WO2011118459A1 - Tôle d'acier laminée à froid à ultra-haute résistance et son procédé de production - Google Patents

Tôle d'acier laminée à froid à ultra-haute résistance et son procédé de production Download PDF

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WO2011118459A1
WO2011118459A1 PCT/JP2011/056128 JP2011056128W WO2011118459A1 WO 2011118459 A1 WO2011118459 A1 WO 2011118459A1 JP 2011056128 W JP2011056128 W JP 2011056128W WO 2011118459 A1 WO2011118459 A1 WO 2011118459A1
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steel sheet
mass
less
rolled steel
ultra
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PCT/JP2011/056128
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English (en)
Japanese (ja)
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正崇 吉野
浩平 長谷川
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Ｊｆｅスチール株式会社
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Priority to CN201180015404.2A priority Critical patent/CN102822375B/zh
Priority to KR1020127021878A priority patent/KR101288701B1/ko
Publication of WO2011118459A1 publication Critical patent/WO2011118459A1/fr

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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
    • 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
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • 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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • 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
    • 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
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • 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
    • C21D2211/008—Martensite

Definitions

  • the present invention relates to an ultra-high-strength cold-rolled steel sheet having a tensile strength of 980 MPa or more and used for a vehicle body structural member such as an automobile center pillar or door impact beam manufactured mainly by press working or roll forming, and a method for manufacturing the same. Is.
  • the martensitic single-phase steel sheet is an upper critical cooling in which a second phase typified by a ferrite phase and a pearlite phase is not formed in a steel sheet having an austenite phase single-phase structure by soaking at a temperature equal to or higher than the Ac 3 transformation point. It is generally understood that it is manufactured by cooling to the Ms point or less at a cooling rate that is higher than or equal to the rate (hereinafter, this cooling is also referred to as “quenching”).
  • the deterioration of the shape of the steel sheet due to the above quenching not only affects the operability in the continuous annealing process and the manufacturability in the subsequent process, but also when the steel sheet is processed into a vehicle structural member by press forming or roll forming. However, it causes problems such as operation troubles in the molding line and adverse effects on the dimensional accuracy of the product. Therefore, in order to stably use the martensitic single-phase steel sheet as a material for the structural member of an automobile body, it is also important that the steel sheet has excellent flatness in addition to high strength.
  • the warp height in the width direction of the product steel plate as shown in FIG. 1 is desired to be 10 mm or less.
  • Patent Document 1 discloses the metal structure of a steel sheet based on the results of investigating the relationship between the warpage height of a steel sheet after continuous annealing with a tensile strength of 1470 MPa to 1960 MPa and the martensite volume ratio in the metal structure.
  • a technique for obtaining predetermined mechanical characteristics and an excellent steel sheet shape by forming a two-phase structure composed of a martensite phase having a volume ratio of 80 to 97% and the balance of a ferrite phase is disclosed.
  • Patent Document 2 after continuous annealing to obtain a martensitic single-phase steel sheet having a tensile strength of 1049 to 1240 MPa, temper rolling is performed so that the average roughness Ra of the steel sheet surface is 1.4 ⁇ m or more.
  • the technique of obtaining a favorable steel plate shape by applying is disclosed.
  • the method of correcting the steel sheet shape by temper rolling as in the technique of Patent Document 2 is not a technique for suppressing the deterioration of the steel sheet shape that occurs during quenching, it is necessary to improve the operability in the continuous annealing process. I can not connect it.
  • shape correction by temper rolling requires, for example, a very high rolling load for a high-strength steel sheet having a tensile strength of 1320 MPa or more, and a sufficient shape correction effect cannot be obtained with existing rolling equipment.
  • the increase in the surface roughness of the steel sheet is unsuitable for applications that require surface aesthetics, and there is a problem that the fatigue characteristics may be deteriorated due to the increase in the surface roughness.
  • the present invention has been made in view of the above problems, and its purpose is to suppress the deterioration of the shape of the steel sheet during quenching in continuous annealing itself, thereby achieving ultrahigh strength cold rolling having high flatness. It is to provide a steel sheet and to propose an advantageous manufacturing method thereof.
