WO2021199370A1 - Method for manufacturing iron-based sintered body - Google Patents

Method for manufacturing iron-based sintered body Download PDF

Info

Publication number
WO2021199370A1
WO2021199370A1 PCT/JP2020/014983 JP2020014983W WO2021199370A1 WO 2021199370 A1 WO2021199370 A1 WO 2021199370A1 JP 2020014983 W JP2020014983 W JP 2020014983W WO 2021199370 A1 WO2021199370 A1 WO 2021199370A1
Authority
WO
WIPO (PCT)
Prior art keywords
sintered body
iron
dewaxing
sintering
atmosphere
Prior art date
Application number
PCT/JP2020/014983
Other languages
French (fr)
Japanese (ja)
Inventor
史有 赤池
智之 小比田
和夫 岩崎
Original Assignee
昭和電工マテリアルズ株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 昭和電工マテリアルズ株式会社 filed Critical 昭和電工マテリアルズ株式会社
Priority to PCT/JP2020/014983 priority Critical patent/WO2021199370A1/en
Priority to JP2022511433A priority patent/JPWO2021199370A1/ja
Publication of WO2021199370A1 publication Critical patent/WO2021199370A1/en

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only

Definitions

  • One embodiment of the present invention relates to a method for producing an iron-based sintered body.
  • the so-called powder metallurgy method in which the green compact obtained by compression molding the raw material powder in a mold is sintered, can be formed into a near-net shape, so that the cutting allowance due to subsequent machining is small and the material loss is small.
  • it is economical because it is possible to mass-produce products of the same shape once a mold is manufactured.
  • the powder metallurgy method has a wide range of alloy designs because it can produce a special alloy that cannot be obtained with an alloy produced by ordinary melting. Therefore, it is widely applied to machine parts such as automobile parts.
  • a sintered body can be obtained by molding a raw material powder such as an iron-based alloy by various molding methods and sintering the obtained molded body.
  • a molded product can be obtained by using a mixed powder in which a lubricant is added to the raw material powder in order to improve the moldability. Since the lubricant contained in the molded product is mainly an organic component, it can be thermally decomposed and removed from the sintered body in the subsequent heat treatment. Before heat-treating the molded body at a high temperature for sintering, there is a method of heat-treating at a relatively low temperature to remove the lubricant or the like from the molded body by thermal decomposition.
  • dewaxing methods there is a method of supplying butane gas to a sintering furnace, burning it with a burner, and directly heating the molded body with the combustion exhaust gas.
  • this method has a problem that it is difficult to control the atmosphere in the furnace so as to be heated uniformly. If the atmosphere in the furnace is uniform, dewaxing can be controlled more accurately, so that lubricant and the like can be appropriately removed from the molded body during dewaxing, and a homogeneous composition can be obtained in the obtained sintered body. Obtainable.
  • Patent Document 1 Japanese Unexamined Patent Publication No. 8-2600002
  • dew point control is performed in dew point control and sintering of an iron-based powder compact in order to prevent MnS-derived stains from being generated on the surface of the sintered body. It is proposed to do.
  • One object of the present invention is to produce an iron-based sintered body having less surface contamination.
  • the dewazing includes removing the raw material powder containing the iron-based powder and the molded product containing zinc stearate, and sintering the dew pointed molded product, and the dew pointing contains nitrogen and water vapor.
  • a water vapor-containing nitrogen atmosphere having a dew point of 0 ° C. or higher and 30 ° C. or lower, to heat the steam-containing nitrogen atmosphere to 100 ° C. or higher and supply it to a dewaxed portion, and to supply the molded product to the dewaxed portion at the dewaked portion.
  • a method for producing an iron-based sintered body which comprises heat-treating the iron-based sintered body at 800 ° C. or lower.
  • FIG. 1 is a schematic cross-sectional view of the dewaxing furnace of the roller hearth furnace used in the examples.
  • FIG. 2 is a photograph of the metal structure of the sintered body of the example observed by a scanning electron microscope (SEM).
  • a method for producing an iron-based sintered body includes removing a raw material powder containing iron-based powder and a molded product containing zinc stearate, and sintering the de-fused molded product.
  • the wax contains nitrogen and water vapor, and prepares a water vapor-containing nitrogen atmosphere having a dew point of 0 ° C. or higher and 30 ° C. or lower, heats the water vapor-containing nitrogen atmosphere to 100 ° C. or higher and supplies it to the dewaxed portion. It is characterized by including heat-treating the molded product at 800 ° C. or lower at the dewaxed portion. According to this, it is possible to produce an iron-based sintered body having less surface stains. Further, according to one embodiment, the strength of the sintered body can be further increased.
  • the thermal decomposition of zinc stearate contained in the molded body is promoted, and the stain on the surface of the obtained sintered body is reduced. can do. Dirt remaining on the surface of the sintered body is mainly observed by organic components such as zinc stearate remaining on the surface of the sintered body.
  • a certain amount of carbon component remains in the obtained sintered body, and the formation of the ferrite phase is suppressed. Therefore, the strength of the sintered body can be further increased.
  • the gas type and dew point of the atmosphere in which the molded body is to be removed since it is only necessary to specify the gas type and dew point of the atmosphere in which the molded body is to be removed, it is possible to heat the inside of the furnace more uniformly in addition to burner combustion as a heat source for the heat treatment for removing the molded body.
  • An indirect heating method such as a radiant tube burner can be used. Therefore, the temperature inside the furnace can be controlled more easily.
  • the molded product can include a raw material powder containing an iron-based powder and zinc stearate.
  • the iron-based powder may be an iron powder, an iron alloy powder, or a combination thereof.
  • the iron-based powder may contain unavoidable impurities.
  • the overall composition preferably contains iron as a main component.
  • iron is preferably 50% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more.
  • the overall composition may contain Cu and the balance may be iron.
  • Cu is preferably contained in an amount of more than 0% by mass and 20% by mass or less with respect to the total amount of the raw material powder.
  • Cu has the effect of diffusing into Fe to increase the material strength. Part of Cu diffuses into the base of Fe during sintering, and part of Cu melts and mixes with Fe to form a copper alloy. Therefore, when the sintered alloy is cooled, the structure is dispersed in the base of the iron-based sintered body in the form of a copper phase or a copper alloy phase.
  • Cu when used in combination with C, it improves the hardenability of the iron matrix to make pearlite finer to increase the strength, and at the time of sintering, it produces high-strength bainite and martensite at a normal cooling rate. It can be promoted to obtain.
  • Cu is not an essential element, but is preferably 0.01% or more, more preferably 0.1% or more, still more preferably 1% or more.
  • Cu is preferably 20% or less, more preferably 15% or less, from the viewpoint of preventing a decrease in material strength. Further, Cu is preferably 10% or less, more preferably 5% or less, still more preferably 3% or less. As a result, the generation of a soft Cu phase can be suppressed to further prevent a decrease in material strength, and the generation of a Cu liquid phase during sintering can be suppressed to further improve the dimensional accuracy of the entire product. Can be enhanced.
  • the overall composition may further include C.
  • C is preferably contained in an amount of more than 0% by mass and 5% by mass or less. A part of C can be dissolved in Fe to improve its strength. If C is excessively blended, there is a problem that brittle cementite is deposited in a network shape. Therefore, C is preferably 0 to 5%, more preferably 0.1 to 3%, and even more preferably 0.5 to 1%. Further, it is preferable that the entire amount of C is precipitated as a solid solution or metal carbide in the matrix. This metal carbide is preferably dispersed and contained in the matrix.
  • the overall composition may contain at least one selected from the group consisting of Cr, Mn, Mo, W, Ni, Co, V, and Nb.
  • each element is preferably contained in an amount of 15% by mass or less as a total amount, more preferably 10% by mass or less, and further preferably 5% by mass or less.
  • the overall composition may further contain Si, P, S, O, N and the like alone or in combination of two or more.
  • Cu can be blended with the raw material powder as an iron alloy powder. Further, Cu can be blended with the raw material powder as a copper powder, a copper alloy powder, or a combination thereof.
  • the metal other than Cu is at least one selected from the group consisting of, for example, iron and Cr, Mn, Mo, W, Ni, Co, V, and Nb as the iron alloy powder to be blended in the raw material powder. Can be blended as an alloy powder with. Further, metals other than Cu can be blended as metal powders of these metals alone.
  • C can be blended with the raw material powder in a solid solution state in the iron powder and / or the iron alloy powder. Further, C can be blended with the raw material powder as a graphite powder in order to increase the compressibility of the molded product. Further, C can be blended in the raw material powder as an organic component such as zinc stearate. Organic components such as zinc stearate are thermally decomposed by dewaxing and sintering, but it is considered that a part of C remains in the sintered body and dissolves in the iron matrix.
  • the raw material powder may contain unavoidable impurities.
  • the total amount of unavoidable impurities is preferably 1% by mass or less, more preferably 0.5% by mass or less, still more preferably 0.1% by mass or less, based on the total amount of the raw material powder.
  • the total amount of Mn and S is preferably 0.2% by mass or less, more preferably 0.1% by mass or less, based on the total amount of the raw material powder. ..
  • the average particle size of the raw material powder is not particularly limited, but is more preferably 20 to 200 ⁇ m from the viewpoint of moldability and sinterability.
  • the average particle size is a volume-based average particle size, and can be specifically measured by a laser diffraction method.
  • the molded product contains zinc stearate. It is preferable that the molded product is molded by filling it in a molding mold in the state of a mixed powder in which zinc stearate and a raw material powder are mixed.
  • a mixed powder in which zinc stearate and a raw material powder are mixed.
  • zinc stearate By mixing zinc stearate with the raw material powder, friction between the particles of the raw material powder is reduced, and when filling the mold, the raw material powder is given fluidity to prevent particle aggregation and filling. You can improve your sex.
  • zinc stearate with the raw material powder it is possible to reduce the friction between the raw material powder and the wall of the molding mold in the process of compressing the raw material powder filled in the molding mold and prevent the molding mold from being worn. ..
  • the pressure distribution becomes uniform when the raw material powder is filled in the molding die and compressed, so that the molding has a more uniform density distribution and excellent strength. You can get a body.
  • Zinc stearate is preferably blended in an amount of 0.05 to 5 parts by mass, more preferably 0.1 to 2 parts by mass, still more preferably 0.5 to 1 part by mass with respect to 100 parts by mass of the raw material powder. .. Zinc stearate is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and further preferably 0.5 parts by mass or more with respect to 100 parts by mass of the raw material powder. Thereby, as described above, the moldability can be further improved. Further, zinc stearate is preferably 5 parts by mass or less, more preferably 2 parts by mass or less, and further preferably 1 part by mass or less with respect to 100 parts by mass of the raw material powder. As a result, zinc stearate is thermally decomposed by heat treatment by dewaxing and sintering, and the amount of organic components remaining in the sintered body can be reduced.
  • the molded product may contain other additives.
  • other additives include amide-based lubricants as lubricants other than zinc stearate.
  • the molded product can be obtained by mixing a raw material powder containing an iron-based powder and zinc stearate to form a mixed powder.
  • the molding method may be either a dry type or a wet type, but a dry type is preferable.
  • pressure molding such as powder compact molding can be preferably used.
  • the molding conditions may be appropriately set according to the composition, size, etc. of the molded product.
  • the molding pressure may be 300 to 1000 MPa, and the pressurization holding time is 0.2 to 2 seconds. good.
  • the apparent density of the molded product may be appropriately set according to the composition of the molded product and the like, and may be, for example, 1 to 8 g / m 3 or 5 to 7 g / m 3 .
  • Dewaxing preferably includes the following steps. (1) Prepare a water vapor-containing nitrogen atmosphere containing nitrogen and water vapor and having a dew point of 0 ° C. or higher and 30 ° C. or lower. (2) Heat the water vapor-containing nitrogen atmosphere to 100 ° C. or higher and supply it to the dewaxed part. (3) Heat-treat the molded product at 800 ° C. or lower at the dewaxed portion.
  • Dewaxing is preferably performed in a water vapor-containing nitrogen atmosphere containing nitrogen and water vapor.
  • the dew point of the water vapor-containing nitrogen atmosphere is preferably 0 ° C. or higher, more preferably 10 ° C. or higher, and even more preferably 12 ° C. or higher.
  • the dew point in the dewaxing atmosphere is preferably 30 ° C. or lower, more preferably 20 ° C. or lower, further preferably 18 ° C. or lower, and even more preferably 16 ° C. or lower. This prevents the carbon component from being excessively separated from the sintered body, so that a sufficient amount of carbon remains in the sintered body and suppresses the formation of the ferrite phase, whereby high-strength sintering is performed. You can get a body.
  • the dew point of the dewaxing atmosphere is preferably 15 ° C. ⁇ 5 ° C., more preferably 15 ° C. ⁇ 3 ° C., and even more preferably 15 ° C. ⁇ 2 ° C. from the viewpoint of controlling the atmosphere supplied into the furnace.
  • the dew point of the atmosphere is the temperature at which condensation starts when the atmosphere containing water vapor is cooled, and can be determined according to the humidity-measurement method of JISZ8806: 2001. Specifically, the dew point of the atmosphere can be measured using a dew point meter. By installing a dew point meter in the atmosphere supply section of the sintering furnace, it is possible to manage the dew point of the atmosphere supplied to the sintering furnace.
  • the water vapor-containing atmosphere is preferably prepared by mixing water vapor and a nitrogen atmosphere.
  • the nitrogen atmosphere is preferably 95% by volume or more, and more preferably 98% by volume or more of nitrogen.
  • the dewaxing atmosphere may further contain an inert gas as well as water vapor and nitrogen.
  • the inert gas include Ar gas and He gas.
  • the dewaxing atmosphere preferably limits the amount of reducing gas used in order to promote the oxidation of organic components.
  • the reducing gas include H 2 gas and CO gas.
  • an atmosphere of dewaxing, H is preferably less than 2 gas 5 vol%, more preferably 3% by volume or less, more preferably 1 vol% or less.
  • H 2 gas when reducing H 2 gas is used in the sintering step, H 2 gas may be mixed in the dewaxing step.
  • the atmosphere of dewaxing H is preferably less than 2 gas 5 vol%, more preferably 3% by volume or less, more preferably 1 vol% or less.
  • the water vapor-containing nitrogen atmosphere supplied to the dewaxed portion is preferably heated before being supplied to the dewaxed portion.
  • the water vapor-containing nitrogen atmosphere supplied to the dewaxed portion is preferably supplied to the deafened portion in a state of being heated to 100 ° C. or higher. This temperature is preferably 100 to 500 ° C, more preferably 300 to 500 ° C.
  • the flow rate of the atmosphere supplied to the sintering furnace for example, preferably 0.5 m 3 / h or more, 1 m 3 / h or more preferably, 2m 3 / h or more is more preferable.
  • the flow rate of the atmosphere supplied to the sintering furnace for example, preferably 60 m 3 / h or less, more preferably 50m 3 / h, 45m 3 / h or less is more preferred.
  • the flow rate of the atmosphere supplied to the sintering furnace is the flow rate of the gas passing through the pipe of the gas pipe supplied to the sintering furnace.
  • the dewaxing temperature is preferably 100 ° C. or higher, preferably 250 ° C. or higher, more preferably 350 ° C. or higher, still more preferably 550 ° C. or higher.
  • the thermal decomposition of the organic component such as zinc stearate contained in the molded product can be further promoted.
  • the dewaxing temperature is preferably 800 ° C. or lower, more preferably 600 ° C. or lower, and even more preferably 580 ° C. or lower. This allows zinc stearate to be sufficiently pyrolyzed without consuming excess energy.
  • the dewaxing temperature may be 800 ° C. or lower.
  • the dewaxing temperature can be obtained by measuring the temperature inside the sintering furnace with a thermocouple. The location where the thermocouple is installed is preferably close to the placement position of the molded body.
  • the dewaxing temperature at the portion where the dewaxing portion of the continuous sintering furnace reaches the maximum temperature is in the above range.
  • the dewaxing time can be appropriately set according to the composition, size, etc. of the molded product, and may be, for example, 10 to 60 minutes or 20 to 40 minutes. It is preferable that this range is at least the time when the dewaxing temperature reaches 100 ° C. or higher.
  • the dewaxing pressure can be appropriately set according to the composition, size, etc. of the molded product, and may be, for example, 1 to 500 Pa or 5 to 100 Pa.
  • a continuous sintering furnace may be used to perform the sintering step without cooling. Further, when a batch type sintering furnace is used, the sintering step may be performed after dewaxing and cooling.
  • the exhaust gas discharged from the sintering furnace at the time of dewaxing can be exhausted after being further thermally decomposed by combustion treatment in consideration of the environmental aspect.
  • the sintering temperature is preferably 1000 ° C. or higher, more preferably 1100 ° C. or higher, and even more preferably 1130 ° C. or higher.
  • the sintering temperature is preferably 1400 ° C. or lower, more preferably 1300 ° C. or lower, and even more preferably 1200 ° C. or lower.
  • the sintering temperature can be obtained by measuring the temperature inside the sintering furnace with a thermocouple.
  • the location where the thermocouple is installed is preferably close to the placement position of the molded body.
  • the sintering temperature at the portion where the maximum temperature is reached in the sintered portion of the continuous sintering furnace is in the above range.
  • the atmosphere of sintering may be an oxidizing gas, a reducing gas, an inert gas, or a mixed gas thereof.
  • a reducing gas can be preferably used to promote sintering.
  • the sintering atmosphere may be, for example, butane reformed gas, ammonia decomposition gas, H 2 gas, and the like. Of these, H 2 gas or a mixed gas of H 2 gas and an inert gas is preferable.
  • the inert gas include N 2 gas and Ar gas.
  • the sintering atmosphere in the case of using a mixed gas of H 2 gas and an inert gas, H 2 gas is preferably 2 to 75 vol%, more preferably 4 to 50% by volume.
  • the dew point in the sintering atmosphere is preferably less than 10 ° C., more preferably 0 ° C. or lower, still more preferably ⁇ 10 ° C. or lower, in order to prevent oxidation of the sintered body due to mixing with water vapor.
  • the lower limit of the dew point in the sintering atmosphere is not particularly limited, but it is preferably ⁇ 80 ° C. or higher, more preferably ⁇ 60 ° C. or higher, from the viewpoint that the lower the dew point is, the more difficult it is to control the dew point of the gas and the higher the management cost.
  • the flow rate of the atmosphere supplied to the sintering furnace for example, preferably 0.5 m 3 / h or more, 1 m 3 / h or more preferably, 2m 3 / h or more is more preferable.
  • the flow rate of the atmosphere supplied to the sintering furnace for example, is preferably from 80 m 3 / h, more preferably not more than 75m 3 / h, 70m 3 / h or less is more preferred.
  • the flow rate of the atmosphere supplied to the sintering furnace is the flow rate of the gas passing through the pipe of the gas pipe supplied to the sintering furnace.
  • the sintering time can be appropriately set according to the composition, size, etc. of the molded product, and may be, for example, 15 minutes to 120 minutes, or 30 minutes to 60 minutes. It is preferable that the sintering temperature is at least 1000 ° C. or higher within this range.
  • the sintering pressure can be appropriately set according to the composition, size, etc. of the molded product, and may be, for example, 1 to 500 Pa or 5 to 100 Pa.
  • the cooling rate after sintering may be 1 to 100 ° C./min and may be 5 to 50 ° C./min.
  • the exhaust gas discharged from the sintering furnace at the time of sintering can be exhausted after being further thermally decomposed by combustion treatment in consideration of the environmental aspect.
  • dewaxing and sintering may be performed in a continuous sintering furnace or a batch type sintering furnace.
  • a continuous sintering furnace for example, a mesh belt furnace, a roller hearth furnace, a tray pusher furnace, a walking beam furnace and the like can be used.
  • the dewaxing part, the sintering part, and the cooling part are continuously arranged in a tunnel-shaped furnace, and the molded product is conveyed from the dewaxing part to the cooling part by a conveying means.
  • a sintering furnace can be used.
  • the molded product may be placed on a tray and conveyed.
  • a partition is provided between the dewaxed portion and the sintered portion so that the transport means and the molded body can pass through, and the dewaxed portion and the sintered portion are separated so that the temperature can be adjusted.
  • the atmospheres in the furnace are not mixed with each other. The same applies to the section between the sintered section and the cooling section.
  • the dewaxing section includes a transporting means, a heating section, an atmosphere supply section, an exhaust section, and a thermocouple.
  • a plurality of heating parts of the dewaxing part may be arranged in order to uniformly heat the inside of the furnace.
  • the heating unit include a radiant tube burner, a metal heater, a ceramic heater such as SiC, and a cup burner using butane gas or the like.
  • a radiant tube burner can be preferably used because it is indirect heating that is less deteriorated by exhaust gas, is not easily affected by the atmosphere inside the furnace, and is easy to maintain and manage.
  • the atmosphere supply section of the dewaxing section supplies a nitrogen atmosphere containing water vapor into the furnace at a predetermined temperature, and a plurality of atmosphere supply sections may be arranged in order to uniformly supply the atmosphere into the furnace. It is advisable to provide a flow meter in the atmosphere supply section of the dewaxing section to adjust the flow rate of the atmosphere supplied into the furnace.
  • the dewaxing portion may be one that heats the molded body in one space having a uniform temperature and atmosphere, or one that heats the molded body by passing the molded body through a plurality of separated spaces having different temperatures and atmospheres. It may be.
  • the first dewaxing portion, the second dewaxing portion, and the third dewaxing portion are arranged along the transporting direction of the molded body from the upstream side in the transporting direction.
  • Each dewaxed portion is separated by a partition to the extent that the transport means and the molded body can pass through, and the temperature and atmosphere can be adjusted in each dewaged portion.
  • the space in which the dewaxing portion is separated is not limited to this number.
  • the temperature of the dewaxed portion on the upstream side in the transport direction is lowered, the temperature of the dewaxed portion on the downstream side in the transport direction is raised, and the temperature is inclined to gradually heat the molded body and zinc stearate. It is possible to prevent shape defects such as cracks in the molded body by slowly proceeding with the removal of organic components such as. Further, by reducing the flow rate of the atmosphere of the dewaxed portion on the upstream side in the transport direction, increasing the flow rate of the atmosphere of the dewaxed portion on the downstream side in the transport direction, and providing an inclination in the flow rate, the molded body is gradually oxidized. The amount of carbon derived from an organic component such as zinc stearate can be adjusted so that a certain amount of carbon remains in the sintered body, which can contribute to the improvement of the strength of the sintered body.
  • the flow rate of the steam-containing nitrogen atmosphere may be reduced or the water vapor-containing nitrogen atmosphere may not be supplied to the dewaked parts adjacent to the sintering furnace. good.
  • the water vapor-containing nitrogen atmosphere is preferably supplied from the same source for simplification of equipment, and the dew point and gas type may be the same.
  • the steam generation method a method using a fixed quantity supply pump and electric heater heating, boiler heating, ultrasonic vibration, or the like can be used. Among them, since the amount of steam generated can be easily adjusted and maintenance is easy, the method using a fixed quantity supply pump and electric heater heating can be preferably used.
  • the steam generator include a water tank section, a water metering supply pump section, a vaporizer, a nitrogen gas supply section for supplying nitrogen gas to the vaporizer, and a steam atmosphere discharge section.
  • water is supplied from the water tank to the vaporizer by the water metering supply pump unit.
  • the water it is preferable to use water from which ionic impurities such as pure water have been removed.
  • Water vapor can be generated by setting the vaporizer at 100 ° C. or higher, preferably 200 ° C. or higher, and more preferably 250 ° C. or higher.
  • Nitrogen gas can be supplied from the nitrogen gas supply unit to the vaporizer to generate a nitrogen atmosphere containing water vapor.
  • the nitrogen atmosphere containing water vapor can be discharged from the water vapor atmosphere discharging part and supplied to the dewaxing part. It is preferable to keep the temperature of the pipe from the water vapor atmosphere discharging part to the dewaxing part at 60 to 100 ° C.
  • the sintered section includes a transporting means, a heating section, an atmosphere supply section, an exhaust section, and a thermocouple.
  • the heating portion of the sintered portion is not particularly limited, and can be appropriately selected and used from those described in the dewaxing portion described above.
  • the atmosphere supply section of the sintered section supplies the atmosphere into the furnace at a predetermined temperature, and a plurality of atmosphere supply sections may be arranged in order to uniformly supply the atmosphere into the furnace. It is advisable to provide a flow meter in the atmosphere supply section of the sintered section to adjust the flow rate of the atmosphere supplied into the furnace.
  • the cooling unit is not particularly limited, and any cooling unit that can be applied to a normal sintering furnace may be used.
  • the transfer means can be driven by a drive motor.
  • one or a plurality of exhaust parts can be provided in the dewaxing part and the sintered part, and the exhaust gas containing the thermally decomposed organic component can be exhausted from the molded body.
  • one or a plurality of thermocouples can be provided in the dewaxed portion and the sintered portion, and the temperature inside the furnace can be controlled in each section.
  • the sintered body produced by one embodiment is not limited to this, but preferably has the following physical properties.
  • the sintered body preferably has a Rockwell hardness of 20 to 70 HRB.
  • the Rockwell hardness of the sintered body is preferably 20 HRB or more, more preferably 30 HRB or more, and even more preferably 40 HRB or more. Thereby, a higher strength sintered body can be provided.
  • the Rockwell hardness of the sintered body is not particularly limited, but may be, for example, 100 HRB or less.
  • the Rockwell hardness of the sintered body can be measured according to the method specified in JIS Z2245.
  • the sintered body preferably has a tensile strength of 220 to 590 MPa.
  • the tensile strength of the sintered body is preferably 220 MPa or more, more preferably 250 MPa or more, and even more preferably 300 MPa or more. Thereby, a higher strength sintered body can be provided.
  • the tensile strength of the sintered body is not particularly limited, but may be, for example, 600 MPa or less.
  • the tensile strength of the sintered body can be measured by preparing ASTM: E8-69 as a test piece and the test method according to the method specified in JIS Z2241.
  • the area ratio of the ferrite phase is preferably 50 area% or less, more preferably 40 area% or less, further preferably 30 area% or less, still more preferably 20 area% or less.
  • the sintered body preferably has a pearlite phase formed in the metal structure, and the pearlite phase is more preferably 60 to 90 area%.
  • the metallographic structure of the sintered body can be observed with a scanning electron microscope.
  • the microstructure, strength, and appearance of the test pieces after dewaxing and sintering were evaluated.
  • "Molding" As the raw material powder, an iron-based powder having a composition of C: 0.8% by mass, Cu: 2.0% by mass, and the balance iron was prepared. 0.8 parts by mass of zinc stearate (“ZNS-730” manufactured by ADEKA Corporation) was added to 100 parts by mass of the iron-based powder, and the mixture was mixed with a V-type mixer for 30 minutes. This mixed powder was compacted into an annular shape having an outer diameter of 90 mm, an inner diameter of 15 mm, and a height of 15 mm to obtain a molded product. The mass of the molded product was 590 g, and the density was 6.9 g / cm 3 .
  • the dewaxing furnace 10 includes a transfer roller 1, a carbon tray T on which a test piece is placed on the transfer roller 1 to transfer the test piece, and a dewaxing portion 2a from the upstream side in the transfer direction. It includes a brazing part 2b and a dewaxing part 2c.
  • the respective degassing portions 2a, 2b, and 2c are separated by a partition plate, and the radiant tube burners 3a, 3b, and 3c arranged in the respective degassing portions 2a, 2b, and 2c, and the respective degassing portions 2a, 2b, and 2c.
  • the temperature inside the dewaxing furnace is controlled by a radiant tube burner, and the molded product on the carbon tray is conveyed by the transfer roller in the transfer direction X.
  • the water vapor-containing nitrogen atmosphere is supplied from the introduction port on the floor surface of the furnace to remove the molded product.
  • the exhaust gas discharged from the dewaxing portion is burned by an exhaust gas combustion device provided in the exhaust port portion, and is discharged from the exhaust hood duct 6.
  • the radiant tube burner of the heat source is isolated from the inside of the furnace by an indirect heating method, and the atmosphere inside the furnace can be kept constant.
  • the conditions for the dewaxing furnace of the roller hearth furnace were as follows. Water vapor was generated by a vaporizer (not shown), and the generated water vapor and a nitrogen atmosphere of 100% by volume of nitrogen were mixed to prepare a water vapor-containing atmosphere at the dew point shown in Table 1.
  • the vaporizer temperature was kept constant at 300 ° C., and the temperatures of the dewaxed portions 2a, 2b, and 2c were kept constant at 250 ° C., 350 ° C., and 550 ° C., respectively.
  • the flow rates of the water vapor-containing nitrogen atmosphere to the dewaxed portions 2a, 2b, and 2c from the vaporizer were kept constant at 2 m 3 / h, 4 m 3 / h, and 0 m 3 / h, respectively.
  • the number of compacts charged was 9 per tray, which was constant.
  • Other deafening conditions are as follows. Dewaxing pressure: 5 Pa. Take off time: 30 minutes.
  • the hydrogen concentration of the dewaxed portions 2a, 2b, and 2c is a numerical value including H 2 gas contained in the atmosphere flowing from the sintering furnace.
  • N 2 gas flow rate of dewaxing unit, the total gas flow rate of N 2 gas flow rate and AX gas flow sintering furnace, H 2 ratio of AX gas flow rate was controlled to be less than 5% by volume ..
  • H 2 ratio of AX gas flow rate was controlled to be less than 5% by volume .
  • the AX gas is an ammonia decomposition gas containing 75% by volume H 2 and 25% N 2.
  • the tensile strength of the sintered body was measured under the following conditions.
  • the tensile strength of the sintered body was measured by preparing ASTM: E8-69 as a test piece and the test method according to the method specified in JIS Z2241.
  • the metallographic structure of the sintered body was observed with a scanning electron microscope (SEM). The SEM photograph is shown in FIG. In addition, the area ratio of the ferrite phase, which is an index of decarburization, was calculated from the SEM photograph.
  • the sintered body of each example had little surface stain and high strength.
  • the dew point of the dewaxing atmosphere was as low as 10 ° C., and the surface of the sintered body was slightly soiled.
  • the dew point of the dewaxing atmosphere was as high as 20 ° C. and 30 ° C., and the strength of the sintered body was slightly lowered.

