WO2015004902A1 - 高炭素熱延鋼板およびその製造方法 - Google Patents
高炭素熱延鋼板およびその製造方法 Download PDFInfo
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- C—CHEMISTRY; METALLURGY
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
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- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
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- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
- C21D1/32—Soft annealing, e.g. spheroidising
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- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
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- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/003—Cementite
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
Definitions
- the present invention relates to a high-carbon hot-rolled steel sheet excellent in hardenability and workability and a method for producing the same, and in particular, a high-carbon hot-rolled steel sheet to which B is added, It relates to the manufacturing method.
- Patent Document 1 as a steel component, C: 0.1 to 1.2%, Si: 0.01 to 2.5%, Mn: 0.1 to 1.5%, P: 0.04% or less (including 0%), S: 0.0005 to 0.05%, Al: 0.2% or less, Te: 0.0005 to 0.05%, and Se: 0.0005 to 0.00.
- One or two of 05%, N: 0.0005 to 0.03%, and the total content of S and one or two of Te and Se is 0.005% to 0.05% steel, the balance being Fe and inevitable impurities, consisting mainly of ferrite and pearlite, the ferrite grain size number specified in JIS G 0552 being 11 or more
- Disclosed is a structural steel having excellent cold workability and low decarburization characteristics.
- Patent Document 1 in addition to the above steel components, Sb: 0.001 to 0.05%, Cr: 0.2 to 2.0%, Mo: 0.1 to 1.0%, Ni : 0.3 to 1.5%, Cu: 1.0% or less, B: 0.005% or less, or one or more of them, Ti: 0.002% to 0.05%, Nb: 0 0.005 to 0.1%, V: 0.03 to 0.3%, one or more, Mg: 0.0002 to 0.01%, Zr: 0.0001 to 0.01%, A mechanical structural steel containing one or more of Ca: 0.0002 to 0.008% is disclosed.
- the steel of the said component composition is hot rough-rolled in the temperature range of 850 degreeC or more and 1000 degrees C or less, and after finish rolling in the temperature range of 700 degreeC or more and 1000 degrees C or less, 500 degreeC or more and 700 degrees C or less Is cooled at a cooling rate in the range of 0.1 ° C./second to less than 5 ° C./second, immediately held at a furnace atmosphere temperature of 650 ° C. to 750 ° C. for 15 minutes to 90 minutes, and then allowed to cool.
- a method for producing a steel for machine structure excellent in cold workability and low decarburization characteristics is disclosed.
- Patent Document 2 as steel components, C%: 0.2 to 0.35%, Si: 0.03 to 0.3%, Mn: 0.15 to 1.2%, Cr: 0% by mass 0.02-1.2%, P: 0.02% or less, S: 0.02% or less, Mo: 0.2% or less, Ti: 0.01-0.10%, B: 0.0005-0 .0050%, and contains at least 0.0003 to 0.5% of Sn, Sb, Bi, and Se, or in addition to the above steel components, Ce: 0.05% or less, Ca : 0.05% or less, Zr: 0.05% or less, Mg: High carbon excellent in workability, hardenability, weldability, carburization resistance and decarburization resistance, containing one or more of 0.05% or less A steel sheet is disclosed.
- Patent Document 2 discloses that when hot-rolling steel having the above composition, the finishing temperature is Ar3 + 10 ° C. to Ar3 + 50 ° C., the coiling temperature is in the range of 550 ° C. to 700 ° C., and then pickling is performed. Disclosed is a method for producing a high carbon steel sheet that is excellent in workability, hardenability, weldability, carburization resistance and decarburization resistance.
- Patent Document 3 in mass%, C: 0.15 to 0.37%, Si: 1% or less, Mn: 2.5% or less, P: 0.1% or less, S: 0.03% or less , Sol.Al: 0.1% or less, N: 0.0005 to 0.0050%, B: 0.0010 to 0.0050%, and at least one of Sb and Sn: 0.003 to 0 in total .10% and satisfying the relationship of 0.50 ⁇ (14 [B]) / (10.8 [N]), with the balance being composed of Fe and inevitable impurities, A high-carbon hot-rolled steel sheet comprising a cementite and having a microstructure in which an average grain size of the ferrite phase is 10 ⁇ m or less and a spheroidization ratio of the cementite is 90% or more; provided that [B], [N ] Represents the contents (mass%) of B and N, respectively.
- Patent Document 3 in addition to the above composition, at least one of Ti, Nb, and V: 0.1% or less in total, or at least one of Ni, Cr, and Mo: 1 in total
- Patent Document 3 discloses that a steel having the above composition is hot-rolled at a finishing temperature not lower than the Ar3 transformation point, cooled to a cooling stop temperature of 550 to 650 ° C. within 10 s, and wound at 500 to 650 ° C.
- a method for producing a high carbon hot-rolled steel sheet is disclosed, characterized by performing spheroidizing annealing of cementite in a temperature range of 640 ° C.
- Patent Document 3 discloses that steel having the above composition is hot-rolled at a finishing temperature equal to or higher than the Ar3 transformation point, and then from 450 ° C. to 600 ° C. at an average cooling rate of 50 ° C./s or higher from a temperature of 650 ° C. or higher.
- a method for producing a high carbon hot-rolled steel sheet is disclosed, characterized in that it is rolled up within 3 s after cooling to the cooling stop temperature of the steel, pickled, and then subjected to spheroidizing annealing of cementite in a temperature range of 640 ° C. or higher and Ac1 transformation point or lower. Has been.
- the hardenability is improved by elements such as Mn, P, B, Cr, Mo and Ni.
- elements such as Mn, P, and B are described as elements that improve hardenability.
- the high carbon hot rolled steel sheet is required to have relatively low hardness and high elongation.
- a high carbon hot rolled steel sheet that can be integrally formed with a cold press for automotive parts that have conventionally been manufactured in multiple processes such as hot forging, cutting, and welding has a hardness of Rockwell hardness HRB. Therefore, characteristics such as 83 or less and total elongation El of 30% or more are required.
- excellent hardenability is desired for the high carbon hot-rolled steel sheet having good workability as described above. For example, it is desired to obtain a Vickers hardness exceeding HV620 after water quenching.
- characteristics such as a hardness of 75 or less in Rockwell hardness HRB and a total elongation El of 38% or more are desired.
- hardenability it is desired to obtain a Vickers hardness of HV440 or higher after water quenching instead of the above-described Vickers hardness exceeding HV620.
- elements such as Mn, P, B, Cr, Mo and Ni are used as described above.
- Mn and the like improve the hardenability, but increase the strength of the hot-rolled steel sheet itself by solid solution strengthening and increase the hardness.
- B is an element that can ensure hardenability at low cost without greatly increasing the hardness of the high-carbon hot-rolled steel sheet before quenching.
- the hardness and ductility after spheroidizing annealing may vary, and if the finishing temperature of hot rolling is particularly high, sufficient ductility may not be obtained.
- the present invention solves the above-mentioned problems, uses steel added with B as a raw material, and even if annealing is performed in a nitrogen atmosphere, stable and excellent hardenability can be obtained.
- High carbon hot-rolled steel sheet having excellent workability such as 83 or less and total elongation El of 30% or more and its manufacturing method, or high carbon having excellent workability such as HRB of 75 or less and total elongation El of 38% or more It aims at providing a hot-rolled steel plate and its manufacturing method.
- the present inventors made Mn content 0.50% or less and a relatively low amount of Mn, and hereby examined the relationship between the manufacturing conditions and workability of the high carbon hot rolled steel sheet to which B was added, hardenability, The following findings were obtained.
- the cementite density in the ferrite grains greatly affects the hardness and total elongation (hereinafter, also simply referred to as elongation) of the high carbon hot rolled steel sheet before quenching.
- the cementite density in the ferrite grains needs to be 0.15 pieces / ⁇ m 2 or less.
- the cementite density in the ferrite grains should be It is necessary to set it to 0.10 piece / micrometer ⁇ 2 > or less. ii)
- the finishing temperature in hot rolling greatly affects the cementite density in the ferrite grains. If the finishing temperature is too high, it is difficult to reduce the cementite density after spheroidizing annealing.
- nitrogen in the atmosphere is nitrogend and concentrated in the steel sheet, and combined with B in the steel sheet to generate BN, so the amount of solute B in the steel sheet is greatly reduced.
- the nitrogen atmosphere is an atmosphere containing 90% by volume or more of nitrogen.
- the finishing temperature in hot rolling tends to be lower at the end of the sheet width
- the following knowledge was obtained as a result of investigating and examining the characteristics in the sheet width direction.
- the finishing temperature is likely to be lower than that of the center portion of the plate width, and as a result, the elongation is reduced and the workability is deteriorated, and the hardness and elongation after annealing are likely to vary in the width direction.
- finish rolling such a variation can be suppressed by raising the temperature of the edge portion of the sheet using an edge heater.
- the variation in Rockwell hardness HRB in the steel plate width direction is 4 or less in HRB.
- the variation of the elongation El can be 3% or less in El.
- the present invention has been made on the basis of such knowledge, and the gist thereof is as follows.
- the C content is% by mass and C: 0.20% or more and 0.40% or less, it consists of ferrite and cementite, and the cementite density in the ferrite grains is 0.10 pieces / ⁇ m 2 or less. It has a microstructure and is hard There 65 exceeds 75 or less in HRB, hardenability and high carbon hot-rolled steel sheet having excellent workability, wherein the total elongation is 38% or more.
