KR20220001828A - Cold-rolled steel sheet, galva-annealed steel sheet and the method for manufacturing the same - Google Patents
Cold-rolled steel sheet, galva-annealed steel sheet and the method for manufacturing the same Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 38
- 239000010959 steel Substances 0.000 title claims abstract description 38
- 239000010960 cold rolled steel Substances 0.000 title claims abstract description 37
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 24
- 238000000034 method Methods 0.000 title claims description 27
- 239000011651 chromium Substances 0.000 claims abstract description 91
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims abstract description 35
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 35
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims abstract description 28
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 28
- 239000011733 molybdenum Substances 0.000 claims abstract description 28
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 23
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 23
- 239000010703 silicon Substances 0.000 claims abstract description 23
- 239000011572 manganese Substances 0.000 claims abstract description 21
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 18
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 18
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 13
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 13
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims abstract description 12
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 12
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 11
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims abstract description 11
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 10
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 10
- 239000011574 phosphorus Substances 0.000 claims abstract description 10
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 10
- 239000011593 sulfur Substances 0.000 claims abstract description 10
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 229910001335 Galvanized steel Inorganic materials 0.000 claims description 26
- 239000008397 galvanized steel Substances 0.000 claims description 26
- 229910000734 martensite Inorganic materials 0.000 claims description 19
- 238000005275 alloying Methods 0.000 claims description 16
- 239000000463 material Substances 0.000 claims description 14
- 229910000859 α-Fe Inorganic materials 0.000 claims description 11
- 238000000137 annealing Methods 0.000 claims description 10
- 238000005246 galvanizing Methods 0.000 claims description 10
- 238000005097 cold rolling Methods 0.000 claims description 9
- 238000005096 rolling process Methods 0.000 claims description 8
- 230000009467 reduction Effects 0.000 claims description 7
- 239000011324 bead Substances 0.000 claims description 6
- 238000005098 hot rolling Methods 0.000 claims description 5
- 239000011159 matrix material Substances 0.000 claims description 5
- 238000010438 heat treatment Methods 0.000 claims description 4
- 238000003303 reheating Methods 0.000 claims description 4
- 238000004804 winding Methods 0.000 claims description 3
- 238000005244 galvannealing Methods 0.000 abstract 1
- 238000007747 plating Methods 0.000 description 24
- 230000000052 comparative effect Effects 0.000 description 9
- 230000000694 effects Effects 0.000 description 7
- 238000000465 moulding Methods 0.000 description 7
- 239000000203 mixture Substances 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- 230000002159 abnormal effect Effects 0.000 description 4
- 230000032683 aging Effects 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 230000007547 defect Effects 0.000 description 4
- 230000000704 physical effect Effects 0.000 description 4
- 238000010791 quenching Methods 0.000 description 4
- 230000000171 quenching effect Effects 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
- 238000005452 bending Methods 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 230000003749 cleanliness Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 2
- 238000010422 painting Methods 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 238000010301 surface-oxidation reaction Methods 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 229910000760 Hardened steel Inorganic materials 0.000 description 1
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- 238000004026 adhesive bonding Methods 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 150000001721 carbon Chemical class 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000032798 delamination Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 229910052840 fayalite Inorganic materials 0.000 description 1
- 239000012634 fragment Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000005554 pickling Methods 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000002436 steel type Substances 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 230000035882 stress Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C47/00—Winding-up, coiling or winding-off metal wire, metal band or other flexible metal material characterised by features relevant to metal processing only
- B21C47/02—Winding-up or coiling
-
- 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
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
-
- 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
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- 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
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0236—Cold rolling
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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
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0273—Final recrystallisation annealing
-
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
- C23C2/06—Zinc or cadmium or alloys based thereon
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/26—After-treatment
- C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
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- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
- C23C2/36—Elongated material
- C23C2/40—Plates; Strips
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
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- Metallurgy (AREA)
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- Crystallography & Structural Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
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- Heat Treatment Of Sheet Steel (AREA)
Abstract
Description
본 발명은 강판 및 그 제조 방법에 관한 것으로서, 보다 상세하게는 냉연 강판, 합금화 용융아연도금 강판 및 그 제조 방법에 관한 것이다. The present invention relates to a steel sheet and a method for manufacturing the same, and more particularly, to a cold rolled steel sheet, an alloyed hot-dip galvanized steel sheet, and a method for manufacturing the same.
