WO2016158159A1 - TÔLE D'ACIER LAMINÉE À FROID HAUTE RÉSISTANCE, AYANT UNE EXCELLENTE APTITUDE AU FAÇONNAGE, DE TRÈS BONNES CARACTÉRISTIQUES DE COLLISION ET UNE RÉSISTANCE À LA TRACTION DE 980 MPa OU PLUS, ET PROCÉDÉ DE PRODUCTION - Google Patents

TÔLE D'ACIER LAMINÉE À FROID HAUTE RÉSISTANCE, AYANT UNE EXCELLENTE APTITUDE AU FAÇONNAGE, DE TRÈS BONNES CARACTÉRISTIQUES DE COLLISION ET UNE RÉSISTANCE À LA TRACTION DE 980 MPa OU PLUS, ET PROCÉDÉ DE PRODUCTION Download PDF

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WO2016158159A1
WO2016158159A1 PCT/JP2016/056168 JP2016056168W WO2016158159A1 WO 2016158159 A1 WO2016158159 A1 WO 2016158159A1 JP 2016056168 W JP2016056168 W JP 2016056168W WO 2016158159 A1 WO2016158159 A1 WO 2016158159A1
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less
temperature
steel sheet
strength
cooling
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PCT/JP2016/056168
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English (en)
Japanese (ja)
Inventor
忠夫 村田
二村　裕一
康二 粕谷
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株式会社神戸製鋼所
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Priority claimed from JP2015225506A external-priority patent/JP6554396B2/ja
Application filed by 株式会社神戸製鋼所 filed Critical 株式会社神戸製鋼所
Priority to MX2017012442A priority Critical patent/MX2017012442A/es
Priority to US15/554,843 priority patent/US20180037964A1/en
Priority to KR1020177030765A priority patent/KR102174558B1/ko
Priority to CN201680017718.9A priority patent/CN107429370B/zh
Priority to EP16772043.2A priority patent/EP3279362B1/fr
Publication of WO2016158159A1 publication Critical patent/WO2016158159A1/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
    • 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
    • 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
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur

Definitions

  • the present invention relates to a high-strength cold-rolled steel sheet having a tensile strength of 980 MPa or more excellent in workability and impact characteristics, and a method for producing the same.
  • the high-strength cold-rolled steel sheet, the high-strength cold-rolled steel sheet, the high-strength electro-galvanized steel sheet formed with the electrogalvanized layer on the surface, and the hot-rolled galvanized layer formed on the surface of the high-strength cold-rolled steel sheet The present invention relates to a high-strength hot-dip galvanized steel sheet, a high-strength galvannealed steel sheet in which an alloyed hot-dip galvanized layer is formed on the surface of the high-strength cold-rolled steel sheet, and methods for producing these.
  • the surface of automobile steel parts is electrogalvanized (hereinafter sometimes referred to as EG), hot dip galvanized (hereinafter sometimes referred to as GI), and alloyed.
  • Steel plates (hereinafter, sometimes collectively referred to as galvanized steel plates) subjected to galvanizing such as hot dip galvanizing (hereinafter sometimes referred to as GA) are often used.
  • galvanized steel sheets are also required to be strengthened and workable in the same manner as the high-strength steel sheets.
  • Patent Document 1 discloses an alloyed hot dip galvanized alloy having a metal structure in which martensite and retained austenite are mixed in ferrite, and having a good press workability with a tensile strength TS of 490 to 880 MPa by strengthening the composite structure.
  • the steel plate which gave is disclosed.
  • Patent Document 2 discloses that a steel sheet structure is composed of a ferrite phase having a volume fraction of 10 to 50%, a tempered martensite phase of 10 to 50%, and the remaining hard phase.
  • a high-strength steel sheet excellent in stretch flangeability having a diameter of 10 ⁇ m or less is disclosed.
  • Patent Document 3 discloses a high-strength galvanized steel sheet having a tensile maximum strength of 900 MPa or more, excellent in impact absorption energy, and capable of achieving both a static ratio comparable to that of a 590 MPa class steel plate and a tensile maximum strength of 900 MPa or more, and a method for producing the same. Is disclosed. This manufacturing method is characterized in that after galvanization, cooling is performed, and rolling is performed using a roll having a roughness (Ra) of 3.0 or less.
  • the present invention has been made paying attention to the above circumstances, and its purpose is a high-strength cold-rolled steel sheet having a tensile strength of 980 MPa or more, and has workability evaluated by ductility and stretch flangeability.
  • An object of the present invention is to provide a high-strength cold-rolled steel sheet that is good and has excellent impact characteristics.
  • Another object of the present invention is to provide a high-strength electrogalvanized steel sheet having an electrogalvanized layer on the surface of the high-strength cold-rolled steel sheet, a high-strength molten metal having a hot-dip galvanized layer on the surface of the high-strength cold-rolled steel sheet.
  • the high-strength cold-rolled steel sheet having a tensile strength of 980 MPa or more according to the present invention that has been able to solve the above-mentioned problems is mass%, C: 0.10% to 0.5%, Si: 1.0% or more. 3% or less, Mn: 1.5% to 7%, P: more than 0% to 0.1%, S: more than 0% to 0.05%, Al: 0.005% to 1%, N: A steel sheet containing more than 0% and 0.01% or less, and O: more than 0% and 0.01% or less, with the balance being iron and inevitable impurities.
  • the gist is that the metal structure at the 1/4 position of the plate thickness satisfies the following (1) to (4).
  • MA is an abbreviation for Martensite-Authentite Constituent.
  • the area ratio of ferrite is 0% or more and 10% or less with respect to the entire metal structure, and the balance includes hardened martensite and residual austenite, It is a hard phase composed of at least one selected from the group consisting of bainitic ferrite, bainite, and tempered martensite.
  • the volume fraction V ⁇ of retained austenite is 5% or more and 30% or less with respect to the entire metal structure.
  • the area ratio V MA of the MA structure in which quenched martensite and retained austenite are combined with respect to the entire metal structure is 3% or more and 25% or less.
  • the average equivalent circle diameter of the tissue is 2.0 ⁇ m or less.
  • the ratio V MA / V ⁇ of the area ratio V MA of the MA structure to the volume ratio V ⁇ of the retained austenite satisfies the following formula (i). 0.50 ⁇ V MA / V ⁇ ⁇ 1.50 (i)
  • the steel sheet as another element, in mass%, (A) at least one selected from the group consisting of Cr: more than 0% and 1% or less and Mo: more than 0% and 1% or less, (B) at least one selected from the group consisting of Ti: more than 0% and 0.15% or less, Nb: more than 0% and 0.15% or less, and V: more than 0% and 0.15% or less, (C) at least one selected from the group consisting of Cu: more than 0% and 1% or less and Ni: more than 0% and 1% or less, (D) B: more than 0% and 0.005% or less, (E) at least one selected from the group consisting of Ca: more than 0% and 0.01% or less, Mg: more than 0% and 0.01% or less, and REM: more than 0% and 0.01% or less, Etc. may be contained.
  • a high-strength electrogalvanized steel sheet having an electrogalvanized layer on the surface of the high-strength cold-rolled steel sheet a high-strength hot-dip galvanized steel sheet having a hot-dip galvanized layer on the surface of the high-strength cold-rolled steel sheet, A high-strength galvannealed steel sheet having an alloyed galvanized layer on the surface of a high-strength cold-rolled steel sheet is also included.