- the C content is% by mass, C: more than 0.40% and 0.53% or less, composed of ferrite and cementite, and the cementite density in the ferrite grains is 0.15 pieces / ⁇ m 2 or less.
- the high-carbon hot-rolled steel sheet having a hard structure and excellent workability as described in [1] above, having a microstructure of HRB of 65 to 83 in terms of HRB and a total elongation of 30% or more .
- the C content is% by mass, C: 0.20% or more and 0.40% or less, composed of ferrite and cementite, and the cementite density in the ferrite grains is 0.10 pieces / ⁇ m 2 or less.
- the high carbon hot-rolled steel sheet having a hard structure and workability as described in [1] above, having a microstructure of HRB of 65 to 75 or less in HRB and a total elongation of 38% or more .
- C content of the steel is mass%, C: 0.40% if: ultra 0.53%, made of ferrite and cementite, have microstructure cementite density of 0.15 cells / [mu] m 2 or less in the ferrite grains, 65 exceeds 83 less hardness in HRB, total High carbon hot rolled steel with elongation of 30% or more A plate is manufactured, and when the C content of the steel is% by mass and C: 0.20% or more and 0.40% or less, the steel is composed of ferrite and cementite, and the cementite density in the ferrite grains is 0.10 pieces.
- It has a microstructure that is less than / ⁇ m 2 , has a hardness of 65 to 75 in HRB and a high carbon hot rolled steel sheet having a total elongation of 38% or more.
- a method for producing an excellent high carbon hot-rolled steel sheet is
- the steel has a C content of mass%, and C: more than 0.40% and 0.53% or less, comprising ferrite and cementite, and the cementite density in the ferrite grains is 0 Quenching according to the above [6], which produces a high-carbon hot-rolled steel sheet having a microstructure of 15 pieces / ⁇ m 2 or less, a hardness of 65 to 83 in HRB, and a total elongation of 30% or more. Of high carbon hot-rolled steel sheet excellent in workability and workability.
- the steel has a C content of mass%, and C: 0.20% or more and 0.40% or less, and is composed of ferrite and cementite, and the cementite density in the ferrite grains is 0. Quenching according to the above [6], which produces a high-carbon hot-rolled steel sheet having a microstructure of 10 pieces / ⁇ m 2 or less, a hardness of 65 to 75 or less, and a total elongation of 38% or more. Of high carbon hot-rolled steel sheet excellent in workability and workability.
- a high carbon hot-rolled steel sheet having excellent hardenability and cold workability (workability) can be produced.
- the high-carbon hot-rolled steel sheet of the present invention is suitable for automotive parts such as gears, transmissions, seat recliners, and hubs that require cold workability on the raw steel sheet. Furthermore, since uniform characteristics can be obtained over the entire width of the steel sheet, it is also preferable from the viewpoint of improving the yield of the raw steel sheet.
- % which is a unit of component content, means “% by mass” unless otherwise specified.
- Composition C 0.20% or more and 0.53% or less C is an important element for obtaining strength after quenching.
- the hardness is 83 or less in HRB and the total elongation (El) is 30% or more
- the hardness after water quenching is over HV620.
- the amount of C is 0.40% or less, the hardness after water quenching cannot be more than HV620 due to the heat treatment after forming the part.
- the C content exceeds 0.40%. There is a need to.
- the C content is more than 0.40% and 0.53% or less.
- the C content is preferably 0.51% or less.
- the C content is preferably 0.45% or more. In this case, the preferable range of C content is 0.45% or more and 0.51% or less.
- C is an important element for obtaining strength after quenching.
- properties such as Rockwell hardness HRB of 75 or less and total elongation El of 38% or more are required, Vickers hardness of HV440 or more is desired after water quenching. If the amount of C is less than 0.20%, HV440 or more cannot be obtained in the hardness after water quenching by the heat treatment after forming the part. For this reason, when the hardness is 75 or less in HRB and the total elongation El is 38% or more, the hardness after water quenching is HV440 or more, so the C amount needs to be 0.20% or more. There is.
- the amount of C exceeds 0.40%, it becomes hard and the toughness and cold workability deteriorate, and the hardness cannot be stably obtained with HRB of 75 or less and total elongation of 38% or more. Therefore, when the hardness is 75 or less in HRB and the total elongation El is 38% or more, the C amount is 0.20% or more and 0.40% or less.
- the C content is preferably 0.26% or more, and when the C content is 0.32% or more, HV440 or more can be stably obtained with water quenching hardness. Therefore, it is more preferable.
- the C content range is 0.20% to 0.53%.
- the C content is more than 0.40% and 0.53% or less.
- the C content is 0.20% or more and 0.40% or less.
- Si 0.10% or less
- Si is an element that increases the strength by solid solution strengthening. As the Si content increases, the steel sheet becomes hard and cold workability deteriorates, so the Si content is 0.10% or less. Preferably it is 0.05% or less, More preferably, it is 0.03% or less. Since Si reduces cold workability, the smaller the amount of Si, the better. On the other hand, if Si is excessively reduced, the refining cost increases, so the Si content is preferably 0.005% or more.
- Mn 0.50% or less
- Mn is an element that improves hardenability, it is also an element that increases strength by solid solution strengthening. If the amount of Mn exceeds 0.50%, the steel sheet becomes too hard and cold workability is lowered. On the other hand, if the amount of Mn exceeds 0.50%, a band structure due to segregation of Mn develops and the steel structure becomes non-uniform, so that variations in hardness and elongation tend to increase. Therefore, the amount of Mn is 0.50% or less. Preferably, the amount of Mn is 0.45% or less, more preferably 0.40% or less. The lower limit is not specified. In the solution treatment at the time of quenching, the Mn content is preferably 0.20% or more in order to suppress the precipitation of graphite and dissolve the total amount of C in the steel sheet to obtain a predetermined quenching hardness.
- P 0.03% or less
- P is an element that increases the strength by solid solution strengthening. If the P content exceeds 0.03%, the steel sheet becomes too hard and cold workability is lowered, and grain boundary embrittlement is caused and the toughness after quenching is deteriorated. Therefore, the P content is 0.03% or less. In order to obtain excellent toughness after quenching, the P content is preferably 0.02% or less. P decreases the cold workability and toughness after quenching, so the smaller the amount of P, the better. On the other hand, if P is reduced excessively, the refining cost increases, so the amount of P is preferably 0.005% or more.
- S 0.010% or less
- S is an element that has to be reduced in order to form sulfides and to reduce the cold workability of the high carbon hot-rolled steel sheet and the toughness after quenching.
- the S amount is 0.010% or less.
- the S content is preferably 0.005% or less. Since S decreases cold workability and toughness after quenching, the smaller the amount of S, the better.
- the amount of S is preferably 0.0005% or more.
- sol. Al 0.10% or less sol.
- the amount of Al is 0.10% or less.
- sol. The Al content is 0.06% or less. Note that sol. Al has a deoxidizing effect, and in order to sufficiently deoxidize, Al is preferably 0.005% or more.
- N 0.0050% or less
- the amount of N exceeds 0.0050%
- the austenite grains become too fine during heating in the quenching process due to the formation of BN and AlN.
- the formation of a ferrite phase is promoted during cooling in the quenching process, the hardness after quenching is reduced, and the toughness after quenching is reduced. Therefore, the N content is 0.0050% or less.
- N is an element that forms BN and AlN, thereby appropriately suppressing the growth of austenite grains during heating in the quenching process and improving the toughness after quenching. 0005% or more is preferable.
- B 0.0005% or more and 0.0050% or less B is an important element that enhances hardenability.
- the amount of B is preferably 0.0010% or more.
- the amount of B exceeds 0.0050%, the recrystallization of austenite after finish rolling is delayed. As a result, the texture of the hot-rolled steel sheet develops, and the anisotropy of the steel sheet after annealing is increased. growing. Thus, when the anisotropy of the steel sheet after annealing increases, earring tends to occur in the drawing.
- the amount of B needs to be 0.0050% or less.
- the amount of B is 0.0035% or less. Therefore, the B amount is set to 0.0005% or more and 0.0050% or less.
- the amount of B is 0.0010% or more and 0.0035% or less.
- Sb, Sn, Bi, Ge, Te, and Se total 0.002% or more and 0.030% or less.
- Sb, Sn, Bi, Ge, Te, and Se are important for suppressing nitriding from the surface layer. It is an element. When the total amount of these elements is less than 0.002%, a sufficient effect is not recognized. For this reason, 1 or more types of Sb, Sn, Bi, Ge, Te, and Se are contained, and the minimum of the total amount of these elements shall be 0.002%. Preferably, the lower limit of the total amount of these elements is 0.005%. On the other hand, even if these elements are added in a total content exceeding 0.030%, the effect of preventing nitriding is saturated.
- the total content of Sb, Sn, Bi, Ge, Te, Se is 0.030% as an upper limit.
- the total content of Sb, Sn, Bi, Ge, Te, Se is 0.020% or less. Therefore, one or more of Sb, Sn, Bi, Ge, Te, and Se are contained, and the total content of these elements is 0.002% or more and 0.030% or less.
- the total content of Sb, Sn, Bi, Ge, Te, Se is 0.005% or more and 0.020% or less.