  • the inventors have intensively studied to solve the above problems of the conventional technology.
  • the deterioration of the shape of the martensitic single-phase steel sheet caused by volume shrinkage due to high-speed cooling during quenching and volume expansion due to martensitic transformation is caused by cooling from the soaking temperature to the Ms point during quenching during continuous annealing. It is divided into primary cooling that cools to the vicinity immediately above and secondary cooling that cools to the temperature below 100 ° C. from the vicinity immediately above the Ms point, and during that time, the steel sheet is held at the temperature near the Ms point for a predetermined time to equalize the steel sheet temperature. Was found to be effective, and the present invention was completed.
  • the present invention includes C: 0.05 to 0.40 mass%, Si: 2.0 mass% or less, Mn: 1.0 to 3.0 mass%, P: 0.05 mass% or less, S: 0.02 mass%.
  • Al 0.01 to 0.05 mass%
  • N less than 0.005 mass%
  • the balance is composed of Fe and inevitable impurities
  • the metal structure is a single martensite phase
  • the ultra-high-strength cold-rolled steel sheet of the present invention is characterized in that the metal structure is a tempered martensite single phase.
  • the ultra-high strength cold-rolled steel sheet of the present invention is characterized in that the tensile strength is 1320 MPa or more.
  • the ultra-high strength cold-rolled steel sheet of the present invention further includes Ti: 0.1 mass% or less, Nb: 0.1 mass% or less, B: 0.0005 to 0.0030 mass%, and Cu: It contains one or two or more selected from 0.20 mass% or less.
  • C 0.05 to 0.40 mass%, Si: 2.0 mass% or less, P: 0.05 mass% or less, S: 0.02 mass% or less, Al: 0.01 to 0.05 mass %, N: less than 0.005 mass%, Mn: 1.0 to 3.0 mass%, and the steel sheet after cold rolling having a component composition with the balance consisting of Fe and inevitable impurities is subjected to continuous annealing and tensile strength
  • the temperature ranges from the soaking temperature not lower than the Ac 3 transformation point to the temperature range of Ms point to Ms point + 200 ° C. determined by the following formula (1).
  • the method for producing an ultra-high strength cold-rolled steel sheet according to the present invention is characterized in that after secondary cooling, it is reheated and tempered at 100 to 250 ° C. for 120 to 1800 seconds.
  • the manufacturing method of the ultra-high strength cold-rolled steel sheet of the present invention is characterized in that primary cooling and secondary cooling are performed by water cooling.
  • the steel sheet after cold rolling in the production method of the present invention further includes Ti: 0.1 mass% or less, Nb: 0.1 mass% or less, B: 0.0005 to 0.0030 mass%.
  • Cu It contains 1 type, or 2 or more types chosen from 0.20 mass% or less, It is characterized by the above-mentioned.
  • the present invention it is possible to suppress the deterioration of the shape itself that occurs at the time of quenching the steel sheet in the continuous annealing process, so that not only the improvement in manufacturability in the continuous annealing process etc., but also the shape correction cost by temper rolling etc. It also contributes greatly to reduction.
  • the technology of the present invention can also be applied to ultra-high-strength steel sheets having a tensile strength of 1320 MPa or more, which is considered difficult to correct the shape in temper rolling, etc., so that the use of ultra-high-strength martensitic single-phase steel sheets is expanded. Also contributes.
  • an ultra-high-strength cold-rolled steel sheet having sufficient flatness can be stably obtained, so that the productivity when manufacturing a structural member for automobiles by press molding or roll molding is improved. And can greatly contribute to quality improvement such as dimensional accuracy.
  • the shape deterioration that occurs in a martensitic single-phase steel sheet during quenching in the continuous annealing process is due to the occurrence of non-uniform stress inside the steel sheet due to volume shrinkage associated with high-speed cooling and volume expansion associated with martensitic transformation. .
  • the volume shrinkage accompanying high-speed cooling and the stress generated thereby increase in proportion to the temperature difference between the temperature at which cooling starts and the temperature at which cooling ends.
  • the volume expansion accompanying the martensitic transformation is uniform when the metal structure after the final cooling is a martensite single phase structure.
  • the influence on the steel sheet shape due to quenching can be considered to be only a uniform volume expansion accompanying martensitic transformation, and the temperature range below the Ms point.
  • the effect of the cooling rate on the steel plate shape is considered to be small.
