includes a primary cooling step in which the object to be heat treated is cooled at a primary cooling rate; and a secondary cooling step of cooling at a high secondary cooling rate.
  • the primary cooling step the heat treatment target is cooled at the primary cooling rate to the primary cooling end temperature (250° C. or higher and 950° C. or lower).
  • This primary cooling step allows carbon in the austenite phase to diffuse toward the graphite side. Therefore, the amount of solid solute carbon in the austenite phase can be reduced. Therefore, excessive distortion of the crystal lattice in the austenite phase can be suppressed. As a result, the coefficient of linear expansion of the iron casting can be further reduced.
  • the heat-treated object is cooled to a first cooling end temperature (-150° C. or higher and 150° C. or lower) at a secondary cooling rate that is higher than the primary cooling rate.
  • This secondary cooling step tends to increase the amount of change in spontaneous volumetric magnetostriction due to temperature change below the Curie point. Therefore, in a temperature change below the Curie point, the volume change due to spontaneous bulk magnetostriction and the volume change due to crystal lattice vibration are likely to cancel each other out. Therefore, it is easy to suppress volume fluctuations due to temperature changes. As a result, it is easier to further reduce the coefficient of linear expansion of iron castings.
  • the primary cooling rate is preferably 0.01°C/min or more and 20°C/min or less
  • the secondary cooling rate is preferably 1°C/min or more and 40000°C/min or less.
  • the secondary cooling rate is preferably 100° C./min or more and 40000° C./min or less.
  • the first holding time is preferably 2.5 hours or more and 25 hours or less.
  • the primary cooling end temperature is preferably 450°C or more and 850°C or less.
  • the first cooling end temperature is preferably 0°C or more and 100°C or less.
  • the heat treatment includes, after the first cooling step, a second holding step in which the object to be heat treated is held at a second holding temperature of 250° C. or more and 950° C. or less, and the second holding step.
  • the second cooling step further includes cooling the heat treatment object to a second cooling end temperature of -150° C. or more and 150° C. or less, and the second holding step cools the heat treatment object to a temperature of 0. It may include holding for a second holding time of 25 hours or more and 25 hours or less.
  • the first cooling step includes cooling the object to be heat treated at a first cooling rate of 0.01° C./min or more and 300° C./min or less.
  • the first cooling rate is preferably 1° C./min or more and 50° C./min or less.
  • the second cooling step includes cooling the heat treatment object at a second cooling rate of 1° C./min or more and 40000° C./min or less.
  • the second cooling rate is preferably 100° C./min or more and 10,000° C./min or less.
  • the first holding time is preferably 2.5 hours or more and 25 hours or less.
  • the first cooling end temperature is preferably 0°C or more and 100°C or less.
  • the second holding temperature is preferably 550°C or more and 950°C or less.
  • the second cooling end temperature is preferably 0°C or more and 50°C or less.
  • the Co content of the casting material is preferably 0.1% by mass or more and 8.0% by mass or less.
  • the content of Mn in the casting material is preferably 0.01% by mass or more and 3.0% by mass or less.
  • the content of Mg in the casting material is preferably 0.01% by mass or more and 0.2% by mass or less.
  • a method according to another aspect of the present invention is a method of manufacturing an iron casting by heat-treating a heat-treated object cast using an austenitic casting material.
  • the heat treatment includes a first holding step in which the heat treatment target is held at a first holding temperature of 850°C or higher and 1250°C or lower, and after the first holding step, the heat treatment target is held at a temperature of -150°C or higher and 150°C or higher. and a first cooling step of cooling to a first cooling end temperature of .degree. C. or lower.
  • the first holding step includes holding the heat treatment object for a first holding time of 0.25 hours or more and 100 hours or less.
  • the first cooling step includes a primary cooling step in which the heat treatment target is cooled at a primary cooling rate, and after the primary cooling step, the heat treatment target is subjected to secondary cooling at a rate higher than the primary cooling rate.
  • the secondary cooling step includes cooling the heat treatment object to a primary cooling end temperature of 250° C. or more and 950° C. or less, and the secondary cooling step includes Preferably, the method includes cooling the object to the first cooling end temperature.
  • the heat treatment includes, after the first cooling step, a second holding step in which the object to be heat treated is held at a second holding temperature of 250° C. or more and 950° C. or less, and the second holding step.
  • the second cooling step further includes cooling the heat treatment object to a second cooling end temperature of -150° C. or more and 150° C. or less, and the second holding step cools the heat treatment object to a temperature of 0. It may include holding for a second holding time of 25 hours or more and 25 hours or less.
  • the iron casting according to one aspect of the present invention is an iron casting manufactured using the method according to the one aspect of the present invention or the method according to another aspect of the present invention.
  • FIG. 1 is a diagram showing an example of an image observed with a microscope of the microstructure of a heat-treated object cast using an austenitic casting material.
  • FIG. 2 is a diagram showing an area occupied by graphite in the image shown in FIG.
  • FIG. 3 is a diagram showing a region occupied by an intermetallic compound mainly composed of iron (Fe) in the image shown in FIG.
  • FIG. 4 is a diagram showing a region occupied by the austenite phase in the image shown in FIG.
  • the iron casting according to the embodiment of the present invention can be manufactured by subjecting a heat-treated object cast using an austenitic casting material to a predetermined heat treatment described below.
  • austenitic casting material means a material in which the main structure of the parent phase (iron base structure excluding graphite) of a cast heat-treated object at room temperature is an austenite phase.
  • the proportion of austenite phase in the matrix of the heat-treated object is 50% or more.
  • the proportion of the austenite phase in the matrix of the heat-treated object is preferably 70% or more, more preferably 80% or more, more preferably 85% or more, and preferably 90% or more. More preferably, it is 95% or more.
  • FIG. 1 is a diagram showing an example of an image observed with a microscope of the microstructure of a heat-treated object cast using an austenitic casting material.
  • FIG. 2 is a diagram showing an area occupied by graphite in the image shown in FIG.
  • FIG. 3 is a diagram showing a region occupied by an intermetallic compound mainly composed of iron (Fe) in the image shown in FIG.
  • FIG. 4 is a diagram showing a region occupied by the austenite phase in the image shown in FIG.
  • the "area of the matrix of the heat-treated object" can be calculated by subtracting the "area of the region occupied by graphite" shown in Figure 2 from the "area of the entire microstructure of the heat-treated object” shown in Figure 1. I can do it.
  • the "area of the austenite phase” is determined by subtracting the "area of the region occupied by the intermetallic compound mainly composed of iron (Fe)" shown in Figure 3 from the "area of the matrix of the heat-treated object” calculated above. It can be calculated. Therefore, the "proportion of the austenite phase in the matrix of the heat-treated object” is calculated by dividing the "area of the austenite phase (see Figure 4)" calculated above by the "area of the matrix of the heat-treated object”. can do.
  • general-purpose image processing software is used to calculate the number of pixels in the area corresponding to each area shown in Figures 1 to 4.
  • the proportion of austenite phase is 84.6% (approximately 85%).
  • the proportion of the austenite phase in the matrix of the heat-treated object is 100%.
  • casting includes casting by various casting methods such as sand casting, metal mold casting, die casting, and lost wax casting.
  • mass % of an element means the percentage of the mass of the element with respect to the mass of the austenitic casting material.
  • the expression “element of X% by mass or more and Y% by mass or less” means that the mass% of the element is X% or more and Y% or less.
  • the notation “0 mass % Y mass % or less of an element” means that the element is not included or that the mass % of the element is Y % or less.
  • the "remainder” means components other than the listed elements among the components constituting the austenitic casting material.
  • the first form of the austenitic casting material (hereinafter referred to as “this material”) contains Ni in an amount of 26.0% by mass to 50.0% by mass, and the balance is Fe and unavoidable elements.
  • the first form of the present material may be referred to as “the first form of the present material (Ni--Fe composition)”.
  • the first form of the present material contains Ni in an amount of 26.0% by mass or more and 50.0% by mass or less.
  • Ni is segregated around graphite by setting the Ni content to 26.0% by mass or more and 50.0% by mass or less. That is, austenite is stabilized by concentrating Ni in the region around graphite.
  • austenite By setting the lower limit of the Ni content to 26.0% by mass, austenite can be stabilized and martensite generation can be suppressed. Therefore, it is possible to suppress a decrease in the ductility of iron castings and to improve the machinability of iron castings.
  • the upper limit of the Ni content to 50.0% by mass, it is possible to suppress an increase in the coefficient of linear expansion. The same applies to the following forms of the present material.
  • the remainder in the first form of the material is Fe and unavoidable elements.
  • unavoidable elements contained in the remainder include P (phosphorus), S (sulfur), Cu (copper), Al (aluminum), Cr (chromium), Mo (molybdenum), V (vanadium), and Ti (titanium). , Zn (zinc), and other elements.
  • the content of unavoidable elements is preferably 10.0% by mass or less in total, more preferably 5.0% by mass or less in total, and 3.0% by mass or less in total. More preferably, the total amount is 1.0% by mass or less. The same applies to the following forms of the present material.
  • the lower limit of the Ni content is preferably 26.5% by mass, more preferably 27.0% by mass, and even more preferably 27.5% by mass.
  • it is 28.0% by mass, more preferably 28.5% by mass, more preferably 29.0% by mass, more preferably 29.5% by mass, More preferably 30.0% by mass, more preferably 30.5% by mass, more preferably 31.0% by mass, more preferably 31.5% by mass, 32. More preferably, it is 0% by mass.
  • the upper limit of the Ni content is preferably 45.0% by mass, more preferably 42.0% by mass, more preferably 41.0% by mass, and 40.0% by mass.
  • the content is more preferably 37.5% by mass, and even more preferably 37.0% by mass. The same applies to the following forms of the present material.
  • the second form of this material contains Ni of 26.0% by mass or more and 50.0% by mass or less, C of 0.1% by mass or more and 3.5% by mass or less, and the balance is Fe and unavoidable elements.
  • the second form of the present material may be referred to as "the second form of the present material (Ni--C--Fe composition)."
  • the second form of the present material contains 0.1% by mass or more and 3.5% by mass or less of C.
  • the liquidus temperature of the present material can be lowered. Therefore, the flowability of this material can be improved.
  • the lower limit of the C content to 0.1% by mass
  • the amount of crystallization or precipitation of graphite can be increased. Therefore, the machinability of iron castings can be improved.
  • the upper limit of the C content to 3.5% by mass, graphite floating (carbon flotation) can be suppressed. Therefore, a decrease in strength and ductility of iron castings can be suppressed.
  • the lower limit of the C content is preferably 0.15% by mass, more preferably 0.2% by mass, and even more preferably 0.4% by mass. Preferably, it is 0.7% by mass, more preferably 1.0% by mass, more preferably 1.25% by mass, more preferably 1.5% by mass, More preferably, it is 1.75% by mass.
  • the upper limit of the content of C is preferably 3.3% by mass, more preferably 3.1% by mass, more preferably 3.0% by mass, and 2.95% by mass. It is more preferably 2.9% by mass, more preferably 2.85% by mass, more preferably 2.8% by mass, and more preferably 2.75% by mass. More preferably, it is 2.7% by mass, more preferably 2.65% by mass, more preferably 2.6% by mass, and more preferably 2.55% by mass. The content is more preferably 2.5% by mass. The same applies to the following forms of the present material.
  • the third form of this material contains Ni of 26.0% by mass or more and 50.0% by mass or less, C of 0.1% by mass or more and 3.5% by mass or less, and 0.1% by mass or more and 3.5% by mass. It contains less than % by mass of Si, and the remainder is Fe and unavoidable elements.
  • the third form of the present material may be referred to as "the third form of the present material (Ni-C-Si-Fe composition)".
  • the third form of the present material contains 0.1% by mass or more and 3.5% by mass or less of Si.
  • the Ni content is 26.0% by mass or more and 50.0% by mass or less
  • the Si content is 0.1% by mass or more and 3.5% by mass or less.
  • the lower limit of the Si content is preferably 0.25% by mass, more preferably 0.5% by mass, and even more preferably 0.75% by mass. It is preferably 1.0% by mass, more preferably 1.2% by mass, even more preferably 1.3% by mass, and even more preferably 1.4% by mass.
  • the upper limit of the Si content is preferably 3.3% by mass, more preferably 3.1% by mass, more preferably 2.9% by mass, and more preferably 2.7% by mass. It is more preferably 2.5% by mass, more preferably 2.3% by mass, and even more preferably 2.1% by mass. The same applies to the following forms of the present material.
  • the fourth form of this material includes 26.0% by mass or more and 50.0% by mass of Ni, 0.1% by mass or more and 3.5% by mass of C, and 0.1% by mass or more and 3.5% by mass. It contains Si of 0.1% by mass or more and 8.0% by mass or less of Co, and the balance is Fe and unavoidable elements.
  • the fourth form of the present material may be referred to as "the fourth form of the present material (Ni-C-Si-Co-Fe composition)".
  • the fourth form of the present material contains 0.1% by mass or more and 8.0% by mass or less of Co.
  • the linear expansion coefficient can be further reduced due to the synergistic effect with Ni.
  • the lower limit of the Co content By setting the lower limit of the Co content to 0.1% by mass, the minimum value of the coefficient of linear expansion can be reduced due to the synergistic effect with Ni.
  • the upper limit of the Co content By setting the upper limit of the Co content to 8.0% by mass, it is possible to suppress the linear expansion coefficient from increasing after reaching a minimum value due to excessive addition of Co. The same applies to the following forms of the present material.
  • the lower limit of the Co content is preferably 0.5% by mass, more preferably 1.0% by mass, and even more preferably 1.5% by mass.
  • it is 2.0% by mass, more preferably 2.5% by mass, more preferably 3.0% by mass, more preferably 3.5% by mass, More preferably, it is 4.0% by mass.
  • the upper limit of the Co content is preferably 7.5% by mass, more preferably 7.0% by mass, more preferably 6.5% by mass, and 6.25% by mass. More preferably, it is 6.0% by mass.
  • the Ni content is 31.0% by mass or more and 34.0% by mass or less
  • the Co content is 4.0% by mass or more and 5.5% by mass or less.
  • the Co content is preferably 5.0% by mass or more and 8.0% by mass or less.
  • the fifth form of this material includes 26.0% by mass or more and 50.0% by mass of Ni, 0.1% by mass or more and 3.5% by mass of C, and 0.1% by mass or more and 3.5% by mass. It contains Si of 0.1% by mass or more and 8.0% by mass or less of Co, and Mn of 0.01% by mass or more and 3.0% by mass or less, and the balance is Fe and unavoidable elements.
  • the fifth form of the present material may be referred to as "the fifth form of the present material (Ni-C-Si-Co-Mn-Fe composition)."
  • the fifth form of the present material contains Mn in an amount of 0.01% by mass or more and 3.0% by mass or less.
  • Mn manganese
  • the fifth form of this material contains Mn in an amount of 0.01% by mass or more and 3.0% by mass or less.
  • the synergistic effect with Ni stabilizes austenite and suppresses the formation of martensite. can do. Therefore, the machinability of iron castings can be improved.
  • austenite can be stabilized even at room temperature.
  • the upper limit of the Mn content to 3.0% by mass, the amount of Mn dissolved in Fe (iron base) can be reduced. Therefore, it is possible to suppress an increase in the coefficient of linear expansion.
  • the lower limit of the Mn content is preferably 0.05% by mass, more preferably 0.07% by mass, and even more preferably 0.08% by mass. It is preferably 0.09% by mass, more preferably 0.1% by mass.
  • the upper limit of the Mn content is preferably 2.5% by mass, more preferably 2.0% by mass, more preferably 1.5% by mass, and 1.0% by mass. It is more preferable that it is, it is more preferable that it is 0.85 mass %, and it is still more preferable that it is 0.7 mass %. The same applies to the following forms of the present material.
  • the sixth form of this material contains Ni of 26.0% by mass or more and 50.0% by mass or less, C of 0.1% by mass or more and 3.5% by mass or less, and 0.1% by mass or more and 3.5% by mass. It contains Si of 0.1% by mass or more and 8.0% by mass or less of Co, and Mg of 0.01% by mass or more and 0.2% by mass or less, and the balance is Fe and unavoidable elements.
  • the sixth form of the present material may be referred to as "the sixth form of the present material (Ni-C-Si-Co-Mg-Fe composition)."
  • the sixth form of the present material contains 0.01% by mass or more and 0.2% by mass or less of Mg.
  • the spheroidizing effect of graphite is enhanced and Mg is segregated in the final solidified part. I can do it.
  • the lower limit of the Mg content By setting the lower limit of the Mg content to 0.01% by mass, the spheroidizing effect of graphite can be enhanced.
  • the upper limit of the Mg content to 0.2% by mass, it is possible to suppress the generation of Mg oxides or sulfides. Therefore, it is possible to suppress a decrease in the flowability of the present material. Furthermore, casting defects in iron castings can be reduced.
  • the lower limit of the Mg content is preferably 0.02% by mass, more preferably 0.03% by mass, and even more preferably 0.04% by mass. preferable.
  • the upper limit of the Mg content is preferably 0.15% by mass, more preferably 0.1% by mass, and even more preferably 0.08% by mass. The same applies to the following forms of the present material.
  • the seventh form of this material contains Ni of 26.0% by mass or more and 50.0% by mass or less, C of 0.1% by mass or more and 3.5% by mass or less, and 0.1% by mass or more and 3.5% by mass. Si of not more than 0.1% by mass and not more than 8.0% by mass, Co of not less than 0.01% by mass and not more than 3.0% by mass, and not less than 0.01% by mass and not more than 0.2% by mass.
  • Mg is included, and the remainder is Fe and inevitable elements.
  • the seventh form of the present material may be referred to as "the seventh form of the present material (Ni-C-Si-Co-Mn-Mg-Fe composition)."
  • the eighth form of this material contains Ni of 26.0% by mass or more and 50.0% by mass or less, C of 0.1% by mass or more and 3.5% by mass or less, and 0.1% by mass or more and 3.5% by mass. It contains Si of 0.01% by mass or more and 3.0% by mass or less of Mn, and the balance is Fe and unavoidable elements.
  • the eighth form of the present material may be referred to as "the eighth form of the present material (Ni-C-Si-Mn-Fe composition)".
  • the ninth form of this material includes Ni of 26.0% by mass or more and 50.0% by mass or less, C of 0.1% by mass or more and 3.5% by mass or less, and 0.1% by mass or more and 3.5% by mass or less. It contains Si of 0.01% by mass or more and 3.0% by mass or less of Mn, and Mg of 0.01% by mass or more and 0.2% by mass or less, and the balance is Fe and unavoidable elements.
  • the ninth form of the present material may be referred to as "the ninth form of the present material (Ni-C-Si-Mn-Mg-Fe composition)".
  • the tenth form of this material includes 26.0% by mass or more and 50.0% by mass of Ni, 0.1% by mass or more and 3.5% by mass of C, and 0.1% by mass or more and 3.5% by mass. It contains Si of 0.01% by mass or more and 0.2% by mass or less of Mg, and the balance is Fe and unavoidable elements.
  • the tenth form of the present material may be referred to as "the tenth form of the present material (Ni-C-Si-Mg-Fe composition)."
  • the first form of heat treatment performed on a heat-treated object cast using this material (hereinafter referred to as "main heat treatment") is to hold the heat-treated object at a first holding temperature of 850°C or higher and 1250°C or lower.
  • the method includes a first holding step and, after the first holding step, a first cooling step of cooling the heat-treated object to a first cooling end temperature of ⁇ 150° C. or more and 150° C. or less.
  • the first holding step includes holding the heat treatment object for a first holding time of 0.25 hours or more and 100 hours or less. Note that the first form of the heat treatment may include other heat treatment steps before and after each of the first holding step and the first cooling step.
  • the heat treatment object cast using this material is sequentially subjected to the first holding step and the first holding step.
  • the coefficient of linear expansion of iron castings can be reduced more reliably.
  • the heat treatment target in the first holding step, is held at a first holding temperature (850°C or more and 1250°C or less) and a first holding time (0.25 hours or more and 100 hours or less). hold it. Then, in a first cooling step after the first holding step, the heat treatment target is cooled to a first cooling end temperature (-150° C. or higher and 150° C. or lower).
  • the first cooling step includes cooling the heat treatment object at a first cooling rate of 0.01° C./min or more and 300° C./min or less.
  • the first cooling rate is preferably 0.01°C/min or more and 20°C/min or less.
  • the first holding time is preferably 2.5 hours or more and 25 hours or less.
  • the first cooling end temperature is preferably 0°C or more and 100°C or less.
  • the lower limit of the first holding temperature is preferably 875°C, more preferably 900°C, more preferably 925°C, and more preferably 950°C.
  • the temperature is more preferably 975°C, more preferably 1000°C, and even more preferably 1025°C.
  • the upper limit of the first holding temperature is preferably 1225°C, more preferably 1200°C, more preferably 1175°C, more preferably 1150°C, and more preferably 1125°C. It is even more preferable. The same applies to the following form of this heat treatment.
  • the lower limit of the first holding time is preferably 0.5 hours, more preferably 1.0 hours, and more preferably 1.5 hours; More preferably 2.0 hours, more preferably 2.5 hours, more preferably 3.0 hours, more preferably 3.5 hours, and more preferably 4.0 hours. It is even more preferable.
  • the upper limit of the first holding time is preferably 90 hours, more preferably 80 hours, more preferably 70 hours, more preferably 60 hours, and 50 hours. more preferably 40 hours, more preferably 30 hours, more preferably 25 hours, more preferably 20 hours, more preferably 15 hours, More preferably, the heating time is 10 hours. The same applies to the following form of this heat treatment.
  • the lower limit of the first cooling end temperature is preferably -125°C, more preferably -100°C, more preferably -75°C, and more preferably -50°C.
  • the temperature is more preferably -25°C, and even more preferably 0°C.
  • the upper limit of the first cooling end temperature is preferably 125°C, more preferably 100°C, more preferably 75°C, and even more preferably 50°C. The same applies to the following form of this heat treatment.
  • the lower limit of the first cooling rate is preferably 0.1°C/min, more preferably 0.2°C/min, and more preferably 0.3°C/min. More preferably, it is 0.4°C/min, more preferably 0.5°C/min, more preferably 0.6°C/min, and more preferably 0.7°C/min. More preferably, it is 0.75°C/min, and even more preferably 0.75°C/min.
  • the upper limit of the first cooling rate is preferably 250°C/min, more preferably 200°C/min, more preferably 150°C/min, and more preferably 100°C/min. is more preferable, more preferably 50°C/min, more preferably 25°C/min, more preferably 10°C/min, even more preferably 5°C/min.
  • the second form of heat treatment includes a first holding step in which the object to be heat treated is held at a first holding temperature of 850°C or more and 1250°C or less, and after the first holding step, the object to be heat treated is heated to -150°C. and a first cooling step of cooling to a first cooling end temperature of 150° C. or less.
  • the first holding step includes holding the heat treatment object for a first holding time of 0.25 hours or more and 100 hours or less.
  • the first cooling process includes a primary cooling process in which the heat treatment target is cooled at a primary cooling rate, and a secondary cooling process in which the heat treatment target is cooled at a secondary cooling rate higher than the primary cooling rate after the primary cooling process.
  • the primary cooling step includes cooling the heat treatment object to a primary cooling end temperature of 250° C. or more and 950° C. or less.
  • the secondary cooling step includes cooling the heat treatment object to a first cooling end temperature (-150° C. or higher and 150° C. or lower).
  • the second form of the main heat treatment may include other heat treatment steps before and after each of the first holding step and the first cooling step.
  • the heat treatment object cast using this material is sequentially subjected to the first holding step and the first holding step.
  • the coefficient of linear expansion of iron castings can be reduced more reliably.
  • the heat treatment target in the first holding step, is held at a first holding temperature (850°C or more and 1250°C or less) and a first holding time (0.25 hours or more and 100 hours or less). hold it. Then, in a first cooling step after the first holding step, the heat treatment target is cooled to a first cooling end temperature (-150° C. or higher and 150° C. or lower).