  • the high-strength cold-rolled steel sheet having excellent workability and impact characteristics according to the present invention and having a tensile strength of 980 MPa or more is a steel that satisfies the above-mentioned composition, and is finished at a rolling rate of 5 to 25% in the final stand of finish rolling.
  • Hot rolling is performed at a rolling end temperature of Ar 3 or higher and 900 ° C. or lower, coiled at a winding temperature of 600 ° C. or lower, cooled to room temperature, cold rolled, and Ac 3 at an average temperature increase rate of 10 ° C./second or higher.
  • a high-strength hot-dip galvanized steel sheet having a tensile strength of 980 MPa or more and excellent workability and impact characteristics according to the present invention is a steel satisfying the above-described component composition, with a rolling rate of 5 to 25% in the final stand of finish rolling, Hot rolling is performed at a finish rolling end temperature of Ar 3 or higher and 900 ° C. or lower, winding is performed at a winding temperature of 600 ° C. or lower, cooled to room temperature, cold rolled, and Ac is heated at an average temperature increase rate of 10 ° C./second or higher.
  • Heat to a temperature range of 3 points or more hold for 50 seconds or more in the temperature range, soak, and at an average cooling rate of 10 ° C / second or more to an arbitrary cooling stop temperature T ° C in a temperature range of 100 ° C or more and Ms point or less It can be manufactured by cooling, heating and holding for 50 seconds or more in the temperature range above the cooling stop temperature T ° C. and below 550 ° C., performing hot dip galvanization within the holding time, and then cooling to room temperature.
  • the high-strength alloyed hot-dip galvanized steel sheet having excellent workability and impact characteristics according to the present invention and having a tensile strength of 980 MPa or more is obtained by using a steel satisfying the above-described component composition at a rolling rate of 5 to 25 in the final stand of finish rolling.
  • % Hot rolling at a finish rolling finish temperature of Ar 3 point to 900 ° C., winding at a winding temperature of 600 ° C. or less, cooling to room temperature, cold rolling, average heating rate of 10 ° C./second or more Heat to a temperature range of Ac 3 points or higher, hold for 50 seconds or more in the temperature range and soak, and average cooling rate 10 ° C./second to any cooling stop temperature T ° C.
  • the component composition and the metal structure are appropriately controlled, high strength cold rolling with a tensile strength of 980 MPa or more excellent in both workability evaluated by ductility and stretch flangeability and impact properties is achieved.
  • Steel sheets, high-strength electrogalvanized steel sheets, high-strength hot-dip galvanized steel sheets, and high-strength galvannealed steel sheets can be provided.
  • the high-strength cold-rolled steel sheet, high-strength electrogalvanized steel sheet, high-strength hot-dip galvanized steel sheet, and high-strength galvannealed steel sheet according to the present invention are particularly excellent in stretch flangeability among workability.
  • the method of manufacturing the said high-strength cold-rolled steel plate, a high-strength electrogalvanized steel plate, a high-strength hot-dip galvanized steel plate, and a high-strength galvannealed steel plate can be provided.
  • the high-strength cold-rolled steel sheet, high-strength electrogalvanized steel sheet, high-strength hot-dip galvanized steel sheet, and high-strength galvannealed steel sheet according to the present invention are extremely useful particularly in industrial fields such as automobiles.
  • FIG. 1 is a schematic explanatory diagram illustrating an example of a heat treatment pattern performed in the example.
  • the present inventors have made extensive studies on a high-strength cold-rolled steel sheet having a tensile strength of 980 MPa or more.
  • the ferrite fraction in the metal structure is set to a predetermined amount or less, the remaining structure is made a hard phase, and the ductility is improved in order to improve the ductility.
  • the ratio V MA / V ⁇ of the area ratio V MA of the MA structure combined with residual austenite and the volume ratio V ⁇ of retained austenite may be appropriately controlled.
  • the ratio V MA / V ⁇ should be set appropriately in order to improve the collision characteristics.
  • the high-strength cold-rolled steel sheet according to the present invention is characterized in that the metal structure at the 1/4 position of the sheet thickness satisfies the following (1) to (4).
  • the area ratio of ferrite is 0% or more and 10% or less with respect to the entire metal structure, and the balance includes hardened martensite and residual austenite, It is a hard phase composed of at least one selected from the group consisting of bainitic ferrite, bainite, and tempered martensite.
  • the volume fraction V ⁇ of retained austenite is 5% or more and 30% or less with respect to the entire metal structure.
  • the area ratio V MA of the MA structure in which quenched martensite and retained austenite are combined with respect to the entire metal structure is 3% or more and 25% or less.
  • the average equivalent circle diameter of the tissue is 2.0 ⁇ m or less.
  • the volume ratio V ⁇ of the retained austenite and the area ratio V MA of the MA structure satisfy the following formula (i). 0.50 ⁇ V MA / V ⁇ ⁇ 1.50 (i)
  • the fractions of the metal structure defined in the above (1) to (3) may differ from the measurement method, so the sum of the fractions may exceed 100%. That is, in (1) above, the metal structure is observed with a scanning electron microscope, and the measured area ratio is a ratio when the entire metal structure is 100%. The area ratio measured using a scanning electron microscope includes hardened martensite and retained austenite as the area ratio of the hard phase. On the other hand, in (2) above, the residual austenite fraction of the metal structure is calculated by the X-ray diffraction method, and in (3) above, the area ratio of the MA structure in which quenched martensite and residual austenite are combined is measured with an optical microscope. Observe at.
  • retained austenite may be referred to as retained ⁇ .
  • MA structure a structure in which quenched martensite and residual ⁇ are combined.
  • the area ratio of ferrite is 0% or more and 10% or less with respect to the entire metal structure. Stretch flangeability can be improved by limiting the ferrite content to 10 area% or less. That is, since the high-strength cold-rolled steel sheet according to the present invention is mainly composed of a hard phase, the strength can be increased. On the other hand, since ferrite is a soft structure, the strength difference from the hard phase is large. Therefore, when the amount of ferrite increases, stretch flangeability decreases. In addition, when the ferrite is excessive, the strength of the steel sheet is lowered, and a tensile strength of 980 MPa or more cannot be ensured.
  • the area ratio of ferrite is 10% or less.
  • the area ratio of ferrite is preferably 7% or less, more preferably 5% or less.
  • the amount of ferrite is preferably as small as possible, and most preferably 0 area%.
  • the balance of the metal structure includes hardened martensite and residual ⁇ as essential structures, and is a hard phase composed of at least one selected from the group consisting of bainitic ferrite, bainite, and tempered martensite. These hard phases are harder than ferrite, and the strength of the steel sheet can be increased to 980 MPa or more by suppressing the amount of ferrite to a predetermined value or less and using the remaining structure as a hard phase.
  • the reason why hardened martensite and residual ⁇ are included as the essential structure is to generate a predetermined amount of MA structure in which hardened martensite and residual ⁇ are combined, as will be described later.
  • the metal structure may include at least one selected from the group consisting of pearlite and cementite in addition to the hard phase.
  • the total area ratio of pearlite and cementite is not particularly limited as long as the effects of the present invention are not impaired. For example, 20% or less is preferable.
  • the total area ratio is more preferably 15% or less, still more preferably 10% or less.
