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WO2016158160A1 - TÔLE D'ACIER LAMINÉE À FROID À HAUTE RÉSISTANCE PRÉSENTANT D'EXCELLENTES CARACTÉRISTIQUES D'APTITUDE AU FAÇONNAGE ET DE COLLISION ET PRÉSENTANT UNE RÉSISTANCE À LA TRACTION SUPÉRIEURE OU ÉGALE À 980 MPa, ET SON PROCÉDÉ DE PRODUCTION - Google Patents

TÔLE D'ACIER LAMINÉE À FROID À HAUTE RÉSISTANCE PRÉSENTANT D'EXCELLENTES CARACTÉRISTIQUES D'APTITUDE AU FAÇONNAGE ET DE COLLISION ET PRÉSENTANT UNE RÉSISTANCE À LA TRACTION SUPÉRIEURE OU ÉGALE À 980 MPa, ET SON PROCÉDÉ DE PRODUCTION Download PDF

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Publication number
WO2016158160A1
WO2016158160A1 PCT/JP2016/056169 JP2016056169W WO2016158160A1 WO 2016158160 A1 WO2016158160 A1 WO 2016158160A1 JP 2016056169 W JP2016056169 W JP 2016056169W WO 2016158160 A1 WO2016158160 A1 WO 2016158160A1
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WIPO (PCT)
Prior art keywords
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temperature
steel sheet
strength
cooling
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PCT/JP2016/056169
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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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Kobe Steel Ltd
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Kobe Steel Ltd
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Publication date
Priority claimed from JP2015225507A external-priority patent/JP6554397B2/ja
Application filed by Kobe Steel Ltd filed Critical Kobe Steel Ltd
Priority to CN201680017729.7A priority Critical patent/CN107429371B/zh
Priority to US15/554,875 priority patent/US20180044752A1/en
Priority to KR1020177030773A priority patent/KR101970095B1/ko
Priority to MX2017012438A priority patent/MX2017012438A/es
Priority to EP16772044.0A priority patent/EP3279363B1/fr
Publication of WO2016158160A1 publication Critical patent/WO2016158160A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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 TS (Tensile Strength) is 590 MPa or more and excellent in moldability, specifically, TS ⁇ EL (EL: Elongation, elongation) is 23000 MPa% or more, a salt warm water test, and a salt spray.
  • TS Torsile Strength
  • EL Elongation, elongation
  • a high-strength cold-rolled steel sheet is disclosed that has excellent post-painting corrosion resistance even in harsh environments such as tests and combined cycle corrosion tests.
  • the metal structure of this steel sheet is a structure containing ferrite, retained austenite, bainite and / or martensite. It is described that the retained austenite has a function of improving the ductility of the steel sheet, that is, a so-called TRIP effect.
  • 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 greater than 10% and 65% or less with respect to the entire metal structure, and the balance includes quenched martensite and retained 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 an Ar 3 point or higher and 900 ° C. or lower, and the winding temperature is 600 ° C. or lower, winding is performed, cooled to room temperature, cold rolled, and 800 ° C. 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 800 ° C./sec or higher at an average temperature increase rate of 10 ° C./second or higher. It is heated to a temperature range of not less than 3 ° C.
  • 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 At a temperature range of 800 ° 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 ductility 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 within a predetermined range, and the remaining structure is made a hard phase, and in order to improve ductility, a predetermined amount of ferrite is generated.
  • the ratio V MA / V ⁇ of the area ratio V MA of the MA structure in which hardened martensite and retained austenite are combined and the volume ratio V ⁇ of retained austenite with respect to the entire metal structure may be appropriately controlled.
  • the MA structure should be made finer, and in order to improve the collision characteristics, the MA structure should be made finer and the ratio V MA / V ⁇ should be controlled appropriately.
  • the present invention has been completed.
  • 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 metal structure When the metal structure is observed with a scanning electron microscope, the area ratio of ferrite is greater than 10% and 65% or less with respect to the entire metal structure, and the balance includes quenched martensite and retained 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 ⁇ . Therefore, the sum of the fractions of the metal structures defined in the above (1) to (3) may exceed 100%.
  • a structure in which quenched martensite and residual ⁇ are combined may be referred to as an MA structure.
  • the area ratio of ferrite when the metal structure is observed with a scanning electron microscope, the area ratio of ferrite is more than 10% and 65% or less with respect to the entire metal structure.
  • Ferrite is a structure that particularly improves the ductility of the workability of a steel sheet.
  • the area ratio of ferrite is set to more than 10%.
  • the area ratio of ferrite is preferably 15% or more, and more preferably 20% or more.
  • the area ratio of ferrite is set to 65% or less.
  • the area ratio of ferrite is preferably 60% or less, more preferably 50% or less.
  • 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 have a structure harder than ferrite, and the strength of the steel sheet can be increased to 980 MPa or more by forming a predetermined amount of ferrite 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 ferrite and a 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 to suppress the formation of carbides, effectively act on the formation of ferrite and residual ⁇ , and ensure 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 contributes to increasing the strength of the steel sheet by improving the hardenability.
  • 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.
  • Winding temperature is set to 600 ° C. or lower, cooled to room temperature, cold-rolled, heated to a temperature range of 800 ° C. or higher and less than Ac 3 points at an average heating rate of 10 ° C./second or higher, and 50 Hold for at least 2 seconds, soak, and cool at an average cooling rate of 10 ° C./second or higher to an arbitrary cooling stop temperature T ° C. in the temperature range of 50 ° C. or higher and Ms point or lower, and then heated to the above cooling stop temperature T ° C. over 550 ° C. It can be produced by holding for 50 seconds or more in the following temperature range and then cooling to room temperature.
  • 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 800 ° C. or more and less than Ac 3 point 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 800 ° C. or higher.