자동차 외판용 강재는 차체 외관을 담당하는 부품으로, 차체 외관의 내덴트성 향상을 위해 고강도화가 추진되어 왔다. 자동차용 외판재는 성형 중 굴곡과 같은 표면결함을 방지하기 위해 성형 전에는 낮은 항복강도를 요구하며, 최종 부품에서는 높은 항복강도 특성을 보여야 한다. 따라서 초기 항복강도가 낮지만, 성형 중 항복강도의 증가량이 크고, 도장 소부 중 소부경화능이 우수하여 최종 제품에서의 항복강도가 높은 이상조직강의 외판 적용이 확대되고 있다. Steel for automobile exterior panels is a part responsible for the exterior of the vehicle body, and strength enhancement has been promoted to improve the dent resistance of the exterior of the vehicle. Exterior panels for automobiles require low yield strength before molding in order to prevent surface defects such as bending during molding, and high yield strength characteristics must be shown in the final part. Therefore, although the initial yield strength is low, the amount of increase in yield strength during molding is large, and the baking hardenability during painting baking is excellent, so the application of abnormal structure steel with high yield strength in final products is expanding.
본 발명의 기술적 사상이 이루고자 하는 기술적 과제는 자동차용 외판재로서 외관 품질 및 합금화 용융아연도금 물성이 우수한 냉연 강판, 합금화 용융아연도금 강판 및 그 제조 방법을 제공하는 것이다. 그러나 이러한 과제는 예시적인 것으로, 본 발명의 기술적 사상은 이에 한정되는 것은 아니다.The technical problem to be achieved by the technical idea of the present invention is to provide a cold-rolled steel sheet, an alloyed hot-dip galvanized steel sheet, and a manufacturing method thereof, which are excellent in appearance quality and alloyed hot-dip galvanized steel sheet as an exterior plate material for automobiles. However, these tasks are exemplary, and the technical spirit of the present invention is not limited thereto.
본 발명의 일 관점에 의하면, 냉연 강판이 제공된다. 상기 냉연 강판은 탄소(C) : 0.01 ~ 0.06중량%, 망간(Mn) : 1.0 ~ 2.5중량%, 황(S) : 0 초과 0.01중량% 이하, 인(P) : 0 초과 0.08중량% 이하, 실리콘(Si) : 0.01 ~ 0.07중량%, 알루미늄(Al) : 0.01 ~ 1.0중량%, 크롬(Cr) : 0 초과 1.5중량% 이하, 몰리브덴(Mo): 0 초과 0.5중량% 이하, 크롬(Cr) 및 몰리브덴[Mo] : 0.3중량%≤[Cr]+0.3[Mo]≤1.5중량% 이 되도록 크롬(Cr) 및 몰리브덴 (Mo) 중 적어도 1종 이상을 포함하며 나머지 철(Fe)과 불가피한 불순물로 이루어지고, 항복강도(YS) : 300MPa 이하, 인장강도 (TS) : 340MPa 이상, 연신율(EL) : 30% 이상, 항복비(YR) : 0.65 이하이다. 예를 들어, 상기 조성범위를 만족하는 냉연 강판의 물성은 항복강도(YS) : 190 ~ 300MPa, 인장강도 (TS) : 340 ~ 530MPa, 연신율(EL) : 30 ~ 40%, 항복비(YR) : 0.45 ~ 0.65일 수 있다.According to one aspect of the present invention, a cold rolled steel sheet is provided. The cold-rolled steel sheet is carbon (C): 0.01 to 0.06% by weight, manganese (Mn): 1.0 to 2.5% by weight, sulfur (S): more than 0 and less than 0.01% by weight, phosphorus (P): more than 0 and 0.08% by weight or less, Silicon (Si): 0.01 to 0.07 wt%, aluminum (Al): 0.01 to 1.0 wt%, chromium (Cr): more than 0 and less than 1.5 wt%, molybdenum (Mo): more than 0 and less than 0.5 wt%, chromium (Cr) And molybdenum [Mo]: contains at least one of chromium (Cr) and molybdenum (Mo) so that 0.3% by weight ≤ [Cr] + 0.3 [Mo] ≤ 1.5% by weight, the remaining iron (Fe) and inevitable impurities and yield strength (YS): 300 MPa or less, tensile strength (TS): 340 MPa or more, elongation (EL): 30% or more, yield ratio (YR): 0.65 or less. For example, the physical properties of a cold-rolled steel sheet satisfying the above composition range are yield strength (YS): 190 to 300 MPa, tensile strength (TS): 340 to 530 MPa, elongation (EL): 30 to 40%, yield ratio (YR) : It may be 0.45 to 0.65.
본 발명의 일 실시예에 의하면, 하기 수식1을 만족할 수 있다. According to an embodiment of the present invention, Equation 1 below may be satisfied.