  • the area ratio of the metal structure may be calculated by observing a 1/4 position of the plate thickness with nital corrosion and then observing with a scanning electron microscope, and the observation magnification may be 1000 times, for example.
  • the volume ratio V ⁇ of the residual ⁇ is set to 5% or more and 30% or less with respect to the entire metal structure.
  • Residual ⁇ has an effect of suppressing the concentration of strain by accelerating hardening of the deformed portion during processing by being deformed by deformation when transformed into martensite when the steel plate is processed. Therefore, the strength-elongation balance of the steel sheet is improved, and the ductility can be improved.
  • the volume ratio of the residual ⁇ needs to be 5% or more.
  • the volume ratio of the residual ⁇ is preferably 6% or more, more preferably 7% or more.
  • the volume ratio of residual ⁇ is set to 30% or less.
  • the volume ratio of the residual ⁇ is preferably 25% or less, more preferably 20% or less.
  • the volume ratio of the residual ⁇ may be obtained by measuring the 1/4 position of the plate thickness by the X-ray diffraction method. Residual ⁇ is present between the laths of bainitic ferrite or included in the MA structure. Since the effect of the residual ⁇ is exhibited regardless of the presence form, in the present invention, the amount of all residual ⁇ measured by the X-ray diffraction method is summed regardless of the presence form to obtain the volume ratio. .
  • the area ratio V MA of the MA structure is 3% or more and 25% or less with respect to the entire metal structure.
  • the MA structure is a structure that improves the strength-elongation balance of the steel sheet and can improve the ductility. In order to exert such an effect, the area ratio of the MA structure needs to be 3% or more.
  • the area ratio of the MA structure is preferably 4% or more, more preferably 5% or more.
  • the area ratio of the MA structure is 25% or less.
  • the area ratio of the MA structure is preferably 23% or less, more preferably 20% or less.
  • the average equivalent circle diameter of the MA structure is 2.0 ⁇ m or less.
  • stretch flangeability and impact characteristics can be improved.
  • it is necessary that the average equivalent circle diameter of the MA structure is 2.0 ⁇ m or less.
  • the average equivalent circle diameter of the MA structure is preferably 1.8 ⁇ m or less, more preferably 1.5 ⁇ m or less. Note that, as the MA structure becomes finer, the stretch flangeability and the impact characteristics become better, so the lower limit of the average equivalent circle diameter of the MA structure is not particularly limited, but about 0.1 ⁇ m is the limit industrially. .
  • the MA structure is a structure in which hardened martensite and residual ⁇ are combined.
  • the hardened martensite is a structure in which untransformed austenite is martensitic transformed in the process of cooling the steel sheet from the heating temperature to room temperature. means. Quenched martensite can be distinguished from tempered martensite tempered by heat treatment by observing with an optical microscope. That is, hardened martensite is observed in white when observed with an optical microscope after repeller corrosion of the metal structure, whereas tempered martensite is observed in gray.
  • the area ratio of the MA structure is a value measured at a position where the steel sheet has a thickness of 1/4.
  • the average equivalent circle diameter of the MA structure is a value obtained by calculating the equivalent circle particle diameter based on the area of each MA structure for all the MA structures recognized in the observation field, and averaging these.
  • both ductility and collision characteristics can be achieved. That is, as described above, in the present invention, the residual ⁇ is positively generated in order to improve the strength-elongation balance that is an index of ductility. As a result, an MA structure is inevitably formed in the steel sheet. Further, when the strength-elongation balance was further examined, when a predetermined amount of residual ⁇ was generated, the area ratio of the MA structure was such that the value of the ratio V MA / V ⁇ was 0.50 or more. it has been found that it is sufficient to control the V MA.
  • the value of the ratio V MA / V ⁇ is preferably 0.55 or more, more preferably 0.60 or more.
  • the ratio V MA / V ⁇ is set to 1.50 or less in order to reduce the area ratio of the quenched martensite in the MA structure and ensure the collision characteristics.
  • the value of the ratio V MA / V ⁇ is preferably 1.40 or less, more preferably 1.30 or less.
  • % means “mass%” for the component composition of the steel sheet.
  • C is an element necessary for ensuring a tensile strength of 980 MPa or more, increasing the stability of residual ⁇ , and ensuring a predetermined amount of residual ⁇ .
  • the C amount is 0.10% or more.
  • the amount of C is preferably 0.12% or more, more preferably 0.15% or more.
  • the C amount is 0.5% or less.
  • the amount of C is preferably 0.40% or less, more preferably 0.30% or less, and still more preferably 0.25% or less.
  • Si is an element that acts as a solid solution strengthening element and contributes to increasing the strength of steel. Si is an element necessary for suppressing the formation of carbides, effectively acting on the generation of residual ⁇ , and ensuring an excellent strength-elongation balance.
  • the Si amount is 1.0% or more.
  • the amount of Si is preferably 1.2% or more, more preferably 1.35% or more, and further preferably 1.5% or more.
  • the Si amount is 3% or less.
  • the amount of Si is preferably 2.8% or less, more preferably 2.6% or less.
  • Mn is an element that improves hardenability, suppresses the formation of ferrite, and contributes to increasing the strength of the steel sheet. Mn is an element necessary for stabilizing ⁇ and generating residual ⁇ .
  • the amount of Mn is 1.5% or more.
  • the amount of Mn is preferably 1.6% or more, more preferably 1.7% or more, further preferably 1.8% or more, and still more preferably 2.0% or more.
  • the amount of Mn is 7% or less.
  • the amount of Mn is preferably 5.0% or less, more preferably 4.0% or less, and still more preferably 3.0% or less.
  • P more than 0% and 0.1% or less
  • P is an impurity element inevitably included, and if it is excessively contained, the weldability of the final product deteriorates. Therefore, in the present invention, the P amount is 0.1% or less.
  • the amount of P is preferably 0.08% or less, more preferably 0.05% or less.
  • the amount of P is preferably as small as possible, but it is industrially difficult to reduce it to 0%. Industrially, the lower limit of the amount of P is 0.0005%.
  • S more than 0% and 0.05% or less
  • S is an inevitably contained impurity element, and if contained excessively, the weldability of the final product deteriorates. Further, S forms sulfide inclusions in the steel sheet and causes the ductility and stretch flangeability of the steel sheet to deteriorate. Therefore, in the present invention, the S amount is 0.05% or less.
  • the amount of S is preferably 0.01% or less, more preferably 0.005% or less.
  • the amount of S should be as small as possible, but it is industrially difficult to make it 0%.
  • the lower limit of the amount of S is industrially 0.0001%.
  • Al is an element that acts as a deoxidizing agent. In order to exert such an effect, the Al content is set to 0.005% or more in the present invention.
  • the amount of Al is more preferably 0.01% or more. However, when the amount of Al becomes excessive, the weldability of the final product is significantly deteriorated. Therefore, in the present invention, the Al amount is 1% or less.
  • the amount of Al is preferably 0.8% or less, more preferably 0.6% or less.
  • N more than 0% and 0.01% or less
  • N is an impure element contained inevitably, and when it is contained excessively, a large amount of nitride precipitates and deteriorates ductility, stretch flangeability, and impact characteristics. Therefore, in the present invention, the N content is 0.01% or less.
  • the N amount is preferably 0.008% or less, more preferably 0.005% or less. Note that the amount of N may be 0.001% or more because a small amount of nitride contributes to increasing the strength of the steel sheet.