Abstract

Disclosed is a method for manufacturing an iron-based sintered body, the method including: dewaxing a raw material powder containing an iron-based powder and a molded body containing zinc stearate; and sintering the dewaxed molded body. The dewaxing includes: preparing a water vapor-containing nitrogen atmosphere that contains nitrogen and water vapor and has a dewpoint of 0-30°C; heating the water vapor-containing nitrogen atmosphere to at least 100°C and supplying the same to a dewaxing part; and subjecting the molded body to a heat treatment at 800°C or lower in the dewaxing part.

Description

鉄基焼結体の製造方法Manufacturing method of iron-based sintered body
　本発明の一実施形態は、鉄基焼結体の製造方法に関する。 One embodiment of the present invention relates to a method for producing an iron-based sintered body.
　原料粉末を金型内で圧縮成形して得られた圧粉体を焼結する、いわゆる粉末冶金法は、ニアネットシェイプに造形できるので、後の機械加工による削り代が少なく材料損失が小さいこと、また一度金型を作製すれば同じ形状の製品が多量に生産できること等の理由から経済性に優れている。また、粉末冶金法は、通常の溶解によって製造される合金で得ることができない特殊な合金を製造できること等の理由から合金設計の幅が広い。このため自動車部品を始めとする機械部品に広く適用されている。 The so-called powder metallurgy method, in which the green compact obtained by compression molding the raw material powder in a mold is sintered, can be formed into a near-net shape, so that the cutting allowance due to subsequent machining is small and the material loss is small. In addition, it is economical because it is possible to mass-produce products of the same shape once a mold is manufactured. In addition, the powder metallurgy method has a wide range of alloy designs because it can produce a special alloy that cannot be obtained with an alloy produced by ordinary melting. Therefore, it is widely applied to machine parts such as automobile parts.
　粉末冶金法では、鉄基合金等の原料粉末を各種の成形方法によって成形し、得られる成形体を焼結することで、焼結体を得ることができる。
　成形方法の一方法として加圧成形では、成形性を高めるために、原料粉末に潤滑剤を添加した混合粉末を用いて成形体を得ることができる。成形体に含まれる潤滑剤は、主に有機成分であるため、その後の熱処理において熱分解されて、焼結体から除去され得る。成形体を焼結するために高温で熱処理する前に、成形体から潤滑剤等を熱分解して除去するために比較的低温で熱処理して脱ろうする方法がある。 In the powder metallurgy method, a sintered body can be obtained by molding a raw material powder such as an iron-based alloy by various molding methods and sintering the obtained molded body.
In pressure molding as one of the molding methods, a molded product can be obtained by using a mixed powder in which a lubricant is added to the raw material powder in order to improve the moldability. Since the lubricant contained in the molded product is mainly an organic component, it can be thermally decomposed and removed from the sintered body in the subsequent heat treatment. Before heat-treating the molded body at a high temperature for sintering, there is a method of heat-treating at a relatively low temperature to remove the lubricant or the like from the molded body by thermal decomposition.
　脱ろう方法の一つとして、焼結炉にブタンガスを供給してバーナーで燃焼し、その燃焼排ガスによって成形体を直接加熱する方法がある。しかし、この方法では、炉内雰囲気を均一に加熱するように制御することが難しい問題がある。炉内雰囲気が均一であれば、脱ろうをより正確に制御することができるため、脱ろうにおいて成形体から潤滑剤等を適切に除去可能とし、さらに、得られる焼結体において均質な組成を得ることができる。 As one of the dewaxing methods, there is a method of supplying butane gas to a sintering furnace, burning it with a burner, and directly heating the molded body with the combustion exhaust gas. However, this method has a problem that it is difficult to control the atmosphere in the furnace so as to be heated uniformly. If the atmosphere in the furnace is uniform, dewaxing can be controlled more accurately, so that lubricant and the like can be appropriately removed from the molded body during dewaxing, and a homogeneous composition can be obtained in the obtained sintered body. Obtainable.
　一方で、脱ろうの炉内に供給されるガス種類についても検討されている。
　特許文献１（特開平８－２６０００２号公報）には、焼結体の表面にＭｎＳ由来の汚れが発生することを防止するために、鉄系圧粉成形体の脱ろう及び焼結において露点管理することが提案されている。 On the other hand, the type of gas supplied to the dewaxing furnace is also being studied.
In Patent Document 1 (Japanese Unexamined Patent Publication No. 8-2600002), dew point control is performed in dew point control and sintering of an iron-based powder compact in order to prevent MnS-derived stains from being generated on the surface of the sintered body. It is proposed to do.
特開平８－２６０００２号公報Japanese Unexamined Patent Publication No. 8-2600002
　しかし、脱ろうにおいてステアリン酸亜鉛の熱分解を促進して、焼結体表面に汚れが残らないようにするためには、さらに脱ろう条件の検討が必要とされる。また、単純に脱ろう条件を強化してステアリン酸亜鉛の熱分解を促進する場合では、鉄基焼結体の金属組織に影響を及ぼす問題がある。
　本発明の一実施形態は、表面の汚れが少ない鉄基焼結体を製造することを一目的とする。 However, in order to promote the thermal decomposition of zinc stearate in dewaxing and prevent stains from remaining on the surface of the sintered body, it is necessary to further study the dewaxing conditions. Further, when the dewaxing condition is simply strengthened to promote the thermal decomposition of zinc stearate, there is a problem that the metal structure of the iron-based sintered body is affected.
One object of the present invention is to produce an iron-based sintered body having less surface contamination.
　本発明の一実施形態は、以下の通りである。
　［１］鉄基粉末を含む原料粉末及びステアリン酸亜鉛を含む成形体を脱ろうすること、及び前記脱ろうした成形体を焼結することを含み、前記脱ろうは、窒素と、水蒸気とを含み、露点が０℃以上３０℃以下である水蒸気含有窒素雰囲気を用意すること、前記水蒸気含有窒素雰囲気を１００℃以上に加熱し脱ろう部に供給すること、及び前記脱ろう部で前記成形体を８００℃以下で熱処理することを含む、鉄基焼結体の製造方法。
　［２］前記水蒸気含有窒素雰囲気を、水蒸気と窒素雰囲気とを混合して用意することを含み、前記窒素雰囲気は、窒素が９５体積％以上である、［１］に記載の鉄基焼結体の製造方法。
　［３］前記脱ろう部の雰囲気は、水素が５体積％未満である、［１］又は［２］に記載の鉄基焼結体の製造方法。
　［４］前記脱ろう部は、前記水蒸気含有窒素雰囲気を２５０℃以上に加熱し脱ろうすることを含む、［１］から［３］のいずれかに記載の鉄基焼結体の製造方法。 One embodiment of the present invention is as follows.
[1] The dewazing includes removing the raw material powder containing the iron-based powder and the molded product containing zinc stearate, and sintering the dew pointed molded product, and the dew pointing contains nitrogen and water vapor. To prepare a water vapor-containing nitrogen atmosphere having a dew point of 0 ° C. or higher and 30 ° C. or lower, to heat the steam-containing nitrogen atmosphere to 100 ° C. or higher and supply it to a dewaxed portion, and to supply the molded product to the dewaxed portion at the dewaked portion. A method for producing an iron-based sintered body, which comprises heat-treating the iron-based sintered body at 800 ° C. or lower.
[2] The iron-based sintered body according to [1], wherein the water vapor-containing nitrogen atmosphere is prepared by mixing water vapor and a nitrogen atmosphere, and the nitrogen atmosphere contains 95% by volume or more of nitrogen. Manufacturing method.
[3] The method for producing an iron-based sintered body according to [1] or [2], wherein the atmosphere of the dewaxed portion is less than 5% by volume of hydrogen.
[4] The method for producing an iron-based sintered body according to any one of [1] to [3], which comprises heating the water vapor-containing nitrogen atmosphere to 250 ° C. or higher to remove the wax.
　［５］前記成形体の原料粉末は、０質量％超過２０質量％以下のＣｕを含み、残部鉄及び不可避不純物からなる、［１］から［４］のいずれかに記載の鉄基焼結体の製造方法。
　［６］前記成形体の原料粉末は、Ｍｎ及びＳが合計量で０．２質量％以下である、［１］から［５］のいずれかに記載の鉄基焼結体の製造方法。
　［７］前記成形体の原料粉末は、０質量％超過５質量％以下のＣをさらに含む、［１］から［６］のいずれかに記載の鉄基焼結体の製造方法。
　［８］前記ステアリン酸亜鉛は、原料粉末１００質量部に対して０．０５～５質量部である、［１］から［７］のいずれかに記載の鉄基焼結体の製造方法。
　［９］前記脱ろうと前記焼結とを連続焼結炉で行う、［１］から［８］のいずれかに記載の鉄基焼結体の製造方法。 [5] The iron-based sintered body according to any one of [1] to [4], wherein the raw material powder of the molded product contains Cu in an amount of more than 0% by mass and 20% by mass or less, and is composed of residual iron and unavoidable impurities. Manufacturing method.
[6] The method for producing an iron-based sintered body according to any one of [1] to [5], wherein the raw material powder of the molded product contains Mn and S in a total amount of 0.2% by mass or less.
[7] The method for producing an iron-based sintered body according to any one of [1] to [6], wherein the raw material powder of the molded product further contains C in excess of 0% by mass and 5% by mass or less.
[8] The method for producing an iron-based sintered body according to any one of [1] to [7], wherein the zinc stearate is 0.05 to 5 parts by mass with respect to 100 parts by mass of the raw material powder.
[9] The method for producing an iron-based sintered body according to any one of [1] to [8], wherein the removal and the sintering are performed in a continuous sintering furnace.
　一実施形態によれば、表面の汚れが少ない鉄基焼結体を製造することができる。 According to one embodiment, it is possible to manufacture an iron-based sintered body with less surface contamination.
図１は、実施例で用いたローラーハース炉の脱ろう炉の断面概略図である。FIG. 1 is a schematic cross-sectional view of the dewaxing furnace of the roller hearth furnace used in the examples. 図２は、実施例の焼結体の金属組織を走査型電子顕微鏡（ＳＥＭ）によって観察した写真である。FIG. 2 is a photograph of the metal structure of the sintered body of the example observed by a scanning electron microscope (SEM).
　以下、本発明の一実施形態について説明するが、以下の例示によって本発明は限定されない。 Hereinafter, an embodiment of the present invention will be described, but the present invention is not limited by the following examples.
　一実施形態による鉄基焼結体の製造方法は、鉄基粉末を含む原料粉末及びステアリン酸亜鉛を含む成形体を脱ろうすること、及び脱ろうした成形体を焼結することを含み、脱ろうは、窒素と、水蒸気とを含み、露点が０℃以上３０℃以下である水蒸気含有窒素雰囲気を用意すること、水蒸気含有窒素雰囲気を１００℃以上に加熱し脱ろう部に供給すること、及び脱ろう部で成形体を８００℃以下で熱処理することを含むことを特徴とする。
　これによれば、表面汚れが少ない鉄基焼結体を製造することができる。さらに、一実施形態によれば、焼結体の強度をより高めることができる。 A method for producing an iron-based sintered body according to an embodiment includes removing a raw material powder containing iron-based powder and a molded product containing zinc stearate, and sintering the de-fused molded product. The wax contains nitrogen and water vapor, and prepares a water vapor-containing nitrogen atmosphere having a dew point of 0 ° C. or higher and 30 ° C. or lower, heats the water vapor-containing nitrogen atmosphere to 100 ° C. or higher and supplies it to the dewaxed portion. It is characterized by including heat-treating the molded product at 800 ° C. or lower at the dewaxed portion.
According to this, it is possible to produce an iron-based sintered body having less surface stains. Further, according to one embodiment, the strength of the sintered body can be further increased.
　一実施形態によれば、成形体を脱ろうする雰囲気のガス種類及び露点を特定することで、成形体に含まれるステアリン酸亜鉛の熱分解を促進し、得られる焼結体表面の汚れを低減することができる。焼結体表面に残る汚れは、主にステアリン酸亜鉛等の有機成分が焼結体表面に残ることで観察される。
　また、一実施形態によれば、成形体を脱ろうする雰囲気のガス種類及び露点を特定することで、得られる焼結体において、ある程度の炭素成分が残るようにして、フェライト相の生成を抑制して、焼結体の強度をより高めることができる。
　また、一実施形態によれば、成形体を脱ろうする雰囲気のガス種類及び露点を特定すればよいため、脱ろうの熱処理の熱源としてバーナー燃焼の他にも、より均一に炉内を加熱可能なラジアントチューブバーナ等の間接加熱方式を用いることができる。そのため、炉内の温度をより簡便に管理することが可能となる。 According to one embodiment, by specifying the gas type and dew point of the atmosphere in which the molded body is removed, the thermal decomposition of zinc stearate contained in the molded body is promoted, and the stain on the surface of the obtained sintered body is reduced. can do. Dirt remaining on the surface of the sintered body is mainly observed by organic components such as zinc stearate remaining on the surface of the sintered body.
Further, according to one embodiment, by specifying the gas type and dew point of the atmosphere in which the molded product is to be removed, a certain amount of carbon component remains in the obtained sintered body, and the formation of the ferrite phase is suppressed. Therefore, the strength of the sintered body can be further increased.
Further, according to one embodiment, since it is only necessary to specify the gas type and dew point of the atmosphere in which the molded body is to be removed, it is possible to heat the inside of the furnace more uniformly in addition to burner combustion as a heat source for the heat treatment for removing the molded body. An indirect heating method such as a radiant tube burner can be used. Therefore, the temperature inside the furnace can be controlled more easily.