수식1 : 4 ≤ 140 * [Si] - 1.7 * [Cr] + 12 * [Al] ≤ 14.8Equation 1: 4 ≤ 140 * [Si] - 1.7 * [Cr] + 12 * [Al] ≤ 14.8
(여기에서, [Si], [Cr] 및 [Al]은 상기 냉연 강판에서 각각 실리콘(Si), 크롬(Cr) 및 알루미늄(Al)의 중량%에 해당한다.)(Here, [Si], [Cr] and [Al] correspond to the weight % of silicon (Si), chromium (Cr) and aluminum (Al) in the cold-rolled steel sheet, respectively.)
본 발명의 일 실시예에 의하면, 최종 미세 조직은 페라이트와 마르텐사이트를 포함하되, 상기 페라이트 기지에 상기 마르텐사이트 조직을 2 ~ 10%로 함유할 수 있다. According to an embodiment of the present invention, the final microstructure includes ferrite and martensite, but may contain 2 to 10% of the martensite structure in the ferrite matrix.
본 발명의 다른 관점에 의하면, 합금화 용융아연도금 강판이 제공된다. 상기 합금화 용융아연도금 강판은 상기 냉연 강판의 표면에 합금화 용융아연도금층을 더 포함한다. According to another aspect of the present invention, an alloyed hot-dip galvanized steel sheet is provided. The alloyed hot-dip galvanized steel sheet further includes an alloyed hot-dip galvanized layer on the surface of the cold-rolled steel sheet.
본 발명의 일 실시예에 의하면, 상기 합금화 용융아연도금층의 감마(Γ)상은 두께가 0.7 ㎛ 이하일 수 있다. According to an embodiment of the present invention, the gamma (Γ) phase of the alloying hot-dip galvanizing layer may have a thickness of 0.7 μm or less.
본 발명의 일 실시예에 의하면, 상기 합금화 용융아연도금층의 HCI(Hat-bead Contrast Index) 지수는 120 이하일 수 있다. According to an embodiment of the present invention, the HCI (Hat-bead Contrast Index) index of the alloyed hot-dip galvanized layer may be 120 or less.
본 발명의 또 다른 관점에 의하면, 냉연 강판의 제조 방법이 제공된다. 상기 냉연 강판의 제조 방법은 (a) 탄소(C) : 0.01 ~ 0.06중량%, 망간(Mn) : 1.0 ~ 2.5중량%, 황(S) : 0 초과 0.01중량% 이하, 인(P) : 0 초과 0.08중량% 이하, 실리콘(Si) : 0.01 ~ 0.07중량%, 알루미늄(Al) : 0.01 ~ 1.0중량%, 크롬(Cr) : 0 초과 1.5중량% 이하, 몰리브덴(Mo): 0 초과 0.5중량% 이하, 크롬(Cr) 및 몰리브덴[Mo] : 0.3중량%≤[Cr]+0.3[Mo]≤1.5중량% 이 되도록 크롬(Cr) 및 몰리브덴 (Mo) 중 적어도 1종 이상을 포함하며 나머지 철(Fe)과 불가피한 불순물로 이루어진 강재를 제공하는 단계; (b) 상기 강재를 재가열온도(SRT) : 1150 ~ 1300℃, 마무리압연온도(FDT) : 820 ~ 920℃, 권취온도(CT) : 560 ~ 700℃인 조건으로 열간 압연하는 단계; (c) 상기 강재를 55 ~ 75%의 압하율로 냉간 압연하는 단계; 및 (d) 상기 강재를 760 ~ 840℃에서 소둔 공정하는 단계; 를 포함한다. According to another aspect of the present invention, a method for manufacturing a cold rolled steel sheet is provided. The manufacturing method of the cold-rolled steel sheet is (a) carbon (C): 0.01 to 0.06 wt%, manganese (Mn): 1.0 to 2.5 wt%, sulfur (S): more than 0 and 0.01 wt% or less, phosphorus (P): 0 More than 0.08 wt%, Silicon (Si): 0.01 to 0.07 wt%, Aluminum (Al): 0.01 to 1.0 wt%, Chromium (Cr): More than 0 and less than 1.5 wt%, Molybdenum (Mo): More than 0 0.5 wt% Hereinafter, chromium (Cr) and molybdenum [Mo] include at least one or more of chromium (Cr) and molybdenum (Mo) so that 0.3 wt% ≤ [Cr] + 0.3 [Mo] ≤ 1.5 wt %, and the remaining iron ( providing a steel material consisting of Fe) and unavoidable impurities; (b) the reheating temperature (SRT) of the steel: 1150 ~ 1300 ℃, finish rolling temperature (FDT): 820 ~ 920 ℃, winding temperature (CT): hot rolling under the conditions of 560 ~ 700 ℃; (c) cold rolling the steel at a reduction ratio of 55 to 75%; And (d) annealing the steel material at 760 ~ 840 ℃; includes
본 발명의 일 실시예에 의하면, 상기 강재는 하기 수식1을 만족할 수 있다.According to an embodiment of the present invention, the steel material may satisfy Equation 1 below.