  • O is an impure element contained inevitably, and when excessively contained, it is an element that deteriorates ductility and collision characteristics. Therefore, in the present invention, the O amount is 0.01% or less.
  • the amount of O is preferably 0.005% or less, more preferably 0.003% or less.
  • the amount of O is preferably as small as possible, but it is industrially difficult to make it 0%.
  • the lower limit of the amount of O is industrially 0.0001%.
  • the cold-rolled steel sheet according to the present invention satisfies the above component composition, and the balance is iron and inevitable impurities.
  • the inevitable impurities include, for example, the above-mentioned P, S, N, and O that may be brought into steel depending on the situation of raw materials, materials, manufacturing equipment, and the like, and other trump elements such as Pb, Bi, Sb, Sn. May be included.
  • the cold-rolled steel sheet according to the present invention further includes other elements, (A) at least one selected from the group consisting of Cr: more than 0% and 1% or less and Mo: more than 0% and 1% or less, (B) at least one selected from the group consisting of Ti: more than 0% and 0.15% or less, Nb: more than 0% and 0.15% or less, and V: more than 0% and 0.15% or less, (C) at least one selected from the group consisting of Cu: more than 0% and 1% or less and Ni: more than 0% and 1% or less, (D) B: more than 0% and 0.005% or less, (E) at least one selected from the group consisting of Ca: more than 0% and 0.01% or less, Mg: more than 0% and 0.01% or less, and REM: more than 0% and 0.01% or less, Etc. may be contained.
  • A at least one selected from the group consisting of Cr: more than 0% and 1% or less and Mo: more than 0% and
  • Cr and Mo are both elements that effectively act to improve the hardenability and improve the strength of the steel sheet.
  • Cr and Mo are each preferably 0.1% or more, and more preferably 0.3% or more.
  • Cr and Mo can be used alone or in combination. When Cr and Mo are used in combination, it is preferably within the above range when contained alone, and the total amount of Cr and Mo is preferably 1.5% or less.
  • Ti, Nb, and V are all elements that have the action of forming carbides and nitrides in the steel sheet, improving the strength of the steel sheet, and refining the old ⁇ grains.
  • Ti, Nb, and V are each preferably 0.005% or more, and more preferably 0.010% or more.
  • Ti, Nb, and V are each preferably 0.15% or less, more preferably 0.12% or less, and still more preferably 0.10% or less.
  • Cu and Ni are elements that effectively act to generate and stabilize residual ⁇ . Moreover, Cu and Ni also have the effect
  • the Ni content is preferably 1% or less, more preferably 0.8% or less, and still more preferably 0.5% or less.
  • Cu and Ni can be used alone or in combination. When Cu and Ni are used in combination, the above-described action is easily exhibited, and by adding Ni, deterioration of hot workability due to addition of Cu is easily suppressed. When Cu and Ni are used in combination, the total amount is preferably 1.5% or less, and more preferably 1.0% or less.
  • [(D) B: more than 0% and 0.005% or less] B is an element that improves hardenability, and is an element that acts to make austenite stably exist up to room temperature.
  • the B content is preferably 0.0005% or more, more preferably 0.0010% or more, and further preferably 0.0015% or more.
  • the B content is preferably 0.005% or less.
  • the amount of B is more preferably 0.004% or less, and still more preferably 0.0035% or less.
  • Ca, Mg, and REM are elements having an action of finely dispersing inclusions in the steel sheet.
  • the Ca, Mg, and REM amounts are each preferably 0.0005% or more, and more preferably 0.0010% or more.
  • the Ca, Mg, and REM amounts are each preferably 0.01% or less, more preferably 0.008% or less, and still more preferably 0.007% or less.
  • REM is an abbreviation for Rare earth metal (rare earth element), and means to include lanthanoid elements, that is, 15 elements from La to Lu, and Sc and Y.
  • the high strength cold-rolled steel sheet according to the present invention has been described above.
  • the high-strength cold-rolled steel sheet may have an electrogalvanized layer, a hot-dip galvanized layer, or an alloyed hot-dip galvanized layer on the surface. That is, the present invention includes a high-strength electrogalvanized steel sheet (hereinafter sometimes referred to as EG steel sheet) having an electrogalvanized layer on the surface of the high-strength cold-rolled steel sheet, and the surface of the high-strength cold-rolled steel sheet.
  • EG steel sheet high-strength electrogalvanized steel sheet
  • High-strength hot-dip galvanized steel sheet (hereinafter sometimes referred to as GI steel sheet), high-strength galvanized steel sheet having an alloyed hot-dip galvanized layer on the surface of the high-strength cold-rolled steel sheet
  • a GA steel plate A plated steel plate (hereinafter sometimes referred to as a GA steel plate) is also included.
  • the high-strength cold-rolled steel sheet is hot-rolled with a steel satisfying the above-described component composition, with a rolling rate of 5 to 25% in the final stand of finish rolling, and a finish rolling end temperature of Ar 3 to 900 ° C.
  • the coiling temperature is set to 600 ° C. or lower, the sheet is cooled to room temperature, cold-rolled, heated to a temperature range of Ac 3 points or higher at an average temperature increase rate of 10 ° C./second or more, and held in the temperature range for 50 seconds or more. Soaking, cooling to an arbitrary cooling stop temperature T ° C. in the temperature range of 100 ° C.
  • the heating temperature is not particularly limited, but is preferably 1000 to 1300 ° C., for example. If the heating temperature is less than 1000 ° C., the solid solution of the carbide becomes insufficient, and it is difficult to obtain sufficient strength. On the other hand, when the heating temperature exceeds 1300 ° C., the structure of the hot-rolled steel sheet is coarsened, and the MA structure of the cold-rolled steel sheet is easily coarsened. As a result, the collision characteristics tend to deteriorate.
  • the rolling ratio needs to be 5% or more.
  • the rolling reduction is preferably 6% or more, more preferably 7% or more, and further preferably 8% or more.
  • the rolling ratio needs to be 25% or less.
  • the rolling reduction is preferably 23% or less, more preferably 20% or less.
  • the finish rolling end temperature needs to be 900 ° C. or less.
  • the finish rolling end temperature is preferably 890 ° C. or lower, more preferably 880 ° C. or lower.
  • the temperature at the Ar 3 point was calculated based on the following formula (ii).
  • [] indicates the content (% by mass) of each element, and the content of elements not included in the steel sheet may be calculated as 0% by mass.
  • Ar 3 point (° C.) 910 ⁇ 310 ⁇ [C] ⁇ 80 ⁇ [Mn] ⁇ 20 ⁇ [Cu] ⁇ 15 ⁇ [Cr] ⁇ 55 ⁇ [Ni] ⁇ 80 ⁇ [Mo] (ii)
  • the winding temperature is 600 ° C. or less.
  • the winding temperature is preferably 580 ° C. or lower, more preferably 570 ° C. or lower, and further preferably 550 ° C. or lower.
  • Cold rolling After hot rolling, it may be wound, cooled to room temperature, pickled according to a conventional method if necessary, and then cold rolled according to a conventional method.
  • the cold rolling rate in the cold rolling may be 30 to 80%, for example.
  • annealing is performed by heating to a temperature range of Ac 3 point or higher at an average temperature increase rate of 10 ° C./second or more, and holding the temperature range for 50 seconds or more and soaking.
  • the said average temperature increase rate shall be 10 degrees C / sec or more.