　一実施形態において、成形体は、鉄基粉末を含む原料粉末及びステアリン酸亜鉛を含むことができる。
　鉄基粉末は、鉄粉末、鉄合金粉末、又はこれらの組み合わせであってよい。鉄基粉末には、不可避不純物が含まれてもよい。 In one embodiment, the molded product can include a raw material powder containing an iron-based powder and zinc stearate.
The iron-based powder may be an iron powder, an iron alloy powder, or a combination thereof. The iron-based powder may contain unavoidable impurities.
　原料粉末において、全体組成は、鉄を主成分として含むことが好ましい。例えば、原料粉末全量に対し、鉄は、５０質量％以上が好ましく、８０質量％以上がより好ましく、９０質量％以上がさらに好ましい。 In the raw material powder, the overall composition preferably contains iron as a main component. For example, with respect to the total amount of the raw material powder, iron is preferably 50% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more.
　原料粉末において、全体組成は、Ｃｕを含み、残部が鉄であってよい。この場合、Ｃｕは、原料粉末全量に対し、０質量％超過２０質量％以下で含むことが好ましい。
　Ｃｕは、Ｆｅに拡散して材料強度を高める作用を有する。
　Ｃｕは、焼結中に一部がＦｅの基地中に拡散し、一部はＦｅを溶かし混んで銅合金を形成する。よって、焼結合金を冷却すると、鉄基焼結体の基地に銅相又は銅合金相の形態で分散した組織状態になる。
　また、Ｃｕは、Ｃと併用した場合に、鉄基地の焼入れ性を改善して、パーライトを微細にして強度を高めたり、焼結の際に通常の冷却速度で強度の高いベイナイトやマルテンサイトを得ることを促進したりすることができる。
　Ｃｕは、必須元素ではないが、０．０１％以上が好ましく、より好ましくは０．１％以上、さらに好ましくは１％以上である。Ｃｕは、材料強度の低下を防止する観点から、２０％以下が好ましく、１５％以下がより好ましい。さらに、Ｃｕは、１０％以下が好ましく、５％以下がより好ましく、３％以下がさらに好ましい。これによって、軟質なＣｕ相の発生を抑制して、材料強度の低下をより防止することができ、また、焼結の際にＣｕ液相の発生を抑制して、製品全体の寸法精度をより高めることができる。 In the raw material powder, the overall composition may contain Cu and the balance may be iron. In this case, Cu is preferably contained in an amount of more than 0% by mass and 20% by mass or less with respect to the total amount of the raw material powder.
Cu has the effect of diffusing into Fe to increase the material strength.
Part of Cu diffuses into the base of Fe during sintering, and part of Cu melts and mixes with Fe to form a copper alloy. Therefore, when the sintered alloy is cooled, the structure is dispersed in the base of the iron-based sintered body in the form of a copper phase or a copper alloy phase.
Further, when Cu is used in combination with C, it improves the hardenability of the iron matrix to make pearlite finer to increase the strength, and at the time of sintering, it produces high-strength bainite and martensite at a normal cooling rate. It can be promoted to obtain.
Cu is not an essential element, but is preferably 0.01% or more, more preferably 0.1% or more, still more preferably 1% or more. Cu is preferably 20% or less, more preferably 15% or less, from the viewpoint of preventing a decrease in material strength. Further, Cu is preferably 10% or less, more preferably 5% or less, still more preferably 3% or less. As a result, the generation of a soft Cu phase can be suppressed to further prevent a decrease in material strength, and the generation of a Cu liquid phase during sintering can be suppressed to further improve the dimensional accuracy of the entire product. Can be enhanced.
　原料粉末において、全体組成は、Ｃをさらに含んでもよい。この場合、Ｃは０質量％超過５質量％以下で含むことが好ましい。
　Ｃは、その一部がＦｅに固溶して強度を向上させることができる。Ｃが過剰に配合されると、脆いセメンタイトがネットワーク状に析出する問題がある。このため、Ｃは０～５％が好ましく、０．１～３％がより好ましく、０．５～１％がさらに好ましい。また、Ｃの全量が基地中に固溶もしくは金属炭化物として析出していることが好ましい。この金属炭化物は、基地中に分散して含まれることが好ましい。 In the raw material powder, the overall composition may further include C. In this case, C is preferably contained in an amount of more than 0% by mass and 5% by mass or less.
A part of C can be dissolved in Fe to improve its strength. If C is excessively blended, there is a problem that brittle cementite is deposited in a network shape. Therefore, C is preferably 0 to 5%, more preferably 0.1 to 3%, and even more preferably 0.5 to 1%. Further, it is preferable that the entire amount of C is precipitated as a solid solution or metal carbide in the matrix. This metal carbide is preferably dispersed and contained in the matrix.
　さらに、原料粉末において、全体組成は、Ｃｒ、Ｍｎ、Ｍｏ、Ｗ、Ｎｉ、Ｃｏ、Ｖ、及びＮｂからなる群から選択される少なくとも１種を含んでもよい。この場合、各元素は合計量として１５質量％以下で含まれることが好ましく、１０質量％以下がより好ましく、５質量％以下がさらに好ましい。
　また、原料粉末において、全体組成は、Ｓｉ、Ｐ、Ｓ、Ｏ、Ｎ等を、１種単独で、又は２種以上を組み合わせてさらに含んでもよい。 Further, in the raw material powder, the overall composition may contain at least one selected from the group consisting of Cr, Mn, Mo, W, Ni, Co, V, and Nb. In this case, each element is preferably contained in an amount of 15% by mass or less as a total amount, more preferably 10% by mass or less, and further preferably 5% by mass or less.
Further, in the raw material powder, the overall composition may further contain Si, P, S, O, N and the like alone or in combination of two or more.
　Ｃｕは、鉄合金粉末として、原料粉末に配合することができる。また、Ｃｕは、原料粉末に銅粉末、銅合金粉末、又はこれらの組み合わせとして配合することができる。
　Ｃｕ以外の他の金属は、原料粉末に配合される鉄合金粉末として、例えば、鉄と、Ｃｒ、Ｍｎ、Ｍｏ、Ｗ、Ｎｉ、Ｃｏ、Ｖ、及びＮｂからなる群から選択される少なくとも１種との合金粉末として配合することができる。また、Ｃｕ以外の金属は、これらの金属単体の金属粉末として配合することができる。 Cu can be blended with the raw material powder as an iron alloy powder. Further, Cu can be blended with the raw material powder as a copper powder, a copper alloy powder, or a combination thereof.
The metal other than Cu is at least one selected from the group consisting of, for example, iron and Cr, Mn, Mo, W, Ni, Co, V, and Nb as the iron alloy powder to be blended in the raw material powder. Can be blended as an alloy powder with. Further, metals other than Cu can be blended as metal powders of these metals alone.
　Ｃは、鉄粉末及び／又は鉄合金粉末に固溶した状態で、原料粉末に配合することができる。また、Ｃは、成形体の圧縮性を高めるために、黒鉛粉末として原料粉末に配合することができる。さらに、Ｃは、ステアリン酸亜鉛等の有機成分として原料粉末に配合することができる。ステアリン酸亜鉛等の有機成分は、脱ろう、焼結によって熱分解されるが、その一部のＣが焼結体に残り、鉄基地に固溶すると考えられる。 C can be blended with the raw material powder in a solid solution state in the iron powder and / or the iron alloy powder. Further, C can be blended with the raw material powder as a graphite powder in order to increase the compressibility of the molded product. Further, C can be blended in the raw material powder as an organic component such as zinc stearate. Organic components such as zinc stearate are thermally decomposed by dewaxing and sintering, but it is considered that a part of C remains in the sintered body and dissolves in the iron matrix.
　原料粉末は、不可避不純物を含み得る。原料粉末全量に対し、不可避不純物は、合計量として１質量％以下が好ましく、０．５質量％以下がより好ましく、０．１質量％以下がさらに好ましい。
　なかでも、原料粉末において、原料としてＭｎ及びＳが添加されない場合に、Ｍｎ及びＳの合計量は、原料粉末全量に対し、０．２質量％以下が好ましく、０．１質量％以下がより好ましい。 The raw material powder may contain unavoidable impurities. The total amount of unavoidable impurities is preferably 1% by mass or less, more preferably 0.5% by mass or less, still more preferably 0.1% by mass or less, based on the total amount of the raw material powder.
Among them, when Mn and S are not added as raw materials in the raw material powder, the total amount of Mn and S is preferably 0.2% by mass or less, more preferably 0.1% by mass or less, based on the total amount of the raw material powder. ..
　原料粉末の平均粒子径は、特に限定されないが、成形性及び焼結性の観点から、２０～２００μｍがより好ましい。
　ここで、平均粒子径は、体積基準の平均粒子径であり、具体的には、レーザ回折法によって測定することができる。 The average particle size of the raw material powder is not particularly limited, but is more preferably 20 to 200 μm from the viewpoint of moldability and sinterability.
Here, the average particle size is a volume-based average particle size, and can be specifically measured by a laser diffraction method.
　成形体にはステアリン酸亜鉛が含まれる。
　成形体は、ステアリン酸亜鉛と原料粉末とを混合した混合粉末の状態で、成形型に充填されて成形されることが好ましい。
　原料粉末にステアリン酸亜鉛が混合されることで、原料粉末の粒子間の摩擦を低減して、成形型への充填に際し、原料粉末に流動性を与えて、粒子の凝集を防止して、充填性を高めることができる。
　また、原料粉末にステアリン酸亜鉛が混合されることで、成形型に充填した原料粉末の圧縮過程で原料粉末と成形型の壁との摩擦を低減し、成形型の摩耗を防止することができる。
　また、原料粉末にステアリン酸亜鉛が混合されることで、原料粉末が成形型に充填されて圧縮される際に、圧力分布が均一になるため、より均一な密度分布で、強度に優れた成形体を得ることができる。 The molded product contains zinc stearate.
It is preferable that the molded product is molded by filling it in a molding mold in the state of a mixed powder in which zinc stearate and a raw material powder are mixed.
By mixing zinc stearate with the raw material powder, friction between the particles of the raw material powder is reduced, and when filling the mold, the raw material powder is given fluidity to prevent particle aggregation and filling. You can improve your sex.
Further, by mixing zinc stearate with the raw material powder, it is possible to reduce the friction between the raw material powder and the wall of the molding mold in the process of compressing the raw material powder filled in the molding mold and prevent the molding mold from being worn. ..
Further, by mixing zinc stearate with the raw material powder, the pressure distribution becomes uniform when the raw material powder is filled in the molding die and compressed, so that the molding has a more uniform density distribution and excellent strength. You can get a body.
　ステアリン酸亜鉛は、原料粉末１００質量部に対して、０．０５～５質量部で配合されることが好ましく、０．１～２質量部がより好ましく、０．５～１質量部がさらに好ましい。
　ステアリン酸亜鉛は、原料粉末１００質量部に対して、０．０５質量部以上が好ましく、０．１質量部以上がより好ましく、０．５質量部以上がさらに好ましい。これによって、上記したように成形性をより高めることができる。
　また、ステアリン酸亜鉛は、原料粉末１００質量部に対して、５質量部以下が好ましく、２質量部以下がより好ましく、１質量部以下がさらに好ましい。これによって、脱ろう、焼結による熱処理によって、ステアリン酸亜鉛が熱分解されて、焼結体に残る有機成分量を低減することができる。 Zinc stearate is preferably blended in an amount of 0.05 to 5 parts by mass, more preferably 0.1 to 2 parts by mass, still more preferably 0.5 to 1 part by mass with respect to 100 parts by mass of the raw material powder. ..
Zinc stearate is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and further preferably 0.5 parts by mass or more with respect to 100 parts by mass of the raw material powder. Thereby, as described above, the moldability can be further improved.
Further, zinc stearate is preferably 5 parts by mass or less, more preferably 2 parts by mass or less, and further preferably 1 part by mass or less with respect to 100 parts by mass of the raw material powder. As a result, zinc stearate is thermally decomposed by heat treatment by dewaxing and sintering, and the amount of organic components remaining in the sintered body can be reduced.
　成形体には、その他の添加剤が含まれてもよい。その他の添加剤として、例えば、ステアリン酸亜鉛以外の潤滑剤として、アミド系潤滑剤等が挙げられる。 The molded product may contain other additives. Examples of other additives include amide-based lubricants as lubricants other than zinc stearate.
　成形体は、鉄基粉末を含む原料粉末と、ステアリン酸亜鉛とを混合し、混合粉末を成形して得ることができる。成形方法としては、乾式及び湿式のいずれであってもよいが、乾式が好ましい。乾式の成形方法としては、圧粉成形等の加圧成形を好ましく用いることができる。 The molded product can be obtained by mixing a raw material powder containing an iron-based powder and zinc stearate to form a mixed powder. The molding method may be either a dry type or a wet type, but a dry type is preferable. As the dry molding method, pressure molding such as powder compact molding can be preferably used.
　成形条件としては、成形体の組成、サイズ等に応じて適宜設定すればよく、例えば、成形圧力３００～１０００ＭＰａであってよく、また、加圧の保持時間は０．２～２秒であってよい。
　成形体の見掛け密度は、成形体の組成等に応じて適宜設定すればよく、例えば、１～８ｇ／ｍ３であってよく、５～７ｇ／ｍ３であってもよい。 The molding conditions may be appropriately set according to the composition, size, etc. of the molded product. For example, the molding pressure may be 300 to 1000 MPa, and the pressurization holding time is 0.2 to 2 seconds. good.
The apparent density of the molded product may be appropriately set according to the composition of the molded product and the like, and may be, for example, 1 to 8 g / m 3 or 5 to 7 g / m 3 .
　次に、成形体を脱ろうする工程について説明する。
　脱ろうは、以下の工程を含むことが好ましい。
　（１）窒素と、水蒸気とを含み、露点が０℃以上３０℃以下である水蒸気含有窒素雰囲気を用意すること。
　（２）水蒸気含有窒素雰囲気を１００℃以上に加熱し脱ろう部に供給すること。
　（３）脱ろう部で成形体を８００℃以下で熱処理すること。 Next, the step of removing the molded body will be described.
Dewaxing preferably includes the following steps.
(1) Prepare a water vapor-containing nitrogen atmosphere containing nitrogen and water vapor and having a dew point of 0 ° C. or higher and 30 ° C. or lower.