  • the soaking temperature is preferably 805 ° C. or higher, more preferably 810 ° C. or higher.
  • the soaking temperature is set to a temperature lower than the Ac 3 point.
  • the soaking temperature is preferably Ac 3 point ⁇ 10 ° C. or lower, more preferably Ac 3 point ⁇ 20 ° C. or lower.
  • 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 lower limit of the cooling stop temperature T is set to 50 ° C. or higher.
  • the cooling stop temperature T is preferably 60 ° C. or higher, more preferably 70 ° 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.
  • Vf indicates the area ratio of ferrite with respect to the entire metal structure.
  • 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 50 ° 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 800 ° C./sec or higher at an average temperature increase rate of 10 ° C./second or higher. It is heated to a temperature range of not less than 3 ° 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 galvannealed steel sheet having a tensile strength of 980 MPa or more and excellent in 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 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 At a temperature range of 800 ° C. or more and less than Ac 3 point, and held in the temperature range for 50 seconds or more, soaking, and an average cooling rate of 10 to an arbitrary cooling stop temperature T ° C.
  • hot-dip galvanization is performed within the holding time, and further alloying treatment is performed.
  • room temperature It can also be manufactured by cooling with. 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 above-described method for producing a high-strength cold-rolled steel sheet according to the present invention. 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 17000 MPa ⁇ % or more.
  • the value of TS ⁇ EL is preferably 17100 MPa ⁇ % or more, more preferably 17200 MPa ⁇ % or more.
  • Stretch flangeability can be evaluated by a strength-hole expansion ratio balance.
  • the product of the tensile strength TS (MPa) and the hole expansion ratio ⁇ (%) is 20,000 MPa ⁇ % or more.
  • the value of TS ⁇ ⁇ is preferably 21000 MPa ⁇ % or more, more preferably 22000 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.
  • Nos. 8 and 11 are examples 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. That is, no. No. 8 was cooled at a cooling stop temperature T of 480 ° C., cooled to 350 ° C. lower than this temperature, and held at 350 ° C. for 300 seconds.
  • Table 2-1 below for convenience, 350 ° C. is described in the reheating temperature column and 300 seconds are described in the reheating holding time column.
  • No. No. 11 was cooled at a cooling stop temperature T of 330 ° C., then cooled to 300 ° C. lower than this temperature, and held at 300 ° C. for 300 seconds.
  • the reheating temperature column is 300 ° C. and the reheating holding time column is 300 seconds.
  • Electrogalvanizing No. shown in Table 2-1 below.
  • No. 2 is an example in which an electrogalvanized steel sheet was manufactured by immersing the test material in a galvanizing bath at 55 ° C., performing electrogalvanizing treatment, 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 category 2, “EG” is described.
  • the Ms point was calculated from the above formula (iv), and the result was It is shown in Table 2-1 and Table 2-2.
  • Tables 2-1 and 2-2 below also show values obtained by subtracting the Ms point temperature from the cooling stop temperature T.
  • 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 17000 MPa ⁇ % or more
  • TS ⁇ ⁇ value is 20000 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 ductility, 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. 3 is an example in which the MA structure was coarsened because the finish rolling finish temperature was too high. 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 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. 5 is an example in which the MA structure is coarsened because the rolling reduction at the final stand during 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. 7 is an example in which the amount of ferrite in the range specified in the present invention could not be secured because soaking was performed at a high temperature exceeding 800 ° C. or more and less than the Ac 3 point temperature range. As a result, the value of TS ⁇ EL became small and ductility could not be improved.
  • No. No. 10 is an example in which the cooling stop temperature T after soaking is less than 50 ° C., so that a predetermined amount of residual ⁇ and MA texture cannot be secured, and the value of V MA / V ⁇ falls below the specified range and becomes smaller. It is. As a result, the value of TS ⁇ EL became small and ductility could not be improved.
  • No. No. 11 is that the rolling reduction at the final stand at the time of finish rolling is too high exceeding the range specified in the present invention, and since reheating holding was not performed after cooling, the MA structure becomes coarse and V MA / V This is an example in which the value of ⁇ has become too large. As a result, 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 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. 16 and 37 are examples in which the MA structure was coarsened because the average temperature increase rate after winding was too small. As a result, the value of TS ⁇ ⁇ became small and the stretch flangeability could not be improved.
  • No. No. 19 is an example in which the MA structure is coarsened because the cooling stop temperature T after soaking was too high exceeding the temperature range of 50 ° C. or more and the Ms point or less. As a result, the value of TS ⁇ ⁇ became small and the stretch flangeability could not be improved.
  • No. No. 25 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. Moreover, the value of TS ⁇ ⁇ was small, and the stretch flangeability could not be improved. Moreover, the value of TS ⁇ VDA was reduced, and the collision characteristics could not be improved.
  • No. Nos. 27 and 38 are examples in which the ferrite was excessively generated because the average cooling rate after soaking was too small. As a result, TS became low. Moreover, the value of TS ⁇ ⁇ was small, and the stretch flangeability could not be improved.
  • No. No. 29 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. No. 33 is an example in which the amount of C is too small, and the amount of residual ⁇ within the range specified in the present invention could not be secured, and the value of V MA / V ⁇ increased beyond the range specified in the present invention. 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 ferrite in 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, so TS is lowered. Further, the value of TS ⁇ ⁇ was decreased, and stretch flangeability was deteriorated.