수식1 : 4 ≤ 140 * [Si] - 1.7 * [Cr] + 12 * [Al] ≤ 14.8Equation 1: 4 ≤ 140 * [Si] - 1.7 * [Cr] + 12 * [Al] ≤ 14.8
(여기에서, [Si], [Cr] 및 [Al]은 상기 강재에서 각각 실리콘(Si), 크롬(Cr) 및 알루미늄(Al)의 중량%에 해당한다.)(Here, [Si], [Cr] and [Al] correspond to the weight percent of silicon (Si), chromium (Cr) and aluminum (Al) in the steel, respectively.)
본 발명의 일 실시예에 의하면, 상기 (a) 내지 (d) 단계를 수행한 후 항복강도(YS) : 300MPa 이하, 인장강도 (TS) : 340MPa 이상, 연신율(EL) : 30% 이상, 항복비(YR) : 0.65 이하일 수 있다. According to an embodiment of the present invention, after performing steps (a) to (d), yield strength (YS): 300 MPa or less, tensile strength (TS): 340 MPa or more, elongation (EL): 30% or more, yield Ratio (YR): may be 0.65 or less.
본 발명의 또 다른 관점에 의하면, 합금화 용융아연도금 강판의 제조 방법이 제공된다. 상기 합금화 용융아연도금 강판의 제조 방법은 상기 방법에 의하여 구현된 냉연 강판에 합금화 용융아연도금층을 형성하는 단계를 더 포함하되, 상기 합금화 용융아연도금층을 형성하기 위한 합금화 열처리 온도는 450 ~ 550℃인 것을 특징으로 한다. According to another aspect of the present invention, a method for manufacturing an alloyed hot-dip galvanized steel sheet is provided. The method for manufacturing the alloyed hot-dip galvanized steel sheet further comprises the step of forming an alloyed hot-dip galvanized layer on the cold-rolled steel sheet implemented by the method, wherein the alloying heat treatment temperature for forming the alloyed hot-dip galvanized layer is 450 to 550 ° C. characterized in that
본 발명의 기술적 사상에 의할 경우, 자동차용 외판재로서 외관 품질 및 합금화 용융아연도금 물성이 우수한 냉연 강판, 합금화 용융아연도금 강판 및 그 제조 방법을 구현할 수 있다. 상술한 본 발명의 효과들은 예시적으로 기재되었고, 이러한 효과들에 의해 본 발명의 범위가 한정되는 것은 아니다.According to the technical idea of the present invention, it is possible to implement a cold-rolled steel sheet, an alloyed hot-dip galvanized steel sheet, and a manufacturing method thereof, which are excellent in appearance quality and alloyed hot-dip galvanized steel sheet as an exterior plate material for automobiles. The above-described effects of the present invention have been described by way of example, and the scope of the present invention is not limited by these effects.
도 1은 본 발명의 일 실시예에 따르는 합금화 용융아연도금 강판의 단면을 촬영한 사진이다.
도 2는 본 발명의 일 실시예에 따르는 합금화 용융아연도금 강판의 도금특성인 HCI 지수를 도출하기 위한 시험평가 기준 및 방법을 도해하는 도면이다.
도 3은 본 발명의 일 실시예에 따르는 냉연 강판 및 합금화 용융아연도금 강판의 제조 방법을 도해하는 순서도이다. 1 is a photograph of a cross-section of an alloyed hot-dip galvanized steel sheet according to an embodiment of the present invention.
2 is a diagram illustrating a test evaluation standard and method for deriving an HCI index, which is a plating characteristic of an alloyed hot-dip galvanized steel sheet according to an embodiment of the present invention.
3 is a flowchart illustrating a method of manufacturing a cold-rolled steel sheet and an alloyed hot-dip galvanized steel sheet according to an embodiment of the present invention.
이하, 첨부된 도면을 참조하여 본 발명의 바람직한 실시예를 상세히 설명하기로 한다. 본 발명의 실시예들은 당해 기술분야에서 통상의 지식을 가진 자에게 본 발명의 기술적 사상을 더욱 완전하게 설명하기 위하여 제공되는 것이며, 하기 실시예는 여러 가지 다른 형태로 변형될 수 있으며, 본 발명의 기술적 사상의 범위가 하기 실시예에 한정되는 것은 아니다. 오히려, 이들 실시예는 본 개시를 더욱 충실하고 완전하게 하고, 당업자에게 본 발명의 기술적 사상을 완전하게 전달하기 위하여 제공되는 것이다. 본 명세서에서 동일한 부호는 시종 동일한 요소를 의미한다. 나아가, 도면에서의 다양한 요소와 영역은 개략적으로 그려진 것이다. 따라서 본 발명의 기술적 사상은 첨부한 도면에 그려진 상대적인 크기나 간격에 의해 제한되지 않는다.Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments of the present invention are provided to more completely explain the technical idea of the present invention to those of ordinary skill in the art, and the following examples may be modified in various other forms, The scope of the technical idea is not limited to the following examples. Rather, these embodiments are provided so as to more fully and complete the present disclosure, and to fully convey the technical spirit of the present invention to those skilled in the art. In this specification, the same reference numerals refer to the same elements throughout. Furthermore, various elements and regions in the drawings are schematically drawn. Therefore, the technical spirit of the present invention is not limited by the relative size or spacing drawn in the accompanying drawings.