(2) Heat the water vapor-containing nitrogen atmosphere to 100 ° C. or higher and supply it to the dewaxed part.
(3) Heat-treat the molded product at 800 ° C. or lower at the dewaxed portion.
　脱ろうは、窒素と水蒸気とを含む水蒸気含有窒素雰囲気下で行うことが好ましい。
　水蒸気含有窒素雰囲気の露点は、０℃以上が好ましく、１０℃以上がより好ましく、１２℃以上がさらに好ましい。これによって、焼結体に残存するステアリン酸亜鉛由来の未分解物の量を低減し、未分解物に由来する焼結体表面の汚れを低減することができる。これは、脱ろうの雰囲気に、ある程度の水蒸気が含まれることで、成形体に含まれる有機成分の酸化が促進され、ステアリン酸亜鉛の熱分解が進行するからと考えられる。
　脱ろうの雰囲気の露点は、３０℃以下が好ましく、２０℃以下がより好ましく、１８℃以下がさらに好ましく、１６℃以下が一層好ましい。これによって、焼結体から炭素成分が過剰に離脱することを防止し、焼結体に十分な量の炭素が残存するようにして、フェライト相の形成を抑制し、これによって高強度の焼結体を得ることができる。
　脱ろうの雰囲気の露点は、炉内に供給される雰囲気の管理の観点から、１５℃±５℃が好ましく、１５℃±３℃がより好ましく、１５℃±２℃がさらに好ましい。 Dewaxing is preferably performed in a water vapor-containing nitrogen atmosphere containing nitrogen and water vapor.
The dew point of the water vapor-containing nitrogen atmosphere is preferably 0 ° C. or higher, more preferably 10 ° C. or higher, and even more preferably 12 ° C. or higher. Thereby, the amount of the undecomposed product derived from zinc stearate remaining in the sintered body can be reduced, and the stain on the surface of the sintered body derived from the undecomposed product can be reduced. It is considered that this is because the dewaxing atmosphere contains a certain amount of water vapor, which promotes the oxidation of the organic components contained in the molded product and promotes the thermal decomposition of zinc stearate.
The dew point in the dewaxing atmosphere is preferably 30 ° C. or lower, more preferably 20 ° C. or lower, further preferably 18 ° C. or lower, and even more preferably 16 ° C. or lower. This prevents the carbon component from being excessively separated from the sintered body, so that a sufficient amount of carbon remains in the sintered body and suppresses the formation of the ferrite phase, whereby high-strength sintering is performed. You can get a body.
The dew point of the dewaxing atmosphere is preferably 15 ° C. ± 5 ° C., more preferably 15 ° C. ± 3 ° C., and even more preferably 15 ° C. ± 2 ° C. from the viewpoint of controlling the atmosphere supplied into the furnace.
　ここで、雰囲気の露点は、水蒸気を含む雰囲気を冷却するときに凝結が開始する温度であり、ＪＩＳＺ８８０６：２００１の湿度－測定方法にしたがって求めることができる。具体的には、雰囲気の露点は露点計を用いて測定することができる。焼結炉の雰囲気の供給部に露点計を設置することで、焼結炉へ供給される雰囲気の露点を管理することができる。 Here, the dew point of the atmosphere is the temperature at which condensation starts when the atmosphere containing water vapor is cooled, and can be determined according to the humidity-measurement method of JISZ8806: 2001. Specifically, the dew point of the atmosphere can be measured using a dew point meter. By installing a dew point meter in the atmosphere supply section of the sintering furnace, it is possible to manage the dew point of the atmosphere supplied to the sintering furnace.
　水蒸気含有雰囲気は、水蒸気と窒素雰囲気とを混合して用意されることが好ましい。この場合に、窒素雰囲気は、窒素が９５体積％以上が好ましく、９８体積％以上がより好ましい。 The water vapor-containing atmosphere is preferably prepared by mixing water vapor and a nitrogen atmosphere. In this case, the nitrogen atmosphere is preferably 95% by volume or more, and more preferably 98% by volume or more of nitrogen.
　脱ろうの雰囲気は、水蒸気及び窒素とともに、不活性ガスをさらに含んでもよい。不活性ガスは、例えば、Ａｒガス、Ｈｅガス等が挙げられる。
　脱ろうの雰囲気は、有機成分の酸化を促進するために、還元性ガスの使用量を制限することが好ましい。還元性ガスとしては、Ｈ２ガス、ＣＯガス等が挙げられる。なかでも、脱ろうの雰囲気は、Ｈ２ガスが５体積％未満が好ましく、３体積％以下がより好ましく、１体積％以下がさらに好ましい。
　脱ろうと焼結とを連続焼結炉を通して行う場合は、焼結工程で用いられる雰囲気が脱ろう工程に逆流して混入することがある。例えば、焼結工程において還元性のＨ２ガスを用いる場合では、脱ろう工程においてＨ２ガスが混入することがある。この場合においても、脱ろうの雰囲気は、Ｈ２ガスが５体積％未満が好ましく、３体積％以下がより好ましく、１体積％以下がさらに好ましい。 The dewaxing atmosphere may further contain an inert gas as well as water vapor and nitrogen. Examples of the inert gas include Ar gas and He gas.
The dewaxing atmosphere preferably limits the amount of reducing gas used in order to promote the oxidation of organic components. Examples of the reducing gas include H 2 gas and CO gas. Among them, an atmosphere of dewaxing, H is preferably less than 2 gas 5 vol%, more preferably 3% by volume or less, more preferably 1 vol% or less.
When de-sintering and sintering are performed through a continuous sintering furnace, the atmosphere used in the sintering process may flow back into the de-sintering process and be mixed. For example, when reducing H 2 gas is used in the sintering step, H 2 gas may be mixed in the dewaxing step. In this case, the atmosphere of dewaxing, H is preferably less than 2 gas 5 vol%, more preferably 3% by volume or less, more preferably 1 vol% or less.
　脱ろう部へ供給する水蒸気含有窒素雰囲気は、脱ろう部に供給する前に加熱されていることが好ましい。例えば、脱ろう部に供給される水蒸気含有窒素雰囲気は、１００℃以上に加熱された状態で、脱ろう部に供給されることが好ましい。この温度は、１００～５００℃が好ましく、３００～５００℃がより好ましい。 The water vapor-containing nitrogen atmosphere supplied to the dewaxed portion is preferably heated before being supplied to the dewaxed portion. For example, the water vapor-containing nitrogen atmosphere supplied to the dewaxed portion is preferably supplied to the deafened portion in a state of being heated to 100 ° C. or higher. This temperature is preferably 100 to 500 ° C, more preferably 300 to 500 ° C.
　脱ろうにおいて、焼結炉に供給する雰囲気の流量は、例えば、０．５ｍ３／ｈ以上が好ましく、１ｍ３／ｈ以上がより好ましく、２ｍ３／ｈ以上がさらに好ましい。
　脱ろうにおいて、焼結炉に供給する雰囲気の流量は、例えば、６０ｍ３／ｈ以下が好ましく、５０ｍ３／ｈ以下がより好ましく、４５ｍ３／ｈ以下がさらに好ましい。
　ここで、焼結炉に供給する雰囲気の流量は、焼結炉に供給するガス管の配管を通過するガスの流量である。 In dewaxing, the flow rate of the atmosphere supplied to the sintering furnace, for example, preferably 0.5 m 3 / h or more, 1 m 3 / h or more preferably, 2m 3 / h or more is more preferable.
In dewaxing, the flow rate of the atmosphere supplied to the sintering furnace, for example, preferably 60 m 3 / h or less, more preferably 50m 3 / h, 45m 3 / h or less is more preferred.
Here, the flow rate of the atmosphere supplied to the sintering furnace is the flow rate of the gas passing through the pipe of the gas pipe supplied to the sintering furnace.
　脱ろうにおいて、脱ろう温度は、１００℃以上が好ましく、２５０℃以上が好ましく、３５０℃以上がより好ましく、５５０℃以上がさらに好ましい。これによって、成形体に含まれる、ステアリン酸亜鉛等の有機成分の熱分解をより促進することができる。
　脱ろうにおいて、脱ろう温度は、８００℃以下が好ましく、６００℃以下がより好ましく、５８０℃以下がさらに好ましい。これによって、過剰なエネルギーを消費することなく、ステアリン酸亜鉛を十分に熱分解することができる。また、引き続く焼結工程において、焼結が進行するため、脱ろう温度は８００℃以下であってよい。
　脱ろう温度は、焼結炉内の温度を熱電対で測定して求めることができる。熱電対の設置箇所は、成形体の載置位置に近いところが好ましい。連続焼結炉において、脱ろう温度に勾配をつけて脱ろうする場合は、連続焼結炉の脱ろう部において最高温度になる箇所の脱ろう温度が上記した範囲となることが好ましい。 In dewaxing, the dewaxing temperature is preferably 100 ° C. or higher, preferably 250 ° C. or higher, more preferably 350 ° C. or higher, still more preferably 550 ° C. or higher. Thereby, the thermal decomposition of the organic component such as zinc stearate contained in the molded product can be further promoted.
In dewaxing, the dewaxing temperature is preferably 800 ° C. or lower, more preferably 600 ° C. or lower, and even more preferably 580 ° C. or lower. This allows zinc stearate to be sufficiently pyrolyzed without consuming excess energy. Further, in the subsequent sintering step, since sintering proceeds, the dewaxing temperature may be 800 ° C. or lower.
The dewaxing temperature can be obtained by measuring the temperature inside the sintering furnace with a thermocouple. The location where the thermocouple is installed is preferably close to the placement position of the molded body. In the continuous sintering furnace, when the dewaxing temperature is defrosted with a gradient, it is preferable that the dewaxing temperature at the portion where the dewaxing portion of the continuous sintering furnace reaches the maximum temperature is in the above range.
　脱ろうの時間は、成形体の組成、サイズ等に応じて適宜設定可能であり、例えば、１０～６０分間であってよく、２０～４０分間であってもよい。少なくとも脱ろう温度が１００℃以上になる時間が、この範囲となることが好ましい。
　脱ろうの圧力は、成形体の組成、サイズ等に応じて適宜設定可能であり、例えば、１～５００Ｐａであってよく、５～１００Ｐａであってもよい。 The dewaxing time can be appropriately set according to the composition, size, etc. of the molded product, and may be, for example, 10 to 60 minutes or 20 to 40 minutes. It is preferable that this range is at least the time when the dewaxing temperature reaches 100 ° C. or higher.
The dewaxing pressure can be appropriately set according to the composition, size, etc. of the molded product, and may be, for example, 1 to 500 Pa or 5 to 100 Pa.
　脱ろう後は、連続焼結炉を用いて、冷却せずに焼結工程を行ってもよい。また、バッチ式の焼結炉を用いる場合は、脱ろう後に、冷却してから焼結工程を行ってもよい。
　脱ろうの際に焼結炉から排出される排ガスは、環境面を考慮して、燃焼処理をして有機成分をさらに熱分解してから排気することができる。 After dewaxing, a continuous sintering furnace may be used to perform the sintering step without cooling. Further, when a batch type sintering furnace is used, the sintering step may be performed after dewaxing and cooling.
The exhaust gas discharged from the sintering furnace at the time of dewaxing can be exhausted after being further thermally decomposed by combustion treatment in consideration of the environmental aspect.
　次に、脱ろうした成形体を焼結する工程について説明する。
　焼結において、焼結温度は、１０００℃以上が好ましく、１１００℃以上がより好ましく、１１３０℃以上がさらに好ましい。これによって、焼結体において、鉄基粉末の粒子間の焼結を促進して、焼結性をより高めることができる。
　焼結において、焼結温度は、１４００℃以下が好ましく、１３００℃以下がより好ましく、１２００℃以下がさらに好ましい。これによって、過剰なエネルギーを消費することなく、焼結性が良好な焼結体を得ることができる。また、過剰な加熱が防止されるため、焼結体から炭素成分が過剰に離脱することを防止し、フェライト相の形成を抑制し、より高強度の焼結体を得ることができる。
　焼結温度は、焼結炉内の温度を熱電対で測定して求めることができる。熱電対の設置箇所は、成形体の載置位置に近いところが好ましい。連続焼結炉において、焼結温度に勾配をつけて焼結する場合は、連続焼結炉の焼結部において最高温度になる箇所の焼結温度が上記した範囲となることが好ましい。 Next, the step of sintering the delaminated molded product will be described.
In sintering, the sintering temperature is preferably 1000 ° C. or higher, more preferably 1100 ° C. or higher, and even more preferably 1130 ° C. or higher. Thereby, in the sintered body, the sintering between the particles of the iron-based powder can be promoted, and the sinterability can be further improved.
In sintering, the sintering temperature is preferably 1400 ° C. or lower, more preferably 1300 ° C. or lower, and even more preferably 1200 ° C. or lower. As a result, it is possible to obtain a sintered body having good sinterability without consuming excessive energy. Further, since excessive heating is prevented, it is possible to prevent the carbon component from being excessively separated from the sintered body, suppress the formation of the ferrite phase, and obtain a sintered body having higher strength.
The sintering temperature can be obtained by measuring the temperature inside the sintering furnace with a thermocouple. The location where the thermocouple is installed is preferably close to the placement position of the molded body. In a continuous sintering furnace, when sintering is performed with a gradient in the sintering temperature, it is preferable that the sintering temperature at the portion where the maximum temperature is reached in the sintered portion of the continuous sintering furnace is in the above range.
　焼結の雰囲気は、酸化性ガス、還元性ガス、不活性ガス、又はこれらの混合ガスであってよい。なかでも、焼結を促進するために還元性ガスを好ましく用いることができる。
　焼結の雰囲気は、例えば、ブタン変成ガス、アンモニア分解ガス、Ｈ２ガス等が挙げられる。なかでも、Ｈ２ガス、又はＨ２ガスと不活性ガスとの混合ガスが好ましい。不活性ガスとしては、Ｎ２ガス、Ａｒガス等が挙げられる。
　例えば、焼結の雰囲気として、Ｈ２ガスと不活性ガスとの混合ガスを用いる場合は、Ｈ２ガスは２～７５体積％が好ましく、４～５０体積％がより好ましい。 The atmosphere of sintering may be an oxidizing gas, a reducing gas, an inert gas, or a mixed gas thereof. Among them, a reducing gas can be preferably used to promote sintering.
The sintering atmosphere may be, for example, butane reformed gas, ammonia decomposition gas, H 2 gas, and the like. Of these, H 2 gas or a mixed gas of H 2 gas and an inert gas is preferable. Examples of the inert gas include N 2 gas and Ar gas.
For example, the sintering atmosphere, in the case of using a mixed gas of H 2 gas and an inert gas, H 2 gas is preferably 2 to 75 vol%, more preferably 4 to 50% by volume.
　焼結の雰囲気の露点は、水蒸気混入による焼結体の酸化を防止するために、１０℃未満が好ましく、０℃以下がより好ましく、－１０℃以下がさらに好ましい。