  • a first holding step it is possible to reduce the solidification segregation of solute elements in the heat-treated object and to reduce the relative difference in crystal orientation (crystal orientation difference) inside each crystal grain constituting the austenite phase. can. This makes it possible to arrange the crystal lattice in the austenite phase. As a result, the coefficient of linear expansion of the iron casting can be reduced.
  • the first cooling step after the first holding step is a primary cooling step in which the object to be heat treated is cooled at the primary cooling rate; and a secondary cooling step in which the object is cooled at a secondary cooling rate that is higher than the primary cooling rate.
  • the heat treatment target is cooled at the primary cooling rate to the primary cooling end temperature (250° C. or higher and 950° C. or lower).
  • This primary cooling step allows carbon in the austenite phase to diffuse toward the graphite side. Therefore, the amount of solid solute carbon in the austenite phase can be reduced. Therefore, excessive distortion of the crystal lattice in the austenite phase can be suppressed.
  • the coefficient of linear expansion of the iron casting can be further reduced.
  • the heat-treated object is cooled to a first cooling end temperature (-150° C. or higher and 150° C. or lower) at a secondary cooling rate that is higher than the primary cooling rate.
  • This secondary cooling step tends to increase the amount of change in spontaneous volumetric magnetostriction due to temperature change below the Curie point. Therefore, in a temperature change below the Curie point, the volume change due to spontaneous bulk magnetostriction and the volume change due to crystal lattice vibration are likely to cancel each other out. Therefore, it is easy to suppress volume fluctuations due to temperature changes. As a result, it is easier to further reduce the coefficient of linear expansion of iron castings.
  • the primary cooling rate is preferably 0.01°C/min or more and 20°C/min or less, and the secondary cooling rate is preferably 1°C/min or more and 40000°C/min or less. .
  • the secondary cooling rate is preferably 100°C/min or more and 40000°C/min or less.
  • the first holding time is preferably 2.5 hours or more and 25 hours or less.
  • the primary cooling end temperature is preferably 450°C or more and 850°C or less.
  • the first cooling end temperature is preferably 0°C or more and 100°C or less.
  • the lower limit of the primary cooling end temperature is preferably 275°C, more preferably 300°C, more preferably 325°C, and most preferably 350°C.
  • the temperature is 375°C, more preferably 400°C, more preferably 425°C, more preferably 450°C, more preferably 475°C, and more preferably 500°C.
  • the temperature is more preferably 525°C, more preferably 550°C, more preferably 575°C, and even more preferably 600°C.
  • the upper limit of the primary cooling end temperature is preferably 925°C, more preferably 900°C, more preferably 875°C, more preferably 850°C, and 825°C. is more preferable, and even more preferably 800°C.
  • the lower limit of the primary cooling rate is preferably 0.1°C/min, more preferably 0.5°C/min, and more preferably 0.75°C/min. is more preferably 1.0°C/min, more preferably 1.25°C/min, more preferably 1.5°C/min, and more preferably 1.75°C/min. It is even more preferable that there be.
  • the upper limit of the primary cooling rate is preferably 17.5°C/min, more preferably 15.0°C/min, more preferably 12.5°C/min, and 10.0°C/min. C/min is more preferable, and even more preferably 7.5 C/min.
  • the lower limit of the secondary cooling rate is preferably 2.5°C/min, more preferably 5°C/min, and preferably 7.5°C/min. More preferably, 10°C/min, more preferably 50°C/min, more preferably 100°C/min, more preferably 200°C/min, and even more preferably 300°C/min. More preferably, it is 400°C/min, more preferably 500°C/min, and even more preferably 600°C/min.
  • the upper limit of the secondary cooling rate is preferably 37,500°C/min, more preferably 35,000°C/min, more preferably 32,500°C/min, and preferably 30,000°C/min. More preferably, it is 27,500°C/min, and even more preferably 25,000°C/min.
  • the third form of heat treatment includes a first holding step in which the object to be heat treated is held at a first holding temperature of 850°C to 1250°C, and after the first holding step, the object to be heat treated is heated to -150°C.
  • a first cooling step in which the object is cooled to a first cooling end temperature of not less than 150°C
  • a second cooling step in which the object to be heat treated is held at a second holding temperature of not less than 250°C and not more than 950°C after the first cooling step.
  • a second cooling step of cooling the heat-treated object to a second cooling end temperature of ⁇ 150° C. or more and 150° C. or less.
  • the first holding step includes holding the heat treatment object for a first holding time of 0.25 hours or more and 100 hours or less.
  • the second holding step includes holding the heat-treated object for a second holding time of 0.25 hours or more and 25 hours or less.
  • the third form of the heat treatment includes other heat treatment steps before and after each of the first holding step, first cooling step, second holding step, and second cooling step. Good too.
  • the heat treatment object cast using the present material is sequentially subjected to the first holding step and the first holding step.
  • the heat treatment target in the first holding step, is held at a first holding temperature (850°C or more and 1250°C or less) and a first holding time (0.25 hours or more and 100 hours or less). hold it. Then, in a first cooling step after the first holding step, the heat treatment target is cooled to a first cooling end temperature (-150° C. or higher and 150° C. or lower).
  • a first holding step it is possible to reduce the solidification segregation of solute elements in the heat-treated object and to reduce the relative difference in crystal orientation (crystal orientation difference) inside each crystal grain constituting the austenite phase. can. This makes it possible to arrange the crystal lattice in the austenite phase. As a result, the coefficient of linear expansion of the iron casting can be reduced.
  • the heat treatment target is held at a second holding temperature (250° C. or higher and 950° C. or lower) in a second holding step after the first cooling step. Then, in a second cooling step after the second holding step, the heat treatment target is cooled to a second cooling end temperature (-150° C. or higher and 150° C. or lower).
  • This second cooling step tends to increase the amount of change in spontaneous volume magnetostriction due to temperature change below the Curie point. Therefore, in a temperature change below the Curie point, the volume change due to spontaneous bulk magnetostriction and the volume change due to crystal lattice vibration are likely to cancel each other out. Therefore, it is easy to suppress volume fluctuations due to temperature changes. As a result, it is easier to further reduce the coefficient of linear expansion of iron castings.
  • the first cooling step preferably includes cooling the heat treatment object at a first cooling rate of 0.01° C./min or more and 300° C./min or less.
  • the first cooling rate is preferably 1° C./min or more and 50° C./min or less.
  • the second cooling step preferably includes cooling the heat-treated object at a second cooling rate of 1° C./min or more and 40000° C./min or less.
  • the second cooling rate is preferably 100° C./min or more and 10000° C./min or less.
  • the first holding time is preferably 2.5 hours or more and 25 hours or less.
  • the first cooling end temperature is preferably 0°C or more and 100°C or less.
  • the second holding temperature is preferably 550°C or more and 950°C or less.
  • the second cooling end temperature is preferably 0°C or more and 50°C or less.
  • the lower limit of the first cooling rate is preferably 1.0°C/min, more preferably 5.0°C/min, and more preferably 7.5°C/min. More preferably, the rate is 10.0°C/min, more preferably 12.0°C/min, and even more preferably 14.0°C/min.
  • the upper limit of the first cooling rate is preferably 250°C/min, more preferably 200°C/min, more preferably 150°C/min, and more preferably 100°C/min. is more preferable, more preferably 75°C/min, more preferably 50°C/min, more preferably 45°C/min, and even more preferably 40°C/min.
  • the lower limit of the second holding temperature is preferably 275°C, more preferably 300°C, more preferably 325°C, and preferably 350°C. more preferably 375°C, more preferably 400°C, more preferably 425°C, more preferably 450°C, more preferably 475°C, and more preferably 500°C.
  • the temperature is more preferably 525°C, more preferably 550°C, more preferably 575°C, and even more preferably 600°C.
  • the upper limit of the second holding temperature is preferably 925°C, more preferably 900°C, more preferably 875°C, more preferably 850°C, and more preferably 825°C. More preferably, the temperature is 800°C.
  • the lower limit of the second holding time is preferably 0.3 hours, more preferably 0.4 hours, more preferably 0.5 hours, More preferably 0.6 hours, more preferably 0.7 hours, more preferably 0.8 hours, more preferably 0.9 hours, and 1.0 hours. It is even more preferable.
  • the upper limit of the second holding time is preferably 20 hours, more preferably 15 hours, more preferably 10 hours, more preferably 9 hours, and more preferably 8 hours. is more preferable, more preferably 7 hours, more preferably 6 hours, and even more preferably 5 hours.
  • the lower limit of the second cooling end temperature is preferably -125°C, more preferably -100°C, more preferably -75°C, and more preferably -50°C.
  • the temperature is more preferably -25°C, and even more preferably 0°C.
  • the upper limit of the second cooling end temperature is preferably 125°C, more preferably 100°C, more preferably 75°C, more preferably 50°C, and even more preferably 40°C.
  • the temperature is more preferably 30°C, and even more preferably 30°C.
  • the lower limit of the second cooling rate is preferably 25°C/min, more preferably 50°C/min, and more preferably 75°C/min.
  • the rate is more preferably 100°C/min, more preferably 200°C/min, even more preferably 300°C/min, and even more preferably 400°C/min.
  • the upper limit of the second cooling rate is preferably 35,000°C/min, more preferably 30,000°C/min, more preferably 25,000°C/min, and 20,000°C/min.
  • the iron casting of the first embodiment is based on the fifth form (Ni-C-Si-Co-Mn-Fe composition) and the seventh form (Ni-C-Si-Co-Mn-Mg-Fe composition) of the present material.
  • the eighth form Ni-C-Si-Mn-Fe composition
  • the ninth form Ni-C-Si-Mn-Mg-Fe composition
  • This is an iron casting obtained by performing the second form of this heat treatment.
  • the linear expansion coefficient of the iron casting can be reduced as described above.
  • the object to be heat treated is cast using an austenitic casting material with a Ni content of 26.0% by mass or more, the Ms point (from austenite to It is easy to lower the temperature at which transformation to martensite begins. Therefore, it is easy to provide iron castings in which martensite generation is suppressed.
  • the solidification segregation of solute elements in the heat treatment object is reduced, and as a result, Ni distributed at a low concentration in the final solidified part of the heat treatment object can be highly concentrated. Thereby, the Ms point in the final solidification part can be further lowered.
  • the generation of martensite is further suppressed. can do. Therefore, it is possible to provide an iron casting in which thermal expansion is reduced and martensite formation is suppressed. The same applies to the following embodiments.
  • the iron casting of the second embodiment is based on the fifth form (Ni-C-Si-Co-Mn-Fe composition) and the seventh form (Ni-C-Si-Co-Mn-Mg-Fe composition) of the present material.
  • This is an iron casting obtained by performing the third form of heat treatment on a heat-treated object cast using the composition) and the ninth form (Ni-C-Si-Mn-Mg-Fe composition).
  • the linear expansion coefficient of the iron casting can be reduced as described above.
  • the iron casting of the third embodiment is based on the fifth form (Ni-C-Si-Co-Mn-Fe composition) and the seventh form (Ni-C-Si-Co-Mn-Mg-Fe composition) of the present material.
  • This is an iron casting obtained by performing the first form of heat treatment on a heat-treated object cast using the composition) and the ninth form (Ni-C-Si-Mn-Mg-Fe composition).
  • the linear expansion coefficient of the iron casting can be reduced as described above.
  • an iron casting with reduced thermal expansion can be provided. Therefore, the iron castings of the above embodiments are suitable for a wide variety of uses that require low thermal expansion (coefficient).
  • uses of the iron castings of the above embodiments include component parts of semiconductor manufacturing equipment, electronic component manufacturing equipment, machine tools, and the like.
  • application examples in operating environments of about 20°C to 50°C include spindle holders for dicers, calibration gauges (gauge blocks, etc.) in semiconductor manufacturing equipment, work stages in machine tools, and wires in wire electrical discharge machines. A holding member is mentioned.
  • examples of applications in use environments of about 20° C. to 100° C. (or 150° C.) include dry vacuum pump parts and card holders for probers in semiconductor manufacturing equipment.
  • Table 1 shows the compositions of Examples in the first embodiment and the compositions of Comparative Examples.
  • Table 2 shows the compositions of Examples in the second embodiment and the compositions of Comparative Examples thereof.
  • Table 3 shows the compositions of Examples in the third embodiment and the compositions of Comparative Examples.
  • the C (carbon) content is the value measured by combustion-infrared absorption method using a material carbon/sulfur analyzer "EMIA-Expert" manufactured by Horiba, Ltd. be.
  • the content (mass%) of Si (silicon), Ni (nickel), Mg (magnesium), and Co (cobalt) was determined using inductively coupled plasma using an emission spectrometer "SPS3520UV” manufactured by Hitachi High-Tech Science Co., Ltd. This is a value measured by emission spectrometry. Further, the contents (mass %) of other elements are values measured by emission spectrometry using an emission spectrometer "PDA-8000" manufactured by Shimadzu Corporation.
  • Table 4 shows the heat treatment conditions and average linear expansion coefficients of the examples in the first embodiment, and the heat treatment conditions and average linear expansion coefficients of comparative examples with respect to these.
  • Table 5 shows the heat treatment conditions and average linear expansion coefficients of the examples in the second embodiment, and the heat treatment conditions and average linear expansion coefficients of comparative examples with respect to these.
  • Table 6 shows the heat treatment conditions and average linear expansion coefficients of the examples in the third embodiment, and the heat treatment conditions and average linear expansion coefficients of the comparative examples.
  • the holding temperature (°C) indicates the temperature at which the heat treatment object is held in the heat treatment furnace (heat treatment apparatus).
  • As the heat treatment furnace a muffle furnace "QUICK TEMPER" manufactured by TEC Co., Ltd. was used.
  • the holding time indicates the time during which the heat treatment object is held in a state where the inside of the heat treatment furnace is kept at the holding temperature.
  • the cooling method refers to a method for cooling the heat-treated object.Furnace cooling is a method in which the heat-treated object is gradually cooled inside the heat treatment furnace, and natural air cooling is a method for cooling the heat-treated object outside the heat treatment furnace. It is a method of cooling in air, and rapid cooling is a method of rapidly cooling the object to be heat treated by immersing it in water, oil, a coolant using dry ice, liquid nitrogen, or the like. Further, the cooling end temperature (° C.) indicates the temperature at which cooling of the heat treatment object by the cooling method ends.
  • the cooling end temperature is the surface temperature of the heat treatment object measured in the heat treatment furnace by bringing the temperature measurement part of the thermocouple into contact with the heat treatment object in the heat treatment furnace.
  • the cooling end temperature in the case of natural air cooling and rapid cooling is the surface temperature of the heat treatment object measured outside the heat treatment furnace by bringing the temperature measurement part of the thermocouple into contact with the heat treatment object outside the heat treatment furnace.
  • the cooling rate (°C/min) or (°C/sec) indicates the amount of change in temperature with respect to the time from the start to the end of cooling of the heat-treated object.
  • the average linear expansion coefficient ( ⁇ 10 -6 /°C) was obtained from an iron casting (Y type B sample material) after the specified heat treatment was applied to the heat treatment object cast by sand casting method.
  • the linear expansion coefficient measurement test piece (diameter 6 mm, length 25 mm) is a value measured according to ASTM standard (ASTM E228-17) using a thermal dilatometer "DIL 402 Expedis Supreme” manufactured by NETZSCH Japan Co., Ltd.
  • the average coefficient of linear expansion up to each temperature (50°C, 100°C, 150°C) in Tables 4 to 6 is shown based on °C.
  • the average linear expansion coefficient at 20°C or more and 50°C or less is 3.51 ⁇ 10 -6 /°C or less (Comparative Example 1-1 is 3.63 ⁇ 10 -6 /°C), average linear expansion coefficient at 20°C to 100°C is 3.58 ⁇ 10 -6 /°C or less (Comparative Example 1-1 is 3.90 ⁇ 10 -6 /°C), 20°C
  • the average linear expansion coefficient at 150°C or lower is 4.09 ⁇ 10 ⁇ 6 /°C or less (4.28 ⁇ 10 ⁇ 6 /°C in Comparative Example 1-1).
  • the thermal expansion of the iron castings can be reduced by setting the primary cooling end temperature to 950° C. or lower (particularly 900° C. or lower).
  • the average linear expansion coefficient at 20°C or more and 50°C or less is 3.51 ⁇ 10 -6 /°C or less (Comparative Example 1-2 is 4.98 ⁇ 10 -6 /°C), average linear expansion coefficient at 20°C to 100°C is 3.58 ⁇ 10 -6 /°C or less (4.87 ⁇ 10 -6 /°C for Comparative Example 1-2), 20°C
  • the average linear expansion coefficient at 150°C or lower is 4.09 ⁇ 10 ⁇ 6 /°C or less (comparative example 1-2 is 4.87 ⁇ 10 ⁇ 6 /°C).
  • the average linear expansion coefficient at 20°C or more and 50°C or less is 3.30 ⁇ 10 -6 /°C or less (Comparative Example 2-1 is 3.54 ⁇ 10 -6 /°C), average linear expansion coefficient at 20°C to 100°C is 3.55 ⁇ 10 -6 /°C or less (Comparative Example 2-1 is 3.78 ⁇ 10 -6 /°C), 20°C Above, the average linear expansion coefficient at 150°C or lower is 4.05 ⁇ 10 ⁇ 6 /°C or lower (comparative example 2-1 is 4.15 ⁇ 10 ⁇ 6 /°C). As described above, in Examples 2-1 to 2-26, by setting the second holding temperature to 950° C. or lower (particularly 900° C. or lower), the thermal expansion of the iron castings can be reduced.
  • the average linear expansion coefficient at 20°C or higher and 50°C or lower is 3.30 ⁇ 10 -6 /°C or less (Comparative Example 2-2 is 5.57 ⁇ 10 -6 /°C), average linear expansion coefficient at 20°C to 100°C is 3.55 ⁇ 10 -6 /°C or less (Comparative Example 2-2 is 5.47 ⁇ 10 -6 /°C), 20°C
  • the average linear expansion coefficient at 150°C or lower is 4.05 ⁇ 10 ⁇ 6 /°C or lower (5.40 ⁇ 10 ⁇ 6 /°C in Comparative Example 2-2).
  • the average linear expansion coefficient at 20°C or higher and 50°C or lower is 3.80 ⁇ 10 -6 /°C or less (Comparative Example 3-1 is 4.53 ⁇ 10 -6 /°C), average linear expansion coefficient at 20°C to 100°C is 4.16 ⁇ 10 -6 /°C or less (comparative example 3-1 is 5.02 ⁇ 10 -6 /°C), 20°C
  • the average linear expansion coefficient at 150°C or lower is 4.84 ⁇ 10 ⁇ 6 /°C or less (5.58 ⁇ 10 ⁇ 6 /°C in Comparative Example 3-1).
  • the thermal expansion of the iron castings can be reduced.
  • the average linear expansion coefficient at 20°C or more and 50°C or less is 3.80 ⁇ 10 -6 /°C or less (Comparative Example 3-2 is 3.89 ⁇ 10 -6 /°C), and the average linear expansion coefficient at temperatures above 20°C and below 100°C was 4.16 ⁇ 10 -6 /°C or less (comparative example 3-2 was 4.17 ⁇ 10 -6 /°C).
  • the thermal expansion of the iron castings can be reduced.
  • the average linear expansion coefficient at 20°C or more and 50°C or less is 3.80 ⁇ 10 -6 /°C or less (Comparative Example 3-3 is 5.87 ⁇ 10 -6 /°C), average linear expansion coefficient at 20°C to 100°C is 4.16 ⁇ 10 -6 /°C or less (Comparative Example 3-3 is 5.72 ⁇ 10 -6 /°C), 20°C Above, the average linear expansion coefficient at 150°C or lower is 4.84 ⁇ 10 ⁇ 6 /°C or less (comparative example 3-3 is 5.67 ⁇ 10 ⁇ 6 /°C). As described above, in Examples 3-1 to 3-13, by setting the first holding temperature to 1250° C. or lower (particularly 1200° C. or lower), the thermal expansion of the iron castings can be reduced.
  • Example 3-9 Comparative Example 3-1 and Comparative Example 3-3
  • the casting materials of Example 3-9, Comparative Example 3-1, and Comparative Example 3-3 do not contain Co.
  • the first holding temperature in Example 3-9 is 850°C or more and 1250°C or less
  • the first holding temperature in Comparative Example 3-1 is 800°C.
  • the first holding temperature of Comparative Example 3-3 is 1300°C.
  • Example 3-9 the average coefficient of linear expansion at temperatures above 20°C and below 150°C is reduced.
  • the average linear expansion coefficient at 20°C or higher and 150°C or lower is 4.84 ⁇ 10 -6 /°C or less (Comparative Example 3-1 is 5.58 ⁇ 10 -6 /°C , Comparative Example 3-3 was 5.67 ⁇ 10 ⁇ 6 /°C).
  • the thermal expansion of the iron casting at high temperatures can be reduced by not containing Co and by setting the first holding temperature to 850° C. or more and 1250° C. or less.
  • Example 3-1 to 3-8 and Examples 3-10 to 3-13 are reduced compared to Comparative Example 3-2.
  • the average linear expansion coefficient at 20°C or higher and 150°C or lower is 4.49 ⁇ 10 -6 / °C or less (comparative example 3-2 was 4.53 ⁇ 10 ⁇ 6 /°C).
  • Co is contained and the first holding temperature is set to 850°C or more and 1250°C or less. This makes it possible to reduce the thermal expansion of iron castings at high temperatures.
  • the present disclosure can also have the following configuration.
  • An iron casting obtained by performing a first heat treatment on a heat treatment object cast using an austenitic casting material The iron casting, wherein performing the first heat treatment includes maintaining the heat treatment object at a first temperature range of 950°C or more and 1200°C or less.
  • the iron casting according to (1), wherein holding in the first temperature range includes holding the heat treatment object for a time range of 1 hour or more and 100 hours or less.
  • Further comprising performing a second heat treatment on the object to be heat treated after performing the first heat treatment The iron casting according to (1) or (2), wherein performing the second heat treatment includes cooling the object to be heat treated to a second temperature range of 300°C or higher and 900°C or lower.
  • cooling to the second temperature range includes cooling the heat-treated object at a cooling rate range of 0.01° C./min to 20° C./min.
  • a method for producing iron castings comprising performing a first heat treatment on a heat treatment object cast using an austenitic casting material, The manufacturing method, wherein performing the first heat treatment includes maintaining the heat treatment target at a first temperature range of 950°C or higher and 1200°C or lower.
  • the manufacturing method according to (11), wherein holding the object in the first temperature range includes holding the object to be heat treated for a time range of 1 hour or more and 100 hours or less.
  • Further comprising performing a second heat treatment on the heat treatment target after performing the first heat treatment The manufacturing method according to (11) or (12), wherein performing the second heat treatment includes cooling the object to be heat treated to a second temperature range of 300°C or higher and 900°C or lower.
  • cooling to the second temperature range includes cooling the heat treatment target at a cooling rate range of 0.01° C./min to 20° C./min.
  • cooling to the third temperature range includes cooling the heat treatment object to a third temperature range of 0° C. or higher and 100° C. or lower.
  • cooling to the third temperature range includes cooling the heat treatment object at a cooling rate range of 1° C./second to 1000° C./second.

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Abstract

The present invention provides a method for producing an iron casting by performing a heat treatment on an object to be heat treated, the object being obtained by casting an austenitic casting material. The heat treatment comprises: a first retention step in which the object to be heat treated is retained at a first retention temperature of 850°C to 1250°C; and a first cooling step in which the object to be heat treated is cooled to a first cooling end temperature of -150°C to 150°C after the first retention step. The first retention step includes retention of the object to be heat treated for a first retention time of 0.25 hour to 100 hours.

Description

鉄鋳物およびそれを製造する方法Iron castings and methods of manufacturing them
　本発明は、鉄鋳物およびそれを製造する方法に関する。 The present invention relates to iron castings and methods of manufacturing them.