  • the difference between the cooling start temperature and the cooling end temperature may be reduced in order to reduce the stress generated in the steel sheet due to the volume shrinkage during quenching. Therefore, in the present invention, after the primary cooling in which the quenching of the steel sheet in the continuous annealing process is cooled from the soaking temperature not lower than the Ac 3 transformation point to the temperature immediately above the Ms point, the steel sheet temperature is maintained at the temperature near the Ms point for a predetermined time. Then, the temperature distribution in the steel sheet was made uniform, and then secondary cooling was performed from the temperature immediately above the Ms point to 100 ° C. or less to cause martensitic transformation. In this way, the steel sheet of the present invention can be manufactured by minimizing the stress generated with volume shrinkage during quenching.
  • C 0.05-0.40 mass%
  • C is an element that stabilizes the austenite phase and is an element necessary for ensuring the strength of the steel sheet.
  • C is less than 0.05 mass%, it is difficult to obtain a martensitic single-phase steel sheet having a desired tensile strength (980 MPa or more).
  • the amount of C exceeds 0.40 mass%, rolling before the continuous annealing process becomes difficult, and the transformation strain and transformation stress accompanying martensitic transformation may remarkably increase to cause firing cracks. This is not preferable in production. Therefore, in the present invention, C is set in the range of 0.05 to 0.40 mass%. The range is preferably from 0.15 to 0 and 30 mass%.
  • Si 2.0 mass% or less
  • Si is a substitutional solid solution strengthening element that is effective for increasing the strength without impairing the workability of the steel sheet.
  • Si is also an element that shifts the Ac 3 transformation point to the high temperature side
  • excessive addition of Si is not preferable because it causes an increase in annealing temperature and an increase in annealing cost.
  • Si is set to 2.0 mass% or less. Preferably it is 1.5 mass% or less.
  • Mn 1.0 to 3.0 mass%
  • Mn is an element that stabilizes the austenite phase and makes it easier to obtain a martensite structure.
  • Mn is less than 1.0 mass%, the hardenability of the steel is not sufficient, and the ferrite phase, the pearlite phase, and the bainite phase start to form early during cooling from the soaking temperature during annealing, and the present invention
  • it is difficult to stably obtain the intended martensite single-phase structure.
  • Mn is in the range of 1.0 to 3.0 mass%.
  • it is in the range of 1.5 to 2.5 mass%.
  • P 0.05 mass% or less
  • P is also an element that segregates at the grain boundary and promotes grain boundary destruction. Therefore, P is set to 0.05 mass% or less. Preferably it is 0.02 mass% or less, More preferably, it is 0.01 mass% or less. In addition, from a viewpoint of improving weldability, 0.008 mass% or less is desirable.
  • S 0.02 mass% or less Since S becomes a sulfide-based inclusion such as MnS and induces a decrease in impact resistance and delayed fracture resistance, it is desirable that S be as low as possible. Therefore, the upper limit of S is 0.02 mass%. Preferably it is 0.002 mass% or less.
  • Al 0.01 to 0.05 mass%
  • Al is an element added for deoxidation in the steelmaking process, and it is necessary to add 0.01 mass% or more in order to obtain a sufficient deoxidation effect. On the other hand, when it adds excessively, the inclusion in a steel plate will increase and the ductility will fall. Therefore, Al is set in the range of 0.01 to 0.05 mass%.
  • N Less than 0.005 mass% N is an element that forms a nitride. In particular, when the content is 0.005 mass% or more, the decrease in ductility at high and low temperatures due to the formation of nitride increases. Therefore, N is limited to less than 0.005 mass%.
  • Nb, Ti, B and Cu can be added to the ultra-high strength cold-rolled steel sheet of the present invention within the following ranges depending on the purpose.
  • Nb 0.1 mass% or less
  • Ti 0.1 mass% or less
  • Nb and Ti are effective elements for refining crystal grains and increasing the strength of a steel sheet.
  • Nb and Ti are added in amounts exceeding 0.1 mass%, the effect is saturated, which is not economically preferable. Therefore, when adding Nb and Ti, respectively, it shall be 0.1 mass% or less.
  • B 0.0005 to 0.0030 mass%
  • B is an element effective for enhancing the hardenability and increasing the steel sheet strength. However, if B is less than 0.0005 mass%, the above-mentioned strength increasing effect cannot be expected. On the other hand, if B exceeds 0.0030 mass%, the hot workability deteriorates, which is not preferable for production. Therefore, when adding B, it is set as the range of 0.0005-0.0030 mass%.
  • Cu 0.20 mass% or less Cu stabilizes the austenite phase, makes it easy to obtain a martensite single-phase structure, and forms a concentrated layer on the surface of the steel sheet in a corrosive environment. It is an element that has the effect of suppressing penetration and improving delayed fracture resistance. However, when the addition amount exceeds 0.20 mass%, these effects are saturated. Therefore, it is preferable to add Cu with an upper limit of 0.20 mass%.
  • the balance other than the above elements is Fe and inevitable impurities. However, addition of other elements is not rejected as long as the effects of the present invention are not impaired.
  • the ultra-high-strength cold-rolled steel sheet of the present invention requires that the metal structure is a martensite single phase.
  • the martensite phase may not be generated in the range of 10 ⁇ m in the thickness direction from the steel sheet surface due to the influence of decarburization or the like in the manufacturing process, it is necessary to exclude this range.