　焼結の雰囲気の露点の下限値は、特に制限されないが、低いほどガスの露点管理が難しく管理費が高額となる観点から、－８０℃以上が好ましく、－６０℃以上がより好ましい。 The dew point in the sintering atmosphere is preferably less than 10 ° C., more preferably 0 ° C. or lower, still more preferably −10 ° C. or lower, in order to prevent oxidation of the sintered body due to mixing with water vapor.
The lower limit of the dew point in the sintering atmosphere is not particularly limited, but it is preferably −80 ° C. or higher, more preferably −60 ° C. or higher, from the viewpoint that the lower the dew point is, the more difficult it is to control the dew point of the gas and the higher the management cost.
　焼結において、焼結炉に供給する雰囲気の流量は、例えば、０．５ｍ３／ｈ以上が好ましく、１ｍ３／ｈ以上がより好ましく、２ｍ３／ｈ以上がさらに好ましい。
　焼結において、焼結炉に供給する雰囲気の流量は、例えば、８０ｍ３／ｈ以下が好ましく、７５ｍ３／ｈ以下がより好ましく、７０ｍ３／ｈ以下がさらに好ましい。
　ここで、焼結炉に供給する雰囲気の流量は、焼結炉に供給するガス管の配管を通過するガスの流量である。 In sintering, the flow rate of the atmosphere supplied to the sintering furnace, for example, preferably 0.5 m 3 / h or more, 1 m 3 / h or more preferably, 2m 3 / h or more is more preferable.
In sintering, the flow rate of the atmosphere supplied to the sintering furnace, for example, is preferably from 80 m 3 / h, more preferably not more than 75m 3 / h, 70m 3 / h or less is more preferred.
Here, the flow rate of the atmosphere supplied to the sintering furnace is the flow rate of the gas passing through the pipe of the gas pipe supplied to the sintering furnace.
　焼結の時間は、成形体の組成、サイズ等に応じて適宜設定可能であり、例えば、１５分～１２０分間であってよく、３０分～６０分間であってもよい。少なくとも焼結温度が１０００℃以上になる時間が、この範囲となることが好ましい。
　焼結の圧力は、成形体の組成、サイズ等に応じて適宜設定可能であり、例えば、１～５００Ｐａであってよく、５～１００Ｐａであってもよい。 The sintering time can be appropriately set according to the composition, size, etc. of the molded product, and may be, for example, 15 minutes to 120 minutes, or 30 minutes to 60 minutes. It is preferable that the sintering temperature is at least 1000 ° C. or higher within this range.
The sintering pressure can be appropriately set according to the composition, size, etc. of the molded product, and may be, for example, 1 to 500 Pa or 5 to 100 Pa.
　焼結後は、空冷してもよいし、冷却速度を制御してもよい。例えば、焼結後の冷却速度は、１～１００℃／分であってよく、５～５０℃／分であってもよい。
　焼結の際に焼結炉から排出される排ガスは、環境面を考慮して、燃焼処理をして有機成分をさらに熱分解してから排気することができる。 After sintering, it may be air-cooled or the cooling rate may be controlled. For example, the cooling rate after sintering may be 1 to 100 ° C./min and may be 5 to 50 ° C./min.
The exhaust gas discharged from the sintering furnace at the time of sintering can be exhausted after being further thermally decomposed by combustion treatment in consideration of the environmental aspect.
　以下、焼結炉の一例について説明する。
　一実施形態において、脱ろう及び焼結は、連続焼結炉で行ってもよいし、バッチ式の焼結炉で行ってもよい。
　連続焼結炉としては、例えば、メッシュベルト炉、ローラーハース炉、トレイプッシャ炉、ウォーキングビーム炉等を用いることができる。
　連続焼結炉としては、脱ろう部と、焼結部と、冷却部とが連続してトンネル状の炉内に配置され、搬送手段によって成形体が脱ろう部から冷却部へと搬送される焼結炉を用いることができる。成形体は、トレイに載置されて搬送されてもよい。
　脱ろう部と焼結部との間は、搬送手段と成形体とが通過可能な程度に、仕切りを設けて置き、脱ろう部と焼結部とを区切って温度調節が可能なようにし、また、炉内雰囲気が互いに混入しないようにするとよい。焼結部と冷却部との間も同様である。 Hereinafter, an example of the sintering furnace will be described.
In one embodiment, dewaxing and sintering may be performed in a continuous sintering furnace or a batch type sintering furnace.
As the continuous sintering furnace, for example, a mesh belt furnace, a roller hearth furnace, a tray pusher furnace, a walking beam furnace and the like can be used.
In the continuous sintering furnace, the dewaxing part, the sintering part, and the cooling part are continuously arranged in a tunnel-shaped furnace, and the molded product is conveyed from the dewaxing part to the cooling part by a conveying means. A sintering furnace can be used. The molded product may be placed on a tray and conveyed.
A partition is provided between the dewaxed portion and the sintered portion so that the transport means and the molded body can pass through, and the dewaxed portion and the sintered portion are separated so that the temperature can be adjusted. In addition, it is preferable that the atmospheres in the furnace are not mixed with each other. The same applies to the section between the sintered section and the cooling section.
　脱ろう部は、搬送手段、加熱部、雰囲気供給部、排気部、熱電対を備える。
　脱ろう部の加熱部は、炉内を均一に加熱するために複数個配置されてもよい。加熱部としては、ラジアントチューブバーナ、金属ヒーター、ＳｉＣ等のセラミックヒーター、ブタンガス等を用いるカップバーナー等が挙げられる。なかでも、排ガスによる劣化が少なく、炉内雰囲気に影響を受けにくい間接加熱であり、保守管理が簡便であることから、ラジアントチューブバーナを好ましく用いることができる。
　脱ろう部の雰囲気供給部は、水蒸気を含ませた窒素雰囲気を所定温度で炉内に供給するものであって、炉内に均一に雰囲気を供給するために複数個配置されてもよい。
　脱ろう部の雰囲気供給部に流量計を設けて、炉内に供給される雰囲気の流量を調節するとよい。 The dewaxing section includes a transporting means, a heating section, an atmosphere supply section, an exhaust section, and a thermocouple.
A plurality of heating parts of the dewaxing part may be arranged in order to uniformly heat the inside of the furnace. Examples of the heating unit include a radiant tube burner, a metal heater, a ceramic heater such as SiC, and a cup burner using butane gas or the like. Among them, a radiant tube burner can be preferably used because it is indirect heating that is less deteriorated by exhaust gas, is not easily affected by the atmosphere inside the furnace, and is easy to maintain and manage.
The atmosphere supply section of the dewaxing section supplies a nitrogen atmosphere containing water vapor into the furnace at a predetermined temperature, and a plurality of atmosphere supply sections may be arranged in order to uniformly supply the atmosphere into the furnace.
It is advisable to provide a flow meter in the atmosphere supply section of the dewaxing section to adjust the flow rate of the atmosphere supplied into the furnace.
　脱ろう部は、温度及び雰囲気が均一な１つの空間において成形体を加熱するものであってもよいし、温度及び雰囲気が異なる区切られた複数の空間に成形体を通過させることで加熱するものであってもよい。
　脱ろう部の一例としては、成形体の搬送方向に沿って、搬送方向上流側から、第１脱ろう部、第２脱ろう部、及び第３脱ろう部が配置される。各脱ろう部は、搬送手段及び成形体が通過可能な程度に仕切りによって区切られ、各脱ろう部において、温度及び雰囲気の調節が可能になっている。なお、脱ろう部が区切られる空間はこの個数に限定されない。
　そして、搬送方向上流側の脱ろう部の温度を低くし、搬送方向下流側の脱ろう部の温度を高くして、温度に傾斜を設けることで、成形体を徐々に加熱し、ステアリン酸亜鉛等の有機成分の除去を緩やかに進行させて、成形体のひび割れ等の形状不良を防止することができる。
　また、搬送方向上流側の脱ろう部の雰囲気の流量を少なくし、搬送方向下流側の脱ろう部の雰囲気の流量を多くし、流量に傾斜を設けることで、成形体を徐々に酸化し、ステアリン酸亜鉛等の有機成分に由来する炭素の除去量を調節し、ある程度の炭素が焼結体に残るようにして、焼結体の強度向上に寄与させることができる。 The dewaxing portion may be one that heats the molded body in one space having a uniform temperature and atmosphere, or one that heats the molded body by passing the molded body through a plurality of separated spaces having different temperatures and atmospheres. It may be.
As an example of the dewaxing portion, the first dewaxing portion, the second dewaxing portion, and the third dewaxing portion are arranged along the transporting direction of the molded body from the upstream side in the transporting direction. Each dewaxed portion is separated by a partition to the extent that the transport means and the molded body can pass through, and the temperature and atmosphere can be adjusted in each dewaged portion. The space in which the dewaxing portion is separated is not limited to this number.
Then, the temperature of the dewaxed portion on the upstream side in the transport direction is lowered, the temperature of the dewaxed portion on the downstream side in the transport direction is raised, and the temperature is inclined to gradually heat the molded body and zinc stearate. It is possible to prevent shape defects such as cracks in the molded body by slowly proceeding with the removal of organic components such as.
Further, by reducing the flow rate of the atmosphere of the dewaxed portion on the upstream side in the transport direction, increasing the flow rate of the atmosphere of the dewaxed portion on the downstream side in the transport direction, and providing an inclination in the flow rate, the molded body is gradually oxidized. The amount of carbon derived from an organic component such as zinc stearate can be adjusted so that a certain amount of carbon remains in the sintered body, which can contribute to the improvement of the strength of the sintered body.
　また、搬送方向に複数の脱ろう部が配置される場合は、焼結炉に隣接する脱ろう部には、水蒸気含有窒素雰囲気の流量を少なくするか、水蒸気含有窒素雰囲気を供給しなくてもよい。これによって、露点の高い雰囲気が焼結部に混入することを防止して、より高温で処理される焼結部において、焼結体の酸化が過剰に進行することを抑制することができる。
　複数の脱ろう部において、水蒸気含有窒素雰囲気は、設備の簡略化のため同じ供給源から供給されることが好ましく、露点及びガス種類は同じであってよい。 Further, when a plurality of dewaxed parts are arranged in the transport direction, the flow rate of the steam-containing nitrogen atmosphere may be reduced or the water vapor-containing nitrogen atmosphere may not be supplied to the dewaked parts adjacent to the sintering furnace. good. As a result, it is possible to prevent an atmosphere having a high dew point from being mixed into the sintered portion, and to prevent excessive oxidation of the sintered body from proceeding in the sintered portion treated at a higher temperature.
In the plurality of dewaxed parts, the water vapor-containing nitrogen atmosphere is preferably supplied from the same source for simplification of equipment, and the dew point and gas type may be the same.
　脱ろう部の雰囲気供給部において、水蒸気生成方法としては、定量供給ポンプと電気ヒーター加熱による方法、ボイラ加熱、超音波振動等を用いることができる。なかでも、水蒸気生成量を調節しやすく、保守管理が簡便であることから、定量供給ポンプと電気ヒーター加熱による方法を好ましく用いることができる。 In the atmosphere supply section of the dewaxing section, as the steam generation method, a method using a fixed quantity supply pump and electric heater heating, boiler heating, ultrasonic vibration, or the like can be used. Among them, since the amount of steam generated can be easily adjusted and maintenance is easy, the method using a fixed quantity supply pump and electric heater heating can be preferably used.
　水蒸気生成装置の他の例としては、水タンク部、水定量供給ポンプ部、気化器、気化器に窒素ガスを供給する窒素ガス供給部、水蒸気雰囲気排出部を備える。
　この例では、まず、水タンクから水定量供給ポンプ部によって水を気化器に供給する。水は、純水等のイオン性の不純物が除去された水を用いることが好ましい。気化器を１００℃以上、好ましくは２００℃以上、より好ましくは２５０℃以上とすることで水蒸気を生成することができる。窒素ガス供給部から気化器に窒素ガスを供給し水蒸気を含む窒素雰囲気を生成することができる。この水蒸気を含む窒素雰囲気を水蒸気雰囲気排出部から排出して、脱ろう部に供給することができる。
　水蒸気雰囲気排出部から脱ろう部への配管は、６０～１００℃に保温しておくことが好ましい。 Other examples of the steam generator include a water tank section, a water metering supply pump section, a vaporizer, a nitrogen gas supply section for supplying nitrogen gas to the vaporizer, and a steam atmosphere discharge section.
In this example, first, water is supplied from the water tank to the vaporizer by the water metering supply pump unit. As the water, it is preferable to use water from which ionic impurities such as pure water have been removed. Water vapor can be generated by setting the vaporizer at 100 ° C. or higher, preferably 200 ° C. or higher, and more preferably 250 ° C. or higher. Nitrogen gas can be supplied from the nitrogen gas supply unit to the vaporizer to generate a nitrogen atmosphere containing water vapor. The nitrogen atmosphere containing water vapor can be discharged from the water vapor atmosphere discharging part and supplied to the dewaxing part.
It is preferable to keep the temperature of the pipe from the water vapor atmosphere discharging part to the dewaxing part at 60 to 100 ° C.
　焼結部は、搬送手段、加熱部、雰囲気供給部、排気部、熱電対を備える。
　焼結部の加熱部は、特に限定されず、上記した脱ろう部で説明したものの中から適宜選択して用いることができる。
　焼結部の雰囲気供給部は、雰囲気を所定温度で炉内に供給するものであって、炉内に均一に雰囲気を供給するために複数個配置されてもよい。
　焼結部の雰囲気供給部に流量計を設けて、炉内に供給される雰囲気の流量を調節するとよい。 The sintered section includes a transporting means, a heating section, an atmosphere supply section, an exhaust section, and a thermocouple.
The heating portion of the sintered portion is not particularly limited, and can be appropriately selected and used from those described in the dewaxing portion described above.