　特許文献１の要約には、一般の鋳鉄材と同様な、良好な鋳造性や加工性を有すると共に、より一層優れた低熱膨張特性を有する鋳鉄材を容易に製造することの出来る方法を提供することが記載されている。また、特許文献１の要約には、鋳造して得られた、炭素が２．５質量％以下、ニッケルが２５質量％以上４０質量％以下の割合で含有する鋳鉄組成を有する鋳物を、５５０℃以上７００℃以下の温度で３時間以上保持した後、少なくとも２００℃までは炉冷によって自然冷却することからなる焼鈍処理を行ない、次いで、そのように焼鈍処理された鋳物を、６００℃以上１１５０℃以下の温度で１．５時間以上保持した後、ファン空冷、水冷または油冷により急冷することからなる溶体化処理を行なうことにより、５０℃以上２００℃以下の温度範囲における熱膨張係数が４×１０－６／℃以下となる低熱膨張鋳鉄材を製造することが記載されている。 The summary of Patent Document 1 provides a method for easily manufacturing a cast iron material that has good castability and workability similar to general cast iron materials, and has even better low thermal expansion characteristics. It is stated that. In addition, the summary of Patent Document 1 states that a casting having a cast iron composition containing 2.5% by mass or less of carbon and 25% by mass or more and 40% by mass or less of nickel obtained by casting is heated to 550°C. After holding the casting at a temperature of 700°C or higher for 3 hours or more, annealing is performed by naturally cooling it by furnace cooling to at least 200°C, and then the annealed casting is heated to a temperature of 600°C or higher and 1150°C. By holding the temperature at the following temperature for 1.5 hours or more and then performing solution treatment, which consists of rapid cooling with fan air cooling, water cooling, or oil cooling, the coefficient of thermal expansion in the temperature range of 50°C to 200°C is 4x. It is described that a cast iron material with a low thermal expansion of 10 -6 /°C or less is produced.
特開２０１０－９５７４７号公報Japanese Patent Application Publication No. 2010-95747
　オーステナイト系の鋳造用材料を用いて熱膨張を低減させた鉄鋳物を提供する。 We provide iron castings with reduced thermal expansion using austenitic casting materials.
　本発明の一態様に係る方法は、オーステナイト系の鋳造用材料を用いて鋳造した熱処理対象物に対して熱処理を行うことにより鉄鋳物を製造する方法である。前記鋳造用材料は、２６．０質量％以上５０．０質量％以下のＮｉと、０．１質量％以上３．５質量％以下のＣと、０．１質量％以上３．５質量％以下のＳｉと、０質量％以上８．０質量％以下のＣｏと、０質量％以上３．０質量％以下のＭｎと、０質量％以上０．２質量％以下のＭｇとを含み、残部がＦｅおよび不可避元素である。前記熱処理は、前記熱処理対象物を８５０℃以上１２５０℃以下の第１の保持温度で保持する第１の保持工程と、前記第１の保持工程の後に、前記熱処理対象物を－１５０℃以上１５０℃以下の第１の冷却終了温度まで冷却する第１の冷却工程とを含む。前記第１の保持工程は、前記熱処理対象物を０．２５時間以上１００時間以下の第１の保持時間で保持することを含む。 A method according to one aspect of the present invention is a method for manufacturing an iron casting by heat-treating a heat-treated object cast using an austenitic casting material. The casting material contains Ni of 26.0% by mass or more and 50.0% by mass or less, C of 0.1% by mass or more and 3.5% by mass or less, and 0.1% by mass or more and 3.5% by mass or less. of Si, 0 mass% to 8.0 mass% Co, 0 mass% to 3.0 mass% Mn, and 0 mass% to 0.2 mass% Mg, with the balance being Fe and inevitable elements. The heat treatment includes a first holding step in which the heat treatment target is held at a first holding temperature of 850°C or higher and 1250°C or lower, and after the first holding step, the heat treatment target is held at a temperature of -150°C or higher and 150°C or higher. and a first cooling step of cooling to a first cooling end temperature of .degree. C. or lower. The first holding step includes holding the heat treatment object for a first holding time of 0.25 hours or more and 100 hours or less.
　この方法においては、第１の保持工程において、熱処理対象物を第１の保持温度（８５０℃以上１２５０℃以下）かつ第１の保持時間（０．２５時間以上１００時間以下）で保持する。そして、第１の保持工程の後の第１の冷却工程において、熱処理対象物を第１の冷却終了温度（－１５０℃以上１５０℃以下）まで冷却する。この第１の保持工程により、熱処理対象物内の溶質元素の凝固偏析を低減するとともに、オーステナイト相を構成する各結晶粒内部の結晶方位の相対的な差（結晶方位差）を小さくすることができる。これにより、オーステナイト相中の結晶格子の配列を整えることができる。その結果、鉄鋳物の線膨張係数を低減させることができる。 In this method, in the first holding step, the heat-treated object is held at a first holding temperature (850° C. or more and 1250° C. or less) and a first holding time (0.25 hours or more and 100 hours or less). Then, in a first cooling step after the first holding step, the heat treatment target is cooled to a first cooling end temperature (-150° C. or higher and 150° C. or lower). Through this first holding step, it is possible to reduce the solidification segregation of solute elements in the heat-treated object and to reduce the relative difference in crystal orientation (crystal orientation difference) inside each crystal grain constituting the austenite phase. can. This makes it possible to arrange the crystal lattice in the austenite phase. As a result, the coefficient of linear expansion of the iron casting can be reduced.
　この方法において、前記第１の冷却工程は、前記熱処理対象物を０．０１℃／分以上３００℃／分以下の第１の冷却速度で冷却することを含むことが好ましい。前記第１の冷却速度は、０．０１℃／分以上２０℃／分以下であることが好ましい。前記第１の保持時間は、２．５時間以上２５時間以下であることが好ましい。前記第１の冷却終了温度は、０℃以上１００℃以下であることが好ましい。 In this method, it is preferable that the first cooling step includes cooling the object to be heat treated at a first cooling rate of 0.01° C./min or more and 300° C./min or less. The first cooling rate is preferably 0.01°C/min or more and 20°C/min or less. The first holding time is preferably 2.5 hours or more and 25 hours or less. The first cooling end temperature is preferably 0°C or more and 100°C or less.
　この方法において、前記第１の冷却工程は、前記熱処理対象物を一次冷却速度で冷却する一次冷却工程と、前記一次冷却工程の後に、前記熱処理対象物を前記一次冷却速度よりも大きい二次冷却速度で冷却する二次冷却工程とを含み、前記一次冷却工程は、前記熱処理対象物を２５０℃以上９５０℃以下の一次冷却終了温度まで冷却することを含み、前記二次冷却工程は、前記熱処理対象物を前記第１の冷却終了温度まで冷却することを含むことが好ましい。 In this method, the first cooling step includes a primary cooling step in which the heat treatment target is cooled at a primary cooling rate, and after the primary cooling step, the heat treatment target is subjected to secondary cooling at a rate higher than the primary cooling rate. The secondary cooling step includes cooling the heat treatment object to a primary cooling end temperature of 250° C. or more and 950° C. or less, and the secondary cooling step includes Preferably, the method includes cooling the object to the first cooling end temperature.
　この方法においては、第１の保持工程の後の第１の冷却工程が、熱処理対象物を一次冷却速度で冷却する一次冷却工程と、一次冷却工程の後に、熱処理対象物を一次冷却速度よりも大きい二次冷却速度で冷却する二次冷却工程とを含む。具体的には、一次冷却工程において、熱処理対象物を一次冷却終了温度（２５０℃以上９５０℃以下）まで一次冷却速度で冷却する。この一次冷却工程により、オーステナイト相中の炭素を黒鉛の側に拡散させることができる。このため、オーステナイト相中の固溶炭素量を低減させることができる。したがって、オーステナイト相中の結晶格子の過剰な歪みを抑制することができる。その結果、鉄鋳物の線膨張係数を一層低減させることができる。さらに、一次冷却工程の後の二次冷却工程において、熱処理対象物を第１の冷却終了温度（－１５０℃以上１５０℃以下）まで一次冷却速度よりも大きい二次冷却速度で冷却する。この二次冷却工程により、キュリー点以下での温度変化に伴う自発体積磁気歪みの変化量を増加させやすい。このため、キュリー点以下での温度変化において、自発体積磁気歪みに起因する体積変化と、結晶格子振動に起因する体積変化とを相殺させやすい。したがって、温度変化に伴う体積変動を抑制しやすい。その結果、鉄鋳物の線膨張係数をより一層低減させやすい。 In this method, the first cooling step after the first holding step includes a primary cooling step in which the object to be heat treated is cooled at a primary cooling rate; and a secondary cooling step of cooling at a high secondary cooling rate. Specifically, in the primary cooling step, the heat treatment target is cooled at the primary cooling rate to the primary cooling end temperature (250° C. or higher and 950° C. or lower). This primary cooling step allows carbon in the austenite phase to diffuse toward the graphite side. Therefore, the amount of solid solute carbon in the austenite phase can be reduced. Therefore, excessive distortion of the crystal lattice in the austenite phase can be suppressed. As a result, the coefficient of linear expansion of the iron casting can be further reduced. Furthermore, in the secondary cooling step after the primary cooling step, the heat-treated object is cooled to a first cooling end temperature (-150° C. or higher and 150° C. or lower) at a secondary cooling rate that is higher than the primary cooling rate. This secondary cooling step tends to increase the amount of change in spontaneous volumetric magnetostriction due to temperature change below the Curie point. Therefore, in a temperature change below the Curie point, the volume change due to spontaneous bulk magnetostriction and the volume change due to crystal lattice vibration are likely to cancel each other out. Therefore, it is easy to suppress volume fluctuations due to temperature changes. As a result, it is easier to further reduce the coefficient of linear expansion of iron castings.
　この方法において、前記一次冷却速度は、０．０１℃／分以上２０℃／分以下であり、前記二次冷却速度は、１℃／分以上４００００℃／分以下であることが好ましい。前記二次冷却速度は、１００℃／分以上４００００℃／分以下であることが好ましい。前記第１の保持時間は、２．５時間以上２５時間以下であることが好ましい。前記一次冷却終了温度は、４５０℃以上８５０℃以下であることが好ましい。前記第１の冷却終了温度は、０℃以上１００℃以下であることが好ましい。 In this method, the primary cooling rate is preferably 0.01°C/min or more and 20°C/min or less, and the secondary cooling rate is preferably 1°C/min or more and 40000°C/min or less. The secondary cooling rate is preferably 100° C./min or more and 40000° C./min or less. The first holding time is preferably 2.5 hours or more and 25 hours or less. The primary cooling end temperature is preferably 450°C or more and 850°C or less. The first cooling end temperature is preferably 0°C or more and 100°C or less.
　この方法において、前記熱処理は、前記第１の冷却工程の後に、前記熱処理対象物を２５０℃以上９５０℃以下の第２の保持温度で保持する第２の保持工程と、前記第２の保持工程の後に、前記熱処理対象物を－１５０℃以上１５０℃以下の第２の冷却終了温度まで冷却する第２の冷却工程とをさらに含み、前記第２の保持工程は、前記熱処理対象物を０．２５時間以上２５時間以下の第２の保持時間で保持することを含むものであってもよい。 In this method, the heat treatment includes, after the first cooling step, a second holding step in which the object to be heat treated is held at a second holding temperature of 250° C. or more and 950° C. or less, and the second holding step. After that, the second cooling step further includes cooling the heat treatment object to a second cooling end temperature of -150° C. or more and 150° C. or less, and the second holding step cools the heat treatment object to a temperature of 0. It may include holding for a second holding time of 25 hours or more and 25 hours or less.
　この方法において、前記第１の冷却工程は、前記熱処理対象物を０．０１℃／分以上３００℃／分以下の第１の冷却速度で冷却することを含むことが好ましい。前記第１の冷却速度は、１℃／分以上５０℃／分以下であることが好ましい。前記第２の冷却工程は、前記熱処理対象物を１℃／分以上４００００℃／分以下の第２の冷却速度で冷却することを含むことが好ましい。前記第２の冷却速度は、１００℃／分以上１００００℃／分以下であることが好ましい。前記第１の保持時間は、２．５時間以上２５時間以下であることが好ましい。前記第１の冷却終了温度は、０℃以上１００℃以下であることが好ましい。前記第２の保持温度は、５５０℃以上９５０℃以下であることが好ましい。前記第２の冷却終了温度は、０℃以上５０℃以下であることが好ましい。 In this method, it is preferable that the first cooling step includes cooling the object to be heat treated at a first cooling rate of 0.01° C./min or more and 300° C./min or less. The first cooling rate is preferably 1° C./min or more and 50° C./min or less. Preferably, the second cooling step includes cooling the heat treatment object at a second cooling rate of 1° C./min or more and 40000° C./min or less. The second cooling rate is preferably 100° C./min or more and 10,000° C./min or less. The first holding time is preferably 2.5 hours or more and 25 hours or less. The first cooling end temperature is preferably 0°C or more and 100°C or less. The second holding temperature is preferably 550°C or more and 950°C or less. The second cooling end temperature is preferably 0°C or more and 50°C or less.
　この方法において、前記鋳造用材料のＣｏの含有量は、０．１質量％以上８．０質量％以下であることが好ましい。前記鋳造用材料のＭｎの含有量は、０．０１質量％以上３．０質量％以下であることが好ましい。前記鋳造用材料のＭｇの含有量は、０．０１質量％以上０．２質量％以下であることが好ましい。 In this method, the Co content of the casting material is preferably 0.1% by mass or more and 8.0% by mass or less. The content of Mn in the casting material is preferably 0.01% by mass or more and 3.0% by mass or less. The content of Mg in the casting material is preferably 0.01% by mass or more and 0.2% by mass or less.
　本発明の他の態様に係る方法は、オーステナイト系の鋳造用材料を用いて鋳造した熱処理対象物に対して熱処理を行うことにより鉄鋳物を製造する方法である。前記熱処理は、前記熱処理対象物を８５０℃以上１２５０℃以下の第１の保持温度で保持する第１の保持工程と、前記第１の保持工程の後に、前記熱処理対象物を－１５０℃以上１５０℃以下の第１の冷却終了温度まで冷却する第１の冷却工程とを含む。前記第１の保持工程は、前記熱処理対象物を０．２５時間以上１００時間以下の第１の保持時間で保持することを含む。 A method according to another aspect of the present invention is a method of manufacturing an iron casting by heat-treating a heat-treated object cast using an austenitic casting material. The heat treatment includes a first holding step in which the heat treatment target is held at a first holding temperature of 850°C or higher and 1250°C or lower, and after the first holding step, the heat treatment target is held at a temperature of -150°C or higher and 150°C or higher. and a first cooling step of cooling to a first cooling end temperature of .degree. C. or lower. The first holding step includes holding the heat treatment object for a first holding time of 0.25 hours or more and 100 hours or less.
　この方法において、前記第１の冷却工程は、前記熱処理対象物を一次冷却速度で冷却する一次冷却工程と、前記一次冷却工程の後に、前記熱処理対象物を前記一次冷却速度よりも大きい二次冷却速度で冷却する二次冷却工程とを含み、前記一次冷却工程は、前記熱処理対象物を２５０℃以上９５０℃以下の一次冷却終了温度まで冷却することを含み、前記二次冷却工程は、前記熱処理対象物を前記第１の冷却終了温度まで冷却することを含むことが好ましい。 In this method, the first cooling step includes a primary cooling step in which the heat treatment target is cooled at a primary cooling rate, and after the primary cooling step, the heat treatment target is subjected to secondary cooling at a rate higher than the primary cooling rate. The secondary cooling step includes cooling the heat treatment object to a primary cooling end temperature of 250° C. or more and 950° C. or less, and the secondary cooling step includes Preferably, the method includes cooling the object to the first cooling end temperature.
　この方法において、前記熱処理は、前記第１の冷却工程の後に、前記熱処理対象物を２５０℃以上９５０℃以下の第２の保持温度で保持する第２の保持工程と、前記第２の保持工程の後に、前記熱処理対象物を－１５０℃以上１５０℃以下の第２の冷却終了温度まで冷却する第２の冷却工程とをさらに含み、前記第２の保持工程は、前記熱処理対象物を０．２５時間以上２５時間以下の第２の保持時間で保持することを含むものであってもよい。 In this method, the heat treatment includes, after the first cooling step, a second holding step in which the object to be heat treated is held at a second holding temperature of 250° C. or more and 950° C. or less, and the second holding step. After that, the second cooling step further includes cooling the heat treatment object to a second cooling end temperature of -150° C. or more and 150° C. or less, and the second holding step cools the heat treatment object to a temperature of 0. It may include holding for a second holding time of 25 hours or more and 25 hours or less.
　本発明の一態様に係る鉄鋳物は、前記本発明の一態様に係る方法または前記本発明の他の態様に係る方法を用いて製造された鉄鋳物である。 The iron casting according to one aspect of the present invention is an iron casting manufactured using the method according to the one aspect of the present invention or the method according to another aspect of the present invention.
図１は、オーステナイト系の鋳造用材料を用いて鋳造した熱処理対象物のミクロ組織について、マイクロスコープにより観察した画像の一例を示す図である。FIG. 1 is a diagram showing an example of an image observed with a microscope of the microstructure of a heat-treated object cast using an austenitic casting material. 図２は、図１に示す画像のうち、黒鉛が占める領域を示す図である。FIG. 2 is a diagram showing an area occupied by graphite in the image shown in FIG. 図３は、図１に示す画像のうち、鉄（Ｆｅ）を主体とした金属間化合物が占める領域を示す図である。FIG. 3 is a diagram showing a region occupied by an intermetallic compound mainly composed of iron (Fe) in the image shown in FIG. 図４は、図１に示す画像のうち、オーステナイト相が占める領域を示す図である。FIG. 4 is a diagram showing a region occupied by the austenite phase in the image shown in FIG.
　以下、添付図面を参照して、本開示に係る鉄鋳物の実施形態を説明する。本発明は、以下の形態に限定されず、特許請求の範囲に規定されたものを含む。なお、以下の説明において、特に言及がない場合には、「第１」や「第２」等の用語は、構成要素を互いに区別するために使用されているだけであり、特定の順位や順番を表すものではない。 Hereinafter, embodiments of iron castings according to the present disclosure will be described with reference to the accompanying drawings. The present invention is not limited to the following forms, but includes what is defined in the claims. In the following explanation, unless otherwise mentioned, terms such as "first" and "second" are used only to distinguish components from each other, and do not imply a specific rank or order. It does not represent.
　本発明の実施形態に係る鉄鋳物は、オーステナイト系の鋳造用材料を用いて鋳造した熱処理対象物に対して、後述する所定の熱処理を行うことにより製造することができる。「オーステナイト系の鋳造用材料」は、鋳造した熱処理対象物の常温における母相（黒鉛を除く鉄基地組織）の主要組織がオーステナイト相となる材料を意味する。例えば、熱処理対象物の母相に占めるオーステナイト相の割合は、５０％以上である。熱処理対象物の母相に占めるオーステナイト相の割合は、７０％以上であることが好ましく、８０％以上であることがより好ましく、８５％以上であることがより好ましく、９０％以上であることがより好ましく、９５％以上であることがさらに好ましい。 The iron casting according to the embodiment of the present invention can be manufactured by subjecting a heat-treated object cast using an austenitic casting material to a predetermined heat treatment described below. "Austenitic casting material" means a material in which the main structure of the parent phase (iron base structure excluding graphite) of a cast heat-treated object at room temperature is an austenite phase. For example, the proportion of austenite phase in the matrix of the heat-treated object is 50% or more. The proportion of the austenite phase in the matrix of the heat-treated object is preferably 70% or more, more preferably 80% or more, more preferably 85% or more, and preferably 90% or more. More preferably, it is 95% or more.
　図１は、オーステナイト系の鋳造用材料を用いて鋳造した熱処理対象物のミクロ組織について、マイクロスコープにより観察した画像の一例を示す図である。図２は、図１に示す画像のうち、黒鉛が占める領域を示す図である。図３は、図１に示す画像のうち、鉄（Ｆｅ）を主体とした金属間化合物が占める領域を示す図である。図４は、図１に示す画像のうち、オーステナイト相が占める領域を示す図である。例えば、「熱処理対象物の母相の面積」は、図１に示す「熱処理対象物のミクロ組織全体の面積」から、図２に示す「黒鉛が占める領域の面積」を除くことにより算出することができる。「オーステナイト相の面積」は、上記により算出した「熱処理対象物の母相の面積」から、図３に示す「鉄（Ｆｅ）を主体とした金属間化合物が占める領域の面積」を除くことにより算出することができる。したがって、「熱処理対象物の母相に占めるオーステナイト相の割合」は、上記により算出した「オーステナイト相の面積（図４参照）」を「熱処理対象物の母相の面積」で除することにより算出することができる。本例では、汎用の画像処理ソフトを用いて、図１から図４に示す各面積に対応する領域の画素数（ピクセル数）を算出しており、その結果、熱処理対象物の母相に占めるオーステナイト相の割合は、８４．６％（約８５％）となっている。なお、図１において、鉄（Ｆｅ）を主体とした金属間化合物が占める領域が形成されない場合、熱処理対象物の母相に占めるオーステナイト相の割合は、１００％となる。 FIG. 1 is a diagram showing an example of an image observed with a microscope of the microstructure of a heat-treated object cast using an austenitic casting material. FIG. 2 is a diagram showing an area occupied by graphite in the image shown in FIG. FIG. 3 is a diagram showing a region occupied by an intermetallic compound mainly composed of iron (Fe) in the image shown in FIG. FIG. 4 is a diagram showing a region occupied by the austenite phase in the image shown in FIG. For example, the "area of the matrix of the heat-treated object" can be calculated by subtracting the "area of the region occupied by graphite" shown in Figure 2 from the "area of the entire microstructure of the heat-treated object" shown in Figure 1. I can do it. The "area of the austenite phase" is determined by subtracting the "area of the region occupied by the intermetallic compound mainly composed of iron (Fe)" shown in Figure 3 from the "area of the matrix of the heat-treated object" calculated above. It can be calculated. Therefore, the "proportion of the austenite phase in the matrix of the heat-treated object" is calculated by dividing the "area of the austenite phase (see Figure 4)" calculated above by the "area of the matrix of the heat-treated object". can do. In this example, general-purpose image processing software is used to calculate the number of pixels in the area corresponding to each area shown in Figures 1 to 4. The proportion of austenite phase is 84.6% (approximately 85%). In addition, in FIG. 1, when a region occupied by an intermetallic compound mainly composed of iron (Fe) is not formed, the proportion of the austenite phase in the matrix of the heat-treated object is 100%.
　本開示において、「鋳造」は、砂型鋳造法、金型鋳造法、ダイカスト法、ロストワックス鋳造法等の各種鋳造法による鋳造を含む。また、元素の「質量％」は、オーステナイト系の鋳造用材料の質量に対する、元素の質量の百分率を意味する。例えば、「Ｘ質量％以上Ｙ質量％以下の元素」の表記は、元素の質量％がＸ％以上Ｙ％以下であることを意味する。例えば、「０質量％Ｙ質量％以下の元素」の表記は、元素を含まないことまたは元素の質量％がＹ％以下であることを意味する。「残部」は、オーステナイト系の鋳造用材料を構成する成分のうち、列挙された元素以外の成分を意味する。 In the present disclosure, "casting" includes casting by various casting methods such as sand casting, metal mold casting, die casting, and lost wax casting. Moreover, "mass %" of an element means the percentage of the mass of the element with respect to the mass of the austenitic casting material. For example, the expression "element of X% by mass or more and Y% by mass or less" means that the mass% of the element is X% or more and Y% or less. For example, the notation "0 mass % Y mass % or less of an element" means that the element is not included or that the mass % of the element is Y % or less. The "remainder" means components other than the listed elements among the components constituting the austenitic casting material.
　＜鋳造用材料の第１の形態＞
　オーステナイト系の鋳造用材料（以下「本材料」という。）の第１の形態は、２６．０質量％以上５０．０質量％以下のＮｉを含み、残部がＦｅおよび不可避元素である。以下、本材料の第１の形態を「本材料の第１の形態（Ｎｉ－Ｆｅ組成）」と称することがある。 <First form of casting material>
The first form of the austenitic casting material (hereinafter referred to as "this material") contains Ni in an amount of 26.0% by mass to 50.0% by mass, and the balance is Fe and unavoidable elements. Hereinafter, the first form of the present material may be referred to as "the first form of the present material (Ni--Fe composition)".