- At least one of Sb, Sn, Bi, Ge, Te, and Se is made 0.002% to 0.030% in total.
- solid solution B can be secured in the steel sheet after annealing.
- ⁇ (solid solution B amount) / (addition B amount) ⁇ ⁇ 100 (%) which is the ratio of the solid solution B amount in the steel sheet to the added B amount, can be set to 70 (%) or more.
- the added B amount is the B content in the steel.
- the balance is Fe and inevitable impurities, but in order to further improve the hardenability, at least one of Ni, Cr, and Mo can be contained in a total amount of 0.50% or less. That is, at least one of Ni, Cr, and Mo can be contained, and the total content of Ni, Cr, and Mo can be 0.50% or less. Since Ni, Cr, and Mo are expensive, the total content is preferably 0.20% or less in order to suppress high costs. In order to obtain the effects described above, the total content of Ni, Cr, and Mo is preferably set to 0.01% or more.
- Microstructure in order to improve the cold workability, it is necessary to spheroidize the cementite after hot rolling to obtain a microstructure composed of ferrite and cementite.
- the cementite density in the ferrite grains is set to 0.15 / hr in order that the hardness is 83 or less in HRB and the total elongation is 30% or more. It is necessary to make it ⁇ m 2 or less.
- the cementite density in the ferrite grains is set to 0.10. Pieces / ⁇ m 2 or less.
- Cementite density in ferrite grains C content of 0.15 / ⁇ m 2 or less when C content is more than 0.40% and 0.53% or less, C content is C: 0.20% or more and 0.40 In the case of% or less, 0.10 pieces / ⁇ m 2 or less
- the steel sheet of the present invention comprises ferrite and cementite. If the cementite density in the ferrite grains is high, it becomes hard due to dispersion strengthening and the elongation decreases. When the C content is more than 0.40% and 0.53% or less, in order to obtain a hardness of 83 or less in HRB and a total elongation of 30% or more, the cementite density in the grains is 0.15 / ⁇ m. Must be 2 or less.
- the cementite density in the ferrite grains may be 0 / ⁇ m 2 .
- the cementite diameter present in the ferrite grains is about 0.15 to 1.8 ⁇ m as the major axis, which is an effective size for precipitation strengthening of the steel sheet. For this reason, in the steel plate of the present invention, the strength can be reduced by reducing the cementite density in the grains.
- the cementite density in the ferrite grain is defined as 0.15 pieces / ⁇ m 2 or less.
- the cementite density in the ferrite grains is set to 0.10.
- Pieces / ⁇ m 2 or less Preferably it is 0.08 piece / micrometer ⁇ 2 > or less, More preferably, it is 0.06 piece / micrometer ⁇ 2 > or less.
- the cementite density in the ferrite grains may be 0 / ⁇ m 2 . It should be noted that the cementite diameter present in the ferrite grains is about 0.15 to 1.8 ⁇ m in the major axis, and is an effective size for precipitation strengthening of the steel sheet.
- the strength is reduced by reducing the cementite density in the grains. be able to. Since cementite at the ferrite grain boundary hardly contributes to dispersion strengthening, the cementite density in the ferrite grain is defined as 0.10 pieces / ⁇ m 2 or less.
- the volume fraction of cementite is about 5.9% to 8.0% or less when the C content is C: more than 0.40% and 0.53% or less, and the C content is 0.20% or more and 0.0. In the case of 40% or less, it is approximately 2.5% or more and 5.9% or less.
- the effect of the present invention is not impaired if the total volume ratio of the remaining structure is about 5% or less. Therefore, the remaining structure such as pearlite may be contained if the total volume ratio is 5% or less.
- the hardness of a steel plate shall be over HRB65. Furthermore, in order to improve the yield of the steel plate as a product, it is preferable that the HRB hardness variation is 4 or less and the elongation variation is 3% or less over the entire width of the steel plate.
- the variation in HRB hardness is the difference between the maximum value and the minimum value of HRB in the sheet width direction of the steel sheet.
- the variation in elongation is the difference between the maximum value and the minimum value of the total elongation in the sheet width direction of the steel sheet.
- the water quenching process is, for example, a process of heating to approximately 850 to 1050 ° C., holding for approximately 0.1 to 600 seconds, and immediately cooling with water.
- the oil quenching process is, for example, a process of heating to approximately 800 to 1050 ° C., holding for approximately 60 to 3600 seconds, and immediately cooling with oil.
- the hardness of the steel sheet is HRB 83 or less and El is 30% or more, as an excellent hardenability, for example, by performing a water quenching process of holding at 870 ° C.
- HV Vickers hardness
- the microstructure after the water quenching process or the oil quenching process is a martensite single phase structure or a mixed structure of martensite phase and bainite phase.
- the high-carbon hot-rolled steel sheet of the present invention is made of steel having the above composition, and after hot rough rolling, finish rolling is performed at a finish temperature of Ar3 transformation point or higher (Ar3 transformation point + 90 ° C) or lower.
- a hot-rolled steel sheet having a desired thickness is obtained by hot rolling and is wound at a winding temperature of 500 ° C. or higher and 700 ° C. or lower and then annealed at an Ac1 transformation point or lower.
- the rolling reduction in finish rolling is preferably 85% or more.
- the difference between the finishing temperature at the center of the sheet width of the steel sheet and the finishing temperature at a position 10 mm from the end of the sheet width may be within 40 ° C. Further preferred.
- the reason for limitation in the manufacturing method of the high carbon hot-rolled steel sheet of the present invention will be described.
- Finishing temperature Ar3 transformation point or higher (Ar3 transformation point + 90 ° C) or lower
- the cementite density in the ferrite grains after annealing is 0.15 / ⁇ m.
- the C content is 0.20% or more and 0.40% or less, in order to reduce the cementite density in the ferrite grains to 0.10 pieces / ⁇ m 2 or less after annealing, the microparticles containing pearlite and proeutectoid ferrite are used.
- the finishing temperature in hot rolling exceeds (Ar3 transformation point + 90 ° C.)
- the proportion of pro-eutectoid ferrite decreases, and a predetermined cementite density cannot be obtained after annealing. That is, when the C content of the steel is more than 0.40% and 0.53% or less, the cementite density in the ferrite grains is 0.15 pieces / ⁇ m 2 or less, and the C content of the steel is 0.20% or more and 0.40. % Or less, the cementite density in the ferrite grains: 0.10 pieces / ⁇ m 2 or less cannot be obtained.
- finishing temperature shall be below (Ar3 transformation point +90 degreeC).
- the finishing temperature is preferably set to (Ar3 transformation point + 70 ° C.) or lower. More preferably, it is less than 850 ° C. or (Ar 3 transformation point + 50 ° C.).
- the finishing temperature is less than the Ar3 transformation point, coarse ferrite grains are formed after hot rolling and after annealing, and the elongation is significantly reduced. For this reason, finishing temperature shall be more than Ar3 transformation point.
- regulated here is the temperature of the steel plate surface in the position of the sheet width center part when finishing rolling is completed.
- Winding temperature 500 ° C. or higher and 700 ° C. or lower
- the hot-rolled steel sheet after finish rolling is cooled and wound into a coil shape at a winding temperature of 500 ° C. or higher and 700 ° C. or lower. If the coiling temperature is too high, the strength of the hot-rolled steel sheet becomes too low, and when it is wound into a coil shape, it may be deformed by its own weight. Therefore, the upper limit of the coiling temperature is set to 700 ° C. On the other hand, when the coiling temperature is too low, the hot-rolled steel sheet is hardened, which is not preferable. Therefore, the lower limit of the coiling temperature is set to 500 ° C.
- Annealing temperature Ac1 transformation point or less
- an annealing temperature shall be below Ac1 transformation point.
- the annealing temperature is preferably 600 ° C. or higher, more preferably 700 ° C. or higher, in order to obtain a predetermined cementite density in the grains.
- the atmospheric gas for annealing any of nitrogen, hydrogen, and a mixed gas of nitrogen and hydrogen can be used.
- the atmosphere gas at the time of annealing may be any of the above gases, but a gas containing 90% by volume or more of nitrogen is preferable from the viewpoint of cost and safety.
- the annealing time is preferably 0.5 to 40 hours. When the annealing time is less than 0.5 hour, the effect of annealing is poor, the target structure is difficult to obtain, and the target hardness and elongation of the steel sheet are difficult to obtain. More preferably, it is 10 hours or more. When the annealing time exceeds 40 hours, the productivity is lowered and the manufacturing cost becomes excessive. Therefore, the annealing time is preferably 40 hours or less.
- both a converter and an electric furnace can be used. Further, the high carbon steel thus melted is made into a slab by ingot-bundling rolling or continuous casting.
- the slab is usually heated and then hot rolled.
- the slab heating temperature is preferably 1280 ° C. or lower in order to avoid deterioration of the surface state due to the scale.
- the material to be rolled may be heated by a heating means such as a sheet bar heater during hot rolling.
- an edge heater in the finish rolling.
- the finishing temperature tends to be lower in the vicinity of the plate width end portion (also referred to as an edge) than in the plate width central portion. For this reason, at the time of finish rolling, it is preferable to raise the temperature of the edge portion of the plate using an edge heater.