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Abstract

L'invention concerne : une tôle d'acier laminée à froid à haute résistance présentant une résistance à la traction supérieure ou égale à 980 MPa, présentant une bonne aptitude au façonnage telle qu'évaluée par ductilité et par la capacité à former des bords par étirage et présentant d'excellentes caractéristiques de collision; et un procédé de production de ladite tôle d'acier. Dans ladite tôle d'acier laminée à froid à haute résistance, la structure métallique, au niveau d'une position à ¼ de l'épaisseur de la tôle, satisfait aux conditions (1) à (4) ci-dessous. (1) Le rapport de surface de ferrite est situé dans la plage allant de 10 à 65 %, inclus, et le complément est une phase dure comprenant au moins un élément choisi dans le groupe constitué par de la ferrite bainitique, de la bainite et de la martensite revenue, ladite phase dure comprenant de la martensite trempée et de l'austénite résiduelle. (2) Le rapport volumique Vγ d'austénite résiduelle est situé dans la plage allant de 5 à 30 %, inclus. (3) Le rapport de surface VMA d'une structure MA, dans laquelle sont combinées de la martensite trempée et de l'austénite résiduelle, est situé dans la plage allant de 3 à 25 %, inclus, et le diamètre de cercle équivalent moyen de la structure MA est inférieur ou égal à 2,0 μm. (4) Le rapport VMA/Vγ du rapport de surface VMA de la structure MA au rapport volumique Vγ de l'austénite résiduelle est situé dans la plage allant de 0,50 à 1,50.
PCT/JP2016/056169 2015-03-31 2016-03-01 TÔLE D'ACIER LAMINÉE À FROID À HAUTE RÉSISTANCE PRÉSENTANT D'EXCELLENTES CARACTÉRISTIQUES D'APTITUDE AU FAÇONNAGE ET DE COLLISION ET PRÉSENTANT UNE RÉSISTANCE À LA TRACTION SUPÉRIEURE OU ÉGALE À 980 MPa, ET SON PROCÉDÉ DE PRODUCTION Ceased WO2016158160A1 (fr)