　（Ｎｉ：ニッケル）
　本材料の第１の形態は、２６．０質量％以上５０．０質量％以下のＮｉを含む。本材料の第１の形態においては、Ｎｉの含有量を２６．０質量％以上５０．０質量％以下にすることで、黒鉛の周囲にＮｉを偏析させている。すなわち、Ｎｉを黒鉛の周囲の領域に濃化させることによりオーステナイトを安定化させている。Ｎｉの含有量の下限を２６．０質量％にすることで、オーステナイトを安定化させてマルテンサイトの生成を抑制することができる。このため、鉄鋳物の延性の低下を抑制するとともに、鉄鋳物の切削性を向上させることができる。また、Ｎｉの含有量の上限を５０．０質量％にすることで、線膨張係数の増加を抑制することができる。本材料の下記形態においても同様である。 (Ni: nickel)
The first form of the present material contains Ni in an amount of 26.0% by mass or more and 50.0% by mass or less. In the first form of the present material, Ni is segregated around graphite by setting the Ni content to 26.0% by mass or more and 50.0% by mass or less. That is, austenite is stabilized by concentrating Ni in the region around graphite. By setting the lower limit of the Ni content to 26.0% by mass, austenite can be stabilized and martensite generation can be suppressed. Therefore, it is possible to suppress a decrease in the ductility of iron castings and to improve the machinability of iron castings. Further, by setting the upper limit of the Ni content to 50.0% by mass, it is possible to suppress an increase in the coefficient of linear expansion. The same applies to the following forms of the present material.
　（Ｆｅ：鉄、不可避元素）
　本材料の第１の形態における残部は、Ｆｅおよび不可避元素である。残部に含まれる不可避元素としては、例えば、Ｐ（リン）、Ｓ（硫黄）、Ｃｕ（銅）、Ａｌ（アルミニウム）、Ｃｒ（クロム）、Ｍｏ（モリブデン）、Ｖ（バナジウム）、Ｔｉ（チタン）、Ｚｎ（亜鉛）等の元素が挙げられる。不可避元素の含有量は、例えば、合計で１０．０質量％以下であることが好ましく、合計で５．０質量％以下であることがより好ましく、合計で３．０質量％以下であることがより好ましく、合計で１．０質量％以下であることがさらに好ましい。本材料の下記形態においても同様である。 (Fe: Iron, inevitable element)
The remainder in the first form of the material is Fe and unavoidable elements. Examples of unavoidable elements contained in the remainder include P (phosphorus), S (sulfur), Cu (copper), Al (aluminum), Cr (chromium), Mo (molybdenum), V (vanadium), and Ti (titanium). , Zn (zinc), and other elements. For example, the content of unavoidable elements is preferably 10.0% by mass or less in total, more preferably 5.0% by mass or less in total, and 3.0% by mass or less in total. More preferably, the total amount is 1.0% by mass or less. The same applies to the following forms of the present material.
　本材料の第１の形態において、Ｎｉの含有量の下限は、２６．５質量％であることが好ましく、２７．０質量％であることがより好ましく、２７．５質量％であることがより好ましく、２８．０質量％であることがより好ましく、２８．５質量％であることがより好ましく、２９．０質量％であることがより好ましく、２９．５質量％であることがより好ましく、３０．０質量％であることがより好ましく、３０．５質量％であることがより好ましく、３１．０質量％であることがより好ましく、３１．５質量％であることがより好ましく、３２．０質量％であることがさらに好ましい。また、Ｎｉの含有量の上限は、４５．０質量％であることが好ましく、４２．０質量％であることがより好ましく、４１．０質量％であることがより好ましく、４０．０質量％であることがより好ましく、３９．５質量％であることがより好ましく、３９．０質量％であることがより好ましく、３８．５質量％であることがより好ましく、３８．０質量％であることがより好ましく、３７．５質量％であることがより好ましく、３７．０質量％であることがさらに好ましい。本材料の下記形態においても同様である。 In the first form of the present material, the lower limit of the Ni content is preferably 26.5% by mass, more preferably 27.0% by mass, and even more preferably 27.5% by mass. Preferably, it is 28.0% by mass, more preferably 28.5% by mass, more preferably 29.0% by mass, more preferably 29.5% by mass, More preferably 30.0% by mass, more preferably 30.5% by mass, more preferably 31.0% by mass, more preferably 31.5% by mass, 32. More preferably, it is 0% by mass. Further, the upper limit of the Ni content is preferably 45.0% by mass, more preferably 42.0% by mass, more preferably 41.0% by mass, and 40.0% by mass. It is more preferable that it is, it is more preferable that it is 39.5 mass %, it is more preferable that it is 39.0 mass %, it is more preferable that it is 38.5 mass %, it is 38.0 mass %. The content is more preferably 37.5% by mass, and even more preferably 37.0% by mass. The same applies to the following forms of the present material.
　＜鋳造用材料の第２の形態＞
　本材料の第２の形態は、２６．０質量％以上５０．０質量％以下のＮｉと、０．１質量％以上３．５質量％以下のＣとを含み、残部がＦｅおよび不可避元素である。以下、本材料の第２の形態を「本材料の第２の形態（Ｎｉ－Ｃ－Ｆｅ組成）」と称することがある。 <Second form of casting material>
The second form of this material contains Ni of 26.0% by mass or more and 50.0% by mass or less, C of 0.1% by mass or more and 3.5% by mass or less, and the balance is Fe and unavoidable elements. be. Hereinafter, the second form of the present material may be referred to as "the second form of the present material (Ni--C--Fe composition)."
　（Ｃ：炭素）
　本材料の第２の形態は、０．１質量％以上３．５質量％以下のＣを含む。本材料の第２の形態においては、Ｃの含有量の下限を０．１質量％にすることで、本材料の液相線温度を低下させることができる。このため、本材料の湯流れ性を向上させることができる。また、Ｃの含有量の下限を０．１質量％にすることで、黒鉛の晶出量または析出量を増加させることができる。このため、鉄鋳物の切削性を向上させることができる。また、Ｃの含有量の上限を３．５質量％にすることで、黒鉛浮上（カーボンフローテーション）を抑制することができる。このため、鉄鋳物の強度や延性の低下を抑制することができる。また、Ｃの含有量の上限を３．５質量％にするとともに、黒鉛化促進元素として作用するＮｉの含有量の上限を５０．０質量％にすることで、Ｃの過剰な黒鉛化を抑制することができる。このため、チャンキー黒鉛の生成を抑制することができる。したがって、鉄鋳物の伸びを向上させることができる。本材料の下記形態においても同様である。 (C: carbon)
The second form of the present material contains 0.1% by mass or more and 3.5% by mass or less of C. In the second form of the present material, by setting the lower limit of the C content to 0.1% by mass, the liquidus temperature of the present material can be lowered. Therefore, the flowability of this material can be improved. Further, by setting the lower limit of the C content to 0.1% by mass, the amount of crystallization or precipitation of graphite can be increased. Therefore, the machinability of iron castings can be improved. Further, by setting the upper limit of the C content to 3.5% by mass, graphite floating (carbon flotation) can be suppressed. Therefore, a decrease in strength and ductility of iron castings can be suppressed. In addition, by setting the upper limit of the content of C to 3.5% by mass and setting the upper limit of the content of Ni, which acts as a graphitization promoting element, to 50.0% by mass, excessive graphitization of C is suppressed. can do. Therefore, generation of chunky graphite can be suppressed. Therefore, the elongation of iron castings can be improved. The same applies to the following forms of the present material.
　本材料の第２の形態において、Ｃの含有量の下限は、０．１５質量％であることが好ましく、０．２質量％であることがより好ましく、０．４質量％であることがより好ましく、０．７質量％であることがより好ましく、１．０質量％であることがより好ましく、１．２５質量％であることがより好ましく、１．５質量％であることがより好ましく、１．７５質量％であることがさらに好ましい。Ｃの含有量の下限を０．７質量％にすることで、凝固時に晶出する黒鉛が共晶状組織を形成する傾向を高めることにより、黒鉛の膨張量を増大させ、引け巣の発生を抑制することができる。また、Ｃの含有量の上限は、３．３質量％であることが好ましく、３．１質量％であることがより好ましく、３．０質量％であることがより好ましく、２．９５質量％であることがより好ましく、２．９質量％であることがより好ましく、２．８５質量％であることがより好ましく、２．８質量％であることがより好ましく、２．７５質量％であることがより好ましく、２．７質量％であることがより好ましく、２．６５質量％であることがより好ましく、２．６質量％であることがより好ましく、２．５５質量％であることがより好ましく、２．５質量％であることがさらに好ましい。本材料の下記形態においても同様である。 In the second form of the present material, the lower limit of the C content is preferably 0.15% by mass, more preferably 0.2% by mass, and even more preferably 0.4% by mass. Preferably, it is 0.7% by mass, more preferably 1.0% by mass, more preferably 1.25% by mass, more preferably 1.5% by mass, More preferably, it is 1.75% by mass. By setting the lower limit of the C content to 0.7% by mass, graphite that crystallizes during solidification increases the tendency to form a eutectic structure, thereby increasing the amount of expansion of graphite and preventing the occurrence of shrinkage cavities. Can be suppressed. Further, the upper limit of the content of C is preferably 3.3% by mass, more preferably 3.1% by mass, more preferably 3.0% by mass, and 2.95% by mass. It is more preferably 2.9% by mass, more preferably 2.85% by mass, more preferably 2.8% by mass, and more preferably 2.75% by mass. More preferably, it is 2.7% by mass, more preferably 2.65% by mass, more preferably 2.6% by mass, and more preferably 2.55% by mass. The content is more preferably 2.5% by mass. The same applies to the following forms of the present material.
　＜鋳造用材料の第３の形態＞
　本材料の第３の形態は、２６．０質量％以上５０．０質量％以下のＮｉと、０．１質量％以上３．５質量％以下のＣと、０．１質量％以上３．５質量％以下のＳｉとを含み、残部がＦｅおよび不可避元素である。以下、本材料の第３の形態を「本材料の第３の形態（Ｎｉ－Ｃ－Ｓｉ－Ｆｅ組成）」と称することがある。 <Third form of casting material>
The third form of this material contains Ni of 26.0% by mass or more and 50.0% by mass or less, C of 0.1% by mass or more and 3.5% by mass or less, and 0.1% by mass or more and 3.5% by mass. It contains less than % by mass of Si, and the remainder is Fe and unavoidable elements. Hereinafter, the third form of the present material may be referred to as "the third form of the present material (Ni-C-Si-Fe composition)".
　（Ｓｉ：ケイ素）
　本材料の第３の形態は、０．１質量％以上３．５質量％以下のＳｉを含む。本材料の第３の形態においては、Ｎｉの含有量を２６．０質量％以上５０．０質量％以下にするとともに、Ｓｉの含有量を０．１質量％以上３．５質量％以下にすることで、黒鉛の周囲にＮｉを偏析させ、その結果、最終凝固部にＳｉを偏析させている。すなわち、Ｎｉを黒鉛の周囲の領域に濃化させることによりオーステナイトを安定化させ、Ｓｉを残液側である最終凝固部に濃化させている。Ｓｉの含有量の下限を０．１質量％にすることで、本材料の液相線温度を低下させやすい。このため、本材料の湯流れ性を向上させやすい。また、Ｓｉの含有量の下限を０．１質量％にすることで、Ｃの含有量に対するＳｉの含有量の割合を増加させることができる。このため、ＣＯガスの形成を抑制することができる。したがって、鉄鋳物の表面に生じるガス欠陥を低減させることができる。また、Ｓｉの含有量の上限を３．５質量％にすることで、ＳｉのＦｅ（鉄基地）への固溶量を低減させることができる。このため、線膨張係数の増加を抑制することができる。また、黒鉛化促進元素として作用するＳｉの含有量の上限を３．５質量％にすることで、Ｃの過剰な黒鉛化を抑制することができる。このため、チャンキー黒鉛の生成を抑制することができる。したがって、鉄鋳物の伸びを向上させることができる。本材料の下記形態においても同様である。 (Si: silicon)
The third form of the present material contains 0.1% by mass or more and 3.5% by mass or less of Si. In the third form of the present material, the Ni content is 26.0% by mass or more and 50.0% by mass or less, and the Si content is 0.1% by mass or more and 3.5% by mass or less. As a result, Ni is segregated around the graphite, and as a result, Si is segregated in the final solidified portion. That is, austenite is stabilized by concentrating Ni in the region around graphite, and Si is condensed in the final solidified part on the residual liquid side. By setting the lower limit of the Si content to 0.1% by mass, the liquidus temperature of the material can be easily lowered. Therefore, it is easy to improve the flowability of this material. Further, by setting the lower limit of the Si content to 0.1% by mass, the ratio of the Si content to the C content can be increased. Therefore, formation of CO gas can be suppressed. Therefore, gas defects occurring on the surface of iron castings can be reduced. Further, by setting the upper limit of the Si content to 3.5% by mass, the amount of Si dissolved in Fe (iron matrix) can be reduced. Therefore, it is possible to suppress an increase in the coefficient of linear expansion. Further, by setting the upper limit of the content of Si, which acts as a graphitization promoting element, to 3.5% by mass, excessive graphitization of C can be suppressed. Therefore, generation of chunky graphite can be suppressed. Therefore, the elongation of iron castings can be improved. The same applies to the following forms of the present material.
　本材料の第３の形態において、Ｓｉの含有量の下限は、０．２５質量％であることが好ましく、０．５質量％であることがより好ましく、０．７５質量％であることがより好ましく、１．０質量％であることが好ましく、１．２質量％であることがより好ましく、１．３質量％であることがより好ましく、１．４質量％であることがさらに好ましい。また、Ｓｉの含有量の上限は、３．３質量％であることが好ましく、３．１質量％であることがより好ましく、２．９質量％であることがより好ましく、２．７質量％であることがより好ましく、２．５質量％であることがより好ましく、２．３質量％であることがより好ましく、２．１質量％であることがさらに好ましい。本材料の下記形態においても同様である。 In the third form of the present material, the lower limit of the Si content is preferably 0.25% by mass, more preferably 0.5% by mass, and even more preferably 0.75% by mass. It is preferably 1.0% by mass, more preferably 1.2% by mass, even more preferably 1.3% by mass, and even more preferably 1.4% by mass. Further, the upper limit of the Si content is preferably 3.3% by mass, more preferably 3.1% by mass, more preferably 2.9% by mass, and more preferably 2.7% by mass. It is more preferably 2.5% by mass, more preferably 2.3% by mass, and even more preferably 2.1% by mass. The same applies to the following forms of the present material.
　＜鋳造用材料の第４の形態＞
　本材料の第４の形態は、２６．０質量％以上５０．０質量％以下のＮｉと、０．１質量％以上３．５質量％以下のＣと、０．１質量％以上３．５質量％以下のＳｉと、０．１質量％以上８．０質量％以下のＣｏとを含み、残部がＦｅおよび不可避元素である。以下、本材料の第４の形態を「本材料の第４の形態（Ｎｉ－Ｃ－Ｓｉ－Ｃｏ－Ｆｅ組成）」と称することがある。 <Fourth form of casting material>
The fourth form of this material includes 26.0% by mass or more and 50.0% by mass of Ni, 0.1% by mass or more and 3.5% by mass of C, and 0.1% by mass or more and 3.5% by mass. It contains Si of 0.1% by mass or more and 8.0% by mass or less of Co, and the balance is Fe and unavoidable elements. Hereinafter, the fourth form of the present material may be referred to as "the fourth form of the present material (Ni-C-Si-Co-Fe composition)".
　（Ｃｏ：コバルト）
　本材料の第４の形態は、０．１質量％以上８．０質量％以下のＣｏを含む。本材料の第４の形態においては、Ｃｏの含有量を０．１質量％以上８．０質量％以下にすることで、Ｎｉとの相乗効果により線膨張係数を一層低減させることができる。Ｃｏの含有量の下限を０．１質量％にすることで、Ｎｉとの相乗効果により線膨張係数の極小値を減少させることができる。また、Ｃｏの含有量の上限を８．０質量％にすることで、Ｃｏの過剰な添加に伴い線膨張係数が極小値を示した後に増加することを抑制することができる。本材料の下記形態においても同様である。 (Co: cobalt)
The fourth form of the present material contains 0.1% by mass or more and 8.0% by mass or less of Co. In the fourth form of the present material, by setting the Co content to 0.1% by mass or more and 8.0% by mass or less, the linear expansion coefficient can be further reduced due to the synergistic effect with Ni. By setting the lower limit of the Co content to 0.1% by mass, the minimum value of the coefficient of linear expansion can be reduced due to the synergistic effect with Ni. Further, by setting the upper limit of the Co content to 8.0% by mass, it is possible to suppress the linear expansion coefficient from increasing after reaching a minimum value due to excessive addition of Co. The same applies to the following forms of the present material.
　本材料の第４の形態において、Ｃｏの含有量の下限は、０．５質量％であることが好ましく、１．０質量％であることがより好ましく、１．５質量％であることがより好ましく、２．０質量％であることがより好ましく、２．５質量％であることがより好ましく、３．０質量％であることがより好ましく、３．５質量％であることがより好ましく、４．０質量％であることがさらに好ましい。また、Ｃｏの含有量の上限は、７．５質量％であることが好ましく、７．０質量％であることがより好ましく、６．５質量％であることがより好ましく、６．２５質量％であることがより好ましく、６．０質量％であることがさらに好ましい。また、Ｎｉの含有量が３１．０質量％以上３４．０質量％以下に対して、Ｃｏの含有量が４．０質量％以上５．５質量％以下であることが好ましい。また、Ｎｉの含有量の下限が２８．５質量％である場合には、Ｃｏの含有量が５．０質量％以上８．０質量％以下であることが好ましい。Ｃｏの含有量の下限および上限をこのようにすることで、Ｎｉとの相乗効果により線膨張係数を一層低減させやすい。本材料の下記形態においても同様である。 In the fourth form of the present material, the lower limit of the Co content is preferably 0.5% by mass, more preferably 1.0% by mass, and even more preferably 1.5% by mass. Preferably, it is 2.0% by mass, more preferably 2.5% by mass, more preferably 3.0% by mass, more preferably 3.5% by mass, More preferably, it is 4.0% by mass. Further, the upper limit of the Co content is preferably 7.5% by mass, more preferably 7.0% by mass, more preferably 6.5% by mass, and 6.25% by mass. More preferably, it is 6.0% by mass. Further, it is preferable that the Ni content is 31.0% by mass or more and 34.0% by mass or less, and the Co content is 4.0% by mass or more and 5.5% by mass or less. Further, when the lower limit of the Ni content is 28.5% by mass, the Co content is preferably 5.0% by mass or more and 8.0% by mass or less. By setting the lower and upper limits of the Co content as above, it is easy to further reduce the linear expansion coefficient due to the synergistic effect with Ni. The same applies to the following forms of the present material.
　＜鋳造用材料の第５の形態＞
　本材料の第５の形態は、２６．０質量％以上５０．０質量％以下のＮｉと、０．１質量％以上３．５質量％以下のＣと、０．１質量％以上３．５質量％以下のＳｉと、０．１質量％以上８．０質量％以下のＣｏと、０．０１質量％以上３．０質量％以下のＭｎとを含み、残部がＦｅおよび不可避元素である。以下、本材料の第５の形態を「本材料の第５の形態（Ｎｉ－Ｃ－Ｓｉ－Ｃｏ－Ｍｎ－Ｆｅ組成）」と称することがある。 <Fifth form of casting material>
The fifth form of this material includes 26.0% by mass or more and 50.0% by mass of Ni, 0.1% by mass or more and 3.5% by mass of C, and 0.1% by mass or more and 3.5% by mass. It contains Si of 0.1% by mass or more and 8.0% by mass or less of Co, and Mn of 0.01% by mass or more and 3.0% by mass or less, and the balance is Fe and unavoidable elements. Hereinafter, the fifth form of the present material may be referred to as "the fifth form of the present material (Ni-C-Si-Co-Mn-Fe composition)."
　（Ｍｎ：マンガン）
　本材料の第５の形態は、０．０１質量％以上３．０質量％以下のＭｎを含む。本材料の第５の形態においては、Ｍｎの含有量を０．０１質量％以上３．０質量％以下にすることで、Ｎｉとの相乗効果によりオーステナイトを安定化させてマルテンサイトの生成を抑制することができる。したがって、鉄鋳物の切削性を向上させることができる。Ｍｎの含有量の下限を０．０１質量％にすることで、常温においてもオーステナイトを安定させることができる。また、Ｍｎの含有量の上限を３．０質量％にすることで、ＭｎのＦｅ（鉄基地）への固溶量を低減させることができる。このため、線膨張係数の増加を抑制することができる。 (Mn: manganese)
The fifth form of the present material contains Mn in an amount of 0.01% by mass or more and 3.0% by mass or less. In the fifth form of this material, by setting the Mn content to 0.01% by mass or more and 3.0% by mass or less, the synergistic effect with Ni stabilizes austenite and suppresses the formation of martensite. can do. Therefore, the machinability of iron castings can be improved. By setting the lower limit of the Mn content to 0.01% by mass, austenite can be stabilized even at room temperature. Further, by setting the upper limit of the Mn content to 3.0% by mass, the amount of Mn dissolved in Fe (iron base) can be reduced. Therefore, it is possible to suppress an increase in the coefficient of linear expansion.
　本材料の第５の形態において、Ｍｎの含有量の下限は、０．０５質量％であることが好ましく、０．０７質量％であることがより好ましく、０．０８質量％であることがより好ましく、０．０９質量％であることがより好ましく、０．１質量％であることがさらに好ましい。また、Ｍｎの含有量の上限は、２．５質量％であることが好ましく、２．０質量％であることがより好ましく、１．５質量％であることがより好ましく、１．０質量％であることがより好ましく、０．８５質量％であることがより好ましく、０．７質量％であることがさらに好ましい。本材料の下記形態においても同様である。 In the fifth form of the present material, the lower limit of the Mn content is preferably 0.05% by mass, more preferably 0.07% by mass, and even more preferably 0.08% by mass. It is preferably 0.09% by mass, more preferably 0.1% by mass. Further, the upper limit of the Mn content is preferably 2.5% by mass, more preferably 2.0% by mass, more preferably 1.5% by mass, and 1.0% by mass. It is more preferable that it is, it is more preferable that it is 0.85 mass %, and it is still more preferable that it is 0.7 mass %. The same applies to the following forms of the present material.
　＜鋳造用材料の第６の形態＞
　本材料の第６の形態は、２６．０質量％以上５０．０質量％以下のＮｉと、０．１質量％以上３．５質量％以下のＣと、０．１質量％以上３．５質量％以下のＳｉと、０．１質量％以上８．０質量％以下のＣｏと、０．０１質量％以上０．２質量％以下のＭｇとを含み、残部がＦｅおよび不可避元素である。以下、本材料の第６の形態を「本材料の第６の形態（Ｎｉ－Ｃ－Ｓｉ－Ｃｏ－Ｍｇ－Ｆｅ組成）」と称することがある。 <Sixth form of casting material>
The sixth form of this material contains Ni of 26.0% by mass or more and 50.0% by mass or less, C of 0.1% by mass or more and 3.5% by mass or less, and 0.1% by mass or more and 3.5% by mass. It contains Si of 0.1% by mass or more and 8.0% by mass or less of Co, and Mg of 0.01% by mass or more and 0.2% by mass or less, and the balance is Fe and unavoidable elements. Hereinafter, the sixth form of the present material may be referred to as "the sixth form of the present material (Ni-C-Si-Co-Mg-Fe composition)."