- the plate width edge vicinity part of the steel plate of the range of 10 mm from the plate width edge part to the plate width center part is hardly used as a product.
- the range from the center of the plate width to 10 mm from the edge is finished at the Ar3 transformation point or more. It is preferable to be rolled.
- the 10 mm position from the end of the plate width is a position of 10 mm from the end of the plate width toward the center of the plate width.
- the difference between the finish temperature at the center of the plate width of the steel plate and the finish temperature at the 10 mm position from the end of the plate width is within 40 ° C. It is preferable. More preferably, it is within 20 ° C.
- the difference between the finishing temperature at the center of the plate width and the finishing temperature at the 10 mm position from the end of the plate width was set to be within 40 ° C.
- the hot-rolled annealed plate thus produced was examined for microstructure, hardness, elongation, and quenching hardness. The results are shown in Table 2 (Table 2-1 and Table 2-2).
- the Ar3 transformation point and Ac1 transformation point shown in Table 1 are obtained from thermal expansion curves.
- the C content of the steel used in Example 1 was in the range of more than 0.40% and 0.53% or less.
- HRB Hardness of steel plate after annealing
- samples were taken at 40 mm intervals from the end of the plate width at the full width of the steel plate after annealing, and each sample was measured at five points using a Rockwell hardness meter (B scale) in the same manner as described above. The average value was obtained. And the highest value and the lowest value were calculated
- JIS No. 5 tensile test specimens were collected in the direction of 0 ° (L direction) with respect to the rolling direction at intervals of 40 mm from the end of the sheet width at the full width of the steel sheet after annealing. Elongation was calculated
- Microstructure of the steel sheet after annealing is obtained by cutting a sample taken from the center of the plate width, polishing the cut surface (thickness cross section in the rolling direction), applying nital corrosion, and using a scanning electron microscope Tissue photographs were taken at a magnification of 3000 times at five locations at 1/4 positions of thickness. Using the photographed structure photograph, the number of cementite having a major axis of 0.15 ⁇ m or more that was not on the grain boundary was measured, and this number was divided by the area of the field of view of the photograph to determine the cementite density in the grain.
- the amount of nitrogen in the surface layer of 150 ⁇ m is the amount of nitrogen contained in the range from the steel plate surface to the depth of 150 ⁇ m in the plate thickness direction. Further, the amount of nitrogen in the surface layer of 150 ⁇ m was determined as follows.
- Cutting was started from the surface of the collected steel plate, the steel plate was cut to a depth of 150 ⁇ m from the surface, and chips generated at this time were collected as samples.
- the amount of N in this sample was measured, and the amount of nitrogen in the surface layer was 150 ⁇ m.
- the amount of nitrogen at the surface layer of 150 ⁇ m and the average amount of N in the steel sheet were determined by measuring each amount of N by an inert gas transportation fusion-thermal conductivity method. If the difference between the nitrogen content of the surface layer 150 ⁇ m thus obtained (the nitrogen content in the range from the surface to a depth of 150 ⁇ m from the surface) and the average N content in the steel sheet (N content in the steel) is 30 mass ppm or less. It can be evaluated that the nitrification can be suppressed.
- Solid solution B amount / added B amount The solid solution B amount was obtained by extracting BN in the steel sheet with 10 (volume%) Br methanol by using a sample taken from the center of the sheet width after annealing. The amount of B added was measured, and the total amount of B added, that is, the amount of B forming BN was subtracted from the B content in the steel. The solid solution B amount / added B amount, which is the ratio of the solid solution B amount thus determined and the added B amount (B content), was determined. If ⁇ solid solution B amount (mass%) / added B amount (mass%) ⁇ ⁇ 100 (%) is 70 (%) or more, it can be evaluated that the decrease in the solid solution B amount can be suppressed.
- Steel plate hardness after quenching (quenching hardness) A flat plate test piece (width 15 mm x length 40 mm x plate thickness 4 mm) is sampled from the center of the width of the steel sheet after annealing, and subjected to quenching treatment by two methods of water cooling and oil cooling at 120 ° C as follows.
- the steel sheet hardness (quenching hardness) after quenching was determined by each method. That is, the quenching treatment is a method in which the flat plate test piece is used and held at 870 ° C. for 30 s and immediately water-cooled (water cooling), and held at 870 ° C. for 30 s and immediately cooled with 120 ° C. oil (120 ° C. oil-cooled). It carried out in.
- the hardness of the cut surface of the test piece after the quenching treatment was measured with a Vickers hardness tester under the condition of a load of 1 kgf to obtain an average hardness, which was defined as the quenching hardness.
- the quenching hardness was determined to be acceptable ( ⁇ ) when the conditions shown in Table 3 were satisfied after water cooling and after 120 ° C. oil cooling, and evaluated as excellent in quenchability.
- ⁇ the hardness after water cooling and the hardness after 120 ° C. oil cooling
- Table 3 shows the quenching hardness according to the C content that can be evaluated as having sufficient quenchability from experience.
- the hot-rolled steel sheet of the present invention example is composed of ferrite and cementite, and the cementite density in the ferrite grains is 0.15 pieces / ⁇ m 2 or less. It can be seen that it has a certain microstructure. In addition, it can be seen that the hot-rolled steel sheet of the present invention has an HRB of 83 or less and a total elongation of 30% or more, and is excellent in cold workability and hardenability.
- H4 is small in both HRB hardness variation and total elongation variation in the plate width direction.
- the HRB hardness variation is 4 or less, and the total elongation variation is 3% or less.
- Sample No. H5 in which the edge heater was not used the difference between the finishing temperature at the center of the plate width and the finishing temperature at a position 10 mm from the end of the plate width was 50 ° C.
- the difference between the finishing temperature at the center of the plate width and the finishing temperature at the 10 mm position from the end of the plate width was set to be within 40 ° C.
- the hot-rolled annealed plate thus produced was examined for the microstructure, hardness, elongation, and quenching hardness in the same manner as in Example 1. The results are shown in Table 5 (Tables 5-1 and 5-2).
- the Ar3 transformation point and Ac1 transformation point shown in Table 4 are obtained from thermal expansion curves.
- the C content of the steel used in Example 2 was in the range of 0.20% to 0.40%.
- HRB Hardness of steel plate after annealing
- samples were taken at 40 mm intervals from the end of the plate width at the full width of the steel plate after annealing, and each sample was measured at five points using a Rockwell hardness meter (B scale) in the same manner as described above. The average value was obtained. And the highest value and the lowest value were calculated
- JIS No. 5 tensile test specimens were collected in the direction of 0 ° (L direction) with respect to the rolling direction at intervals of 40 mm from the end of the sheet width at the full width of the steel sheet after annealing. Elongation was calculated
- Microstructure of the steel sheet after annealing is obtained by cutting a sample taken from the center of the plate width, polishing the cut surface (thickness cross section in the rolling direction), applying nital corrosion, and using a scanning electron microscope Tissue photographs were taken at a magnification of 3000 times at five locations at 1/4 positions of thickness. Using the photographed structure photograph, the number of cementite having a major axis of 0.15 ⁇ m or more that was not on the grain boundary was measured, and this number was divided by the area of the field of view of the photograph to determine the cementite density in the grain.
- Example 2 For the steel plate after annealing, as in Example 1, the difference between the nitrogen amount of the surface layer of 150 ⁇ m and the average N amount in the steel plate, (solid solution B amount) / (addition B amount) was obtained. The results are shown in Table 5 (Tables 5-1 and 5-2).
- the amount of nitrogen in the surface layer of 150 ⁇ m is the amount of nitrogen contained in the range from the steel plate surface to the depth of 150 ⁇ m in the plate thickness direction. Further, the amount of nitrogen in the surface layer of 150 ⁇ m was determined as follows.
- Cutting was started from the surface of the collected steel plate, the steel plate was cut to a depth of 150 ⁇ m from the surface, and chips generated at this time were collected as a sample.
- the amount of N in this sample was measured, and the amount of nitrogen in the surface layer was 150 ⁇ m.
- the amount of nitrogen in the surface layer of 150 ⁇ m and the average amount of N in the steel sheet were determined by measuring each amount of N by an inert gas melting-thermal conductivity method. If the difference between the nitrogen content of the surface layer 150 ⁇ m thus obtained (the nitrogen content in the range from the surface to a depth of 150 ⁇ m from the surface) and the average N content in the steel sheet (N content in the steel) is 30 mass ppm or less. It can be evaluated that the nitrification can be suppressed.
- Solid solution B amount / added B amount The solid solution B amount was obtained by extracting BN in the steel sheet with 10 (volume%) Br methanol by using a sample taken from the center of the sheet width after annealing. The amount of B added was measured, and the total amount of B added, that is, the amount of B forming BN was subtracted from the B content in the steel. The solid solution B amount / added B amount, which is the ratio of the solid solution B amount thus determined and the added B amount (B content), was determined. If ⁇ solid solution B amount (mass%) / added B amount (mass%) ⁇ ⁇ 100 (%) is 70 (%) or more, it can be evaluated that the decrease in the solid solution B amount can be suppressed.
- the quenching hardness was determined to be acceptable ( ⁇ ) when the conditions shown in Table 6 were satisfied after water cooling and after 120 ° C. oil cooling, and were evaluated as having excellent hardenability. Moreover, when any of the hardness after water cooling and the hardness after 120 ° C. oil cooling did not satisfy the conditions shown in Table 6, it was determined to be rejected (x) and evaluated to be inferior in hardenability. Table 6 shows the quenching hardness according to the C content, which can be evaluated as having sufficient quenchability from experience.