냉연 강판 및 합금화 용융아연도금 강판Cold-rolled steel sheet and alloyed hot-dip galvanized steel sheet
자동차 외판용 강재는 차체 외관을 담당하는 부품으로, 차체 외관의 내덴트성 향상을 위해 고강도화가 추진되어 왔다. 강재의 강도는 항복강도와 인장강도로 구분할 수 있으며, 차체 외관의 영구 보존능을 향상시키기 위해서는 강재의 탄성변형과 소성변형의 임계 응력인 항복강도가 높아야 한다. 그러나, 자동차용 외판재는 성형 중 굴곡과 같은 표면결함을 방지하기 위해 성형 전에는 낮은 항복강도를 요구하며, 최종 부품에서는 높은 항복강도 특성을 보여야 한다. Steel for automobile exterior panels is a part responsible for the exterior of the vehicle body, and strength enhancement has been promoted to improve the dent resistance of the exterior of the vehicle. The strength of steel can be divided into yield strength and tensile strength, and in order to improve the permanent preservation of the exterior of the body, the yield strength, which is the critical stress of elastic and plastic deformation of the steel, must be high. However, in order to prevent surface defects such as bending during molding, automotive exterior panels require low yield strength before molding, and the final part must show high yield strength characteristics.
따라서 초기 항복강도가 낮지만, 성형 중 항복강도의 증가량이 크고, 도장 소부 중 소부경화능이 우수하여 최종 제품에서의 항복강도가 높은 이상조직강의 외판 적용이 확대되고 있다. 이상조직강은 페라이트 기지에 경질의 마르텐사이트가 포함된 복합조직강으로 외판재에 적합한 항복강도 특성을 가질 뿐만 아니라, 내시효특성이 우수하여 기존에 극저탄소강으로 제조된 소부경화강에 비해 우수한 점들을 많이 보유하고 있다. 이러한 이상조직강은 주로 내식성 및 용접성이 우수한 합금화용융아연도금 처리를 적용하여 자동차용 외판재로 사용 되고 있다. Therefore, although the initial yield strength is low, the amount of increase in yield strength during molding is large, and the baking hardenability during painting baking is excellent, so the application of abnormal structure steel with high yield strength in final products is expanding. Ideal structure steel is a composite structure steel containing hard martensite on a ferrite matrix, and not only has a yield strength characteristic suitable for an outer plate material, but also has excellent aging resistance properties, which is superior to that of bake hardened steel manufactured with ultra-low carbon steel. It has a lot of points. These abnormal structure steels are mainly used as exterior plates for automobiles by applying hot-dip galvanizing treatment with excellent corrosion resistance and weldability.
이상조직강에 첨가되는 실리콘(Si)은 페라이트의 청정도를 향상시켜 연성을 저하시키지 않으면서 강도를 향상 시킬 수 있는 합금원소로 널리 사용 되고 있다. 하지만, 실리콘(Si)이 과량 첨가될 시 스케일에 의한 표면 결함이 쉽게 발생하는 문제점을 보인다. 또한, 실리콘(Si) 함량이 감소할 경우 합금화가 가속화 되어 프레스 성형시 도금박리가 발생하는데, 이는 덴트를 유발하여 자동차용 외판재로서 적용성을 열화시키는 원인이 된다. 따라서, 이상조직강의 상분율 제어를 위해서는 탄소, 망간, 크롬, 몰리브덴과 같은 소입성 원소의 첨가가 필수적이다. Silicon (Si) added to abnormally structured steel is widely used as an alloying element that can improve strength without reducing ductility by improving the cleanliness of ferrite. However, when silicon (Si) is excessively added, there is a problem in that surface defects due to scale easily occur. In addition, when the silicon (Si) content is reduced, alloying is accelerated and plating peeling occurs during press forming, which causes dents and deteriorates applicability as an exterior plate material for automobiles. Therefore, it is essential to add hardenable elements such as carbon, manganese, chromium, and molybdenum to control the phase fraction of abnormally structured steel.