　（Ｍｇ：マグネシウム）
　本材料の第６の形態は、０．０１質量％以上０．２質量％以下のＭｇを含む。本材料の第６の形態においては、Ｍｇの含有量を０．０１質量％以上０．２質量％以下にすることで、黒鉛の球状化作用を高めるとともに、最終凝固部にＭｇを偏析させることができる。Ｍｇの含有量の下限を０．０１質量％にすることで、黒鉛の球状化作用を高めることができる。また、Ｍｇの含有量の上限を０．２質量％にすることで、Ｍｇの酸化物または硫化物の生成を抑制することができる。このため、本材料の湯流れ性の低下を抑制することができる。さらに、鉄鋳物の鋳造欠陥を低減させることができる。 (Mg: Magnesium)
The sixth form of the present material contains 0.01% by mass or more and 0.2% by mass or less of Mg. In the sixth form of this material, by setting the Mg content to 0.01% by mass or more and 0.2% by mass or less, the spheroidizing effect of graphite is enhanced and Mg is segregated in the final solidified part. I can do it. By setting the lower limit of the Mg content to 0.01% by mass, the spheroidizing effect of graphite can be enhanced. Further, by setting the upper limit of the Mg content to 0.2% by mass, it is possible to suppress the generation of Mg oxides or sulfides. Therefore, it is possible to suppress a decrease in the flowability of the present material. Furthermore, casting defects in iron castings can be reduced.
　本材料の第６の形態において、Ｍｇの含有量の下限は、０．０２質量％であることが好ましく、０．０３質量％であることがより好ましく、０．０４質量％であることがさらに好ましい。また、Ｍｇの含有量の上限は、０．１５質量％であることが好ましく、０．１質量％であることがより好ましく、０．０８質量％であることがさらに好ましい。本材料の下記形態においても同様である。 In the sixth form of the present material, the lower limit of the Mg content is preferably 0.02% by mass, more preferably 0.03% by mass, and even more preferably 0.04% by mass. preferable. Further, the upper limit of the Mg content is preferably 0.15% by mass, more preferably 0.1% by mass, and even more preferably 0.08% by mass. The same applies to the following forms of the present material.
　＜鋳造用材料の第７の形態＞
　本材料の第７の形態は、２６．０質量％以上５０．０質量％以下のＮｉと、０．１質量％以上３．５質量％以下のＣと、０．１質量％以上３．５質量％以下のＳｉと、０．１質量％以上８．０質量％以下のＣｏと、０．０１質量％以上３．０質量％以下のＭｎと、０．０１質量％以上０．２質量％以下のＭｇとを含み、残部がＦｅおよび不可避元素である。以下、本材料の第７の形態を「本材料の第７の形態（Ｎｉ－Ｃ－Ｓｉ－Ｃｏ－Ｍｎ－Ｍｇ－Ｆｅ組成）」と称することがある。 <Seventh form of casting material>
The seventh form of this material contains Ni of 26.0% by mass or more and 50.0% by mass or less, C of 0.1% by mass or more and 3.5% by mass or less, and 0.1% by mass or more and 3.5% by mass. Si of not more than 0.1% by mass and not more than 8.0% by mass, Co of not less than 0.01% by mass and not more than 3.0% by mass, and not less than 0.01% by mass and not more than 0.2% by mass The following Mg is included, and the remainder is Fe and inevitable elements. Hereinafter, the seventh form of the present material may be referred to as "the seventh form of the present material (Ni-C-Si-Co-Mn-Mg-Fe composition)."
　＜鋳造用材料の第８の形態＞
　本材料の第８の形態は、２６．０質量％以上５０．０質量％以下のＮｉと、０．１質量％以上３．５質量％以下のＣと、０．１質量％以上３．５質量％以下のＳｉと、０．０１質量％以上３．０質量％以下のＭｎとを含み、残部がＦｅおよび不可避元素である。以下、本材料の第８の形態を「本材料の第８の形態（Ｎｉ－Ｃ－Ｓｉ－Ｍｎ－Ｆｅ組成）」と称することがある。 <Eighth form of casting material>
The eighth form of this material contains Ni of 26.0% by mass or more and 50.0% by mass or less, C of 0.1% by mass or more and 3.5% by mass or less, and 0.1% by mass or more and 3.5% by mass. It contains Si of 0.01% by mass or more and 3.0% by mass or less of Mn, and the balance is Fe and unavoidable elements. Hereinafter, the eighth form of the present material may be referred to as "the eighth form of the present material (Ni-C-Si-Mn-Fe composition)".
　＜鋳造用材料の第９の形態＞
　本材料の第９の形態は、２６．０質量％以上５０．０質量％以下のＮｉと、０．１質量％以上３．５質量％以下のＣと、０．１質量％以上３．５質量％以下のＳｉと、０．０１質量％以上３．０質量％以下のＭｎと、０．０１質量％以上０．２質量％以下のＭｇとを含み、残部がＦｅおよび不可避元素である。以下、本材料の第９の形態を「本材料の第９の形態（Ｎｉ－Ｃ－Ｓｉ－Ｍｎ－Ｍｇ－Ｆｅ組成）」と称することがある。 <Ninth form of casting material>
The ninth form of this material includes Ni of 26.0% by mass or more and 50.0% by mass or less, C of 0.1% by mass or more and 3.5% by mass or less, and 0.1% by mass or more and 3.5% by mass or less. It contains Si of 0.01% by mass or more and 3.0% by mass or less of Mn, and Mg of 0.01% by mass or more and 0.2% by mass or less, and the balance is Fe and unavoidable elements. Hereinafter, the ninth form of the present material may be referred to as "the ninth form of the present material (Ni-C-Si-Mn-Mg-Fe composition)".
　＜鋳造用材料の第１０の形態＞
　本材料の第１０の形態は、２６．０質量％以上５０．０質量％以下のＮｉと、０．１質量％以上３．５質量％以下のＣと、０．１質量％以上３．５質量％以下のＳｉと、０．０１質量％以上０．２質量％以下のＭｇとを含み、残部がＦｅおよび不可避元素である。以下、本材料の第１０の形態を「本材料の第１０の形態（Ｎｉ－Ｃ－Ｓｉ－Ｍｇ－Ｆｅ組成）」と称することがある。 <Tenth form of casting material>
The tenth form of this material includes 26.0% by mass or more and 50.0% by mass of Ni, 0.1% by mass or more and 3.5% by mass of C, and 0.1% by mass or more and 3.5% by mass. It contains Si of 0.01% by mass or more and 0.2% by mass or less of Mg, and the balance is Fe and unavoidable elements. Hereinafter, the tenth form of the present material may be referred to as "the tenth form of the present material (Ni-C-Si-Mg-Fe composition)."
　＜熱処理の第１の形態＞
　本材料を用いて鋳造した熱処理対象物に対して行う熱処理（以下「本熱処理」という。）の第１の形態は、熱処理対象物を８５０℃以上１２５０℃以下の第１の保持温度で保持する第１の保持工程と、第１の保持工程の後に、熱処理対象物を－１５０℃以上１５０℃以下の第１の冷却終了温度まで冷却する第１の冷却工程とを含む。本熱処理の第１の形態において、第１の保持工程は、熱処理対象物を０．２５時間以上１００時間以下の第１の保持時間で保持することを含む。なお、本熱処理の第１の形態は、第１の保持工程および第１の冷却工程の各工程の前後に他の熱処理工程を含むものであってもよい。本熱処理の第１の形態において、上記各工程の前後に他の熱処理工程を含むものでない場合には、本材料を用いて鋳造した熱処理対象物に対して順に、第１の保持工程と、第１の冷却工程とのみを行うことにより、熱処理対象物に対して予期せぬ熱影響が作用することを防止することができる。したがって、鉄鋳物の線膨張係数をより確実に低減させることができる。 <First form of heat treatment>
The first form of heat treatment performed on a heat-treated object cast using this material (hereinafter referred to as "main heat treatment") is to hold the heat-treated object at a first holding temperature of 850°C or higher and 1250°C or lower. The method includes a first holding step and, after the first holding step, a first cooling step of cooling the heat-treated object to a first cooling end temperature of −150° C. or more and 150° C. or less. In the first form of this heat treatment, the first holding step includes holding the heat treatment object for a first holding time of 0.25 hours or more and 100 hours or less. Note that the first form of the heat treatment may include other heat treatment steps before and after each of the first holding step and the first cooling step. In the first form of this heat treatment, if other heat treatment steps are not included before or after each of the above steps, the heat treatment object cast using this material is sequentially subjected to the first holding step and the first holding step. By performing only the first cooling step, it is possible to prevent unexpected thermal effects from acting on the object to be heat treated. Therefore, the coefficient of linear expansion of iron castings can be reduced more reliably.
　本熱処理の第１の形態においては、第１の保持工程において、熱処理対象物を第１の保持温度（８５０℃以上１２５０℃以下）かつ第１の保持時間（０．２５時間以上１００時間以下）で保持する。そして、第１の保持工程の後の第１の冷却工程において、熱処理対象物を第１の冷却終了温度（－１５０℃以上１５０℃以下）まで冷却する。この第１の保持工程により、熱処理対象物内の溶質元素の凝固偏析を低減するとともに、オーステナイト相を構成する各結晶粒内部の結晶方位の相対的な差（結晶方位差）を小さくすることができる。これにより、オーステナイト相中の結晶格子の配列を整えることができる。その結果、鉄鋳物の線膨張係数を低減させることができる。 In the first form of this heat treatment, in the first holding step, the heat treatment target is held at a first holding temperature (850°C or more and 1250°C or less) and a first holding time (0.25 hours or more and 100 hours or less). hold it. Then, in a first cooling step after the first holding step, the heat treatment target is cooled to a first cooling end temperature (-150° C. or higher and 150° C. or lower). Through this first holding step, it is possible to reduce the solidification segregation of solute elements in the heat-treated object and to reduce the relative difference in crystal orientation (crystal orientation difference) inside each crystal grain constituting the austenite phase. can. This makes it possible to arrange the crystal lattice in the austenite phase. As a result, the coefficient of linear expansion of the iron casting can be reduced.
　本熱処理の第１の形態において、第１の冷却工程は、熱処理対象物を０．０１℃／分以上３００℃／分以下の第１の冷却速度で冷却することを含む。第１の冷却速度は、０．０１℃／分以上２０℃／分以下であることが好ましい。第１の保持時間は、２．５時間以上２５時間以下であることが好ましい。第１の冷却終了温度は、０℃以上１００℃以下であることが好ましい。 In the first form of this heat treatment, the first cooling step includes cooling the heat treatment object at a first cooling rate of 0.01° C./min or more and 300° C./min or less. The first cooling rate is preferably 0.01°C/min or more and 20°C/min or less. The first holding time is preferably 2.5 hours or more and 25 hours or less. The first cooling end temperature is preferably 0°C or more and 100°C or less.
　本熱処理の第１の形態において、第１の保持温度の下限は、８７５℃であることが好ましく、９００℃であることがより好ましく、９２５℃であることがより好ましく、９５０℃であることがより好ましく、９７５℃であることがより好ましく、１０００℃であることがより好ましく、１０２５℃であることがさらに好ましい。また、第１の保持温度の上限は、１２２５℃であることが好ましく、１２００℃であることがより好ましく、１１７５℃であることがより好ましく、１１５０℃であることがより好ましく、１１２５℃であることがさらに好ましい。本熱処理の下記形態においても同様である。 In the first form of this heat treatment, the lower limit of the first holding temperature is preferably 875°C, more preferably 900°C, more preferably 925°C, and more preferably 950°C. The temperature is more preferably 975°C, more preferably 1000°C, and even more preferably 1025°C. Further, the upper limit of the first holding temperature is preferably 1225°C, more preferably 1200°C, more preferably 1175°C, more preferably 1150°C, and more preferably 1125°C. It is even more preferable. The same applies to the following form of this heat treatment.
　本熱処理の第１の形態において、第１の保持時間の下限は、０．５時間であることが好ましく、１．０時間であることがより好ましく、１．５時間であることがより好ましく、２．０時間であることがより好ましく、２．５時間であることがより好ましく、３．０時間であることがより好ましく、３．５時間であることがより好ましく、４．０時間であることがさらに好ましい。また、第１の保持時間の上限は、９０時間であることが好ましく、８０時間であることがより好ましく、７０時間であることがより好ましく、６０時間であることがより好ましく、５０時間であることがより好ましく、４０時間であることがより好ましく、３０時間であることがより好ましく、２５時間であることがより好ましく、２０時間であることがより好ましく、１５時間であることがより好ましく、１０時間であることがさらに好ましい。本熱処理の下記形態においても同様である。 In the first form of this heat treatment, the lower limit of the first holding time is preferably 0.5 hours, more preferably 1.0 hours, and more preferably 1.5 hours; More preferably 2.0 hours, more preferably 2.5 hours, more preferably 3.0 hours, more preferably 3.5 hours, and more preferably 4.0 hours. It is even more preferable. Further, the upper limit of the first holding time is preferably 90 hours, more preferably 80 hours, more preferably 70 hours, more preferably 60 hours, and 50 hours. more preferably 40 hours, more preferably 30 hours, more preferably 25 hours, more preferably 20 hours, more preferably 15 hours, More preferably, the heating time is 10 hours. The same applies to the following form of this heat treatment.
　本熱処理の第１の形態において、第１の冷却終了温度の下限は、－１２５℃であることが好ましく、－１００℃であることがより好ましく、－７５℃であることがより好ましく、－５０℃であることがより好ましく、－２５℃であることがより好ましく、０℃であることがさらに好ましい。また、第１の冷却終了温度の上限は、１２５℃であることが好ましく、１００℃であることがより好ましく、７５℃であることがより好ましく、５０℃であることがさらに好ましい。本熱処理の下記形態においても同様である。 In the first form of this heat treatment, the lower limit of the first cooling end temperature is preferably -125°C, more preferably -100°C, more preferably -75°C, and more preferably -50°C. The temperature is more preferably -25°C, and even more preferably 0°C. Further, the upper limit of the first cooling end temperature is preferably 125°C, more preferably 100°C, more preferably 75°C, and even more preferably 50°C. The same applies to the following form of this heat treatment.
　本熱処理の第１の形態において、第１の冷却速度の下限は、０．１℃／分であることが好ましく、０．２℃／分であることがより好ましく、０．３℃／分であることがより好ましく、０．４℃／分であることがより好ましく、０．５℃／分であることがより好ましく、０．６℃／分であることがより好ましく、０．７℃／分であることがより好ましく、０．７５℃／分であることがさらに好ましい。また、第１の冷却速度の上限は、２５０℃／分であることが好ましく、２００℃／分であることがより好ましく、１５０℃／分であることがより好ましく、１００℃／分であることがより好ましく、５０℃／分であることがより好ましく、２５℃／分であることがより好ましく、１０℃／分であることがより好ましく、５℃／分であることがさらに好ましい。 In the first form of this heat treatment, the lower limit of the first cooling rate is preferably 0.1°C/min, more preferably 0.2°C/min, and more preferably 0.3°C/min. More preferably, it is 0.4°C/min, more preferably 0.5°C/min, more preferably 0.6°C/min, and more preferably 0.7°C/min. More preferably, it is 0.75°C/min, and even more preferably 0.75°C/min. Further, the upper limit of the first cooling rate is preferably 250°C/min, more preferably 200°C/min, more preferably 150°C/min, and more preferably 100°C/min. is more preferable, more preferably 50°C/min, more preferably 25°C/min, more preferably 10°C/min, even more preferably 5°C/min.
　＜熱処理の第２の形態＞
　本熱処理の第２の形態は、熱処理対象物を８５０℃以上１２５０℃以下の第１の保持温度で保持する第１の保持工程と、第１の保持工程の後に、熱処理対象物を－１５０℃以上１５０℃以下の第１の冷却終了温度まで冷却する第１の冷却工程とを含む。本熱処理の第２の形態において、第１の保持工程は、熱処理対象物を０．２５時間以上１００時間以下の第１の保持時間で保持することを含む。第１の冷却工程は、熱処理対象物を一次冷却速度で冷却する一次冷却工程と、一次冷却工程の後に、熱処理対象物を一次冷却速度よりも大きい二次冷却速度で冷却する二次冷却工程とを含む。第１の冷却工程において、一次冷却工程は、熱処理対象物を２５０℃以上９５０℃以下の一次冷却終了温度まで冷却することを含む。二次冷却工程は、熱処理対象物を第１の冷却終了温度（－１５０℃以上１５０℃以下）まで冷却することを含む。なお、本熱処理の第２の形態は、第１の保持工程および第１の冷却工程の各工程の前後に他の熱処理工程を含むものであってもよい。本熱処理の第２の形態において、上記各工程の前後に他の熱処理工程を含むものでない場合には、本材料を用いて鋳造した熱処理対象物に対して順に、第１の保持工程と、第１の冷却工程とのみを行うことにより、熱処理対象物に対して予期せぬ熱影響が作用することを防止することができる。したがって、鉄鋳物の線膨張係数をより確実に低減させることができる。 <Second form of heat treatment>
The second form of heat treatment includes a first holding step in which the object to be heat treated is held at a first holding temperature of 850°C or more and 1250°C or less, and after the first holding step, the object to be heat treated is heated to -150°C. and a first cooling step of cooling to a first cooling end temperature of 150° C. or less. In the second form of this heat treatment, the first holding step includes holding the heat treatment object for a first holding time of 0.25 hours or more and 100 hours or less. The first cooling process includes a primary cooling process in which the heat treatment target is cooled at a primary cooling rate, and a secondary cooling process in which the heat treatment target is cooled at a secondary cooling rate higher than the primary cooling rate after the primary cooling process. including. In the first cooling step, the primary cooling step includes cooling the heat treatment object to a primary cooling end temperature of 250° C. or more and 950° C. or less. The secondary cooling step includes cooling the heat treatment object to a first cooling end temperature (-150° C. or higher and 150° C. or lower). Note that the second form of the main heat treatment may include other heat treatment steps before and after each of the first holding step and the first cooling step. In the second form of this heat treatment, if other heat treatment steps are not included before or after each of the above steps, the heat treatment object cast using this material is sequentially subjected to the first holding step and the first holding step. By performing only the first cooling step, it is possible to prevent unexpected thermal effects from acting on the object to be heat treated. Therefore, the coefficient of linear expansion of iron castings can be reduced more reliably.
　本熱処理の第２の形態においては、第１の保持工程において、熱処理対象物を第１の保持温度（８５０℃以上１２５０℃以下）かつ第１の保持時間（０．２５時間以上１００時間以下）で保持する。そして、第１の保持工程の後の第１の冷却工程において、熱処理対象物を第１の冷却終了温度（－１５０℃以上１５０℃以下）まで冷却する。この第１の保持工程により、熱処理対象物内の溶質元素の凝固偏析を低減するとともに、オーステナイト相を構成する各結晶粒内部の結晶方位の相対的な差（結晶方位差）を小さくすることができる。これにより、オーステナイト相中の結晶格子の配列を整えることができる。その結果、鉄鋳物の線膨張係数を低減させることができる。 In the second form of this heat treatment, in the first holding step, the heat treatment target is held at a first holding temperature (850°C or more and 1250°C or less) and a first holding time (0.25 hours or more and 100 hours or less). hold it. Then, in a first cooling step after the first holding step, the heat treatment target is cooled to a first cooling end temperature (-150° C. or higher and 150° C. or lower). Through this first holding step, it is possible to reduce the solidification segregation of solute elements in the heat-treated object and to reduce the relative difference in crystal orientation (crystal orientation difference) inside each crystal grain constituting the austenite phase. can. This makes it possible to arrange the crystal lattice in the austenite phase. As a result, the coefficient of linear expansion of the iron casting can be reduced.
　さらに、本熱処理の第２の形態においては、第１の保持工程の後の第１の冷却工程が、熱処理対象物を一次冷却速度で冷却する一次冷却工程と、一次冷却工程の後に、熱処理対象物を一次冷却速度よりも大きい二次冷却速度で冷却する二次冷却工程とを含む。具体的には、一次冷却工程において、熱処理対象物を一次冷却終了温度（２５０℃以上９５０℃以下）まで一次冷却速度で冷却する。この一次冷却工程により、オーステナイト相中の炭素を黒鉛の側に拡散させることができる。このため、オーステナイト相中の固溶炭素量を低減させることができる。したがって、オーステナイト相中の結晶格子の過剰な歪みを抑制することができる。その結果、鉄鋳物の線膨張係数を一層低減させることができる。さらに、一次冷却工程の後の二次冷却工程において、熱処理対象物を第１の冷却終了温度（－１５０℃以上１５０℃以下）まで一次冷却速度よりも大きい二次冷却速度で冷却する。この二次冷却工程により、キュリー点以下での温度変化に伴う自発体積磁気歪みの変化量を増加させやすい。このため、キュリー点以下での温度変化において、自発体積磁気歪みに起因する体積変化と、結晶格子振動に起因する体積変化とを相殺させやすい。したがって、温度変化に伴う体積変動を抑制しやすい。その結果、鉄鋳物の線膨張係数をより一層低減させやすい。 Furthermore, in the second form of the heat treatment, the first cooling step after the first holding step is a primary cooling step in which the object to be heat treated is cooled at the primary cooling rate; and a secondary cooling step in which the object is cooled at a secondary cooling rate that is higher than the primary cooling rate. Specifically, in the primary cooling step, the heat treatment target is cooled at the primary cooling rate to the primary cooling end temperature (250° C. or higher and 950° C. or lower). This primary cooling step allows carbon in the austenite phase to diffuse toward the graphite side. Therefore, the amount of solid solute carbon in the austenite phase can be reduced. Therefore, excessive distortion of the crystal lattice in the austenite phase can be suppressed. As a result, the coefficient of linear expansion of the iron casting can be further reduced. Furthermore, in the secondary cooling step after the primary cooling step, the heat-treated object is cooled to a first cooling end temperature (-150° C. or higher and 150° C. or lower) at a secondary cooling rate that is higher than the primary cooling rate. This secondary cooling step tends to increase the amount of change in spontaneous volumetric magnetostriction due to temperature change below the Curie point. Therefore, in a temperature change below the Curie point, the volume change due to spontaneous bulk magnetostriction and the volume change due to crystal lattice vibration are likely to cancel each other out. Therefore, it is easy to suppress volume fluctuations due to temperature changes. As a result, it is easier to further reduce the coefficient of linear expansion of iron castings.
　本熱処理の第２の形態において、一次冷却速度は、０．０１℃／分以上２０℃／分以下であり、二次冷却速度は、１℃／分以上４００００℃／分以下であることが好ましい。二次冷却速度は、１００℃／分以上４００００℃／分以下であることが好ましい。第１の保持時間は、２．５時間以上２５時間以下であることが好ましい。一次冷却終了温度は、４５０℃以上８５０℃以下であることが好ましい。第１の冷却終了温度は、０℃以上１００℃以下であることが好ましい。 In the second form of this heat treatment, the primary cooling rate is preferably 0.01°C/min or more and 20°C/min or less, and the secondary cooling rate is preferably 1°C/min or more and 40000°C/min or less. . The secondary cooling rate is preferably 100°C/min or more and 40000°C/min or less. The first holding time is preferably 2.5 hours or more and 25 hours or less. The primary cooling end temperature is preferably 450°C or more and 850°C or less. The first cooling end temperature is preferably 0°C or more and 100°C or less.
　本熱処理の第２の形態において、一次冷却終了温度の下限は、２７５℃であることが好ましく、３００℃であることがより好ましく、３２５℃であることがより好ましく、３５０℃であることがより好ましく、３７５℃であることがより好ましく、４００℃であることがより好ましく、４２５℃であることがより好ましく、４５０℃であることがより好ましく、４７５℃であることがより好ましく、５００℃であることがより好ましく、５２５℃であることがより好ましく、５５０℃であることがより好ましく、５７５℃であることがより好ましく、６００℃であることがさらに好ましい。また、一次冷却終了温度の上限は、９２５℃であることが好ましく、９００℃であることがより好ましく、８７５℃であることがより好ましく、８５０℃であることがより好ましく、８２５℃であることがより好ましく、８００℃であることがさらに好ましい。 In the second form of this heat treatment, the lower limit of the primary cooling end temperature is preferably 275°C, more preferably 300°C, more preferably 325°C, and most preferably 350°C. Preferably, the temperature is 375°C, more preferably 400°C, more preferably 425°C, more preferably 450°C, more preferably 475°C, and more preferably 500°C. The temperature is more preferably 525°C, more preferably 550°C, more preferably 575°C, and even more preferably 600°C. Further, the upper limit of the primary cooling end temperature is preferably 925°C, more preferably 900°C, more preferably 875°C, more preferably 850°C, and 825°C. is more preferable, and even more preferably 800°C.