  • an austenite phase may remain in the matrix structure of the steel sheet, which is called a retained austenite phase. If the residual austenite phase is less than 0.5% in volume ratio, it can be regarded as a martensite single phase structure.
  • carbides, nitrides, and inclusions are inevitably present in the steel sheet structure, but these are not included in the evaluation when determining whether or not these are martensite single phase structures.
  • the ultra-high-strength cold-rolled steel sheet of the present invention has a martensitic single phase as-quenched metal structure, but when subjected to a tempering treatment described later after secondary cooling, it becomes a tempered martensite single-phase structure. .
  • the residual austenite phase needs to be less than 0.5% in volume ratio.
  • the manufacturing method of the ultra high strength cold-rolled steel sheet of the present invention is characterized by the continuous annealing process described below.
  • a conventionally known manufacturing method is adopted. can do.
  • the reason for limitation of the continuous annealing process which is the feature of the present invention will be described.
  • the steel sheet structure before quenching needs to be an austenite single phase, so the soaking temperature in the continuous annealing is set to the Ac 3 transformation point or higher.
  • the Ac 3 transformation point was described in “Metal Heat Treatment Technology Handbook 3rd Edition” (Metal Heat Treatment Technology Handbook Editorial Committee: Nikkan Kogyo Shimbun, (1966), p. 137) from the chemical composition of the steel sheet.
  • the following formula (2); Ac 3 (° C.) 910 ⁇ 203 ⁇ C 1/2 + 44.7 ⁇ Si ⁇ 30 ⁇ Mn ⁇ 20 ⁇ Cu + 700 ⁇ P + 400 ⁇ Al + 400 ⁇ Ti (2)
  • the element symbol in the above formula represents the content (mass%) of each element. Can be used to calculate.
  • the soaking time above the Ac 3 transformation point is preferably 30 to 1200 seconds, and more preferably 300 to 900 seconds from the viewpoint of suppressing the annealing cost.
  • the cooling stop temperature in the quenching process be as low as possible.
  • the primary cooling stop temperature is less than the Ms point, stress due to volume shrinkage due to rapid cooling and volume expansion unevenness due to martensitic transformation is generated inside the steel sheet, causing shape deterioration. Therefore, in the present invention, in order to reduce stress generated due to volume shrinkage accompanying cooling, a primary cooling step in which the quenching step is cooled from the soaking temperature to a temperature immediately above the Ms point, and from the vicinity immediately above the Ms point to 100. It was decided to control separately from the secondary cooling step of cooling to below ° C.
  • the cooling stop temperature in the primary cooling needs to be in the temperature range from the Ms point to the Ms point + 200 ° C. in the vicinity immediately above the Ms point.
  • the martensitic transformation proceeds, and stress due to volume expansion due to the martensitic transformation is generated, so that the effect of suppressing shape deterioration cannot be obtained.
  • a second phase such as a ferrite phase or a pearlite phase may be generated in the subsequent holding step, and if the secondary cooling start temperature increases, The accompanying volume shrinkage becomes large, leading to deterioration of the shape.
  • the element symbol in the above formula represents the content (mass%) of each element. Can be used to calculate.
  • the average cooling rate in the primary cooling needs to be 20 ° C./second or more. This is because, at an average cooling rate of less than 20 ° C./second, a second phase such as a ferrite phase and a pearlite phase is generated before the primary cooling stop temperature is reached, and a martensite single phase structure cannot be obtained.
  • the steel sheet after the primary cooling described above needs to be held in the temperature range of Ms point to Ms point + 200 ° C., which is the primary cooling stop temperature, for 0.1 to 60 seconds in order to make the temperature in the steel plate uniform.
  • the holding time in this holding process is shorter than 0.1 seconds, temperature unevenness due to the difference in cooling rate in the plate thickness direction or width direction of the steel plate is not sufficiently eliminated, so it is sufficient for reducing the stress in the steel plate. The effect is not obtained.
  • the holding time in the holding step is set in the range of 0.1 to 60 seconds.
  • the range is preferably 2 to 30 seconds.
  • Secondary cooling step After completion of the holding step, secondary cooling is performed from the primary cooling stop temperature (Ms point to Ms point + 200 ° C.) to 100 ° C. or lower at an average cooling rate of 100 ° C./second or higher in order to obtain a martensite single phase structure. Cooling needs to be done. When the average cooling rate is less than 100 ° C./second, a second phase such as a ferrite phase, a pearlite phase, or a bainite phase is generated during cooling, and a martensite single phase structure cannot be obtained.