  • the average temperature rising rate is preferably 12 ° C./second or more, more preferably 15 ° C./second or more.
  • the upper limit of the average heating rate is not particularly limited, but is usually about 100 ° C./second at the maximum.
  • the soaking temperature is set to Ac 3 point or higher.
  • the soaking temperature is preferably Ac 3 point + 10 ° C. or higher, more preferably Ac 3 point + 20 ° C. or higher.
  • the upper limit of the soaking temperature is not particularly limited, but if the soaking temperature is too high, austenite may be coarsened, and therefore, Ac 3 point + 100 ° C. or lower is preferable, and Ac 3 point + 50 ° C. or lower is more preferable.
  • the soaking time is set to 50 seconds or more.
  • the soaking time is more preferably 60 seconds or longer.
  • the upper limit of the soaking time is not particularly limited, but if the soaking time is too long, the concentration of Mn into the austenite phase proceeds, the Ms point may decrease, and the MA structure may increase and become coarse. Therefore, the soaking time is preferably 3600 seconds or less, more preferably 3000 seconds or less.
  • the soaking in the above temperature range does not need to be held at the same temperature, and may be varied by heating, cooling and changing in the above temperature range.
  • the temperature of the Ac 3 point can be calculated based on the following formula (iii) described in “Leslie Steel Material Chemistry” (Maruzen Co., Ltd., issued May 31, 1985, page 273).
  • [] indicates the content (% by mass) of each element, and the content of elements not included in the steel sheet may be calculated as 0% by mass.
  • the cooling stop temperature T is set to be equal to or lower than the temperature at the Ms point.
  • the cooling stop temperature T is preferably Ms point ⁇ 20 ° C. or lower, more preferably Ms point ⁇ 50 ° C. or lower.
  • the minimum of the cooling stop temperature T shall be 100 degreeC or more.
  • the cooling stop temperature T is preferably 110 ° C. or higher, more preferably 120 ° C. or higher.
  • the temperature of the Ms point can be calculated based on the following formula (iv).
  • [] indicates the content (% by mass) of each element, and the content of elements not included in the steel sheet may be calculated as 0% by mass.
  • Ms point (° C.) 561-474 ⁇ [C] ⁇ 33 ⁇ [Mn] ⁇ 17 ⁇ [Ni] ⁇ 17 ⁇ [Cr] ⁇ 21 ⁇ [Mo] (iv)
  • the average cooling rate to the cooling stop temperature T in the above temperature range is 10 ° C./second or more after the above-mentioned soaking is maintained.
  • the said average cooling rate shall be 10 degrees C / sec or more.
  • the average cooling rate is preferably 15 ° C./second or more, more preferably 20 ° C./second or more.
  • the upper limit of the said average cooling rate is not specifically limited, You may cool by water cooling or oil cooling.
  • the reheating temperature is preferably T + 20 ° C. or higher, more preferably T + 30 ° C. or higher, and further preferably T + 50 ° C. or higher.
  • the reheating temperature is set to 550 ° C. or lower.
  • the reheating temperature is preferably 520 ° C. or lower, more preferably 500 ° C. or lower, and further preferably 450 ° C. or lower.
  • reheating means heating from the cooling stop temperature T, that is, raising the temperature, as the wording indicates. Therefore, the reheating temperature is higher than the cooling stop temperature T, and the reheating temperature is the same as the cooling stop temperature T even if the reheating temperature is, for example, a temperature range of 100 ° C. or more and 550 ° C. or less. If the reheating temperature is lower than the cooling stop temperature T, it does not correspond to the reheating of the present invention.
  • the temperature After reheating to the above-mentioned cooling stop temperature T ° C. or more and 550 ° C. or less, the temperature is maintained for 50 seconds or more in the temperature range.
  • the reheat holding time is less than 50 seconds, the MA structure is excessively generated and ductility cannot be improved. Further, since the MA structure becomes coarse and the average equivalent circle diameter cannot be controlled appropriately, the stretch flangeability cannot be improved. Further, since the ratio V MA / V ⁇ of the area ratio V MA of the MA structure to the volume ratio V ⁇ of the residual ⁇ cannot be appropriately controlled, the collision characteristics cannot be improved. Furthermore, the hard phase cannot be tempered sufficiently, and the transformation of untransformed austenite to bainitic ferrite or bainite does not proceed sufficiently.
  • the reheating holding time is 50 seconds or more.
  • the reheating holding time is preferably 80 seconds or longer, more preferably 100 seconds or longer, and further preferably 200 seconds or longer.
  • the upper limit of the reheating holding time is not particularly limited, but when the holding time is increased, productivity is lowered and tensile strength tends to be lowered. From such a viewpoint, the reheating holding time is preferably 1500 seconds or less, and more preferably 1000 seconds or less.
  • the average cooling rate at the time of cooling is not specifically limited, For example, it is preferable that it is 0.1 degree-C / second or more, More preferably, it is 0.4 degree-C / second or more. Moreover, it is preferable that an average cooling rate is 200 degrees C / second or less, for example, More preferably, it is 150 degrees C / second or less.
  • the high-strength cold-rolled steel sheet according to the present invention obtained by cooling to room temperature may be subjected to electrogalvanizing, hot-dip galvanizing, or alloyed hot-dip galvanizing according to a conventional method.
  • the high-strength cold-rolled steel sheet may be energized while being immersed in a zinc solution at 50 to 60 ° C. (particularly 55 ° C.) to perform electrogalvanizing treatment.
  • the amount of plating adhesion is not particularly limited, and may be, for example, about 10 to 100 g / m 2 per side.
  • the high-strength cold-rolled steel sheet may be immersed in a hot dip galvanizing bath at 300 ° C. or higher and 550 ° C. or lower to perform hot dip galvanizing treatment.
  • the plating time may be appropriately adjusted so as to ensure a desired plating adhesion amount, and is preferably set to 1 to 10 seconds, for example.
  • the alloyed hot dip galvanizing may be performed after the hot dip galvanizing.
  • the alloying treatment temperature is not particularly limited, it is preferably 450 ° C. or more, more preferably 460 ° C. or more, and further preferably 480 ° C. or more because alloying does not proceed sufficiently if the alloying treatment temperature is too low. However, if the alloying treatment temperature is too high, alloying proceeds too much, the Fe concentration in the plating layer becomes high, and the plating adhesion deteriorates. From such a viewpoint, the alloying treatment temperature is preferably 550 ° C. or less, more preferably 540 ° C. or less, and further preferably 530 ° C. or less.
  • the alloying treatment time is not particularly limited, and may be adjusted so that hot dip galvanizing is alloyed. The alloying treatment time is, for example, 10 to 60 seconds.
  • a high-strength hot-dip galvanized steel sheet having a tensile strength of 980 MPa or more and excellent workability and impact characteristics according to the present invention is a steel satisfying the above-described component composition, with a rolling rate of 5 to 25% in the final stand of finish rolling, Hot rolling is performed at a finish rolling end temperature of Ar 3 or higher and 900 ° C. or lower, winding is performed at a winding temperature of 600 ° C. or lower, cooled to room temperature, cold rolled, and Ac is heated at an average temperature increase rate of 10 ° C./second or higher.