- L4 is small in both HRB hardness variation and total elongation variation in the plate width direction.
- sample numbers L1, L3, and L4 have a HRB hardness variation of 4 or less and a total elongation variation of 3% or less.
- the difference between the finishing temperature at the center of the plate width and the finishing temperature at a position 10 mm from the end of the plate width was 50 ° C.
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Abstract
Description
i)焼入れ前の高炭素熱延鋼板の硬度、全伸び(以下、単に伸びともいう)には、フェライト粒内のセメンタイト密度が大きく影響する。硬さがHRBで83以下、かつ、全伸び(El)が30%以上を確保するためには、フェライト粒内のセメンタイト密度を0.15個/μm2以下とする必要がある。また、焼入れ前の高炭素熱延鋼板の硬度、全伸びとして、硬さがHRBで75以下、かつ、全伸び(El)が38%以上を確保するためには、フェライト粒内のセメンタイト密度を0.10個/μm2以下とする必要がある。
ii)フェライト粒内のセメンタイト密度には、熱間圧延における仕上温度が大きく影響する。仕上温度が高くなりすぎると、球状化焼鈍後にセメンタイト密度を小さくすることが困難となる。
iii)窒素雰囲気で焼鈍を施す場合、雰囲気中の窒素が浸窒して鋼板中に濃化し、鋼板中のBと結合してBNを生成するため、鋼板中の固溶B量が大幅に低下する。なお、窒素雰囲気とは、窒素を90体積%以上含む雰囲気である。一方、Sb、Sn、Bi、Ge、Te、Seの少なくとも1種を鋼中に添加することで、このような浸窒を防止し、固溶B量の低下を抑制して高い焼入れ性が得られる。
iv)板幅端部近傍は、板幅中央部に比べて仕上温度が低下しやすく、その結果伸びが低下し加工性が劣化して、焼鈍後の硬さ、伸びが幅方向でばらつきやすい。仕上圧延に際して、エッジヒーターを用いて板幅端部を昇温することで、このようなばらつきを抑制できる。
v)エッジヒーターを用いて、特に板幅中央部と板幅端部との温度差を40℃以内とすることで、鋼板板幅方向のロックウェル硬さHRBのばらつきをHRBで4以下、全伸びElのばらつきをElで3%以下とできる。
C:0.20%以上0.53%以下
Cは、焼入れ後の強度を得るために重要な元素である。上記したように、硬さがHRBで83以下、かつ、全伸び(El)が30%以上とする場合、水焼入れ後の硬さがHV620超えであることが望まれている。C量が0.40%以下の場合、部品に成形した後の熱処理によって、水焼入れ後の硬さでHV620超えを得られない。このため、硬さがHRBで83以下、かつ、全伸び(El)が30%以上とする場合には、水焼入れ後の硬さをHV620超えを得るため、C量は0.40%超にする必要がある。しかし、C量が0.53%を超えると硬質化し、靭性や冷間加工性が劣化する。したがって、硬さがHRBで83以下、かつ、全伸び(El)が30%以上とする場合には、C量は0.40%超0.53%以下とする。なお、部品によっては特に優れた成形性が要求されることもあり、0.51%を超えると成形性が劣化しやすくなるため、C量は0.51%以下が好ましい。また、C量が0.45%以上になると確実に所望の硬さ(水焼入れ後の硬さでHV620超え)を得ることができるため、C量は0.45%以上とすることが好ましい。この場合の好ましいC量の範囲は、0.45%以上0.51%以下である。
Siは固溶強化により強度を上昇させる元素である。Si量の増加とともに鋼板が硬質化し、冷間加工性が劣化するため、Si量は0.10%以下とする。好ましくは0.05%以下、より好ましくは0.03%以下である。Siは冷間加工性を低下させるため、Si量は少ないほど好ましい。一方、過度にSiを低減すると精錬コストが増大するため、Si量は0.005%以上が好ましい。
Mnは焼入れ性を向上させる元素であるが、一方、固溶強化により強度を上昇させる元素でもある。Mn量が0.50%を超えると、鋼板が硬質化しすぎて冷間加工性が低下する。またMn量が0.50%を超えると、Mnの偏析に起因したバンド組織が発達し、鋼組織が不均一になるため、硬度や伸びのばらつきが大きくなる傾向にある。したがって、Mn量は0.50%以下とする。好ましくは、Mn量は0.45%以下であり、より好ましくは0.40%以下である。なお、下限はとくに指定しない。焼入れ時の溶体化処理において、グラファイト析出を抑制して鋼板中の全C量を固溶して所定の焼入れ硬さを得るためには、Mn量は0.20%以上とすることが好ましい。
Pは固溶強化により強度を上昇させる元素である。P量が0.03%を超えて増加すると、鋼板が硬質化しすぎて冷間加工性が低下し、また、粒界脆化を招き、焼入れ後の靭性が劣化する。したがって、P量は0.03%以下とする。優れた焼入れ後の靭性を得るには、P量は0.02%以下が好ましい。Pは冷間加工性および焼入れ後の靭性を低下させるため、P量は少ないほど好ましい。一方、過度にPを低減すると精錬コストが増大するため、P量は0.005%以上が好ましい。
Sは硫化物を形成し、高炭素熱延鋼板の冷間加工性および焼入れ後の靭性を低下させるため、低減しなければならない元素である。S量が0.010%を超えると、高炭素熱延鋼板の冷間加工性および焼入れ後の靭性が著しく劣化する。したがって、S量は0.010%以下とする。優れた冷間加工性および焼入れ後の靭性を得るには、S量は0.005%以下が好ましい。Sは冷間加工性および焼入れ後の靭性を低下させるため、S量は少ないほど好ましい。一方、過度にSを低減すると精錬コストが増大するため、S量は0.0005%以上が好ましい。
sol.Al(酸可溶性アルミニウム)量が0.10%を超えると、焼入れ処理の加熱時にAlNが生成してオーステナイト粒が微細化し過ぎる。この結果、焼入れ処理の冷却時にフェライト相の生成が促進されて、鋼組織がフェライトとマルテンサイトとなり、焼入れ後の硬さが低下するとともに、焼入れ後の靭性が劣化する。したがって、sol.Al量は0.10%以下とする。好ましくはsol.Al量は0.06%以下とする。なお、sol.Alは脱酸の効果を有しており、十分に脱酸するためには、0.005%以上とすることが好ましい。
N量が0.0050%を超えると、BNの形成により固溶B量が低下する。また、N量が0.0050%を超えると、BN、AlNの形成により焼入れ処理の加熱時にオーステナイト粒が微細化し過ぎる。この結果、焼入れ処理の冷却時にフェライト相の生成が促進されて、焼入れ後の硬さが低下するとともに、焼入れ後の靭性が低下する。したがって、N量は0.0050%以下とする。下限はとくに規定しない。なお、上記したように、NはBN、AlNを形成し、これにより焼入れ処理の加熱時にオーステナイト粒の成長を適度に抑制し、焼入れ後の靭性を向上させる元素であるため、N量は0.0005%以上が好ましい。
Bは焼入れ性を高める重要な元素である。B量が0.0005%未満の場合、十分な効果が認められないため、B量は0.0005%以上とする必要がある。B量は0.0010%以上とすることが好ましい。一方、B量が0.0050%超えの場合、仕上圧延後のオーステナイトの再結晶が遅延し、その結果、熱延鋼板の集合組織(texture)が発達し、焼鈍後の鋼板の異方性が大きくなる。このように焼鈍後の鋼板の異方性が大きくなると、絞り成形においてイアリング(earring)が発生しやすくなる。また、ギアやトランスミッションなどの円筒形状部品に鋼板を冷間プレスした場合には、鋼板の異方性が大きくなると、十分な真円度(circularity)が得られなくなる。鋼板の冷間プレス後の真円度が十分でないと、ギアやトランスミッションなどの真円度が求められる部品には、冷間プレスによる一体成型を適用できなくなる等の問題が発生する。このため、B量は0.0050%以下とする必要がある。好ましくは、B量は0.0035%以下である。したがって、B量は0.0005%以上0.0050%以下とする。好ましくは、B量は0.0010%以上0.0035%以下である。
Sb、Sn、Bi、Ge、Te、Seは表層からの浸窒抑制に重要な元素である。これら元素の合計の量が0.002%未満の場合、十分な効果が認められない。このため、Sb、Sn、Bi、Ge、Te、Seの1種以上を含有し、かつ、これら元素の合計量の下限を0.002%とする。好ましくは、これら元素の合計量の下限は0.005%である。一方、これらの元素を、その含有量の合計で0.030%超えとして添加しても、浸窒防止効果は飽和する。また、これらの元素は粒界に偏析する傾向があるため、これらの元素の含有量を合計で0.030%超えとすると、含有量が高くなりすぎ、粒界脆化を引き起こす可能性がある。したがって、Sb、Sn、Bi、Ge、Te、Seの含有量の合計は0.030%を上限とする。好ましくは、Sb、Sn、Bi、Ge、Te、Seの含有量の合計は0.020%以下である。よって、Sb、Sn、Bi、Ge、Te、Seのうち1種以上を含有し、これら元素の含有量の合計を0.002%以上0.030%以下とする。好ましくは、Sb、Sn、Bi、Ge、Te、Seの含有量の合計は、0.005%以上0.020%以下である。