  • the stress generated by the volume shrinkage accompanying cooling that occurs in this step and the volume expansion accompanying martensite transformation reduces the temperature difference from the martensite transformation point by the primary cooling, and the volume shrinkage generated in this step Can be suppressed to a minimum by making the temperature in the steel plate uniform in the holding step and reducing the generation of uneven stress in the steel plate width direction.
  • the steel plate subjected to the above-described quenching treatment has a predetermined strength and sufficient flatness, so that it can be made as it is, but in order to improve toughness and workability, 100 A tempering treatment for 120 to 1800 seconds may be performed at a temperature of ⁇ 250 ° C. If the tempering temperature is lower than 100 ° C. or the tempering time is shorter than 120 seconds, the tempering effect cannot be sufficiently obtained. On the other hand, if the tempering temperature is higher than 250 ° C. or the tempering time is longer than 1800 seconds, the softening of the martensite phase proceeds excessively, resulting in a significant decrease in strength and an increase in manufacturing cost. More preferable tempering conditions are in the range of 130 to 220 ° C. ⁇ 300 to 1200 seconds.
  • the cooling after the tempering treatment is not particularly limited and may be either air cooling or water cooling. In addition, it is preferable to perform this tempering process using the overaging zone of a continuous annealing line.
  • the steel sheet after continuous annealing does not need to be subjected to temper rolling for the purpose of shape correction, but from the viewpoint of surface roughness adjustment and material adjustment of the steel sheet, temper rolling is appropriately performed. Also good.
  • Thickness of steel of steel symbols A to S having the composition shown in Table 1 is made into a slab, the slab is heated to 1250 ° C., and then finished by hot rolling with a finish rolling finish temperature of 900 ° C.
  • An 8 mm hot-rolled steel sheet was taken up at a winding temperature of 650 ° C. Thereafter, the hot-rolled steel sheet was pickled to remove the surface scale, and then cold-rolled to obtain a cold-rolled steel sheet having a plate thickness of 1.0 mm and a plate width of 800 to 1400 mm.
  • the cold-rolled steel sheet is soaked under the conditions described in Table 2 and then subjected to continuous annealing that is quenched through primary cooling, holding, and secondary cooling, or further subjected to tempering treatment.
  • a rolled steel sheet was obtained.
  • Table 1 the Ms point and Ac 3 transformation point obtained from the above-described formulas (1) and (2) from the chemical components of each steel type are also shown.
  • the maximum warp height in the width direction was measured by the method shown in FIG. Specifically, the steel plate was placed on a surface plate, and the distance from the surface plate to the lower surface of the steel plate at the position where the height of the steel plate was the highest was measured. Moreover, the test piece was extract
  • each of the steel sheets of Examples 1 to 13 has a martensite single-phase structure (tempered martensite single-phase structure), and the maximum warp height of the warp generated in the steel sheet is 6 mm or less, which is highly flat.
  • the martensite single-phase structure intended by the present invention is obtained, but the maximum warp height of warpage is as large as 23 mm, and sufficient flatness is not obtained.
  • the steel sheet of the present invention has a hole expansion ratio ⁇ , which is an index of tensile characteristics and stretch flange characteristics, having a value equivalent to that of a martensite single phase steel sheet (No.
  • the cooling rate of the primary cooling step is lower than the range of the present invention.
  • No. 15 since all austenite phases were transformed into ferrite phases or pearlite phases during primary cooling, no martensite single phase structure was obtained.
  • No. 1 in which the primary cooling stop temperature is higher than the range of the present invention.
  • No. 16 no pearlite phase was generated, but most of the austenite phase was transformed into a ferrite phase, and a predetermined metal structure was not obtained.
  • the holding time in the holding step is longer than the range of the present invention.
  • No. 17 since a large amount of ferrite phase and pearlite phase are generated during the holding step, a predetermined metal structure is not obtained.
  • the cooling rate in the secondary cooling step was less than the cooling rate of the present invention.
  • No. 18 since a ferrite phase and a pearlite phase were generated during cooling from the primary cooling stop temperature to the Ms point, a martensite single phase structure was not obtained. From the above results, the martensitic single-phase steel sheet according to the present invention can achieve excellent flatness while having the same strength and processing characteristics as the martensitic single-phase steel sheet manufactured by the conventional method. It was confirmed that it was possible.
  • the ultra-high-strength martensitic single-phase steel sheet obtained by the present invention produces automotive structural members such as automobile door impact beams and center pillars formed by press molding or roll molding with high productivity and dimensional accuracy. It can make a big contribution.