　本熱処理の第２の形態において、一次冷却速度の下限は、０．１℃／分であることが好ましく、０．５℃／分であることがより好ましく、０．７５℃／分であることがより好ましく、１．０℃／分であることがより好ましく、１．２５℃／分であることがより好ましく、１．５℃／分であることがより好ましく、１．７５℃／分であることがさらに好ましい。また、一次冷却速度の上限は、１７．５℃／分であることが好ましく、１５．０℃／分であることがより好ましく、１２．５℃／分であることがより好ましく、１０．０℃／分であることがより好ましく、７．５℃／分であることがさらに好ましい。 In the second form of this heat treatment, the lower limit of the primary cooling rate is preferably 0.1°C/min, more preferably 0.5°C/min, and more preferably 0.75°C/min. is more preferably 1.0°C/min, more preferably 1.25°C/min, more preferably 1.5°C/min, and more preferably 1.75°C/min. It is even more preferable that there be. Further, the upper limit of the primary cooling rate is preferably 17.5°C/min, more preferably 15.0°C/min, more preferably 12.5°C/min, and 10.0°C/min. C/min is more preferable, and even more preferably 7.5 C/min.
　本熱処理の第２の形態において、二次冷却速度の下限は、２．５℃／分であることが好ましく、５℃／分であることがより好ましく、７．５℃／分であることがより好ましく、１０℃／分であることがより好ましく、５０℃／分であることがより好ましく、１００℃／分であることがより好ましく２００℃／分であることがより好ましく、３００℃／分であることがより好ましく、４００℃／分であることがより好ましく、５００℃／分であることがより好ましく、６００℃／分であることがさらに好ましい。また、二次冷却速度の上限は、３７５００℃／分であることが好ましく、３５０００℃／分であることがより好ましく、３２５００℃／分であることがより好ましく、３００００℃／分であることがより好ましく、２７５００℃／分であることがより好ましく、２５０００℃／分であることがさらに好ましい。 In the second form of this heat treatment, the lower limit of the secondary cooling rate is preferably 2.5°C/min, more preferably 5°C/min, and preferably 7.5°C/min. More preferably, 10°C/min, more preferably 50°C/min, more preferably 100°C/min, more preferably 200°C/min, and even more preferably 300°C/min. More preferably, it is 400°C/min, more preferably 500°C/min, and even more preferably 600°C/min. Further, the upper limit of the secondary cooling rate is preferably 37,500°C/min, more preferably 35,000°C/min, more preferably 32,500°C/min, and preferably 30,000°C/min. More preferably, it is 27,500°C/min, and even more preferably 25,000°C/min.
　＜熱処理の第３の形態＞
　本熱処理の第３の形態は、熱処理対象物を８５０℃以上１２５０℃以下の第１の保持温度で保持する第１の保持工程と、第１の保持工程の後に、熱処理対象物を－１５０℃以上１５０℃以下の第１の冷却終了温度まで冷却する第１の冷却工程と、第１の冷却工程の後に、熱処理対象物を２５０℃以上９５０℃以下の第２の保持温度で保持する第２の保持工程と、第２の保持工程の後に、熱処理対象物を－１５０℃以上１５０℃以下の第２の冷却終了温度まで冷却する第２の冷却工程とを含む。本熱処理の第３の形態において、第１の保持工程は、熱処理対象物を０．２５時間以上１００時間以下の第１の保持時間で保持することを含む。第２の保持工程は、熱処理対象物を０．２５時間以上２５時間以下の第２の保持時間で保持することを含む。なお、本熱処理の第３の形態は、第１の保持工程、第１の冷却工程、第２の保持工程および第２の冷却工程の各工程の前後に他の熱処理工程を含むものであってもよい。本熱処理の第３の形態において、上記各工程の前後に他の熱処理工程を含むものでない場合には、本材料を用いて鋳造した熱処理対象物に対して順に、第１の保持工程と、第１の冷却工程と、第２の保持工程と、第２の冷却工程とのみを行うことにより、熱処理対象物に対して予期せぬ熱影響が作用することを防止することができる。したがって、鉄鋳物の線膨張係数をより確実に低減させることができる。 <Third form of heat treatment>
The third form of heat treatment includes a first holding step in which the object to be heat treated is held at a first holding temperature of 850°C to 1250°C, and after the first holding step, the object to be heat treated is heated to -150°C. A first cooling step in which the object is cooled to a first cooling end temperature of not less than 150°C, and a second cooling step in which the object to be heat treated is held at a second holding temperature of not less than 250°C and not more than 950°C after the first cooling step. and, after the second holding step, a second cooling step of cooling the heat-treated object to a second cooling end temperature of −150° C. or more and 150° C. or less. In the third form of this heat treatment, the first holding step includes holding the heat treatment object for a first holding time of 0.25 hours or more and 100 hours or less. The second holding step includes holding the heat-treated object for a second holding time of 0.25 hours or more and 25 hours or less. Note that the third form of the heat treatment includes other heat treatment steps before and after each of the first holding step, first cooling step, second holding step, and second cooling step. Good too. In the third form of the present heat treatment, if other heat treatment steps are not included before or after each of the above steps, the heat treatment object cast using the present material is sequentially subjected to the first holding step and the first holding step. By performing only the first cooling step, the second holding step, and the second cooling step, it is possible to prevent unexpected thermal effects from acting on the object to be heat treated. Therefore, the coefficient of linear expansion of iron castings can be reduced more reliably.
　本熱処理の第３の形態においては、第１の保持工程において、熱処理対象物を第１の保持温度（８５０℃以上１２５０℃以下）かつ第１の保持時間（０．２５時間以上１００時間以下）で保持する。そして、第１の保持工程の後の第１の冷却工程において、熱処理対象物を第１の冷却終了温度（－１５０℃以上１５０℃以下）まで冷却する。この第１の保持工程により、熱処理対象物内の溶質元素の凝固偏析を低減するとともに、オーステナイト相を構成する各結晶粒内部の結晶方位の相対的な差（結晶方位差）を小さくすることができる。これにより、オーステナイト相中の結晶格子の配列を整えることができる。その結果、鉄鋳物の線膨張係数を低減させることができる。 In the third form of this heat treatment, in the first holding step, the heat treatment target is held at a first holding temperature (850°C or more and 1250°C or less) and a first holding time (0.25 hours or more and 100 hours or less). hold it. Then, in a first cooling step after the first holding step, the heat treatment target is cooled to a first cooling end temperature (-150° C. or higher and 150° C. or lower). Through this first holding step, it is possible to reduce the solidification segregation of solute elements in the heat-treated object and to reduce the relative difference in crystal orientation (crystal orientation difference) inside each crystal grain constituting the austenite phase. can. This makes it possible to arrange the crystal lattice in the austenite phase. As a result, the coefficient of linear expansion of the iron casting can be reduced.
　さらに、本熱処理の第３の形態においては、第１の冷却工程の後の第２の保持工程において、熱処理対象物を第２の保持温度（２５０℃以上９５０℃以下）で保持する。そして、第２の保持工程の後の第２の冷却工程において、熱処理対象物を第２の冷却終了温度（－１５０℃以上１５０℃以下）まで冷却する。この第２の冷却工程により、キュリー点以下での温度変化に伴う自発体積磁気歪みの変化量を増加させやすい。このため、キュリー点以下での温度変化において、自発体積磁気歪みに起因する体積変化と、結晶格子振動に起因する体積変化とを相殺させやすい。したがって、温度変化に伴う体積変動を抑制しやすい。その結果、鉄鋳物の線膨張係数をより一層低減させやすい。 Furthermore, in the third form of this heat treatment, the heat treatment target is held at a second holding temperature (250° C. or higher and 950° C. or lower) in a second holding step after the first cooling step. Then, in a second cooling step after the second holding step, the heat treatment target is cooled to a second cooling end temperature (-150° C. or higher and 150° C. or lower). This second cooling step tends to increase the amount of change in spontaneous volume magnetostriction due to temperature change below the Curie point. Therefore, in a temperature change below the Curie point, the volume change due to spontaneous bulk magnetostriction and the volume change due to crystal lattice vibration are likely to cancel each other out. Therefore, it is easy to suppress volume fluctuations due to temperature changes. As a result, it is easier to further reduce the coefficient of linear expansion of iron castings.
　本熱処理の第３の形態において、第１の冷却工程は、熱処理対象物を０．０１℃／分以上３００℃／分以下の第１の冷却速度で冷却することを含むことが好ましい。第１の冷却速度は、１℃／分以上５０℃／分以下であることが好ましい。第２の冷却工程は、熱処理対象物を１℃／分以上４００００℃／分以下の第２の冷却速度で冷却することを含むことが好ましい。第２の冷却速度は、１００℃／分以上１００００℃／分以下であることが好ましい。第１の保持時間は、２．５時間以上２５時間以下であることが好ましい。第１の冷却終了温度は、０℃以上１００℃以下であることが好ましい。第２の保持温度は、５５０℃以上９５０℃以下であることが好ましい。第２の冷却終了温度は、０℃以上５０℃以下であることが好ましい。 In the third form of heat treatment, the first cooling step preferably includes cooling the heat treatment object at a first cooling rate of 0.01° C./min or more and 300° C./min or less. The first cooling rate is preferably 1° C./min or more and 50° C./min or less. The second cooling step preferably includes cooling the heat-treated object at a second cooling rate of 1° C./min or more and 40000° C./min or less. The second cooling rate is preferably 100° C./min or more and 10000° C./min or less. The first holding time is preferably 2.5 hours or more and 25 hours or less. The first cooling end temperature is preferably 0°C or more and 100°C or less. The second holding temperature is preferably 550°C or more and 950°C or less. The second cooling end temperature is preferably 0°C or more and 50°C or less.
　本熱処理の第３の形態において、第１の冷却速度の下限は、１．０℃／分であることが好ましく、５．０℃／分であることがより好ましく、７．５℃／分であることがより好ましく、１０．０℃／分であることがより好ましく、１２．０℃／分であることがより好ましく、１４．０℃／分であることがさらに好ましい。また、第１の冷却速度の上限は、２５０℃／分であることが好ましく、２００℃／分であることがより好ましく、１５０℃／分であることがより好ましく、１００℃／分であることがより好ましく、７５℃／分であることがより好ましく、５０℃／分であることがより好ましく、４５℃／分であることがより好ましく、４０℃／分であることがさらに好ましい。 In the third form of this heat treatment, the lower limit of the first cooling rate is preferably 1.0°C/min, more preferably 5.0°C/min, and more preferably 7.5°C/min. More preferably, the rate is 10.0°C/min, more preferably 12.0°C/min, and even more preferably 14.0°C/min. Further, the upper limit of the first cooling rate is preferably 250°C/min, more preferably 200°C/min, more preferably 150°C/min, and more preferably 100°C/min. is more preferable, more preferably 75°C/min, more preferably 50°C/min, more preferably 45°C/min, and even more preferably 40°C/min.
　本熱処理の第３の形態において、第２の保持温度の下限は、２７５℃であることが好ましく、３００℃であることがより好ましく、３２５℃であることがより好ましく、３５０℃であることがより好ましく、３７５℃であることがより好ましく、４００℃であることがより好ましく、４２５℃であることがより好ましく、４５０℃であることがより好ましく、４７５℃であることがより好ましく、５００℃であることがより好ましく、５２５℃であることがより好ましく、５５０℃であることがより好ましく、５７５℃であることがより好ましく、６００℃であることがさらに好ましい。また、第２の保持温度の上限は、９２５℃であることが好ましく、９００℃であることがより好ましく、８７５℃であることがより好ましく、８５０℃であることがより好ましく、８２５℃であることがより好ましく、８００℃であることがさらに好ましい。 In the third embodiment of the heat treatment, the lower limit of the second holding temperature is preferably 275°C, more preferably 300°C, more preferably 325°C, and preferably 350°C. more preferably 375°C, more preferably 400°C, more preferably 425°C, more preferably 450°C, more preferably 475°C, and more preferably 500°C. The temperature is more preferably 525°C, more preferably 550°C, more preferably 575°C, and even more preferably 600°C. Further, the upper limit of the second holding temperature is preferably 925°C, more preferably 900°C, more preferably 875°C, more preferably 850°C, and more preferably 825°C. More preferably, the temperature is 800°C.
　本熱処理の第３の形態において、第２の保持時間の下限は、０．３時間であることが好ましく、０．４時間であることがより好ましく、０．５時間であることがより好ましく、０．６時間であることがより好ましく、０．７時間であることがより好ましく、０．８時間であることがより好ましく、０．９時間であることがより好ましく、１．０時間であることがさらに好ましい。また、第２の保持時間の上限は、２０時間であることが好ましく、１５時間であることがより好ましく、１０時間であることがより好ましく、９時間であることがより好ましく、８時間であることがより好ましく、７時間であることがより好ましく、６時間であることがより好ましく、５時間であることがさらに好ましい。 In the third embodiment of the present heat treatment, the lower limit of the second holding time is preferably 0.3 hours, more preferably 0.4 hours, more preferably 0.5 hours, More preferably 0.6 hours, more preferably 0.7 hours, more preferably 0.8 hours, more preferably 0.9 hours, and 1.0 hours. It is even more preferable. Further, the upper limit of the second holding time is preferably 20 hours, more preferably 15 hours, more preferably 10 hours, more preferably 9 hours, and more preferably 8 hours. is more preferable, more preferably 7 hours, more preferably 6 hours, and even more preferably 5 hours.
　本熱処理の第３の形態において、第２の冷却終了温度の下限は、－１２５℃であることが好ましく、－１００℃であることがより好ましく、－７５℃であることがより好ましく、－５０℃であることがより好ましく、－２５℃であることがより好ましく、０℃であることがさらに好ましい。また、第２の冷却終了温度の上限は、１２５℃であることが好ましく、１００℃であることがより好ましく、７５℃であることがより好ましく、５０℃であることがより好ましく、４０℃であることがより好ましく、３０℃であることがさらに好ましい。 In the third form of this heat treatment, the lower limit of the second cooling end temperature is preferably -125°C, more preferably -100°C, more preferably -75°C, and more preferably -50°C. The temperature is more preferably -25°C, and even more preferably 0°C. Further, the upper limit of the second cooling end temperature is preferably 125°C, more preferably 100°C, more preferably 75°C, more preferably 50°C, and even more preferably 40°C. The temperature is more preferably 30°C, and even more preferably 30°C.
　本熱処理の第３の形態において、第２の冷却速度の下限は、２５℃／分であることが好ましく、５０℃／分であることがより好ましく、７５℃／分であることがより好ましく、１００℃／分であることがより好ましく、２００℃／分であることがより好ましく、３００℃／分であることがより好ましく、４００℃／分であることがさらに好ましい。また、第２の冷却速度の上限は、３５０００℃／分であることが好ましく、３００００℃／分であることがより好ましく、２５０００℃／分であることがより好ましく、２００００℃／分であることがより好ましく、１５０００℃／分であることがより好ましく、１００００℃／分であることがより好ましく、９０００℃／分であることがより好ましく、８０００℃／分であることがより好ましく、７０００℃／分であることがより好ましく、６０００℃／分であることがさらに好ましい。 In the third embodiment of the present heat treatment, the lower limit of the second cooling rate is preferably 25°C/min, more preferably 50°C/min, and more preferably 75°C/min. The rate is more preferably 100°C/min, more preferably 200°C/min, even more preferably 300°C/min, and even more preferably 400°C/min. Further, the upper limit of the second cooling rate is preferably 35,000°C/min, more preferably 30,000°C/min, more preferably 25,000°C/min, and 20,000°C/min. is more preferable, 15000°C/min is more preferable, 10000°C/min is more preferable, 9000°C/min is more preferable, 8000°C/min is more preferable, 7000°C It is more preferable that it is 6000 degreeC/min, and it is still more preferable that it is 6000 degreeC/min.
　＜第１の実施形態＞
　第１の実施形態の鉄鋳物は、本材料の第５の形態（Ｎｉ－Ｃ－Ｓｉ－Ｃｏ－Ｍｎ－Ｆｅ組成）、第７の形態（Ｎｉ－Ｃ－Ｓｉ－Ｃｏ－Ｍｎ－Ｍｇ－Ｆｅ組成）、第８の形態（Ｎｉ－Ｃ－Ｓｉ－Ｍｎ－Ｆｅ組成）および第９の形態（Ｎｉ－Ｃ－Ｓｉ－Ｍｎ－Ｍｇ－Ｆｅ組成）を用いて鋳造した熱処理対象物に対して、本熱処理の第２の形態を行うことにより得られる鉄鋳物である。第１の実施形態の鉄鋳物においては、本熱処理の第２の形態を行うことにより、上述のとおり、鉄鋳物の線膨張係数を低減させることができる。 <First embodiment>
The iron casting of the first embodiment is based on the fifth form (Ni-C-Si-Co-Mn-Fe composition) and the seventh form (Ni-C-Si-Co-Mn-Mg-Fe composition) of the present material. For heat-treated objects cast using the eighth form (Ni-C-Si-Mn-Fe composition) and the ninth form (Ni-C-Si-Mn-Mg-Fe composition), This is an iron casting obtained by performing the second form of this heat treatment. In the iron casting of the first embodiment, by performing the second form of main heat treatment, the linear expansion coefficient of the iron casting can be reduced as described above.
　また、第１の実施形態の鉄鋳物においては、Ｎｉの含有量が２６．０質量％以上であるオーステナイト系の鋳造用材料を用いて熱処理対象物を鋳造しているため、Ｍｓ点（オーステナイトからマルテンサイトへの変態が始まる温度）を低下させやすい。したがって、マルテンサイトの生成を抑制した鉄鋳物を提供しやすい。さらに、本熱処理の第２の形態における第１の保持工程において、熱処理対象物内の溶質元素の凝固偏析が低減される結果、熱処理対象物内の最終凝固部に低濃度で分布しているＮｉを高濃度化することができる。これにより、最終凝固部におけるＭｓ点を一層低下させることができる。このため、第１の保持工程の後の第１の冷却工程において、熱処理対象物を第１の冷却終了温度（－１５０℃以上１５０℃以下）まで冷却する際に、マルテンサイトの生成を一層抑制することができる。したがって、熱膨張を低減させるとともにマルテンサイトの生成を抑制した鉄鋳物を提供することができる。下記実施形態においても同様である。 In addition, in the iron casting of the first embodiment, since the object to be heat treated is cast using an austenitic casting material with a Ni content of 26.0% by mass or more, the Ms point (from austenite to It is easy to lower the temperature at which transformation to martensite begins. Therefore, it is easy to provide iron castings in which martensite generation is suppressed. Furthermore, in the first holding step in the second form of the heat treatment, the solidification segregation of solute elements in the heat treatment object is reduced, and as a result, Ni distributed at a low concentration in the final solidified part of the heat treatment object can be highly concentrated. Thereby, the Ms point in the final solidification part can be further lowered. Therefore, in the first cooling step after the first holding step, when the heat-treated object is cooled to the first cooling end temperature (-150°C or more and 150°C or less), the generation of martensite is further suppressed. can do. Therefore, it is possible to provide an iron casting in which thermal expansion is reduced and martensite formation is suppressed. The same applies to the following embodiments.
　＜第２の実施形態＞
　第２の実施形態の鉄鋳物は、本材料の第５の形態（Ｎｉ－Ｃ－Ｓｉ－Ｃｏ－Ｍｎ－Ｆｅ組成）、第７の形態（Ｎｉ－Ｃ－Ｓｉ－Ｃｏ－Ｍｎ－Ｍｇ－Ｆｅ組成）および第９の形態（Ｎｉ－Ｃ－Ｓｉ－Ｍｎ－Ｍｇ－Ｆｅ組成）を用いて鋳造した熱処理対象物に対して、本熱処理の第３の形態を行うことにより得られる鉄鋳物である。第２の実施形態の鉄鋳物においては、本熱処理の第３の形態を行うことにより、上述のとおり、鉄鋳物の線膨張係数を低減させることができる。 <Second embodiment>
The iron casting of the second embodiment is based on the fifth form (Ni-C-Si-Co-Mn-Fe composition) and the seventh form (Ni-C-Si-Co-Mn-Mg-Fe composition) of the present material. This is an iron casting obtained by performing the third form of heat treatment on a heat-treated object cast using the composition) and the ninth form (Ni-C-Si-Mn-Mg-Fe composition). . In the iron casting of the second embodiment, by performing the third form of main heat treatment, the linear expansion coefficient of the iron casting can be reduced as described above.
　＜第３の実施形態＞
　第３の実施形態の鉄鋳物は、本材料の第５の形態（Ｎｉ－Ｃ－Ｓｉ－Ｃｏ－Ｍｎ－Ｆｅ組成）、第７の形態（Ｎｉ－Ｃ－Ｓｉ－Ｃｏ－Ｍｎ－Ｍｇ－Ｆｅ組成）および第９の形態（Ｎｉ－Ｃ－Ｓｉ－Ｍｎ－Ｍｇ－Ｆｅ組成）を用いて鋳造した熱処理対象物に対して、本熱処理の第１の形態を行うことにより得られる鉄鋳物である。第３の実施形態の鉄鋳物においては、本熱処理の第１の形態を行うことにより、上述のとおり、鉄鋳物の線膨張係数を低減させることができる。 <Third embodiment>
The iron casting of the third embodiment is based on the fifth form (Ni-C-Si-Co-Mn-Fe composition) and the seventh form (Ni-C-Si-Co-Mn-Mg-Fe composition) of the present material. This is an iron casting obtained by performing the first form of heat treatment on a heat-treated object cast using the composition) and the ninth form (Ni-C-Si-Mn-Mg-Fe composition). . In the iron casting of the third embodiment, by performing the first form of main heat treatment, the linear expansion coefficient of the iron casting can be reduced as described above.
　上記実施形態によれば、熱膨張を低減させた鉄鋳物を提供することができる。したがって、上記実施形態の鉄鋳物は、低い熱膨張（係数）が求められる多種多様な用途に好適である。上記実施形態の鉄鋳物の用途の例としては、半導体製造装置、電子部品製造装置、工作機械等の構成部品等が挙げられる。例えば、２０℃から５０℃程度の使用環境における適用例としては、半導体製造装置関連では、ダイサーのスピンドルホルダ、校正ゲージ（ゲージブロック等）、工作機械関連では、ワークステージ、ワイヤー放電加工機のワイヤー保持部材が挙げられる。また、２０℃から１００℃（または１５０℃）程度の使用環境における適用例としては、半導体製造装置関連では、ドライ真空ポンプ部品、プローバのカードホルダが挙げられる。 According to the above embodiment, an iron casting with reduced thermal expansion can be provided. Therefore, the iron castings of the above embodiments are suitable for a wide variety of uses that require low thermal expansion (coefficient). Examples of uses of the iron castings of the above embodiments include component parts of semiconductor manufacturing equipment, electronic component manufacturing equipment, machine tools, and the like. For example, application examples in operating environments of about 20°C to 50°C include spindle holders for dicers, calibration gauges (gauge blocks, etc.) in semiconductor manufacturing equipment, work stages in machine tools, and wires in wire electrical discharge machines. A holding member is mentioned. In addition, examples of applications in use environments of about 20° C. to 100° C. (or 150° C.) include dry vacuum pump parts and card holders for probers in semiconductor manufacturing equipment.