본 발명은 자동차용 외판재로써 외관 품질 및 합금화용융아연 도금물성(내박리성)이 우수한 항복강도≤300MPa급, 인장강도≥340MPa급, 연신율≥30%, 항복비≤0.65, 내시효≥1년의 이상조직강을 제조하기 위한 성분 및 제조 조건을 제공하고자 한다. The present invention is an automobile exterior plate, with excellent appearance quality and alloying hot-dip galvanized properties (peel resistance), yield strength ≤ 300 MPa class, tensile strength ≥ 340 MPa class, elongation ≥ 30%, yield ratio ≤ 0.65, aging resistance ≥ 1 year It is intended to provide the ingredients and manufacturing conditions for manufacturing the ideally structured steel of
상기 물성을 만족하기 위해, 본 발명의 일 실시예에 따른 냉연 강판은 탄소(C) : 0.01 ~ 0.06중량%, 망간(Mn) : 1.0 ~ 2.5중량%, 황(S) : 0 초과 0.01중량% 이하, 인(P) : 0 초과 0.08중량% 이하, 실리콘(Si) : 0.01 ~ 0.07중량%, 알루미늄(Al) : 0.01 ~ 1.0중량%, 크롬(Cr) : 0 초과 1.5중량% 이하, 몰리브덴(Mo): 0 초과 0.5중량% 이하, 크롬(Cr) 및 몰리브덴[Mo] : 0.3중량%≤[Cr]+0.3[Mo]≤1.5중량% 이 되도록 크롬(Cr) 및 몰리브덴 (Mo) 중 적어도 1종 이상을 포함하며 나머지 철(Fe)과 불가피한 불순물로 이루어진다. In order to satisfy the above physical properties, the cold rolled steel sheet according to an embodiment of the present invention has carbon (C): 0.01 to 0.06 wt%, manganese (Mn): 1.0 to 2.5 wt%, sulfur (S): more than 0 0.01 wt% or less, phosphorus (P): greater than 0 and less than or equal to 0.08% by weight, silicon (Si): 0.01 to 0.07% by weight, aluminum (Al): 0.01 to 1.0% by weight, chromium (Cr): greater than 0, 1.5% by weight or less, molybdenum ( Mo): greater than 0 and 0.5% by weight or less, chromium (Cr) and molybdenum [Mo]: at least 1 of chromium (Cr) and molybdenum (Mo) so that 0.3% by weight ≤ [Cr] + 0.3 [Mo] ≤ 1.5% by weight It contains more than one species and consists of the remaining iron (Fe) and unavoidable impurities.
탄소[C]: 0.01중량% ~ 0.06중량%Carbon [C]: 0.01 wt% to 0.06 wt%
마르텐사이트 조직은 오스테나이트 조직에서 무확산 변태에 의한 과포화 탄소를 함유한 조직으로, 탄소는 이러한 마르텐사이트 조직 형성에 기여한다. 탄소의 함량이 0.01중량% 미만일 경우, 마르텐사이트 조직을 형성하기 어렵다. 탄소 함량이 0.06중량%를 초과하는 경우, 강도가 증가하고 연성이 감소하여 연신율 30% 이상을 확보하기 어렵다.The martensitic structure is a structure containing supersaturated carbon due to diffusionless transformation in the austenitic structure, and carbon contributes to the formation of the martensitic structure. When the content of carbon is less than 0.01% by weight, it is difficult to form a martensitic structure. When the carbon content exceeds 0.06% by weight, strength increases and ductility decreases, so it is difficult to secure an elongation of 30% or more.
망간[Mn]: 1.0중량% ~ 2.5중량%Manganese [Mn]: 1.0 wt% ~ 2.5 wt%
망간은 효과적인 소입성 원소로서, 소둔 처리 후 냉각시 마르텐사이트 형성에 기여한다. 망간의 함량이 1.0중량% 미만일 경우, 소입성이 충분히 확보되지 않고 오스테나이트 상의 안정화가 어려워 이상조직 구현이 어렵다. 망간의 함량이 2.5중량%를 초과할 경우 연성이 감소하고 표면산화에 의해 표면품질 열화를 초래할 수 있다.Manganese is an effective hardenable element and contributes to martensite formation upon cooling after annealing. When the manganese content is less than 1.0% by weight, hardenability is not sufficiently ensured, and it is difficult to stabilize the austenite phase, making it difficult to implement an ideal structure. When the manganese content exceeds 2.5 wt%, ductility may decrease and surface quality may deteriorate due to surface oxidation.