本発明では、冷間加工性を向上させるため、熱間圧延後にセメンタイトの球状化焼鈍を行い、フェライトとセメンタイトからなるミクロ組織とする必要がある。特にC含有量が0.40%超0.53%以下の場合に、硬さがHRBで83以下、全伸びが30%以上とするには、フェライト粒内のセメンタイト密度を0.15個/μm2以下とする必要がある。また、特にC含有量が0.20%以上0.40%以下の場合に、硬さがHRBで75以下、全伸びが38%以上とするには、フェライト粒内のセメンタイト密度を0.10個/μm2以下とする必要がある。
本発明の鋼板は、フェライトとセメンタイトからなる。フェライト粒内のセメンタイト密度が高いと分散強化により硬質化し、伸びが低下する。C含有量が0.40%超0.53%以下の場合に、硬さがHRBで83以下、全伸びが30%以上を得るためには、粒内のセメンタイト密度を0.15個/μm2以下とする必要がある。好ましくは0.13個/μm2以下であり、さらに好ましくは0.10個/μm2以下である。フェライト粒内のセメンタイト密度は0個/μm2であってもよい。なお、フェライト粒内に存在するセメンタイト径は長径で0.15~1.8μm程度であり、鋼板の析出強化に有効なサイズである。このため、本発明の鋼板では、粒内のセメンタイト密度を低下することで強度低下を図ることができる。一方、フェライト粒界のセメンタイトは分散強化にほとんど寄与しないので、フェライト粒内のセメンタイト密度を0.15個/μm2以下と規定する。
本発明では、ギア、トランスミッション、シートリクライナーなどの自動車用部品を冷間プレスで成形するため優れた加工性が必要である。また、焼入れ処理により硬さを大きくして耐磨耗性を付与する必要がある。そのためには、焼入れ性を向上させ、すなわち優れた焼入れ性を有し、かつ鋼板の硬さを低減してHRB83以下とし、伸びを高めてElを30%以上とする必要がある。特に優れた加工性が必要とされる場合、HRB75以下とし、伸びを高めてElを38%以上とする必要がある。鋼板の硬さは、低いほど加工性の観点から望ましいが、硬さを低減するためには焼鈍時間を長くしなければならず、製造コストが増大する。このため、鋼板の硬さはHRB65超えとする。さらに、製品である鋼板の歩留りを向上するうえで、鋼板の全板幅にてHRB硬さのばらつきを4以下、伸びのばらつきを3%以下にすることが好ましい。これらの機械特性は以下の製造条件によって達成される。ここでHRB硬さのばらつきとは、鋼板の板幅方向におけるHRBの最大値と最小値の差である。ここで、伸びのばらつきとは、鋼板の板幅方向における全伸びの最大値と最小値の差である。
本発明の高炭素熱延鋼板は、上記のような組成の鋼を素材とし、熱間粗圧延後に仕上温度:Ar3変態点以上(Ar3変態点+90℃)以下で仕上圧延を施す熱間圧延により所望の板厚の熱延鋼板とし、巻取温度:500℃以上700℃以下で巻き取り、次いでAc1変態点以下で焼鈍を施して製造される。なお、仕上圧延における圧下率は85%以上とすることが好ましい。仕上圧延に際しては、エッジヒーターを使用することが好ましく、エッジヒーターを使用して鋼板の板幅中央部の仕上温度と板幅端部から10mm位置の仕上温度の差を40℃以内とすることがさらに好ましい。
以下、本発明の高炭素熱延鋼板の製造方法における限定理由について説明する。
C含有量が0.40%超0.53%以下の場合に、焼鈍後にフェライト粒内のセメンタイト密度を、0.15個/μm2以下にするには、パーライトと初析フェライトを有するミクロ組織の熱延鋼板をベースとして焼鈍を施す必要がある。また、C含有量が0.20%以上0.40%以下の場合に、焼鈍後にフェライト粒内のセメンタイト密度を0.10個/μm2以下にするには、パーライトと初析フェライトを有するミクロ組織の熱延鋼板をベースとして焼鈍を施す必要がある。熱間圧延における仕上温度が(Ar3変態点+90℃)を超えて高くなると、初析フェライトの割合が小さくなり、焼鈍後所定のセメンタイト密度が得られない。すなわち、鋼のC含有量が0.40%超0.53%以下の場合フェライト粒内のセメンタイト密度:0.15個/μm2以下、鋼のC含有量が0.20%以上0.40%以下の場合フェライト粒内のセメンタイト密度:0.10個/μm2以下が得られない。このため、仕上温度は(Ar3変態点+90℃)以下とする。初析フェライトの割合を十分に確保するためには、仕上温度を(Ar3変態点+70℃)以下とすることが好ましい。より好ましくは、850℃未満あるいは(Ar3変態点+50℃)未満である。一方、仕上温度がAr3変態点未満では、熱間圧延後および焼鈍後に粗大なフェライト粒が形成され、伸びが著しく低下する。このため、仕上温度はAr3変態点以上とする。なお、ここで規定する仕上温度は、仕上圧延が完了する際の板幅中央部の位置における鋼板表面の温度である。
仕上圧延後の熱延鋼板は、冷却して500℃以上700℃以下の巻取温度でコイル形状に巻き取られる。巻取温度が高すぎると熱延鋼板の強度が低くなり過ぎて、コイル形状に巻き取られた際、コイルの自重で変形する場合があるため、操業上好ましくない。したがって巻取温度の上限を700℃とする。一方、巻取温度が低すぎると熱延鋼板が硬質化するため好ましくない。したがって巻取温度の下限を500℃とする。
焼鈍温度がAc1変態点を超えると、オーステナイトが析出し、焼鈍後の冷却過程において粗大なパーライト組織が形成され、不均一な組織となる。このため、焼鈍温度はAc1変態点以下とする。下限はとくに定めない。所定の粒内のセメンタイト密度を得るには焼鈍温度は600℃以上が好ましく、より好ましくは700℃以上である。なお、焼鈍の際の雰囲気ガスは、窒素、水素、窒素と水素の混合ガスのいずれも使用できる。また、焼鈍の際の雰囲気ガスは、前記のガスのいずれであってもよいが、コストおよび安全性の観点から、窒素を90体積%以上含むガスが好ましい。また、焼鈍時間は0.5時間~40時間とすることが好ましい。焼鈍時間が0.5時間未満であると、焼鈍の効果が乏しく、目標とする組織が得にくく、目標とする鋼板の硬さおよび伸びが得にくい。より好ましくは10時間以上である。焼鈍時間が40時間を超えると、生産性が低下し、製造コストが過大となるため、焼鈍時間は40時間以下とすることが好ましい。
また、鋼板の板幅方向での仕上温度の差が大きくなると、鋼板の硬さや伸びがばらつきやすくなる。特に板幅方向での仕上温度の差が40℃を超えると、このばらつきが大きくなりやすい。このため、エッジヒーターを使用して板幅端部の温度を昇温する際は、鋼板の板幅中央部の仕上温度と板幅端部から10mm位置の仕上温度の差を40℃以内とすることが好ましい。より好ましくは20℃以内である。
焼鈍後の鋼板(原板)の板幅中央部から試料を採取し、ロックウェル硬度計(Bスケール)を用いて5点測定し、平均値を求めた。
焼鈍後の鋼板(原板)から、圧延方向に対して0°の方向(L方向)に切り出したJIS5号引張試験片を用いて、島津製作所AG10TB AG/XRの引張試験機にて10mm/分で引張試験を行い、破断したサンプルを突き合わせて伸びを求めた。
焼鈍後の鋼板のミクロ組織は、板幅中央部から採取した試料を切断し、切断面(圧延方向板厚断面)を研磨後、ナイタール腐食を施し、走査型電子顕微鏡を用いて、板厚の1/4位置の5箇所で3000倍の倍率で組織写真を撮影した。撮影した組織写真を用いて、粒界上になく、長径が0.15μm以上のセメンタイトの個数を測定し、この個数を写真の視野の面積で除して、粒内のセメンタイト密度を求めた。
焼鈍後の鋼板の板幅中央部から採取した試料を用い、表層150μmの窒素量および鋼板中平均N量を測定して、表層150μmの窒素量と鋼板中の平均N量の差を求めた。ここで表層150μmの窒素量とは、鋼板表面から板厚方向に150μm深さまでの範囲に含有される窒素量である。また、表層150μmの窒素量は以下のようにして求めた。採取した鋼板の表面から切削を開始し、表面から150μmの深さまで鋼板を切削し、この際に発生した切りくず(chip)をサンプルとして採取した。このサンプル中のN量を測定し、表層150μmの窒素量とした。表層150μmの窒素量と鋼板中平均N量は、不活性ガス融解-熱伝導度法(inert gas transportation fusion-thermal conductivity method)により各N量を測定し求めた。このようにして求めた表層150μmの窒素量(表面~表面から150μm深さの範囲の窒素量)と鋼板中の平均N量(鋼中のN含有量)の差が30質量ppm以下であれば、浸窒を抑制できていると評価できる。
固溶B量は、焼鈍後の鋼板の板幅中央部から採取した試料を用い、鋼板中のBNを10(体積%)Brメタノールで抽出し、BNを形成しているB量を測定し、全添加B量、すなわち鋼中のB含有量からBNを形成しているB量を差し引き求めた。このようにして求めた固溶B量と、添加したB量(B含有量)の比である固溶B量/添加B量を求めた。{固溶B量(質量%)/添加B量(質量%)}×100(%)が70(%)以上であれば、固溶B量の低下を抑制できていると評価できる。
焼鈍後の鋼板の板幅中央部から平板試験片(幅15mm×長さ40mm×板厚4mm)を採取し、以下のように水冷、120℃油冷の2通りの方法により焼入れ処理を施して、各々の方法で焼入れ後の鋼板硬さ(焼入れ硬さ)を求めた。すなわち、焼入れ処理は、上記平板試験片を用いて、870℃で30s保持して直ちに水冷する方法(水冷)、870℃で30s保持して直ちに120℃油で冷却する方法(120℃油冷)で実施した。焼入れ特性は焼入れ処理後の試験片の切断面について、ビッカース硬さ試験機で荷重1kgfの条件下で硬さを5点測定して平均硬さを求め、これを焼入れ硬さとした。焼入れ硬さは、表3の条件を水冷後硬さ、120℃油冷後硬さともに満足した場合、合格(○)と判定し、焼入れ性に優れると評価した。また、水冷後硬さ、120℃油冷後硬さのいずれかが表3に示す条件を満足しない場合、不合格(×)とし、焼入れ性に劣ると評価した。なお表3は、経験上、焼入れ性が十分であると評価できる、C含有量に応じた焼入れ硬さを表したものである。