  • Heat to a temperature range of 3 points or more hold for 50 seconds or more in the temperature range, soak, and at an average cooling rate of 10 ° C / second or more to an arbitrary cooling stop temperature T ° C in a temperature range of 100 ° C or more and Ms point or less It can also be produced by cooling and heating and holding for 50 seconds or more in the temperature range above the cooling stop temperature T ° C. and below 550 ° C., and after performing hot dip galvanization within the holding time, cooling to room temperature. That is, the process until heating to a temperature range above the cooling stop temperature T ° C. and below 550 ° C.
  • the hot dip galvanizing may be performed within the holding time in the reheating temperature range, that is, in the temperature range of the cooling stop temperature T ° C. or higher and 550 ° C. or lower, and a specific plating method can be adopted. For example, if a steel sheet heated to a temperature range above the cooling stop temperature T ° C. and below 550 ° C. is immersed in a plating bath adjusted to a temperature in the range above the cooling stop temperature T ° C. and below 550 ° C., hot dip galvanizing treatment is performed. Good.
  • the plating time may be appropriately adjusted so that a desired plating amount can be secured within the reheating and holding time.
  • the plating time is preferably 1 to 10 seconds, for example.
  • the reheating temperature when only the heating is performed may be different from the temperature of the plating bath when the hot dip galvanizing is performed.
  • heating or cooling from one temperature to the other may be performed.
  • Examples of the heating method include furnace heating and induction heating.
  • the high-strength alloyed hot-dip galvanized steel sheet having excellent workability and impact characteristics according to the present invention and having a tensile strength of 980 MPa or more is obtained by using a steel satisfying the above-described component composition at a rolling rate of 5 to 25 in the final stand of finish rolling.
  • % Hot rolling at a finish rolling finish temperature of Ar 3 point to 900 ° C., winding at a winding temperature of 600 ° C. or less, cooling to room temperature, cold rolling, average heating rate of 10 ° C./second or more Heat to a temperature range of Ac 3 points or higher, hold for 50 seconds or more in the temperature range and soak, and average cooling rate 10 ° C./second to any cooling stop temperature T ° C.
  • Cooling Can also be manufactured. That is, the process until heating to a temperature range above the cooling stop temperature T ° C. and below 550 ° C. is the same as the manufacturing method of the high-strength cold-rolled steel sheet according to the present invention described above, and the cooling stop temperature T ° C. above 550 ° C. What is necessary is just to carry out holding
  • the alloying treatment temperature is not particularly limited, it is preferably 450 ° C. or higher, more preferably 460 ° C. or higher, and further preferably 480 ° C. or higher because alloying does not proceed sufficiently if the alloying temperature is too low. However, if the alloying treatment temperature is too high, alloying proceeds too much, the Fe concentration in the plating layer becomes high, and the plating adhesion deteriorates. From such a viewpoint, the alloying treatment temperature is preferably 550 ° C. or less, more preferably 540 ° C. or less, and further preferably 530 ° C. or less.
  • the alloying treatment time is not particularly limited, and may be adjusted so that hot dip galvanizing is alloyed.
  • the alloying treatment time is, for example, 10 to 60 seconds. Since the alloying process is performed after the hot dip galvanizing process is performed for a predetermined time in the temperature range of the above cooling stop temperature T ° C. to 550 ° C., the time required for the alloying process exceeds the above cooling stop temperature T ° C. It is not included in the holding time in the temperature range of 550 ° C. or lower.
  • the hot dip galvanization within the holding time in the temperature range above the cooling stop temperature T ° C. and below 550 ° C., and performing the alloying treatment as necessary it may be cooled to room temperature.
  • the average cooling rate at the time of cooling is not specifically limited, For example, it is preferable that it is 0.1 degree-C / second or more, More preferably, it is 0.4 degree-C / second or more. Moreover, it is preferable that an average cooling rate is 200 degrees C / second or less, for example, More preferably, it is 150 degrees C / second or less.
  • the high-strength cold-rolled steel sheet according to the present invention has a tensile strength of 980 MPa or more.
  • the tensile strength is preferably 1000 MPa or more, more preferably 1010 MPa or more.
  • strength cold-rolled steel plate is excellent in workability evaluated by ductility and stretch flangeability, and also is excellent in a collision characteristic.
  • the ductility can be evaluated by a strength-elongation balance.
  • the product of the tensile strength TS (MPa) and the elongation EL (%) is 13000 MPa ⁇ % or more.
  • the value of TS ⁇ EL is preferably 13100 MPa ⁇ % or more, and more preferably 13200 MPa ⁇ % or more.
  • the stretch flangeability can be evaluated by a balance between strength and hole expansion rate.
  • the product of the tensile strength TS (MPa) and the hole expansion rate ⁇ (%) is passed 40000 MPa ⁇ % or more.
  • the value of TS ⁇ ⁇ is preferably 41000 MPa ⁇ % or more, more preferably 42000 MPa ⁇ % or more.
  • the impact characteristics can be evaluated by the strength-VDA bending angle balance.
  • the product of the tensile strength TS (MPa) and the VDA bending angle (°) is 90000 MPa ⁇ ° or more.
  • the value of the TS ⁇ VDA bending angle is preferably 90500 MPa ⁇ ° or more, and more preferably 91000 MPa ⁇ ° or more.
  • the thickness of the high-strength cold-rolled steel sheet according to the present invention is not particularly limited, but is preferably a thin steel sheet of 6 mm or less, for example.
  • Table 1 The components shown in Table 1 below were contained, and the balance was produced by melting steel composed of iron and inevitable impurities, and subjected to hot rolling, cold rolling, and continuous annealing to produce cold rolled steel sheets.
  • “-” means that no element is contained.
  • Table 1 below shows the temperature at the Ar 3 point calculated based on the above formula (ii) and the temperature at the Ac 3 point calculated based on the above formula (iii).
  • FIG. 1 1 is a heating step
  • 2 is a soaking step
  • 3 is a cooling step
  • 4 is a reheating and holding step
  • 5 is a cooling stop temperature.
  • cooling was performed at an average cooling rate shown in Table 2-1 or Table 2-2 below to a cooling stop temperature T ° C shown in Table 2-1 or Table 2-2 below.
  • Table 2-1 or Table 2-2 below show the reheating holding time.
  • Tables 2-1 and 2-2 below show values calculated by subtracting the cooling stop temperature T from the reheating temperature.
  • the Ms point was calculated from the above formula (iv), and the results are shown in Table 2-1 and Table 2-2 below.
  • Tables 2-1 and 2-2 below also show values obtained by subtracting the Ms point temperature from the cooling stop temperature T.
  • No. shown in Table 2-1 below. 11, No. shown in Table 2-2 below. No. 29 is an example in which the reheating and holding step is not performed after the cooling is stopped at the cooling stop temperature T shown in Table 2-1 or Table 2-2 below. That is, no. No. 11 was cooled at a cooling stop temperature T of 440 ° C., cooled to 350 ° C. lower than this temperature, and held at 350 ° C. for 600 seconds. In Table 2-1 below, for convenience, 350 ° C. is described in the reheating temperature column and 600 seconds are described in the reheating holding time column. No. No. 29 was cooled at a cooling stop temperature T of 350 ° C., cooled to 330 ° C. lower than this temperature, and held at 330 ° C. for 300 seconds. In Table 2-2 below, for convenience, 330 ° C. is described in the reheating temperature column, and 300 seconds are described in the reheating holding time column.
  • Electrogalvanizing No. shown in Table 2-1 below.