황[S]: 0.01중량%이하Sulfur [S]: 0.01 wt% or less
황은 MnS를 형성하여 소입원소인 망간의 첨가 효과를 감소시키며 함량 증가에 따라 개재물, 석출물이 증가하여 성형성에 영향을 미치므로 황의 함량을 0.01중량% 이하로 제한한다. Sulfur forms MnS to reduce the effect of adding manganese, a quenching element, and as the content increases, inclusions and precipitates increase to affect moldability, so the sulfur content is limited to 0.01 wt% or less.
인[P]: 0.08중량% 이하Phosphorus [P]: 0.08 wt% or less
인은 인장강도와 항복강도를 동시에 증가시키는 고용강화 원소로, P의 함량이 0.08중량%를 초과하여 첨가하게 되면 합금화를 저하시켜 합금화용융강판의 미합금을 유발하므로 인의 함량을 0.08중량% 이하로 제한한다.Phosphorus is a solid solution strengthening element that simultaneously increases tensile strength and yield strength. When the content of P is added in excess of 0.08% by weight, it lowers alloying and causes unalloying of the molten alloyed steel sheet. limit
실리콘[Si]: 0.01중량% ~ 0.07중량%Silicon [Si]: 0.01 wt% to 0.07 wt%
실리콘은 페라이트의 청정도를 향상시켜 연성을 저하시키지 않으면서 강도를 향상시킬 수 있는 합금원소이다. 실리콘이 0.01중량% 미만으로 첨가되면 합금화가 가속되어 합금화 용융아연강판의 도금층 취성을 유발하는 도금층(도 1 참조)인 감마(Γ, Gamma)상의 두께가 증가하여 도금박리가 발생한다. 한편, 실리콘이 0.07중량%를 초과하여 첨가되면 산세성이 열위한 페열라이트(Fayalite)계 산화물이 형성되어 외관 품질을 열화시키고 표면결함을 유발하기 때문에 그 함량을 0.01 ~ 0.07중량%로 제한한다. 참고로, 도 1의 합금화 용융아연도금 강판의 단면에서 감마상(Fe3Zn10), 델타상(FeZn7), 제타상(FeZn13)을 확인할 수 있다. Silicon is an alloying element that can improve strength without reducing ductility by improving the cleanliness of ferrite. When silicon is added in an amount of less than 0.01% by weight, alloying is accelerated, and the thickness of the gamma (Γ, Gamma) phase, which is the plating layer (see FIG. 1), which causes the plating layer brittleness of the alloyed hot-dip galvanized steel sheet, increases, and plating peeling occurs. On the other hand, when silicon is added in excess of 0.07% by weight, a fayalite-based oxide having poor pickling properties is formed, which deteriorates the appearance quality and causes surface defects, so the content is limited to 0.01 to 0.07% by weight. For reference, a gamma phase (Fe 3 Zn 10 ), a delta phase (FeZn 7 ), and a zeta phase (FeZn 13 ) can be confirmed in the cross section of the alloyed hot-dip galvanized steel sheet of FIG. 1 .
알루미늄[Al]: 0.01중량% ~ 1.0중량%Aluminum [Al]: 0.01 wt% to 1.0 wt%
알루미늄은 탈산제로서 사용될 뿐만 아니라, 소둔 중 온도 변화에 따른 변태량을 감소시켜 재질 편차를 감소시킬 수 있다. 또한 첨가 시 목표 이상분율 형성을 위한 온도를 상승시켜 이상조직강의 고온 소둔을 가능하게 한다. 고온 소둔시 페라이트 결정립 성장을 통해 고연신 특성을 확보할 수 있다. 그러나, 알루미늄 함량이 1.0중량%를 초과할 경우, 제강성 개재물 증가 및 소둔 중 표면산화 현상을 초래할 수 있기 때문에 그 함량을 0.01 ~ 1.0중량%로 제한한다. Aluminum is not only used as a deoxidizer, but also reduces the amount of transformation according to temperature change during annealing, thereby reducing material deviation. In addition, when adding, the temperature for forming the target ideal fraction is increased, thereby enabling high-temperature annealing of the ideal-structured steel. High elongation characteristics can be secured through ferrite grain growth during high-temperature annealing. However, when the aluminum content exceeds 1.0% by weight, the content is limited to 0.01 to 1.0% by weight because it may cause an increase in steel-making inclusions and surface oxidation during annealing.
크롬[Cr]: 1.5중량%이하Chromium [Cr]: 1.5 wt% or less
크롬은 마르텐사이트 형성을 위해 첨가 하는 소입 원소로 1.5중량% 이상 첨가 시 그 효과가 수렴하고, 제조원가를 상승시키므로 그 함량을 1.5중량% 이하로 제한한다. Chromium is a quenching element added to form martensite, and when 1.5 wt% or more is added, the effect is converged and the manufacturing cost is increased, so the content is limited to 1.5 wt% or less.