The atmosphere supply section of the sintered section supplies the atmosphere into the furnace at a predetermined temperature, and a plurality of atmosphere supply sections may be arranged in order to uniformly supply the atmosphere into the furnace.
It is advisable to provide a flow meter in the atmosphere supply section of the sintered section to adjust the flow rate of the atmosphere supplied into the furnace.
　冷却部は、特に限定されずに、通常の焼結炉に適用可能なものを用いればよい。
　連続焼結炉において、搬送手段は駆動モータによって駆動させることができる。また、連続焼結炉において、脱ろう部及び焼結部には１個又は複数個の排気部を設けることができ、成形体から熱分解された有機成分を含む排ガスを排気することができる。また、連続焼結炉において、脱ろう部及び焼結部には１個又は複数個の熱電対を設けることができ、各区画において、炉内温度の管理をすることができる。 The cooling unit is not particularly limited, and any cooling unit that can be applied to a normal sintering furnace may be used.
In a continuous sintering furnace, the transfer means can be driven by a drive motor. Further, in the continuous sintering furnace, one or a plurality of exhaust parts can be provided in the dewaxing part and the sintered part, and the exhaust gas containing the thermally decomposed organic component can be exhausted from the molded body. Further, in the continuous sintering furnace, one or a plurality of thermocouples can be provided in the dewaxed portion and the sintered portion, and the temperature inside the furnace can be controlled in each section.
　一実施形態によって製造される焼結体は、この限りでないが、以下の物性を備えることが好ましい。 The sintered body produced by one embodiment is not limited to this, but preferably has the following physical properties.
　焼結体は、ロックウェル硬さが２０～７０ＨＲＢが好ましい。
　焼結体のロックウェル硬さは、２０ＨＲＢ以上が好ましく、３０ＨＲＢ以上がより好ましく、４０ＨＲＢ以上がさらに好ましい。これによって、より高強度の焼結体を提供することができる。
　焼結体のロックウェル硬さは、特に限定されないが、例えば、１００ＨＲＢ以下であってよい。 The sintered body preferably has a Rockwell hardness of 20 to 70 HRB.
The Rockwell hardness of the sintered body is preferably 20 HRB or more, more preferably 30 HRB or more, and even more preferably 40 HRB or more. Thereby, a higher strength sintered body can be provided.
The Rockwell hardness of the sintered body is not particularly limited, but may be, for example, 100 HRB or less.
　ここで、焼結体のロックウェル硬さは、ＪＩＳ　Ｚ　２２４５に規定されている方法にしたがって測定することができる。 Here, the Rockwell hardness of the sintered body can be measured according to the method specified in JIS Z2245.
　焼結体は、引張強さが２２０～５９０ＭＰａが好ましい。
　焼結体の引張強さは、２２０ＭＰａ以上が好ましく、２５０ＭＰａ以上がより好ましく、３００ＭＰａ以上がさらに好ましい。これによって、より高強度の焼結体を提供することができる。
　焼結体の引張強さは、特に限定されないが、例えば、６００ＭＰａ以下であってよい。 The sintered body preferably has a tensile strength of 220 to 590 MPa.
The tensile strength of the sintered body is preferably 220 MPa or more, more preferably 250 MPa or more, and even more preferably 300 MPa or more. Thereby, a higher strength sintered body can be provided.
The tensile strength of the sintered body is not particularly limited, but may be, for example, 600 MPa or less.
　ここで、焼結体の引張強さは、試験片としてＡＳＴＭ：Ｅ８－６９を作製して、試験方法はＪＩＳ　Ｚ２２４１に規定されている方法に従って測定することができる。 Here, the tensile strength of the sintered body can be measured by preparing ASTM: E8-69 as a test piece and the test method according to the method specified in JIS Z2241.
　焼結体は、金属組織において、フェライト相の面積比が５０面積％以下が好ましく、４０面積％以下がより好ましく、３０面積％以下がさらに好ましく、２０面積％以下が一層好ましい。フェライト相をより低減することで、より高強度の焼結体を得ることができる。焼結体は、金属組織において、パーライト相が形成されることが好ましく、パーライト相が６０～９０面積％がより好ましい。
　焼結体の金属組織は、走査型電子顕微鏡によって観察することができる。 In the metal structure of the sintered body, the area ratio of the ferrite phase is preferably 50 area% or less, more preferably 40 area% or less, further preferably 30 area% or less, still more preferably 20 area% or less. By further reducing the ferrite phase, a sintered body having higher strength can be obtained. The sintered body preferably has a pearlite phase formed in the metal structure, and the pearlite phase is more preferably 60 to 90 area%.
The metallographic structure of the sintered body can be observed with a scanning electron microscope.
　以下、本発明を実施例により具体的に説明するが、本発明はこれらの実施例に限定されるものではない。 Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.
　脱ろう、焼結後の試験片の微細組織、強度、外観について評価した。
　「成形」
　原料粉末として、Ｃ：０．８質量％、Ｃｕ：２．０質量％、残部鉄からなる組成の鉄基粉末を用意した。鉄基粉末１００質量部に０．８質量部のステアリン酸亜鉛（株式会社ＡＤＥＫＡ製「ＺＮＳ－７３０」）を添加し、Ｖ型ミキサーで３０分間混合した。この混合粉末を外径９０ｍｍ、内径１５ｍｍ、高さ１５ｍｍの円環状に圧粉して成形体を得た。成形体の質量は、５９０ｇであり、密度は６．９ｇ／ｃｍ３であった。 The microstructure, strength, and appearance of the test pieces after dewaxing and sintering were evaluated.
"Molding"
As the raw material powder, an iron-based powder having a composition of C: 0.8% by mass, Cu: 2.0% by mass, and the balance iron was prepared. 0.8 parts by mass of zinc stearate (“ZNS-730” manufactured by ADEKA Corporation) was added to 100 parts by mass of the iron-based powder, and the mixture was mixed with a V-type mixer for 30 minutes. This mixed powder was compacted into an annular shape having an outer diameter of 90 mm, an inner diameter of 15 mm, and a height of 15 mm to obtain a molded product. The mass of the molded product was 590 g, and the density was 6.9 g / cm 3 .
　「脱ろう」
　脱ろう及び焼結は、ローラーハース炉（ＮＲ－１号炉）に成形体を通すことで行った。
　ローラーハース炉の脱ろう炉の断面概略図を図１に示す。
　この図において、脱ろう炉１０は、搬送ローラ１を備え、搬送ローラ１上に試験片を載置して試験片を搬送するカーボントレイＴと、搬送方向の上流側から脱ろう部２ａ、脱ろう部２ｂ、及び脱ろう部２ｃとを備える。それぞれの脱ろう部２ａ、２ｂ、２ｃが仕切り板によって区分けされ、それぞれの脱ろう部２ａ、２ｂ、２ｃに配置されたラジアントチューブバーナ３ａ、３ｂ、３ｃ、それぞれの脱ろう部２ａ、２ｂ、２ｃに水蒸気含有窒素雰囲気を供給するためのガス導入口部４ａ、４ｂ、４ｃ、脱ろう部２ｂ、２ｃからの排気を排出する排気口部５を備える。
　脱ろう炉内はラジアントチューブバーナで温度が制御され、搬送方向Ｘに、搬送ローラでカーボントレイ上の成形体が搬送される。水蒸気含有窒素雰囲気は炉内床面の導入口部から供給され、成形体を脱ろうする。脱ろう部から排出される排気は、排気口部に設けられた排ガス燃焼装置で燃焼処理し、排気フード・ダクト６から排出される。
　熱源のラジアントチューブバーナは間接加熱方式で炉内と隔離しており、炉内雰囲気を一定に保つことができる。 "Let's take off"
Dewaxing and sintering were performed by passing the molded product through a roller hearth furnace (NR-1 furnace).
A schematic cross-sectional view of the dewaxing furnace of the roller hearth furnace is shown in FIG.
In this figure, the dewaxing furnace 10 includes a transfer roller 1, a carbon tray T on which a test piece is placed on the transfer roller 1 to transfer the test piece, and a dewaxing portion 2a from the upstream side in the transfer direction. It includes a brazing part 2b and a dewaxing part 2c. The respective degassing portions 2a, 2b, and 2c are separated by a partition plate, and the radiant tube burners 3a, 3b, and 3c arranged in the respective degassing portions 2a, 2b, and 2c, and the respective degassing portions 2a, 2b, and 2c. Is provided with a gas introduction port 4a, 4b, 4c for supplying a water vapor-containing nitrogen atmosphere, and an exhaust port 5 for discharging exhaust gas from the dewaxing parts 2b, 2c.
The temperature inside the dewaxing furnace is controlled by a radiant tube burner, and the molded product on the carbon tray is conveyed by the transfer roller in the transfer direction X. The water vapor-containing nitrogen atmosphere is supplied from the introduction port on the floor surface of the furnace to remove the molded product. The exhaust gas discharged from the dewaxing portion is burned by an exhaust gas combustion device provided in the exhaust port portion, and is discharged from the exhaust hood duct 6.
The radiant tube burner of the heat source is isolated from the inside of the furnace by an indirect heating method, and the atmosphere inside the furnace can be kept constant.
　ローラーハース炉の脱ろう炉の条件は、以下の通りとした。
　不図示の気化器によって水蒸気を発生させ、発生させた水蒸気と、窒素１００体積％の窒素雰囲気とを混合して、表１に示す露点の水蒸気含有雰囲気を用意した。
　気化器温度を３００℃、脱ろう部２ａ、２ｂ、２ｃの温度をそれぞれ２５０℃、３５０℃、５５０℃で一定とした。また、気化器から脱ろう部２ａ、２ｂ、２ｃへの水蒸気含有窒素雰囲気の流量をそれぞれ２ｍ３／ｈ、４ｍ３／ｈ、０ｍ３／ｈで一定とした。成形体の投入数は１トレイに９個で一定とした。
　その他の脱ろう条件は、以下の通りとした。
　脱ろう圧力：５Ｐａ。
　脱ろう時間：３０分。 The conditions for the dewaxing furnace of the roller hearth furnace were as follows.
Water vapor was generated by a vaporizer (not shown), and the generated water vapor and a nitrogen atmosphere of 100% by volume of nitrogen were mixed to prepare a water vapor-containing atmosphere at the dew point shown in Table 1.
The vaporizer temperature was kept constant at 300 ° C., and the temperatures of the dewaxed portions 2a, 2b, and 2c were kept constant at 250 ° C., 350 ° C., and 550 ° C., respectively. Further, the flow rates of the water vapor-containing nitrogen atmosphere to the dewaxed portions 2a, 2b, and 2c from the vaporizer were kept constant at 2 m 3 / h, 4 m 3 / h, and 0 m 3 / h, respectively. The number of compacts charged was 9 per tray, which was constant.
Other deafening conditions are as follows.
Dewaxing pressure: 5 Pa.
Take off time: 30 minutes.
　「焼結」
　次いで、ローラーハース炉の焼結炉に成形体を通した。焼結条件は、以下の通りとした。
　焼結温度：１１３０℃。
　焼結圧力：１０Ｐａ。
　焼結雰囲気：４体積％Ｈ２＋９６体積％Ｎ２。
　焼結雰囲気の露点：－６０℃。
　ガス流量：Ｎ２ガス３４ｍ３／ｈ。ＡＸガス２ｍ３／ｈ。
　焼結時間：４０分。
　冷却速度：室温まで４０℃／分。 "Sintering"
Then, the molded product was passed through the sintering furnace of the roller hearth furnace. The sintering conditions were as follows.
Sintering temperature: 1130 ° C.
Sintering pressure: 10 Pa.
Sintering atmosphere: 4% by volume H 2 + 96% by volume N 2 .
Dew point of sintered atmosphere: -60 ° C.
Gas flow rate: N 2 gas 34 m 3 / h. AX gas 2m 3 / h.
Sintering time: 40 minutes.
Cooling rate: 40 ° C / min to room temperature.
　脱ろう部２ａ、２ｂ、２ｃの水素濃度は、焼結炉から流入する雰囲気に含まれるＨ２ガスを含む数値である。脱ろう部のＮ２ガス流量と、焼結炉のＮ２ガス流量及びＡＸガス流量との合計ガス流量に対して、ＡＸガス流量のＨ２割合が、５体積％未満となるように制御した。これによって、焼結炉から脱ろう炉へ流入するＨ２ガスを考慮しても、脱ろう炉の水素濃度を５体積％未満とすることができた。ＡＸガスは、７５体積％Ｈ２と２５％Ｎ２を含むアンモニア分解ガスである。 The hydrogen concentration of the dewaxed portions 2a, 2b, and 2c is a numerical value including H 2 gas contained in the atmosphere flowing from the sintering furnace. And N 2 gas flow rate of dewaxing unit, the total gas flow rate of N 2 gas flow rate and AX gas flow sintering furnace, H 2 ratio of AX gas flow rate was controlled to be less than 5% by volume .. Thus, even in consideration of H 2 gas flowing from the sintering furnace to dewaxing furnace, it could be less than 5 vol% of hydrogen concentration in the dewaxing reactor. The AX gas is an ammonia decomposition gas containing 75% by volume H 2 and 25% N 2.
　「評価」
　得られた焼結体について、以下の評価を行った。結果を表１に示す。
　（焼結体の汚れ）
　焼結体の表面を目視で観察し、以下の基準で焼結体の汚れを評価した。
　Ａ：汚れが観察されなかった。
　Ｂ：汚れが少し観察された。 "evaluation"
The obtained sintered body was evaluated as follows. The results are shown in Table 1.
(Dirt on the sintered body)
The surface of the sintered body was visually observed, and the dirt on the sintered body was evaluated according to the following criteria.
A: No dirt was observed.
B: Some stains were observed.
　（焼結体の強度）
　焼結体の引張強さを以下の条件で測定した。
　焼結体の引張強さは、試験片としてＡＳＴＭ：Ｅ８－６９を作製し、試験方法はＪＩＳ　Ｚ２２４１に規定されている方法に従って測定した。 (Strength of sintered body)
The tensile strength of the sintered body was measured under the following conditions.
The tensile strength of the sintered body was measured by preparing ASTM: E8-69 as a test piece and the test method according to the method specified in JIS Z2241.
　（焼結体の微細構造）
　焼結体の金属組織を走査型電子顕微鏡（ＳＥＭ）によって観察した。ＳＥＭ写真を図２に示す。また、ＳＥＭ写真から、脱炭の指標となるフェライト相の面積比を算出した。 (Microstructure of sintered body)
The metallographic structure of the sintered body was observed with a scanning electron microscope (SEM). The SEM photograph is shown in FIG. In addition, the area ratio of the ferrite phase, which is an index of decarburization, was calculated from the SEM photograph.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１に示す通り、各実施例の焼結体は、表面汚れが少なく、高強度であった。例１では、脱ろうの雰囲気の露点が１０℃と低く、焼結体の表面汚れが若干発生した。例４及び５では、脱ろうの雰囲気の露点が２０℃、３０℃と高く、焼結体の強度が若干低下した。 As shown in Table 1, the sintered body of each example had little surface stain and high strength. In Example 1, the dew point of the dewaxing atmosphere was as low as 10 ° C., and the surface of the sintered body was slightly soiled. In Examples 4 and 5, the dew point of the dewaxing atmosphere was as high as 20 ° C. and 30 ° C., and the strength of the sintered body was slightly lowered.