Priority Applications (5)

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CN201680017729.7A CN107429371B (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
US15/554,875 US20180044752A1 (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
KR1020177030773A KR101970095B1 (ko) 2015-03-31 2016-03-01 가공성 및 충돌 특성이 우수한 인장 강도 980MPa 이상의 고강도 냉연 강판 및 그의 제조 방법
MX2017012438A MX2017012438A (es) 2015-03-31 2016-03-01 Lamina de acero laminada en frio de alta resistencia que tiene excelentes caracteristicas de capacidad de trabajo y colision y que tiene resistencia a la tension de 980 mpa o mas, y un metodo para producir el mismo.
EP16772044.0A EP3279363B1 (fr) 2015-03-31 2016-03-01 TÔLE D'ACIER LAMINÉE À FROID À HAUTE RÉSISTANCE PRÉSENTANT D'EXCELLENTES CARACTÉRISTIQUES D'APTITUDE AU FAÇONNAGE ET DE COLLISION ET PRÉSENTANT UNE RÉSISTANCE À LA TRACTION SUPÉRIEURE OU ÉGALE À 980 MPa, ET SON PROCÉDÉ DE PRODUCTION

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JP2015-071438 2015-03-31
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JP2015-225507 2015-11-18
JP2015225507A JP6554397B2 (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

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JP2019505691A (ja) * 2015-12-21 2019-02-28 アルセロールミタル 改善された延性及び成形加工性を有する高強度鋼板を製造するための方法並びに得られた鋼板
WO2019155014A1 (fr) * 2018-02-08 2019-08-15 Tata Steel Ijmuiden B.V. Procédé de façonnage d'un article à partir d'une ébauche d'acier revêtue de zinc ou d'alliage de zinc
JP2019143199A (ja) * 2018-02-21 2019-08-29 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、並びにそれらの製造方法
WO2020080493A1 (fr) * 2018-10-17 2020-04-23 日本製鉄株式会社 Tôle d'acier et procédé de fabrication d'une tôle d'acier
JP2023507953A (ja) * 2019-12-18 2023-02-28 ポスコホールディングス インコーポレーティッド 加工性に優れた高強度鋼板及びその製造方法
JP2023507956A (ja) * 2019-12-18 2023-02-28 ポスコホールディングス インコーポレーティッド 加工性に優れた高強度鋼板及びその製造方法

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JP2019505691A (ja) * 2015-12-21 2019-02-28 アルセロールミタル 改善された延性及び成形加工性を有する高強度鋼板を製造するための方法並びに得られた鋼板
EP3749789A1 (fr) * 2018-02-08 2020-12-16 Tata Steel IJmuiden B.V. Procédé de façonnage d'un article à partir d'une ébauche d'acier revêtue de zinc ou d'alliage de zinc
WO2019155014A1 (fr) * 2018-02-08 2019-08-15 Tata Steel Ijmuiden B.V. Procédé de façonnage d'un article à partir d'une ébauche d'acier revêtue de zinc ou d'alliage de zinc
US11519044B2 (en) 2018-02-08 2022-12-06 Tata Steel Ijmuiden B.V. Method of shaping an article from a zinc or zinc alloy coated steel blank
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JP2019143199A (ja) * 2018-02-21 2019-08-29 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、並びにそれらの製造方法
JP6760543B1 (ja) * 2018-10-17 2020-09-23 日本製鉄株式会社 鋼板及び鋼板の製造方法
WO2020080493A1 (fr) * 2018-10-17 2020-04-23 日本製鉄株式会社 Tôle d'acier et procédé de fabrication d'une tôle d'acier
JP2023507953A (ja) * 2019-12-18 2023-02-28 ポスコホールディングス インコーポレーティッド 加工性に優れた高強度鋼板及びその製造方法
JP2023507956A (ja) * 2019-12-18 2023-02-28 ポスコホールディングス インコーポレーティッド 加工性に優れた高強度鋼板及びその製造方法
JP7554827B2 (ja) 2019-12-18 2024-09-20 ポスコホールディングス インコーポレーティッド 加工性に優れた高強度鋼板及びその製造方法
JP7554828B2 (ja) 2019-12-18 2024-09-20 ポスコホールディングス インコーポレーティッド 加工性に優れた高強度鋼板及びその製造方法

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