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Abstract

L'invention concerne une tôle d'acier laminée à froid à ultra-haute résistance ayant une planéité élevée et une structure martensitique monophasée, qui est obtenue en supprimant la détérioration de la forme d'une tôle d'acier lors du procédé de durcissement en recuit continu. L'invention concerne spécifiquement un procédé de production par recuit continu après laminage à froid d'une tôle d'acier laminée à froid à ultra-haute résistance qui présente une résistance à la traction d'au moins 980 MPa. Ladite tôle d'acier contient, en pourcentage massique, 0,05-0,40 % de C, 2,0 % ou moins de Si, 0,05 % ou moins de P, 0,02 % ou moins de S, 0,01-0,05 % d'Al, moins de 0,005 % de N et 1,0-3,0 % de Mn, le solde étant du fer et les inévitables impuretés. Lors du recuit continu, la tôle d'acier est principalement refroidie depuis une température d'égalisation qui est supérieure ou égale au point de transformation Ac3 jusqu'à une gamme de température allant du point Ms jusqu'au point Ms + 200 °C à une température moyenne de refroidissement de 20 °C/seconde ou plus, et après maintien de la tôle d'acier résultante à l'intérieur de la gamme de température précitée pendant 0,1-60 secondes, la tôle est refroidie jusqu'à 100 °C ou moins à une vitesse moyenne de refroidissement de 100 °C/seconde ou plus, pour obtenir ainsi une tôle d'acier laminée à froid à ultra-haute résistance ayant une planéité de 10 mm ou moins.
PCT/JP2011/056128 2010-03-24 2011-03-09 Tôle d'acier laminée à froid à ultra-haute résistance et son procédé de production WO2011118459A1 (fr)

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CN201180015404.2A CN102822375B (zh) 2010-03-24 2011-03-09 超高强度冷轧钢板及其制造方法
KR1020127021878A KR101288701B1 (ko) 2010-03-24 2011-03-09 초고강도 냉연 강판 및 그 제조 방법

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Cited By (6)

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CN104126022A (zh) * 2011-11-28 2014-10-29 安赛乐米塔尔研发有限公司 具有1700至2200MPa拉伸强度的马氏体钢
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CN112126757A (zh) 2019-06-24 2020-12-25 宝山钢铁股份有限公司 一种厚向变强度硬度冷轧带钢及其制造方法
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JPWO2014196645A1 (ja) * 2013-06-07 2017-02-23 新日鐵住金株式会社 熱処理鋼材及びその製造方法
EP3006586A4 (fr) * 2013-06-07 2017-03-08 Nippon Steel & Sumitomo Metal Corporation Matériau d'acier traité thermiquement et son procédé de production
US10435761B2 (en) 2013-06-07 2019-10-08 Nippon Steel Corporation Heat-treated steel material and method of manufacturing the same
US10718033B2 (en) 2014-05-29 2020-07-21 Nippon Steel Corporation Heat-treated steel material and method of manufacturing the same
EP3825433A4 (fr) * 2018-08-22 2021-05-26 JFE Steel Corporation Tôle d'acier à haute résistance et son procédé de production
EP3825432A4 (fr) * 2018-08-22 2021-05-26 JFE Steel Corporation Tôle d'acier de haute résistance et procédé de production pour celle-ci
US11846002B2 (en) 2018-08-22 2023-12-19 Jfe Steel Corporation High-strength steel sheet and method for manufacturing same
US11898230B2 (en) 2018-08-22 2024-02-13 Jfe Steel Corporation High-strength steel sheet and method for manufacturing same
WO2023037878A1 (fr) * 2021-09-09 2023-03-16 日本製鉄株式会社 Tôle d'acier laminée à froid et son procédé de fabrication

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KR20120112813A (ko) 2012-10-11
CN102822375A (zh) 2012-12-12

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