Claims (9)

  1. 　鉄基粉末を含む原料粉末及びステアリン酸亜鉛を含む成形体を脱ろうすること、及び前記脱ろうした成形体を焼結することを含み、
    　前記脱ろうは、窒素と、水蒸気とを含み、露点が０℃以上３０℃以下である水蒸気含有窒素雰囲気を用意すること、前記水蒸気含有窒素雰囲気を１００℃以上に加熱し脱ろう部に供給すること、及び前記脱ろう部で前記成形体を８００℃以下で熱処理することを含む、鉄基焼結体の製造方法。     Includes dewaxing a molded body containing a raw material powder containing an iron-based powder and zinc stearate, and sintering the dewaxed molded body.
    The dewaxing includes nitrogen and water vapor, and prepares a water vapor-containing nitrogen atmosphere having a dew point of 0 ° C. or more and 30 ° C. or less, and heats the water vapor-containing nitrogen atmosphere to 100 ° C. or more and supplies the dew point to the dewaxing part. A method for producing an iron-based sintered body, which comprises heat-treating the molded body at 800 ° C. or lower at the dew point.
  2. 　前記水蒸気含有窒素雰囲気を、水蒸気と窒素雰囲気とを混合して用意することを含み、前記窒素雰囲気は、窒素が９５体積％以上である、請求項１に記載の鉄基焼結体の製造方法。 The method for producing an iron-based sintered body according to claim 1, wherein the water vapor-containing nitrogen atmosphere is prepared by mixing water vapor and a nitrogen atmosphere, and the nitrogen atmosphere contains 95% by volume or more of nitrogen. ..
  3. 　前記脱ろう部の雰囲気は、水素が５体積％未満である、請求項１又は２に記載の鉄基焼結体の製造方法。 The method for producing an iron-based sintered body according to claim 1 or 2, wherein the atmosphere of the dewaxed portion is less than 5% by volume of hydrogen.
  4. 　前記脱ろう部は、前記水蒸気含有窒素雰囲気を２５０℃以上に加熱し脱ろうすることを含む、請求項１から３のいずれか１項に記載の鉄基焼結体の製造方法。 The method for producing an iron-based sintered body according to any one of claims 1 to 3, wherein the dewaxing portion includes heating the water vapor-containing nitrogen atmosphere to 250 ° C. or higher to dewax.
  5. 　前記成形体の原料粉末は、０質量％超過２０質量％以下のＣｕを含み、残部鉄及び不可避不純物からなる、請求項１から４のいずれか１項に記載の鉄基焼結体の製造方法。 The method for producing an iron-based sintered body according to any one of claims 1 to 4, wherein the raw material powder of the molded product contains Cu in an amount of more than 0% by mass and 20% by mass or less, and is composed of residual iron and unavoidable impurities. ..
  6. 　前記成形体の原料粉末は、Ｍｎ及びＳが合計量で０．２質量％以下である、請求項１から５のいずれか１項に記載の鉄基焼結体の製造方法。 The method for producing an iron-based sintered body according to any one of claims 1 to 5, wherein the raw material powder of the molded product contains Mn and S in a total amount of 0.2% by mass or less.
  7. 　前記成形体の原料粉末は、０質量％超過５質量％以下のＣをさらに含む、請求項１から６のいずれか１項に記載の鉄基焼結体の製造方法。 The method for producing an iron-based sintered body according to any one of claims 1 to 6, wherein the raw material powder of the molded product further contains C in an amount of more than 0% by mass and 5% by mass or less.
  8. 　前記ステアリン酸亜鉛は、原料粉末１００質量部に対して０．０５～５質量部である、請求項１から７のいずれか１項に記載の鉄基焼結体の製造方法。 The method for producing an iron-based sintered body according to any one of claims 1 to 7, wherein the zinc stearate is 0.05 to 5 parts by mass with respect to 100 parts by mass of the raw material powder.
  9. 　前記脱ろうと前記焼結とを連続焼結炉で行う、請求項１から８のいずれか１項に記載の鉄基焼結体の製造方法。 The method for producing an iron-based sintered body according to any one of claims 1 to 8, wherein the removal and the sintering are performed in a continuous sintering furnace.
PCT/JP2020/014983 2020-04-01 2020-04-01 Method for manufacturing iron-based sintered body WO2021199370A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
PCT/JP2020/014983 WO2021199370A1 (en) 2020-04-01 2020-04-01 Method for manufacturing iron-based sintered body
JP2022511433A JPWO2021199370A1 (en) 2020-04-01 2020-04-01