  • No. 15 is an example in which an electrogalvanized steel sheet was manufactured by immersing the above specimen in a galvanizing bath at 55 ° C. and subjecting it to electrogalvanizing treatment, followed by washing with water and drying. Galvanized treatment was performed with a current density between 40A / dm 2. The amount of galvanized adhesion was 40 g / m 2 per side.
  • washing materials such as alkaline aqueous solution degreasing, water washing, and pickling were appropriately performed to produce test materials having an electrogalvanized layer on the surface of the cold rolled steel sheet.
  • Table 2-1 below no. In the column of 15 categories, “EG” is described.
  • the structure other than ferrite, pearlite, and cementite calculated by the above point calculation method was used as the hard phase. That is, a value obtained by subtracting the area ratio of ferrite and the total area ratio of pearlite and cementite from 100% was calculated as the area ratio of the hard phase, and the results are shown in Tables 3-1 and 3-2 below.
  • the hard phase contains hardened martensite and residual ⁇ , and is at least selected from the group consisting of bainitic ferrite, bainite, and tempered martensite. There was one.
  • V ⁇ of residual ⁇ (Volume ratio V ⁇ of residual ⁇ )
  • the obtained specimen is polished to 1/4 position of the plate thickness using # 1000 to # 1500 sandpaper, and the surface is further electropolished to a depth of 10 to 20 ⁇ m, and then an X-ray diffractometer is used.
  • the volume fraction V ⁇ of residual ⁇ was measured.
  • “RINT 1500” manufactured by Rigaku Corporation was used as an X-ray diffraction apparatus, a Co target was used, 40 kV-200 mA was output, and a range of 40 ° to 130 ° was measured at 2 ⁇ .
  • the case where the tensile strength was 980 MPa or more was evaluated as acceptable with high strength, and the case where the tensile strength was less than 980 MPa was evaluated as unacceptable due to insufficient strength.
  • TS ⁇ EL indicates a strength-elongation balance and is an index for evaluating ductility.
  • TS ⁇ hole expansion ratio ⁇ was calculated. The calculation results are shown in Table 3-1 and Table 3-2 below.
  • the value of TS ⁇ ⁇ indicates a balance between strength and hole expansion rate, and is an index for evaluating stretch flangeability.
  • VDA238-100 VDA238-100
  • German Automobile Manufacturers Association a bending test is performed under the following conditions, and the displacement at the maximum load measured in the bending test is converted into an angle based on the VDA standard. The bending angle was determined. The conversion results are shown in Table 3-1 and Table 3-2 below.
  • TS value is 980 MPa or more
  • TS ⁇ EL value is 13000 MPa ⁇ % or more
  • TS ⁇ ⁇ value is 40000 MPa ⁇ % or more
  • TS ⁇ VDA value is 90000 MPa ⁇ ° or more.
  • the present invention was regarded as an example of the present invention, and the pass was listed in the column for comprehensive evaluation in Table 3-1 and Table 3-2 below.
  • a case where any one of the TS value, TS ⁇ EL value, TS ⁇ ⁇ value, or TS ⁇ VDA value does not satisfy the above acceptance criteria is used as a comparative example. Failures are listed in the column for overall evaluation in Table 3-2.
  • Table 2-1 From Table 1, Table 2-1, Table 2-2, Table 3-1, and Table 3-2, it can be considered as follows.
  • examples where “pass” is described in the column of comprehensive evaluation are both steel sheets that satisfy the requirements specified in the present invention, and are in accordance with the tensile strength TS. All of the defined TS ⁇ EL value, TS ⁇ ⁇ value, and TS ⁇ VDA value satisfy the acceptance standard value. It can be seen that these steel sheets have good workability evaluated by ductility and stretch flangeability, particularly excellent stretch flangeability, and excellent impact characteristics.
  • the example described as “Fail” in the column of comprehensive evaluation is a steel sheet that does not satisfy any of the requirements defined in the present invention, and is at least one of ductility, stretch flangeability, and impact characteristics. One could not improve. Details are as follows.
  • No. No. 2 was cooled to a very low temperature of 25 ° C., where the cooling stop temperature T after soaking was below 100 ° C., so that a predetermined amount of residual ⁇ and MA texture could not be secured, and the value of V MA / V ⁇ was within the specified range It is an example below. As a result, the value of TS ⁇ EL became small and ductility could not be improved.
  • No. Nos. 3 and 38 are examples in which the MA structure is coarsened because the average temperature increase rate after winding is too small. As a result, the value of TS ⁇ ⁇ became small and the stretch flangeability could not be improved.
  • No. No. 4 is an example in which the MA structure is coarsened because the cooling stop temperature T after soaking is too high exceeding the temperature range of 100 ° C. or more and the Ms point or less.
  • the value of TS ⁇ ⁇ became small and the stretch flangeability could not be improved.
  • the value of TS ⁇ VDA was reduced, and the collision characteristics could not be improved.
  • No. No. 7 is an example in which the MA structure is coarsened because the finish rolling finish temperature is too high. As a result, the value of TS ⁇ ⁇ became small and the stretch flangeability could not be improved.
  • No. No. 8 is an example in which the MA structure is coarsened because the winding temperature is too high. As a result, the value of TS ⁇ ⁇ became small and the stretch flangeability could not be improved.
  • No. Nos. 9 and 39 are examples in which ferrite was excessively generated because the average cooling rate after soaking was too small. As a result, the value of TS ⁇ ⁇ became small and the stretch flangeability could not be improved.
  • the cooling stop temperature T after soaking was too high exceeding the temperature range of 100 ° C. or more and the Ms point or less, and the value of V MA / V ⁇ was too large because the reheating was not held after cooling. It is an example. As a result, the value of TS ⁇ VDA was reduced, and the collision characteristics could not be improved.
  • No. No. 13 is an example in which the MA structure is coarsened because the rolling reduction at the final stand at the time of finish rolling is too high beyond the range defined in the present invention.
  • the value of TS ⁇ ⁇ became small and the stretch flangeability could not be improved.
  • the value of TS ⁇ VDA was reduced, and the collision characteristics could not be improved.
  • No. No. 14 is an example in which the MA structure becomes coarse because the rolling reduction at the final stand at the time of finish rolling is too low below the range defined in the present invention. As a result, the value of TS ⁇ ⁇ became small and the stretch flangeability could not be improved.
  • No. No. 16 is an example in which the ferrite is excessively generated because the soaking is performed at a temperature lower than the Ac 3 point. As a result, the value of TS ⁇ ⁇ became small and the stretch flangeability could not be improved.
  • No. No. 23 is an example in which the MA structure is coarsened because the reheating holding time is too short. As a result, the value of TS ⁇ ⁇ became small and the stretch flangeability could not be improved. Moreover, MA structure
  • No. No. 24 is an example in which since the reheating temperature performed after cooling was too high, decomposition of austenite occurred and a predetermined amount of residual ⁇ and MA structure could not be secured. As a result, TS became low.
  • No. 33 is an example in which the amount of C is too small, and is an example in which the amount of residual ⁇ within the range specified in the present invention cannot be secured. As a result, the value of TS ⁇ EL was decreased and ductility was deteriorated.
  • No. 34 is an example in which the amount of Si is too small, and the amount of residual ⁇ within the range specified in the present invention could not be secured. As a result, the value of TS ⁇ EL was decreased and ductility was deteriorated.