　＜実施例＞
　表１に、第１の実施形態における実施例の組成と、これらに対する比較例の組成とを示している。表２に、第２の実施形態における実施例の組成と、これらに対する比較例の組成とを示している。表３に、第３の実施形態における実施例の組成と、これらに対する比較例の組成とを示している。表１から表３において、Ｃ（炭素）の含有量（質量％）は、株式会社堀場製作所製の材料炭素・硫黄分析装置「ＥＭＩＡ－Ｅｘｐｅｒｔ」を用いて燃焼－赤外線吸収法により測定した値である。また、Ｓｉ（ケイ素）、Ｎｉ（ニッケル）、Ｍｇ（マグネシウム）およびＣｏ（コバルト）の含有量（質量％）は、株式会社日立ハイテクサイエンス製の発光分光分析装置「ＳＰＳ３５２０ＵＶ」を用いて誘導結合プラズマ発光分光分析法により測定した値である。また、その他の元素の含有量（質量％）は、株式会社島津製作所製の発光分光分析装置「ＰＤＡ－８０００」を用いて発光分光分析法により測定した値である。 <Example>
Table 1 shows the compositions of Examples in the first embodiment and the compositions of Comparative Examples. Table 2 shows the compositions of Examples in the second embodiment and the compositions of Comparative Examples thereof. Table 3 shows the compositions of Examples in the third embodiment and the compositions of Comparative Examples. In Tables 1 to 3, the C (carbon) content (mass%) is the value measured by combustion-infrared absorption method using a material carbon/sulfur analyzer "EMIA-Expert" manufactured by Horiba, Ltd. be. In addition, the content (mass%) of Si (silicon), Ni (nickel), Mg (magnesium), and Co (cobalt) was determined using inductively coupled plasma using an emission spectrometer "SPS3520UV" manufactured by Hitachi High-Tech Science Co., Ltd. This is a value measured by emission spectrometry. Further, the contents (mass %) of other elements are values measured by emission spectrometry using an emission spectrometer "PDA-8000" manufactured by Shimadzu Corporation.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　表４に、第１の実施形態における実施例の熱処理条件および平均線膨張係数と、これらに対する比較例の熱処理条件および平均線膨張係数を示している。表５に、第２の実施形態における実施例の熱処理条件および平均線膨張係数と、これらに対する比較例の熱処理条件および平均線膨張係数を示している。表６に、第３の実施形態における実施例の熱処理条件および平均線膨張係数と、これらに対する比較例の熱処理条件および平均線膨張係数を示している。表４から表６において、保持温度（℃）は、熱処理炉（熱処理装置）内において熱処理対象物を保持する温度を示している。なお、熱処理炉は、株式会社テック製のマッフル炉「ＱＵＩＣＫ　ＴＥＭＰＥＲ」を用いた。また、保持時間（時間）は、熱処理炉内を当該保持温度にした状態で熱処理対象物を保持する時間を示している。また、冷却方法は、熱処理対象物を冷却する方法を示しており、炉冷は、熱処理対象物を熱処理炉内で徐々に冷却する方法であり、自然空冷は、熱処理対象物を熱処理炉外の空気中で冷却する方法であり、急冷は、熱処理対象物を水、油、ドライアイスを用いた冷却剤、液体窒素等に浸漬して速やかに冷却する方法である。また、冷却終了温度（℃）は、当該冷却方法による熱処理対象物の冷却を終了する温度を示している。炉冷の場合の冷却終了温度は、熱処理炉内の熱処理対象物に対して熱電対の測温部を接触させることにより、熱処理炉内で測定した熱処理対象物の表面温度である。自然空冷および急冷の場合の冷却終了温度は、熱処理炉外の熱処理対象物に対して熱電対の測温部を接触させることにより、熱処理炉外で測定した熱処理対象物の表面温度である。また、冷却速度（℃／分）または（℃／秒）は、熱処理対象物の冷却を開始して終了するまでの時間に対する温度の変化量を示している。また、平均線膨張係数（×１０－６／℃）は、砂型鋳造法により鋳造した熱処理対象物に対して所定の熱処理を施した後の鉄鋳物（Ｙ形Ｂ号供試材）から採取した線膨張係数測定試験片（直径６ｍｍ、長さ２５ｍｍ）について、ＮＥＴＺＳＣＨ　Ｊａｐａｎ株式会社製の熱膨張計「ＤＩＬ　４０２　Ｅｘｐｅｄｉｓ　Ｓｕｐｒｅｍｅ」を用いてＡＳＴＭ規格（ＡＳＴＭ　Ｅ２２８－１７）に従って測定した値であり、２０℃を基準として表４から表６における各温度（５０℃、１００℃、１５０℃）までの平均線膨張係数を示している。 Table 4 shows the heat treatment conditions and average linear expansion coefficients of the examples in the first embodiment, and the heat treatment conditions and average linear expansion coefficients of comparative examples with respect to these. Table 5 shows the heat treatment conditions and average linear expansion coefficients of the examples in the second embodiment, and the heat treatment conditions and average linear expansion coefficients of comparative examples with respect to these. Table 6 shows the heat treatment conditions and average linear expansion coefficients of the examples in the third embodiment, and the heat treatment conditions and average linear expansion coefficients of the comparative examples. In Tables 4 to 6, the holding temperature (°C) indicates the temperature at which the heat treatment object is held in the heat treatment furnace (heat treatment apparatus). As the heat treatment furnace, a muffle furnace "QUICK TEMPER" manufactured by TEC Co., Ltd. was used. Further, the holding time (hour) indicates the time during which the heat treatment object is held in a state where the inside of the heat treatment furnace is kept at the holding temperature. In addition, the cooling method refers to a method for cooling the heat-treated object.Furnace cooling is a method in which the heat-treated object is gradually cooled inside the heat treatment furnace, and natural air cooling is a method for cooling the heat-treated object outside the heat treatment furnace. It is a method of cooling in air, and rapid cooling is a method of rapidly cooling the object to be heat treated by immersing it in water, oil, a coolant using dry ice, liquid nitrogen, or the like. Further, the cooling end temperature (° C.) indicates the temperature at which cooling of the heat treatment object by the cooling method ends. In the case of furnace cooling, the cooling end temperature is the surface temperature of the heat treatment object measured in the heat treatment furnace by bringing the temperature measurement part of the thermocouple into contact with the heat treatment object in the heat treatment furnace. The cooling end temperature in the case of natural air cooling and rapid cooling is the surface temperature of the heat treatment object measured outside the heat treatment furnace by bringing the temperature measurement part of the thermocouple into contact with the heat treatment object outside the heat treatment furnace. Further, the cooling rate (°C/min) or (°C/sec) indicates the amount of change in temperature with respect to the time from the start to the end of cooling of the heat-treated object. In addition, the average linear expansion coefficient (×10 -6 /°C) was obtained from an iron casting (Y type B sample material) after the specified heat treatment was applied to the heat treatment object cast by sand casting method. The linear expansion coefficient measurement test piece (diameter 6 mm, length 25 mm) is a value measured according to ASTM standard (ASTM E228-17) using a thermal dilatometer "DIL 402 Expedis Supreme" manufactured by NETZSCH Japan Co., Ltd. The average coefficient of linear expansion up to each temperature (50°C, 100°C, 150°C) in Tables 4 to 6 is shown based on °C.
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000006
Figure JPOXMLDOC01-appb-T000006
　（実施例１－１から実施例１－３０と比較例１－１との比較）
　表４に示すように、実施例１－１から実施例１－３０の一次冷却終了温度は９５０℃以下であるのに対して、比較例１－１の一次冷却終了温度は１０００℃である。表４に示すように、実施例１－１から実施例１－３０では、比較例１－１と比べて、２０℃以上５０℃以下における平均線膨張係数、２０℃以上１００℃以下における平均線膨張係数および２０℃以上１５０℃以下における平均線膨張係数がそれぞれ低減している。具体的には、実施例１－１から実施例１－３０では、２０℃以上５０℃以下における平均線膨張係数が３．５１×１０－６／℃以下（比較例１－１は３．６３×１０－６／℃）、２０℃以上１００℃以下における平均線膨張係数が３．５８×１０－６／℃以下（比較例１－１は３．９０×１０－６／℃）、２０℃以上１５０℃以下における平均線膨張係数が４．０９×１０－６／℃以下（比較例１－１は４．２８×１０－６／℃）となっている。このように、実施例１－１から実施例１－３０では、一次冷却終了温度を９５０℃以下（特に９００℃以下）にすることにより、鉄鋳物の熱膨張を低減させることができる。 (Comparison of Examples 1-1 to 1-30 and Comparative Example 1-1)
As shown in Table 4, the primary cooling end temperature of Examples 1-1 to 1-30 is 950°C or lower, whereas the primary cooling end temperature of Comparative Example 1-1 is 1000°C. As shown in Table 4, in Examples 1-1 to 1-30, compared to Comparative Example 1-1, the average linear expansion coefficient at 20°C or more and 50°C or less, and the average linear expansion coefficient at 20°C or more and 100°C or less The coefficient of expansion and the average coefficient of linear expansion between 20°C and 150°C are reduced. Specifically, in Examples 1-1 to 1-30, the average linear expansion coefficient at 20°C or more and 50°C or less is 3.51×10 -6 /°C or less (Comparative Example 1-1 is 3.63 ×10 -6 /°C), average linear expansion coefficient at 20°C to 100°C is 3.58 × 10 -6 /°C or less (Comparative Example 1-1 is 3.90 × 10 -6 /°C), 20°C The average linear expansion coefficient at 150°C or lower is 4.09×10 −6 /°C or less (4.28×10 −6 /°C in Comparative Example 1-1). Thus, in Examples 1-1 to 1-30, the thermal expansion of the iron castings can be reduced by setting the primary cooling end temperature to 950° C. or lower (particularly 900° C. or lower).
　（実施例１－１から実施例１－３０と比較例１－２との比較）
　表４に示すように、実施例１－１から実施例１－３０の一次冷却終了温度は２５０℃以上であるのに対して、比較例１－２の一次冷却終了温度は２００℃である。表４に示すように、実施例１－１から実施例１－３０では、比較例１－２と比べて、２０℃以上５０℃以下における平均線膨張係数、２０℃以上１００℃以下における平均線膨張係数および２０℃以上１５０℃以下における平均線膨張係数がそれぞれ低減している。具体的には、実施例１－１から実施例１－３０では、２０℃以上５０℃以下における平均線膨張係数が３．５１×１０－６／℃以下（比較例１－２は４．９８×１０－６／℃）、２０℃以上１００℃以下における平均線膨張係数が３．５８×１０－６／℃以下（比較例１－２は４．８７×１０－６／℃）、２０℃以上１５０℃以下における平均線膨張係数が４．０９×１０－６／℃以下（比較例１－２は４．８７×１０－６／℃）となっている。このように、実施例１－１から実施例１－３０では、一次冷却終了温度を２５０℃以上（特に３００℃以上）にすることにより、鉄鋳物の熱膨張を低減させることができる。 (Comparison of Examples 1-1 to 1-30 and Comparative Example 1-2)
As shown in Table 4, the primary cooling end temperature of Examples 1-1 to 1-30 is 250°C or higher, whereas the primary cooling end temperature of Comparative Example 1-2 is 200°C. As shown in Table 4, in Examples 1-1 to 1-30, compared to Comparative Example 1-2, the average linear expansion coefficient at 20°C or higher and 50°C or lower, and the average linear expansion coefficient at 20°C or higher and 100°C or lower. The coefficient of expansion and the average coefficient of linear expansion between 20°C and 150°C are reduced. Specifically, in Examples 1-1 to 1-30, the average linear expansion coefficient at 20°C or more and 50°C or less is 3.51×10 -6 /°C or less (Comparative Example 1-2 is 4.98 ×10 -6 /°C), average linear expansion coefficient at 20°C to 100°C is 3.58 × 10 -6 /°C or less (4.87 × 10 -6 /°C for Comparative Example 1-2), 20°C The average linear expansion coefficient at 150°C or lower is 4.09×10 −6 /°C or less (comparative example 1-2 is 4.87×10 −6 /°C). As described above, in Examples 1-1 to 1-30, by setting the primary cooling end temperature to 250° C. or higher (particularly 300° C. or higher), the thermal expansion of the iron castings can be reduced.
　（実施例２－１から実施例２－２６と比較例２－１との比較）
　表５に示すように、実施例２－１から実施例２－２６の第２の保持温度は９５０℃以下であるのに対して、比較例２－１の第２の保持温度は１０００℃である。表５に示すように、実施例２－１から実施例２－２６では、比較例２－１と比べて、２０℃以上５０℃以下における平均線膨張係数、２０℃以上１００℃以下における平均線膨張係数および２０℃以上１５０℃以下における平均線膨張係数がそれぞれ低減している。具体的には、実施例２－１から実施例２－２６では、２０℃以上５０℃以下における平均線膨張係数が３．３０×１０－６／℃以下（比較例２－１は３．５４×１０－６／℃）、２０℃以上１００℃以下における平均線膨張係数が３．５５×１０－６／℃以下（比較例２－１は３．７８×１０－６／℃）、２０℃以上１５０℃以下における平均線膨張係数が４．０５×１０－６／℃以下（比較例２－１は４．１５×１０－６／℃）となっている。このように、実施例２－１から実施例２－２６では、第２の保持温度を９５０℃以下（特に９００℃以下）にすることにより、鉄鋳物の熱膨張を低減させることができる。 (Comparison of Examples 2-1 to 2-26 and Comparative Example 2-1)
As shown in Table 5, the second holding temperature of Examples 2-1 to 2-26 is 950°C or lower, whereas the second holding temperature of Comparative Example 2-1 is 1000°C. be. As shown in Table 5, in Examples 2-1 to 2-26, compared to Comparative Example 2-1, the average linear expansion coefficient at 20°C or higher and 50°C or lower, and the average linear expansion coefficient at 20°C or higher and 100°C or lower. The coefficient of expansion and the average coefficient of linear expansion between 20°C and 150°C are reduced. Specifically, in Examples 2-1 to 2-26, the average linear expansion coefficient at 20°C or more and 50°C or less is 3.30×10 -6 /°C or less (Comparative Example 2-1 is 3.54 ×10 -6 /°C), average linear expansion coefficient at 20°C to 100°C is 3.55 × 10 -6 /°C or less (Comparative Example 2-1 is 3.78 × 10 -6 /°C), 20°C Above, the average linear expansion coefficient at 150°C or lower is 4.05×10 −6 /°C or lower (comparative example 2-1 is 4.15×10 −6 /°C). As described above, in Examples 2-1 to 2-26, by setting the second holding temperature to 950° C. or lower (particularly 900° C. or lower), the thermal expansion of the iron castings can be reduced.
　（実施例２－１から実施例２－２６と比較例２－２との比較）
　表５に示すように、実施例２－１から実施例２－２６の第２の保持温度は２５０℃以上であるのに対して、比較例２－２の第２の保持温度は２００℃である。表５に示すように、実施例２－１から実施例２－２６では、比較例２－２と比べて、２０℃以上５０℃以下における平均線膨張係数、２０℃以上１００℃以下における平均線膨張係数および２０℃以上１５０℃以下における平均線膨張係数がそれぞれ低減している。具体的には、実施例２－１から実施例２－２６では、２０℃以上５０℃以下における平均線膨張係数が３．３０×１０－６／℃以下（比較例２－２は５．５７×１０－６／℃）、２０℃以上１００℃以下における平均線膨張係数が３．５５×１０－６／℃以下（比較例２－２は５．４７×１０－６／℃）、２０℃以上１５０℃以下における平均線膨張係数が４．０５×１０－６／℃以下（比較例２－２は５．４０×１０－６／℃）となっている。このように、実施例２－１から実施例２－２６では、第２の保持温度を２５０℃以上（特に３００℃以上）にすることにより、鉄鋳物の熱膨張を低減させることができる。 (Comparison of Examples 2-1 to 2-26 and Comparative Example 2-2)
As shown in Table 5, the second holding temperature of Examples 2-1 to 2-26 is 250°C or higher, whereas the second holding temperature of Comparative Example 2-2 is 200°C. be. As shown in Table 5, in Examples 2-1 to 2-26, compared to Comparative Example 2-2, the average linear expansion coefficient at 20°C or higher and 50°C or lower, and the average linear expansion coefficient at 20°C or higher and 100°C or lower. The coefficient of expansion and the average coefficient of linear expansion between 20°C and 150°C are reduced. Specifically, in Examples 2-1 to 2-26, the average linear expansion coefficient at 20°C or higher and 50°C or lower is 3.30×10 -6 /°C or less (Comparative Example 2-2 is 5.57 ×10 -6 /°C), average linear expansion coefficient at 20°C to 100°C is 3.55 × 10 -6 /°C or less (Comparative Example 2-2 is 5.47 × 10 -6 /°C), 20°C The average linear expansion coefficient at 150°C or lower is 4.05×10 −6 /°C or lower (5.40×10 −6 /°C in Comparative Example 2-2). Thus, in Examples 2-1 to 2-26, by setting the second holding temperature to 250° C. or higher (particularly 300° C. or higher), the thermal expansion of the iron castings can be reduced.
　（実施例３－１から実施例３－１３と比較例３－１との比較）
　表６に示すように、実施例３－１から実施例３－１３の第１の保持温度は８５０℃以上であるのに対して、比較例３－１の第１の保持温度は８００℃である。表６に示すように、実施例３－１から実施例３－１３では、比較例３－１と比べて、２０℃以上５０℃以下における平均線膨張係数、２０℃以上１００℃以下における平均線膨張係数および２０℃以上１５０℃以下における平均線膨張係数がそれぞれ低減している。具体的には、実施例３－１から実施例３－１３では、２０℃以上５０℃以下における平均線膨張係数が３．８０×１０－６／℃以下（比較例３－１は４．５３×１０－６／℃）、２０℃以上１００℃以下における平均線膨張係数が４．１６×１０－６／℃以下（比較例３－１は５．０２×１０－６／℃）、２０℃以上１５０℃以下における平均線膨張係数が４．８４×１０－６／℃以下（比較例３－１は５．５８×１０－６／℃）となっている。このように、実施例３－１から実施例３－１３では、第１の保持温度を８５０℃以上（特に９５０℃以上）にすることにより、鉄鋳物の熱膨張を低減させることができる。 (Comparison of Examples 3-1 to 3-13 and Comparative Example 3-1)
As shown in Table 6, the first holding temperature of Examples 3-1 to 3-13 is 850°C or higher, whereas the first holding temperature of Comparative Example 3-1 is 800°C. be. As shown in Table 6, in Examples 3-1 to 3-13, compared to Comparative Example 3-1, the average linear expansion coefficient at 20°C or higher and 50°C or lower, and the average linear expansion coefficient at 20°C or higher and 100°C or lower. The coefficient of expansion and the average coefficient of linear expansion between 20°C and 150°C are reduced. Specifically, in Examples 3-1 to 3-13, the average linear expansion coefficient at 20°C or higher and 50°C or lower is 3.80×10 -6 /°C or less (Comparative Example 3-1 is 4.53 ×10 -6 /°C), average linear expansion coefficient at 20°C to 100°C is 4.16 × 10 -6 /°C or less (comparative example 3-1 is 5.02 × 10 -6 /°C), 20°C The average linear expansion coefficient at 150°C or lower is 4.84×10 −6 /°C or less (5.58×10 −6 /°C in Comparative Example 3-1). Thus, in Examples 3-1 to 3-13, by setting the first holding temperature to 850° C. or higher (particularly 950° C. or higher), the thermal expansion of the iron castings can be reduced.
　（実施例３－１から実施例３－１３と比較例３－２との比較）
　表６に示すように、実施例３－１から実施例３－１３の第１の保持温度は８５０℃以上であるのに対して、比較例３－２の第１の保持温度は８００℃である。表６に示すように、実施例３－１から実施例３－１３では、比較例３－２と比べて、２０℃以上５０℃以下における平均線膨張係数および２０℃以上１００℃以下における平均線膨張係数がそれぞれ低減している。具体的には、実施例３－１から実施例３－１３では、２０℃以上５０℃以下における平均線膨張係数が３．８０×１０－６／℃以下（比較例３－２は３．８９×１０－６／℃）、２０℃以上１００℃以下における平均線膨張係数が４．１６×１０－６／℃以下（比較例３－２は４．１７×１０－６／℃）となっている。このように、実施例３－１から実施例３－１３では、第１の保持温度を８５０℃以上（特に９５０℃以上）にすることにより、鉄鋳物の熱膨張を低減させることができる。 (Comparison of Examples 3-1 to 3-13 and Comparative Example 3-2)
As shown in Table 6, the first holding temperature of Examples 3-1 to 3-13 is 850°C or higher, whereas the first holding temperature of Comparative Example 3-2 is 800°C. be. As shown in Table 6, in Examples 3-1 to 3-13, compared to Comparative Example 3-2, the average linear expansion coefficient at 20°C or more and 50°C or less and the average linear expansion coefficient at 20°C or more and 100°C or less The expansion coefficients are respectively reduced. Specifically, in Examples 3-1 to 3-13, the average linear expansion coefficient at 20°C or more and 50°C or less is 3.80 × 10 -6 /°C or less (Comparative Example 3-2 is 3.89 ×10 -6 /°C), and the average linear expansion coefficient at temperatures above 20°C and below 100°C was 4.16 × 10 -6 /°C or less (comparative example 3-2 was 4.17 × 10 -6 /°C). There is. Thus, in Examples 3-1 to 3-13, by setting the first holding temperature to 850° C. or higher (particularly 950° C. or higher), the thermal expansion of the iron castings can be reduced.
　（実施例３－１から実施例３－１３と比較例３－３との比較）
　表６に示すように、実施例３－１から実施例３－１３の第１の保持温度は１２５０℃以下であるのに対して、比較例３－３の第１の保持温度は１３００℃である。表６に示すように、実施例３－１から実施例３－１３では、比較例３－３と比べて、２０℃以上５０℃以下における平均線膨張係数、２０℃以上１００℃以下における平均線膨張係数および２０℃以上１５０℃以下における平均線膨張係数がそれぞれ低減している。具体的には、実施例３－１から実施例３－１３では、２０℃以上５０℃以下における平均線膨張係数が３．８０×１０－６／℃以下（比較例３－３は５．８７×１０－６／℃）、２０℃以上１００℃以下における平均線膨張係数が４．１６×１０－６／℃以下（比較例３－３は５．７２×１０－６／℃）、２０℃以上１５０℃以下における平均線膨張係数が４．８４×１０－６／℃以下（比較例３－３は５．６７×１０－６／℃）となっている。このように、実施例３－１から実施例３－１３では、第１の保持温度を１２５０℃以下（特に１２００℃以下）にすることにより、鉄鋳物の熱膨張を低減させることができる。 (Comparison of Examples 3-1 to 3-13 and Comparative Example 3-3)
As shown in Table 6, the first holding temperature of Examples 3-1 to 3-13 is 1250°C or lower, whereas the first holding temperature of Comparative Example 3-3 is 1300°C. be. As shown in Table 6, in Examples 3-1 to 3-13, compared to Comparative Example 3-3, the average linear expansion coefficient at 20°C or higher and 50°C or lower, and the average linear expansion coefficient at 20°C or higher and 100°C or lower. The coefficient of expansion and the average coefficient of linear expansion between 20°C and 150°C are reduced. Specifically, in Examples 3-1 to 3-13, the average linear expansion coefficient at 20°C or more and 50°C or less is 3.80 × 10 -6 /°C or less (Comparative Example 3-3 is 5.87 ×10 -6 /°C), average linear expansion coefficient at 20°C to 100°C is 4.16 × 10 -6 /°C or less (Comparative Example 3-3 is 5.72 × 10 -6 /°C), 20°C Above, the average linear expansion coefficient at 150°C or lower is 4.84×10 −6 /°C or less (comparative example 3-3 is 5.67×10 −6 /°C). As described above, in Examples 3-1 to 3-13, by setting the first holding temperature to 1250° C. or lower (particularly 1200° C. or lower), the thermal expansion of the iron castings can be reduced.