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/JP2020/014983 WO2021199370A1 (en) 2020-04-01 2020-04-01 Method for manufacturing iron-based sintered body

Publications (1)

Publication Number Publication Date
WO2021199370A1 true WO2021199370A1 (en) 2021-10-07

Family

ID=77929902

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2020/014983 WO2021199370A1 (en) 2020-04-01 2020-04-01 Method for manufacturing iron-based sintered body

Country Status (2)

Country Link
JP (1) JPWO2021199370A1 (en)
WO (1) WO2021199370A1 (en)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62109902A (en) * 1985-11-08 1987-05-21 Kobe Steel Ltd Method for sintering green compact of iron-base powder
JPH10121108A (en) * 1996-10-09 1998-05-12 Osaka Oxygen Ind Ltd Production of sintered metal and its device

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62109902A (en) * 1985-11-08 1987-05-21 Kobe Steel Ltd Method for sintering green compact of iron-base powder
JPH10121108A (en) * 1996-10-09 1998-05-12 Osaka Oxygen Ind Ltd Production of sintered metal and its device

Also Published As

Publication number Publication date
JPWO2021199370A1 (en) 2021-10-07

Similar Documents

Publication Publication Date Title
JP4368245B2 (en) Hard particle dispersion type iron-based sintered alloy
JP6212632B2 (en) Method for producing a steel compact
US2637671A (en) Powder metallurgy method of making steel cutting tools
KR20180058755A (en) Broken separated iron-based material
US6358298B1 (en) Iron-graphite composite powders and sintered articles produced therefrom
JP2005526178A (en) Method for producing a sintered part from a sinterable material
JP2010090470A (en) Iron-based sintered alloy and method for producing the same
EP2200769B1 (en) Method of producing a sinter-hardened component
CA2922018A1 (en) Alloy steel powder for powder metallurgy and method of producing iron-based sintered body
KR20170054516A (en) A pre-alloyed iron- based powder, an iron-based powder mixture containing the pre-alloyed iron-based powder and a method for making pressed and sintered components from the iron-based powder mixture
JP2020500261A (en) Free graphite containing powder
US6019937A (en) Press and sinter process for high density components
JP4376826B2 (en) Co-Cr alloy pellet and method for producing the same
WO2021199370A1 (en) Method for manufacturing iron-based sintered body
JP5929084B2 (en) Alloy steel powder for powder metallurgy, iron-based sintered material and method for producing the same
US10583487B2 (en) Method of producing alloyed metallic products
Tosangthum et al. Effect of boron addition and sintering atmosphere on precipitation in sintered Fe-Mo-C steels
Weber et al. Optimised sintering route for cold work tool steels
JP5834372B2 (en) Method for producing Fe-Cu-C sintered material
JP2003239002A (en) Iron based powdery mixture and method of producing iron based sintered compact
Schade et al. MICROSTRUCTURE AND MECHANICAL PROPERTIES OF A BAINITIC POWDER METALLURGY STEEL.
JP4301657B2 (en) Manufacturing method of high strength sintered alloy steel
Danninger et al. Powder metallurgy steels for highly loaded precision parts
JP2011214097A (en) Alloy-steel-powder mixed powder with small variation of sintering strength
JP2023088598A (en) Composite metal material, hardened composite metal material, method for producing hardened composite metal material and hardened composite metal component

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 20928287

Country of ref document: EP

Kind code of ref document: A1

ENP Entry into the national phase

Ref document number: 2022511433

Country of ref document: JP

Kind code of ref document: A

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 20928287

Country of ref document: EP

Kind code of ref document: A1