  • No. No. 35 is an example in which the amount of Mn is too small, the hardenability is insufficient, and ferrite is generated excessively. As a result, the value of TS ⁇ ⁇ was decreased, and the stretch flangeability deteriorated.
  • No. No. 41 is an example in which a predetermined amount of residual ⁇ could not be secured because the cooling stop temperature T after soaking was below 100 ° C. As a result, the value of TS ⁇ EL became small and ductility could not be improved.

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Abstract

L'invention concerne : une tôle d'acier laminée à froid haute résistance ayant une résistance à la traction de 980 MPa ou plus, une bonne aptitude au façonnage telle qu'évaluée par la ductilité et l'aptitude à l'étirement des bordures et d'excellentes caractéristiques de collision; et un procédé de production de ladite tôle d'acier. Dans cette tôle d'acier laminée à froid haute résistance, la structure métallique au niveau d'une position correspondant au quart de l'épaisseur de la tôle satisfait les conditions (1) à (4) ci-dessous. (1) Le rapport surfacique de ferrite va de 0 à 10 % compris, le reste étant une phase dure comprenant au moins un élément choisi dans le groupe constitué de ferrite bainitique, bainite et martensite revenue, ladite phase dure comprenant de la martensite trempée et de l'austénite résiduelle. (2) Le rapport volumique Vy d'austénite résiduelle va de 5 à 30 % compris. (3) Le rapport surfacique VMA d'une structure MA combinant martensite trempée et austénite résiduelle va de 3 à 25 % compris, et le diamètre de cercle équivalent moyen de la structure MA est inférieur ou égal à 2,0 μm. (4) Le rapport VMA/Vγ, rapportant le rapport d'aire VMA de structure MA au rapport volumique Vy d'austénite résiduelle va de 0,50 à 1,50.
PCT/JP2016/056168 2015-03-31 2016-03-01 TÔLE D'ACIER LAMINÉE À FROID HAUTE RÉSISTANCE, AYANT UNE EXCELLENTE APTITUDE AU FAÇONNAGE, DE TRÈS BONNES CARACTÉRISTIQUES DE COLLISION ET UNE RÉSISTANCE À LA TRACTION DE 980 MPa OU PLUS, ET PROCÉDÉ DE PRODUCTION WO2016158159A1 (fr)

Priority Applications (5)

Application Number Priority Date Filing Date Title
MX2017012442A MX2017012442A (es) 2015-03-31 2016-03-01 Lamina de acero laminada en frio de alta resistencia que tiene excelentes caracteristicas de capacidad trabajo y colision y que tiene una resistencia a la tension de 980 mpa o mas, y metodo para producir el mismo.
US15/554,843 US20180037964A1 (en) 2015-03-31 2016-03-01 HIGH-STRENGTH COLD-ROLLED STEEL SHEET HAVING EXCELLENT FORMABILITY AND COLLISION CHARACTERISTICS AND HAVING TENSILE STRENGTH OF 980 MPa OR MORE, AND METHOD FOR PRODUCING SAME
KR1020177030765A KR102174558B1 (ko) 2015-03-31 2016-03-01 가공성 및 충돌 특성이 우수한 인장 강도 980MPa 이상의 고강도 냉연 강판 및 그의 제조 방법
CN201680017718.9A CN107429370B (zh) 2015-03-31 2016-03-01 加工性和碰撞特性优异且抗拉强度为980MPa以上的高强度冷轧钢板及其制造方法
EP16772043.2A EP3279362B1 (fr) 2015-03-31 2016-03-01 TÔLE D'ACIER LAMINÉE À FROID HAUTE RÉSISTANCE, AYANT UNE EXCELLENTE APTITUDE AU FAÇONNAGE, DE TRÈS BONNES CARACTÉRISTIQUES DE COLLISION ET UNE RÉSISTANCE À LA TRACTION DE 980 MPa OU PLUS, ET PROCÉDÉ DE PRODUCTION

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JP2015071437 2015-03-31
JP2015-071437 2015-03-31
JP2015225506A JP6554396B2 (ja) 2015-03-31 2015-11-18 加工性および衝突特性に優れた引張強度が９８０ＭＰａ以上の高強度冷延鋼板、およびその製造方法
JP2015-225506 2015-11-18

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Publication number Priority date Publication date Assignee Title
JP6213696B1 (ja) * 2016-12-05 2017-10-18 新日鐵住金株式会社 高強度鋼板
WO2019188190A1 (fr) * 2018-03-26 2019-10-03 株式会社神戸製鋼所 Plaque d'acier à haute résistance et plaque d'acier plaquée de zinc à haute résistance
JP2019173156A (ja) * 2018-03-26 2019-10-10 株式会社神戸製鋼所 高強度鋼板および高強度亜鉛めっき鋼板
WO2023063350A1 (fr) * 2021-10-14 2023-04-20 日本製鉄株式会社 Tôle d'acier laminée à chaud

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WO2009099079A1 (fr) * 2008-02-08 2009-08-13 Jfe Steel Corporation Tôle d'acier galvanisée à chaud à résistance élevée présentant une excellente aptitude au traitement et son procédé de fabrication
WO2010029983A1 (fr) * 2008-09-10 2010-03-18 Ｊｆｅスチール株式会社 Plaque d'acier à haute résistance et son procédé de fabrication
WO2014092025A1 (fr) * 2012-12-12 2014-06-19 株式会社神戸製鋼所 Plaque d'acier à résistance élevée et son procédé de fabrication
WO2015151427A1 (fr) * 2014-03-31 2015-10-08 Ｊｆｅスチール株式会社 Tôle d'acier laminée à froid à haute résistance et à haut coefficient d'élasticité et procédé de production s'y rapportant

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WO2010029983A1 (fr) * 2008-09-10 2010-03-18 Ｊｆｅスチール株式会社 Plaque d'acier à haute résistance et son procédé de fabrication
WO2014092025A1 (fr) * 2012-12-12 2014-06-19 株式会社神戸製鋼所 Plaque d'acier à résistance élevée et son procédé de fabrication
WO2015151427A1 (fr) * 2014-03-31 2015-10-08 Ｊｆｅスチール株式会社 Tôle d'acier laminée à froid à haute résistance et à haut coefficient d'élasticité et procédé de production s'y rapportant

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6213696B1 (ja) * 2016-12-05 2017-10-18 新日鐵住金株式会社 高強度鋼板
WO2018105003A1 (fr) * 2016-12-05 2018-06-14 新日鐵住金株式会社 Tôle d'acier à résistance mécanique élevée
WO2019188190A1 (fr) * 2018-03-26 2019-10-03 株式会社神戸製鋼所 Plaque d'acier à haute résistance et plaque d'acier plaquée de zinc à haute résistance
JP2019173156A (ja) * 2018-03-26 2019-10-10 株式会社神戸製鋼所 高強度鋼板および高強度亜鉛めっき鋼板
CN111954723A (zh) * 2018-03-26 2020-11-17 株式会社神户制钢所 高强度钢板以及高强度镀锌钢板
CN111954723B (zh) * 2018-03-26 2022-09-02 株式会社神户制钢所 高强度钢板以及高强度镀锌钢板
JP7134106B2 (ja) 2018-03-26 2022-09-09 株式会社神戸製鋼所 高強度鋼板および高強度亜鉛めっき鋼板
WO2023063350A1 (fr) * 2021-10-14 2023-04-20 日本製鉄株式会社 Tôle d'acier laminée à chaud

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