　（実施例３－９と比較例３－１および比較例３－３との比較）
　表３に示すように、実施例３－９、比較例３－１および比較例３－３の鋳造用材料は、Ｃｏを含有しない。また、表６に示すように、実施例３－９の第１の保持温度は８５０℃以上１２５０℃以下であるのに対して、比較例３－１の第１の保持温度は８００℃であり、比較例３－３の第１の保持温度は１３００℃である。表６に示すように、いずれもＣｏを含有しない、実施例３－９と比較例３－１および比較例３－３とを比較すると、実施例３－９では、比較例３－１および比較例３－３と比べて、２０℃以上１５０℃以下における平均線膨張係数が低減している。具体的には、実施例３－９では、２０℃以上１５０℃以下における平均線膨張係数が４．８４×１０－６／℃以下（比較例３－１は５．５８×１０－６／℃、比較例３－３は５．６７×１０－６／℃）となっている。このように、実施例３－９では、Ｃｏを含有させず、かつ、第１の保持温度を８５０℃以上１２５０℃以下にすることにより、高温における鉄鋳物の熱膨張を低減させることができる。 (Comparison of Example 3-9 and Comparative Example 3-1 and Comparative Example 3-3)
As shown in Table 3, the casting materials of Example 3-9, Comparative Example 3-1, and Comparative Example 3-3 do not contain Co. Further, as shown in Table 6, the first holding temperature in Example 3-9 is 850°C or more and 1250°C or less, whereas the first holding temperature in Comparative Example 3-1 is 800°C. , the first holding temperature of Comparative Example 3-3 is 1300°C. As shown in Table 6, when comparing Example 3-9 with Comparative Example 3-1 and Comparative Example 3-3, both of which do not contain Co, it is found that in Example 3-9, Comparative Example 3-1 and Comparative Example 3-3 do not contain Co. Compared to Example 3-3, the average coefficient of linear expansion at temperatures above 20°C and below 150°C is reduced. Specifically, in Example 3-9, the average linear expansion coefficient at 20°C or higher and 150°C or lower is 4.84×10 -6 /°C or less (Comparative Example 3-1 is 5.58×10 -6 /°C , Comparative Example 3-3 was 5.67×10 −6 /°C). As described above, in Example 3-9, the thermal expansion of the iron casting at high temperatures can be reduced by not containing Co and by setting the first holding temperature to 850° C. or more and 1250° C. or less.
　（実施例３－１から実施例３－８および実施例３－１０から実施例３－１３と比較例３－２との比較）
　表３に示すように、実施例３－１から実施例３－８、実施例３－１０から実施例３－１３および比較例３－２の鋳造用材料は、Ｃｏを含有する。また、表６に示すように、実施例３－１から実施例３－８および実施例３－１０から実施例３－１３の第１の保持温度は８５０℃以上１２５０℃以下であるのに対して、比較例３－２の第１の保持温度は８００℃である。表６に示すように、いずれもＣｏを含有する、実施例３－１から実施例３－８および実施例３－１０から実施例３－１３と比較例３－２とを比較すると、実施例３－１から実施例３－８および実施例３－１０から実施例３－１３では、比較例３－２と比べて、２０℃以上１５０℃以下における平均線膨張係数が低減している。具体的には、実施例３－１から実施例３－８および実施例３－１０から実施例３－１３では、２０℃以上１５０℃以下における平均線膨張係数が４．４９×１０－６／℃以下（比較例３－２は４．５３×１０－６／℃）となっている。このように、実施例３－１から実施例３－８および実施例３－１０から実施例３－１３では、Ｃｏを含有させ、かつ、第１の保持温度を８５０℃以上１２５０℃以下にすることにより、高温における鉄鋳物の熱膨張を低減させることができる。 (Comparison of Examples 3-1 to 3-8, Examples 3-10 to 3-13, and Comparative Example 3-2)
As shown in Table 3, the casting materials of Examples 3-1 to 3-8, Examples 3-10 to 3-13, and Comparative Example 3-2 contain Co. Further, as shown in Table 6, the first holding temperature of Examples 3-1 to 3-8 and Examples 3-10 to 3-13 is 850°C or more and 1250°C or less. Therefore, the first holding temperature of Comparative Example 3-2 is 800°C. As shown in Table 6, when Comparative Example 3-2 is compared with Examples 3-1 to 3-8 and Examples 3-10 to 3-13, all of which contain Co, In Examples 3-1 to 3-8 and Examples 3-10 to 3-13, the average linear expansion coefficients at 20° C. or higher and 150° C. or lower are reduced compared to Comparative Example 3-2. Specifically, in Examples 3-1 to 3-8 and Examples 3-10 to 3-13, the average linear expansion coefficient at 20°C or higher and 150°C or lower is 4.49×10 -6 / ℃ or less (comparative example 3-2 was 4.53×10 −6 /℃). In this way, in Examples 3-1 to 3-8 and Examples 3-10 to 3-13, Co is contained and the first holding temperature is set to 850°C or more and 1250°C or less. This makes it possible to reduce the thermal expansion of iron castings at high temperatures.
　なお、本開示は、下記の構成をとることもできる。
　（１）
　オーステナイト系の鋳造用材料を用いて鋳造した熱処理対象物に対して第１の熱処理を行うことにより得られる鉄鋳物であって、
　前記第１の熱処理を行うことは、前記熱処理対象物を９５０℃以上１２００℃以下の第１の温度範囲で保持することを含む、鉄鋳物。
　（２）
　前記第１の温度範囲で保持することは、前記熱処理対象物を１時間以上１００時間以下の時間範囲で保持することを含む、（１）に記載の鉄鋳物。
　（３）
　前記第１の熱処理を行うことの後に、前記熱処理対象物に対して第２の熱処理を行うことをさらに含み、
　前記第２の熱処理を行うことは、前記熱処理対象物を３００℃以上９００℃以下の第２の温度範囲まで冷却することを含む、（１）または（２）に記載の鉄鋳物。
　（４）
　前記第２の温度範囲まで冷却することは、前記熱処理対象物を０．０１℃／分以上２０℃／分以下の冷却速度範囲で冷却することを含む、（３）に記載の鉄鋳物。
　（５）
　前記第２の熱処理を行うことの後に、前記熱処理対象物に対して第３の熱処理を行うことをさらに含み、
　前記第３の熱処理を行うことは、前記熱処理対象物を０℃以上１００℃以下の第３の温度範囲まで冷却することを含む、（３）または（４）に記載の鉄鋳物。
　（６）
　前記第３の温度範囲まで冷却することは、前記熱処理対象物を１℃／秒以上１０００℃／秒以下の冷却速度範囲で冷却することを含む、（５）に記載の鉄鋳物。
　（７）
　前記鋳造用材料は、２６．０質量％以上４２．０質量％以下のＮｉを含み、残部がＦｅおよび不可避元素である、（１）から（６）のいずれか一項に記載の鉄鋳物。
　（８）
　前記鋳造用材料は、０．３質量％以上３．５質量％以下のＣをさらに含む、（７）に記載の鉄鋳物。
　（９）
　前記鋳造用材料は、０．１質量％以上３．０質量％以下のＳｉをさらに含む、（７）または（８）に記載の鉄鋳物。
　（１０）
　前記鋳造用材料は、０．００１質量％以上８．０質量％以下のＣｏをさらに含む、（７）から（９）のいずれか一項に記載の鉄鋳物。
　（１１）
　オーステナイト系の鋳造用材料を用いて鋳造した熱処理対象物に対して第１の熱処理を行うことを含む鉄鋳物の製造方法であって、
　前記第１の熱処理を行うことは、前記熱処理対象物を９５０℃以上１２００℃以下の第１の温度範囲で保持することを含む、製造方法。
　（１２）
　前記第１の温度範囲で保持することは、前記熱処理対象物を１時間以上１００時間以下の時間範囲で保持することを含む、（１１）に記載の製造方法。
　（１３）
　前記第１の熱処理を行うことの後に、前記熱処理対象物に対して第２の熱処理を行うことをさらに含み、
　前記第２の熱処理を行うことは、前記熱処理対象物を３００℃以上９００℃以下の第２の温度範囲まで冷却することを含む、（１１）または（１２）に記載の製造方法。
　（１４）
　前記第２の温度範囲まで冷却することは、前記熱処理対象物を０．０１℃／分以上２０℃／分以下の冷却速度範囲で冷却することを含む、（１３）に記載の製造方法。
　（１５）
　前記第２の熱処理を行うことの後に、前記熱処理対象物に対して第３の熱処理を行うことをさらに含み、
　前記第３の熱処理を行うことは、前記熱処理対象物を０℃以上１００℃以下の第３の温度範囲まで冷却することを含む、（１３）または（１４）に記載の製造方法。
　（１６）
　前記第３の温度範囲まで冷却することは、前記熱処理対象物を１℃／秒以上１０００℃／秒以下の冷却速度範囲で冷却することを含む、（１５）に記載の製造方法。 Note that the present disclosure can also have the following configuration.
(1)
An iron casting obtained by performing a first heat treatment on a heat treatment object cast using an austenitic casting material,
The iron casting, wherein performing the first heat treatment includes maintaining the heat treatment object at a first temperature range of 950°C or more and 1200°C or less.
(2)
The iron casting according to (1), wherein holding in the first temperature range includes holding the heat treatment object for a time range of 1 hour or more and 100 hours or less.
(3)
Further comprising performing a second heat treatment on the object to be heat treated after performing the first heat treatment,
The iron casting according to (1) or (2), wherein performing the second heat treatment includes cooling the object to be heat treated to a second temperature range of 300°C or higher and 900°C or lower.
(4)
The iron casting according to (3), wherein cooling to the second temperature range includes cooling the heat-treated object at a cooling rate range of 0.01° C./min to 20° C./min.
(5)
Further comprising performing a third heat treatment on the heat treatment target after performing the second heat treatment,
The iron casting according to (3) or (4), wherein performing the third heat treatment includes cooling the heat treatment object to a third temperature range of 0° C. or more and 100° C. or less.
(6)
The iron casting according to (5), wherein cooling to the third temperature range includes cooling the heat treatment object at a cooling rate range of 1° C./second to 1000° C./second.
(7)
The iron casting according to any one of (1) to (6), wherein the casting material contains 26.0% by mass or more and 42.0% by mass or less of Ni, and the remainder is Fe and unavoidable elements.
(8)
The iron casting according to (7), wherein the casting material further contains 0.3% by mass or more and 3.5% by mass or less of C.
(9)
The iron casting according to (7) or (8), wherein the casting material further contains 0.1% by mass or more and 3.0% by mass or less of Si.
(10)
The iron casting according to any one of (7) to (9), wherein the casting material further contains 0.001% by mass or more and 8.0% by mass or less of Co.
(11)
A method for producing iron castings, the method comprising performing a first heat treatment on a heat treatment object cast using an austenitic casting material,
The manufacturing method, wherein performing the first heat treatment includes maintaining the heat treatment target at a first temperature range of 950°C or higher and 1200°C or lower.
(12)
The manufacturing method according to (11), wherein holding the object in the first temperature range includes holding the object to be heat treated for a time range of 1 hour or more and 100 hours or less.
(13)
Further comprising performing a second heat treatment on the heat treatment target after performing the first heat treatment,
The manufacturing method according to (11) or (12), wherein performing the second heat treatment includes cooling the object to be heat treated to a second temperature range of 300°C or higher and 900°C or lower.
(14)
The manufacturing method according to (13), wherein cooling to the second temperature range includes cooling the heat treatment target at a cooling rate range of 0.01° C./min to 20° C./min.
(15)
Further comprising performing a third heat treatment on the heat treatment target after performing the second heat treatment,
The manufacturing method according to (13) or (14), wherein performing the third heat treatment includes cooling the heat treatment object to a third temperature range of 0° C. or higher and 100° C. or lower.
(16)
The manufacturing method according to (15), wherein cooling to the third temperature range includes cooling the heat treatment object at a cooling rate range of 1° C./second to 1000° C./second.

Claims (27)

  1. 　オーステナイト系の鋳造用材料を用いて鋳造した熱処理対象物に対して熱処理を行うことにより鉄鋳物を製造する方法であって、
    　前記鋳造用材料は、２６．０質量％以上５０．０質量％以下のＮｉと、０．１質量％以上３．５質量％以下のＣと、０．１質量％以上３．５質量％以下のＳｉと、０質量％以上８．０質量％以下のＣｏと、０質量％以上３．０質量％以下のＭｎと、０質量％以上０．２質量％以下のＭｇとを含み、残部がＦｅおよび不可避元素であり、
    　前記熱処理は、
    　前記熱処理対象物を８５０℃以上１２５０℃以下の第１の保持温度で保持する第１の保持工程と、
    　前記第１の保持工程の後に、前記熱処理対象物を－１５０℃以上１５０℃以下の第１の冷却終了温度まで冷却する第１の冷却工程と、
    　を含み、
    　前記第１の保持工程は、前記熱処理対象物を０．２５時間以上１００時間以下の第１の保持時間で保持することを含む、方法。     A method for manufacturing iron castings by heat-treating a heat-treated object cast using an austenitic casting material, the method comprising:
    The casting material contains Ni of 26.0% by mass or more and 50.0% by mass or less, C of 0.1% by mass or more and 3.5% by mass or less, and 0.1% by mass or more and 3.5% by mass or less. of Si, 0 mass% to 8.0 mass% Co, 0 mass% to 3.0 mass% Mn, and 0 mass% to 0.2 mass% Mg, with the balance being Fe and inevitable elements,
    The heat treatment is
    a first holding step of holding the heat-treated object at a first holding temperature of 850° C. or higher and 1250° C. or lower;
    After the first holding step, a first cooling step of cooling the heat treatment object to a first cooling end temperature of −150° C. or higher and 150° C. or lower;
    including;
    The method, wherein the first holding step includes holding the heat treatment object for a first holding time of 0.25 hours or more and 100 hours or less.
  2. 　請求項１において、
    　前記第１の冷却工程は、前記熱処理対象物を０．０１℃／分以上３００℃／分以下の第１の冷却速度で冷却することを含む、方法。     In claim 1,
    The method, wherein the first cooling step includes cooling the heat treatment object at a first cooling rate of 0.01° C./min or more and 300° C./min or less.
  3. 　請求項２において、
    　前記第１の冷却速度は、０．０１℃／分以上２０℃／分以下である、方法。     In claim 2,
    The method, wherein the first cooling rate is 0.01°C/min or more and 20°C/min or less.
  4. 　請求項１から３のいずれか一項において、
    　前記第１の保持時間は、２．５時間以上２５時間以下である、方法。     In any one of claims 1 to 3,
    The method, wherein the first holding time is 2.5 hours or more and 25 hours or less.
  5. 　請求項１から４のいずれか一項において、
    　前記第１の冷却終了温度は、０℃以上１００℃以下である、方法。     In any one of claims 1 to 4,
    The method, wherein the first cooling end temperature is 0°C or more and 100°C or less.
  6. 　請求項１において、
    　前記第１の冷却工程は、
    　前記熱処理対象物を一次冷却速度で冷却する一次冷却工程と、
    　前記一次冷却工程の後に、前記熱処理対象物を前記一次冷却速度よりも大きい二次冷却速度で冷却する二次冷却工程と、
    　を含み、
    　前記一次冷却工程は、前記熱処理対象物を２５０℃以上９５０℃以下の一次冷却終了温度まで冷却することを含み、
    　前記二次冷却工程は、前記熱処理対象物を前記第１の冷却終了温度まで冷却することを含む、方法。     In claim 1,
    The first cooling step includes:
    a primary cooling step of cooling the heat treatment target at a primary cooling rate;
    After the primary cooling process, a secondary cooling process in which the heat treatment target is cooled at a secondary cooling rate that is higher than the primary cooling rate;
    including;
    The primary cooling step includes cooling the heat treatment object to a primary cooling end temperature of 250° C. or more and 950° C. or less,
    The method, wherein the secondary cooling step includes cooling the heat treatment object to the first cooling end temperature.
  7. 　請求項６において、
    　前記一次冷却速度は、０．０１℃／分以上２０℃／分以下であり、
    　前記二次冷却速度は、１℃／分以上４００００℃／分以下である、方法。     In claim 6,
    The primary cooling rate is 0.01°C/min or more and 20°C/min or less,
    The method, wherein the secondary cooling rate is 1°C/min or more and 40000°C/min or less.
  8. 　請求項７において、
    　前記二次冷却速度は、１００℃／分以上４００００℃／分以下である、方法。     In claim 7,
    The method, wherein the secondary cooling rate is 100°C/min or more and 40000°C/min or less.
  9. 　請求項６から８のいずれか一項において、
    　前記第１の保持時間は、２．５時間以上２５時間以下である、方法。     In any one of claims 6 to 8,
    The method, wherein the first holding time is 2.5 hours or more and 25 hours or less.
  10. 　請求項６から９のいずれか一項において、
    　前記一次冷却終了温度は、４５０℃以上８５０℃以下である、方法。     In any one of claims 6 to 9,
    The method, wherein the primary cooling end temperature is 450°C or more and 850°C or less.
  11. 　請求項６から１０のいずれか一項において、
    　前記第１の冷却終了温度は、０℃以上１００℃以下である、方法。     In any one of claims 6 to 10,
    The method, wherein the first cooling end temperature is 0°C or more and 100°C or less.
  12. 　請求項１において、
    　前記熱処理は、
    　前記第１の冷却工程の後に、前記熱処理対象物を２５０℃以上９５０℃以下の第２の保持温度で保持する第２の保持工程と、
    　前記第２の保持工程の後に、前記熱処理対象物を－１５０℃以上１５０℃以下の第２の冷却終了温度まで冷却する第２の冷却工程と、
    　をさらに含み、
    　前記第２の保持工程は、前記熱処理対象物を０．２５時間以上２５時間以下の第２の保持時間で保持することを含む、方法。     In claim 1,
    The heat treatment is
    After the first cooling step, a second holding step of holding the heat treatment target at a second holding temperature of 250° C. or more and 950° C. or less;
    After the second holding step, a second cooling step of cooling the heat treatment object to a second cooling end temperature of −150° C. or higher and 150° C. or lower;
    further including;
    The second holding step includes holding the heat-treated object for a second holding time of 0.25 hours or more and 25 hours or less.
  13. 　請求項１２において、
    　前記第１の冷却工程は、前記熱処理対象物を０．０１℃／分以上３００℃／分以下の第１の冷却速度で冷却することを含む、方法。     In claim 12,
    The method, wherein the first cooling step includes cooling the heat treatment object at a first cooling rate of 0.01° C./min or more and 300° C./min or less.
  14. 　請求項１３において、
    　前記第１の冷却速度は、１℃／分以上５０℃／分以下である、方法。     In claim 13,
    The method, wherein the first cooling rate is 1° C./min or more and 50° C./min or less.
  15. 　請求項１２から１４のいずれか一項において、
    　前記第２の冷却工程は、前記熱処理対象物を１℃／分以上４００００℃／分以下の第２の冷却速度で冷却することを含む、方法。     In any one of claims 12 to 14,
    The second cooling step includes cooling the heat treatment object at a second cooling rate of 1° C./min or more and 40,000° C./min or less.
  16. 　請求項１５において、
    　前記第２の冷却速度は、１００℃／分以上１００００℃／分以下である、方法。     In claim 15,
    The method, wherein the second cooling rate is 100° C./min or more and 10000° C./min or less.
  17. 　請求項１２から１６のいずれか一項において、
    　前記第１の保持時間は、２．５時間以上２５時間以下である、方法。     In any one of claims 12 to 16,
    The method, wherein the first holding time is 2.5 hours or more and 25 hours or less.
  18. 　請求項１２から１７のいずれか一項において、
    　前記第１の冷却終了温度は、０℃以上１００℃以下である、方法。     In any one of claims 12 to 17,
    The method, wherein the first cooling end temperature is 0°C or more and 100°C or less.
  19. 　請求項１２から１８のいずれか一項において、
    　前記第２の保持温度は、５５０℃以上９５０℃以下である、方法。     In any one of claims 12 to 18,
    The method, wherein the second holding temperature is 550°C or more and 950°C or less.
  20. 　請求項１２から１９のいずれか一項において、
    　前記第２の冷却終了温度は、０℃以上５０℃以下である、方法。     In any one of claims 12 to 19,
    The method, wherein the second cooling end temperature is 0°C or more and 50°C or less.
  21. 　請求項１から２０のいずれか一項において、
    　前記鋳造用材料のＣｏの含有量は、０．１質量％以上８．０質量％以下である、方法。     In any one of claims 1 to 20,
    The method, wherein the Co content of the casting material is 0.1% by mass or more and 8.0% by mass or less.
  22. 　請求項１から２１のいずれか一項において、
    　前記鋳造用材料のＭｎの含有量は、０．０１質量％以上３．０質量％以下である、方法。     In any one of claims 1 to 21,
    The method, wherein the Mn content of the casting material is 0.01% by mass or more and 3.0% by mass or less.
  23. 　請求項１から２２のいずれか一項において、
    　前記鋳造用材料のＭｇの含有量は、０．０１質量％以上０．２質量％以下である、方法。     In any one of claims 1 to 22,
    The Mg content of the casting material is 0.01% by mass or more and 0.2% by mass or less.
  24. 　オーステナイト系の鋳造用材料を用いて鋳造した熱処理対象物に対して熱処理を行うことにより鉄鋳物を製造する方法であって、
    　前記熱処理は、
    　前記熱処理対象物を８５０℃以上１２５０℃以下の第１の保持温度で保持する第１の保持工程と、
    　前記第１の保持工程の後に、前記熱処理対象物を－１５０℃以上１５０℃以下の第１の冷却終了温度まで冷却する第１の冷却工程と、
    　を含み、
    　前記第１の保持工程は、前記熱処理対象物を０．２５時間以上１００時間以下の第１の保持時間で保持することを含む、方法。     A method for manufacturing iron castings by heat-treating a heat-treated object cast using an austenitic casting material, the method comprising:
    The heat treatment is
    a first holding step of holding the heat-treated object at a first holding temperature of 850° C. or higher and 1250° C. or lower;
    After the first holding step, a first cooling step of cooling the heat treatment object to a first cooling end temperature of −150° C. or higher and 150° C. or lower;
    including;
    The method, wherein the first holding step includes holding the heat treatment object for a first holding time of 0.25 hours or more and 100 hours or less.
  25. 　請求項２４において、
    　前記第１の冷却工程は、
    　前記熱処理対象物を一次冷却速度で冷却する一次冷却工程と、
    　前記一次冷却工程の後に、前記熱処理対象物を前記一次冷却速度よりも大きい二次冷却速度で冷却する二次冷却工程と、
    　を含み、
    　前記一次冷却工程は、前記熱処理対象物を２５０℃以上９５０℃以下の一次冷却終了温度まで冷却することを含み、
    　前記二次冷却工程は、前記熱処理対象物を前記第１の冷却終了温度まで冷却することを含む、方法。     In claim 24,
    The first cooling step includes:
    a primary cooling step of cooling the heat treatment target at a primary cooling rate;
    After the primary cooling process, a secondary cooling process in which the heat treatment target is cooled at a secondary cooling rate that is higher than the primary cooling rate;
    including;
    The primary cooling step includes cooling the heat treatment object to a primary cooling end temperature of 250° C. or more and 950° C. or less,
    The method, wherein the secondary cooling step includes cooling the heat treatment object to the first cooling end temperature.
  26. 　請求項２４において、
    　前記熱処理は、
    　前記第１の冷却工程の後に、前記熱処理対象物を２５０℃以上９５０℃以下の第２の保持温度で保持する第２の保持工程と、
    　前記第２の保持工程の後に、前記熱処理対象物を－１５０℃以上１５０℃以下の第２の冷却終了温度まで冷却する第２の冷却工程と、
    　をさらに含み、
    　前記第２の保持工程は、前記熱処理対象物を０．２５時間以上２５時間以下の第２の保持時間で保持することを含む、方法。     In claim 24,
    The heat treatment is
    After the first cooling step, a second holding step of holding the heat treatment target at a second holding temperature of 250° C. or more and 950° C. or less;
    After the second holding step, a second cooling step of cooling the heat treatment object to a second cooling end temperature of −150° C. or higher and 150° C. or lower;
    further including;
    The second holding step includes holding the heat-treated object for a second holding time of 0.25 hours or more and 25 hours or less.
  27. 　請求項１から２６のいずれか一項に記載の方法を用いて製造された鉄鋳物。 An iron casting manufactured using the method according to any one of claims 1 to 26.
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JPH04141545A (en) * 1990-10-01 1992-05-15 Kurimoto Ltd High temperature low thermal expansion cast iron
JP2000119793A (en) * 1998-10-13 2000-04-25 Toshiba Corp Low expansion cast iron with low temperature stability, and its manufacture
JP2003138336A (en) * 2001-10-31 2003-05-14 Kogi Corp Low thermal expansion cast steel
JP2019173110A (en) * 2018-03-29 2019-10-10 虹技株式会社 Spheroidal graphite cast iron and manufacturing method therefor

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