焼鈍後の鋼板(原板)の板幅中央部から試料を採取し、ロックウェル硬度計(Bスケール)を用いて5点測定し、平均値を求めた。
焼鈍後の鋼板(原板)から、圧延方向に対して0°の方向(L方向)に切り出したJIS5号引張試験片を用いて、島津製作所AG10TB AG/XRの引張試験機にて10mm/分で引張試験を行い、破断したサンプルを突き合わせて伸びを求めた。
焼鈍後の鋼板のミクロ組織は、板幅中央部から採取した試料を切断し、切断面(圧延方向板厚断面)を研磨後、ナイタール腐食を施し、走査型電子顕微鏡を用いて、板厚の1/4位置の5箇所で3000倍の倍率で組織写真を撮影した。撮影した組織写真を用いて、粒界上になく、長径が0.15μm以上のセメンタイトの個数を測定し、この個数を写真の視野の面積で除して、粒内のセメンタイト密度を求めた。
焼鈍後の鋼板の板幅中央部から採取した試料を用い、表層150μmの窒素量および鋼板中平均N量を測定して、表層150μmの窒素量と鋼板中の平均N量の差を求めた。ここで表層150μmの窒素量とは、鋼板表面から板厚方向に150μm深さまでの範囲に含有される窒素量である。また、表層150μmの窒素量は以下のようにして求めた。採取した鋼板の表面から切削を開始し、表面から150μmの深さまで鋼板を切削し、この際に発生した切りくずをサンプルとして採取した。このサンプル中のN量を測定し、表層150μmの窒素量とした。表層150μmの窒素量と鋼板中平均N量は、不活性ガス融解-熱伝導度法により各N量を測定し求めた。このようにして求めた表層150μmの窒素量(表面~表面から150μm深さの範囲の窒素量)と鋼板中の平均N量(鋼中のN含有量)の差が30質量ppm以下であれば、浸窒を抑制できていると評価できる。
固溶B量は、焼鈍後の鋼板の板幅中央部から採取した試料を用い、鋼板中のBNを10(体積%)Brメタノールで抽出し、BNを形成しているB量を測定し、全添加B量、すなわち鋼中のB含有量からBNを形成しているB量を差し引き求めた。このようにして求めた固溶B量と、添加したB量(B含有量)の比である固溶B量/添加B量を求めた。{固溶B量(質量%)/添加B量(質量%)}×100(%)が70(%)以上であれば、固溶B量の低下を抑制できていると評価できる。
実施例1と同様に、焼鈍後の鋼板の板幅中央部から平板試験片(幅15mm×長さ40mm×板厚4mm)を採取し、以下のように水冷、120℃油冷の2通りの方法により焼入れ処理を施して、各々の方法で焼入れ後の鋼板硬さ(焼入れ硬さ)を求めた。すなわち、焼入れ処理は、上記平板試験片を用いて、870℃で30s保持して直ちに水冷する方法(水冷)、870℃で30s保持して直ちに120℃油で冷却する方法(120℃油冷)で実施した。焼入れ特性は焼入れ処理後の試験片の切断面について、ビッカース硬さ試験機で荷重1kgfの条件下で硬さを5点測定して平均硬さを求め、これを焼入れ硬さとした。焼入れ硬さは、表6の条件を水冷後硬さ、120℃油冷後硬さともに満足した場合、合格(○)と判定し、焼入れ性に優れると評価した。また、水冷後硬さ、120℃油冷後硬さのいずれかが表6に示す条件を満足しない場合、不合格(×)とし、焼入れ性に劣ると評価した。なお表6は、経験上、焼入れ性が十分であると評価できる、C含有量に応じた焼入れ硬さを表したものである。
Claims (11)
- 質量%で、C:0.20%以上0.53%以下、Si:0.10%以下、Mn:0.50%以下、P:0.03%以下、S:0.010%以下、sol.Al:0.10%以下、N:0.0050%以下、B:0.0005%以上0.0050%以下を含有し、さらにSb、Sn、Bi、Ge、Te、Seのうち1種以上を合計で0.002%以上0.030%以下含有し、残部がFeおよび不可避的不純物からなる組成を有し、C含有量が、質量%で、C:0.40%超0.53%以下の場合、フェライトとセメンタイトからなり、前記フェライト粒内のセメンタイト密度が0.15個/μm2以下であるミクロ組織を有し、硬さがHRBで65超え83以下、全伸びが30%以上であり、C含有量が、質量%で、C:0.20%以上0.40%以下の場合、フェライトとセメンタイトからなり、前記フェライト粒内のセメンタイト密度が0.10個/μm2以下であるミクロ組織を有し、硬さがHRBで65超え75以下、全伸びが38%以上であることを特徴とする高炭素熱延鋼板。
- 前記C含有量が、質量%で、C:0.40%超0.53%以下であり、フェライトとセメンタイトからなり、前記フェライト粒内のセメンタイト密度が0.15個/μm2以下であるミクロ組織を有し、硬さがHRBで65超え83以下、全伸びが30%以上であることを特徴とする請求項1に記載の高炭素熱延鋼板。
- 前記C含有量が、質量%で、C:0.20%以上0.40%以下であり、フェライトとセメンタイトからなり、前記フェライト粒内のセメンタイト密度が0.10個/μm2以下であるミクロ組織を有し、硬さがHRBで65超え75以下、全伸びが38%以上であることを特徴とする請求項1に記載の高炭素熱延鋼板。
- さらに、質量%で、Ni、Cr、Moのうちの少なくとも1種を合計で0.50%以下含有することを特徴とする請求項1から3のいずれか1項に記載の高炭素熱延鋼板。
- 鋼板幅方向のHRB硬さのばらつきが4以下、全伸びのばらつきが3%以下であることを特徴とする請求項1から4のいずれか1項に記載の高炭素熱延鋼板。
- 質量%で、C:0.20%以上0.53%以下、Si:0.10%以下、Mn:0.50%以下、P:0.03%以下、S:0.010%以下、sol.Al:0.10%以下、N:0.0050%以下、B:0.0005%以上0.0050%以下を含有し、さらにSb、Sn、Bi、Ge、Te、Seのうち1種以上を合計で0.002%以上0.030%以下含有し、残部がFeおよび不可避的不純物からなる組成を有する鋼を、熱間粗圧延後、仕上温度:Ar3変態点以上(Ar3変態点+90℃)以下で仕上圧延し、巻取温度:500℃以上700℃以下で巻き取った後、Ac1変態点以下で焼鈍して、前記鋼のC含有量が、質量%で、C:0.40%超0.53%以下の場合、フェライトとセメンタイトからなり、前記フェライト粒内のセメンタイト密度が0.15個/μm2以下であるミクロ組織を有し、硬さがHRBで65超え83以下、全伸びが30%以上である高炭素熱延鋼板を製造し、前記鋼のC含有量が、質量%で、C:0.20%以上0.40%以下の場合、フェライトとセメンタイトからなり、前記フェライト粒内のセメンタイト密度が0.10個/μm2以下であるミクロ組織を有し、硬さがHRBで65超え75以下、全伸びが38%以上である高炭素熱延鋼板を製造することを特徴とする、高炭素熱延鋼板の製造方法。
- 前記鋼のC含有量が、質量%で、C:0.40%超0.53%以下であることを特徴とする、フェライトとセメンタイトからなり、前記フェライト粒内のセメンタイト密度が0.15個/μm2以下であるミクロ組織を有し、硬さがHRBで65超え83以下、全伸びが30%以上である高炭素熱延鋼板を製造する、請求項6に記載の高炭素熱延鋼板の製造方法。
- 前記鋼のC含有量が、質量%で、C:0.20%以上0.40%以下であることを特徴とする、フェライトとセメンタイトからなり、前記フェライト粒内のセメンタイト密度が0.10個/μm2以下であるミクロ組織を有し、硬さがHRBで65超え75以下、全伸びが38%以上である高炭素熱延鋼板を製造する、請求項6に記載の高炭素熱延鋼板の製造方法。
- 前記鋼が、さらに、質量%で、Ni、Cr、Moのうちの少なくとも1種を合計で0.50%以下含有することを特徴とする請求項6から8のいずれか1項に記載の高炭素熱延鋼板の製造方法。
- 前記仕上圧延に際し、エッジヒーターを使用することを特徴とする請求項6から9のいずれか1項に記載の高炭素熱延鋼板の製造方法。
- 前記仕上圧延に際し、エッジヒーターを使用して、鋼板の板幅中央部の仕上温度と板幅端部から10mm位置の仕上温度の差を40℃以内とすることを特徴とする請求項10に記載の高炭素熱延鋼板の製造方法。
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WO2015146174A1 (ja) * | 2014-03-28 | 2015-10-01 | Jfeスチール株式会社 | 高炭素熱延鋼板およびその製造方法 |
WO2015146173A1 (ja) * | 2014-03-28 | 2015-10-01 | Jfeスチール株式会社 | 高炭素熱延鋼板およびその製造方法 |
CN109468532A (zh) * | 2018-11-06 | 2019-03-15 | 包头钢铁(集团)有限责任公司 | 一种变速器齿轮用钢及其生产方法 |
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CN107034413B (zh) * | 2016-12-12 | 2018-10-16 | 武汉钢铁有限公司 | 低淬透性耐磨带钢及其制造方法 |
KR102209555B1 (ko) | 2018-12-19 | 2021-01-29 | 주식회사 포스코 | 강도 편차가 적은 열연 소둔 강판, 부재 및 이들의 제조방법 |
WO2020158357A1 (ja) * | 2019-01-30 | 2020-08-06 | Jfeスチール株式会社 | 高炭素熱延鋼板およびその製造方法 |
WO2021241604A1 (ja) * | 2020-05-28 | 2021-12-02 | Jfeスチール株式会社 | 耐摩耗鋼板および耐摩耗鋼板の製造方法 |
Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2001062997A1 (fr) * | 2000-02-23 | 2001-08-30 | Kawasaki Steel Corporation | Feuille d'acier resistant a une traction elevee, laminee a chaud et dotee d'excellentes proprietes de resistance au durcissement, au vieillissement et a la deformation et procede de fabrication associe |
JP2004250768A (ja) | 2003-02-21 | 2004-09-09 | Nippon Steel Corp | 冷間加工性と低脱炭性に優れた機械構造用鋼及びその製造方法 |
JP2004315836A (ja) | 2003-04-10 | 2004-11-11 | Nippon Steel Corp | 加工性、焼き入れ性、溶接性、耐浸炭および耐脱炭性に優れた高炭素鋼板およびその製造方法 |
JP2007277696A (ja) * | 2005-10-05 | 2007-10-25 | Jfe Steel Kk | 極軟質高炭素熱延鋼板およびその製造方法 |
JP2007291495A (ja) * | 2006-03-28 | 2007-11-08 | Jfe Steel Kk | 極軟質高炭素熱延鋼板およびその製造方法 |
JP2010255066A (ja) | 2009-04-28 | 2010-11-11 | Jfe Steel Corp | 高炭素熱延鋼板およびその製造方法 |
WO2013102982A1 (ja) * | 2012-01-05 | 2013-07-11 | Jfeスチール株式会社 | 焼入れ性に優れる面内異方性の小さい高炭素熱延鋼板およびその製造方法 |
WO2013102986A1 (ja) * | 2012-01-05 | 2013-07-11 | Jfeスチール株式会社 | 高炭素熱延鋼板およびその製造方法 |
Family Cites Families (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH07268546A (ja) * | 1994-03-30 | 1995-10-17 | Sumitomo Metal Ind Ltd | 二層組織構造を有する高炭素鋼線材およびその製造方法 |
CN1123317A (zh) * | 1995-08-30 | 1996-05-29 | 陈旸 | 润滑油氧化还原再生新工艺 |
JPH0987805A (ja) * | 1995-09-26 | 1997-03-31 | Sumitomo Metal Ind Ltd | 高炭素薄鋼板およびその製造方法 |
NL1003762C2 (nl) * | 1996-08-08 | 1998-03-04 | Hoogovens Staal Bv | Staalsoort, staalband en werkwijze ter vervaardiging daarvan. |
JP2001073033A (ja) | 1999-09-03 | 2001-03-21 | Nisshin Steel Co Ltd | 局部延性に優れた中・高炭素鋼板の製造方法 |
JP2007029145A (ja) | 2005-07-22 | 2007-02-08 | Aruze Corp | ゲームシステム及びセンターサーバ |
JP5076347B2 (ja) * | 2006-03-31 | 2012-11-21 | Jfeスチール株式会社 | ファインブランキング加工性に優れた鋼板およびその製造方法 |
JP5162924B2 (ja) | 2007-02-28 | 2013-03-13 | Jfeスチール株式会社 | 缶用鋼板およびその製造方法 |
KR100928788B1 (ko) | 2007-12-28 | 2009-11-25 | 주식회사 포스코 | 용접성이 우수한 고강도 박강판과 그 제조방법 |
JP5056876B2 (ja) | 2010-03-19 | 2012-10-24 | Jfeスチール株式会社 | 冷間加工性と焼入れ性に優れた熱延鋼板およびその製造方法 |
JP5594226B2 (ja) * | 2011-05-18 | 2014-09-24 | Jfeスチール株式会社 | 高炭素薄鋼板およびその製造方法 |
JP5812048B2 (ja) | 2013-07-09 | 2015-11-11 | Jfeスチール株式会社 | 焼入れ性および加工性に優れる高炭素熱延鋼板およびその製造方法 |
-
2014
- 2014-07-08 EP EP14822734.1A patent/EP3020839B1/en active Active
- 2014-07-08 CN CN201480039480.0A patent/CN105378133B/zh active Active
- 2014-07-08 CN CN201810076655.5A patent/CN108315637B/zh active Active
- 2014-07-08 MX MX2016000009A patent/MX2016000009A/es active IP Right Grant
- 2014-07-08 KR KR1020157035764A patent/KR101853533B1/ko active IP Right Grant
- 2014-07-08 US US14/903,842 patent/US10400298B2/en active Active
- 2014-07-08 EP EP17150099.4A patent/EP3190202B1/en active Active
- 2014-07-08 WO PCT/JP2014/003605 patent/WO2015004902A1/ja active Application Filing
-
2016
- 2016-01-07 MX MX2020006052A patent/MX2020006052A/es unknown
Patent Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2001062997A1 (fr) * | 2000-02-23 | 2001-08-30 | Kawasaki Steel Corporation | Feuille d'acier resistant a une traction elevee, laminee a chaud et dotee d'excellentes proprietes de resistance au durcissement, au vieillissement et a la deformation et procede de fabrication associe |
JP2004250768A (ja) | 2003-02-21 | 2004-09-09 | Nippon Steel Corp | 冷間加工性と低脱炭性に優れた機械構造用鋼及びその製造方法 |
JP2004315836A (ja) | 2003-04-10 | 2004-11-11 | Nippon Steel Corp | 加工性、焼き入れ性、溶接性、耐浸炭および耐脱炭性に優れた高炭素鋼板およびその製造方法 |
JP2007277696A (ja) * | 2005-10-05 | 2007-10-25 | Jfe Steel Kk | 極軟質高炭素熱延鋼板およびその製造方法 |
JP2007291495A (ja) * | 2006-03-28 | 2007-11-08 | Jfe Steel Kk | 極軟質高炭素熱延鋼板およびその製造方法 |
JP2010255066A (ja) | 2009-04-28 | 2010-11-11 | Jfe Steel Corp | 高炭素熱延鋼板およびその製造方法 |
WO2013102982A1 (ja) * | 2012-01-05 | 2013-07-11 | Jfeスチール株式会社 | 焼入れ性に優れる面内異方性の小さい高炭素熱延鋼板およびその製造方法 |
WO2013102986A1 (ja) * | 2012-01-05 | 2013-07-11 | Jfeスチール株式会社 | 高炭素熱延鋼板およびその製造方法 |
Non-Patent Citations (1)
Title |
---|
See also references of EP3020839A4 |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2015146174A1 (ja) * | 2014-03-28 | 2015-10-01 | Jfeスチール株式会社 | 高炭素熱延鋼板およびその製造方法 |
WO2015146173A1 (ja) * | 2014-03-28 | 2015-10-01 | Jfeスチール株式会社 | 高炭素熱延鋼板およびその製造方法 |
US10844454B2 (en) | 2014-03-28 | 2020-11-24 | Jfe Steel Corporation | High-carbon hot-rolled steel sheet and method for manufacturing the same |
CN109468532A (zh) * | 2018-11-06 | 2019-03-15 | 包头钢铁(集团)有限责任公司 | 一种变速器齿轮用钢及其生产方法 |
CN109468532B (zh) * | 2018-11-06 | 2020-09-29 | 包头钢铁(集团)有限责任公司 | 一种变速器齿轮用钢及其生产方法 |
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