몰리브덴[Mo]: 0.5중량%이하Molybdenum [Mo]: 0.5 wt% or less
몰리브덴은 마르텐사이트 형성을 위해 첨가 하는 소입 원소로 0.5중량% 이상 첨가시 그 효과가 수렴하고, 제조원가를 상승 시키므로 그 함량을 0.5% 이하로 제한한다.Molybdenum is a quenching element added to form martensite, and when more than 0.5% by weight is added, the effect is converged and the manufacturing cost is increased, so the content is limited to 0.5% or less.
크롬[Cr] 및 몰리브덴[Mo]의 첨가량Addition amount of chromium [Cr] and molybdenum [Mo]
[Cr] +0.3[Mo] 이 0.3중량% 미만일 경우, 크롬과 몰리브덴 첨가에 따른 소입성 강화 효과를 충분히 발휘하기 어렵고, 1.5중량%를 초과하는 경우 소입성 효과가 포화되어 효율 대비 가격경제성이 떨어지므로 0.3중량%≤[Cr] + 0.3[Mo]≤1.5중량%로 제한한다. When [Cr] +0.3 [Mo] is less than 0.3% by weight, it is difficult to sufficiently exhibit the hardenability strengthening effect due to the addition of chromium and molybdenum, and when it exceeds 1.5% by weight, the hardenability effect is saturated and price economical compared to efficiency is poor Therefore, it is limited to 0.3 wt%≤[Cr] + 0.3[Mo]≤1.5 wt%.
실리콘[Si], 크롬[Cr], 알루미늄[Al]의 첨가량Addition amount of silicon [Si], chromium [Cr], aluminum [Al]
140 * [Si] - 1.7 * [Cr] + 12 * [Al]의 수식(여기에서, [Si], [Cr] 및 [Al]은 상기 냉연 강판에서 각각 실리콘(Si), 크롬(Cr) 및 알루미늄(Al)의 중량%에 해당)에 각 성분별 중량%로 대입하였을 때, 수식 결과값이 4 미만일 때 도금 박리가 발생하며, 수식 결과값이 14.8을 초과할 때 에지 또는 스팟(Spot)성 미도금이 발생하므로 그 범위를 4 ~ 14.8로 관리한다. The formulas of 140 * [Si] - 1.7 * [Cr] + 12 * [Al] (here, [Si], [Cr] and [Al] are silicon (Si), chromium (Cr) and When substituting the weight % for each component in (corresponding to the weight % of aluminum (Al)), plating peeling occurs when the formula result is less than 4, and when the formula result value exceeds 14.8, edge or spot properties Since non-plating occurs, the range is managed as 4 ~ 14.8.
상기 조성범위를 만족하는 냉연 강판의 물성은 항복강도(YS) : 300MPa 이하, 인장강도 (TS) : 340MPa 이상, 연신율(EL) : 30% 이상, 항복비(YR) : 0.65 이하이다. 예를 들어, 상기 조성범위를 만족하는 냉연 강판의 물성은 항복강도(YS) : 190 ~ 300MPa, 인장강도 (TS) : 340 ~ 530MPa, 연신율(EL) : 30 ~ 40%, 항복비(YR) : 0.45 ~ 0.65일 수 있다. 또한, 상기 냉연 강판의 최종 미세 조직은 페라이트와 마르텐사이트를 포함하되, 상기 페라이트 기지에 상기 마르텐사이트 조직을 2 ~ 10%의 비율로 함유할 수 있다. The physical properties of the cold rolled steel sheet satisfying the above composition range are: yield strength (YS): 300 MPa or less, tensile strength (TS): 340 MPa or more, elongation (EL): 30% or more, and yield ratio (YR): 0.65 or less. For example, the physical properties of a cold-rolled steel sheet satisfying the above composition range are yield strength (YS): 190 to 300 MPa, tensile strength (TS): 340 to 530 MPa, elongation (EL): 30 to 40%, yield ratio (YR) : It may be 0.45 to 0.65. In addition, the final microstructure of the cold-rolled steel sheet includes ferrite and martensite, and may contain the martensite structure in the ferrite matrix in a ratio of 2 to 10%.
특히, 자동차용 외판재는 성형 중 칫수 정밀도 향상을 위해 저항복 특성을 보여야 하며, 이를 구현하기 위해 본 발명은 항복비(YP/TS)를 0.65이하로 관리함이 바람직하다. 동시에 1년 이상 내시효성을 확보하기 위해서는 경질상(Martensite) 분율을 2.0% 이상 확보하는 것이 바람직하다. 따라서 본 발명은 페라이트 기지에 마르텐사이트 조직을 2.0% 이상 함유한 강종의 제조방법을 포함한다. In particular, the exterior plate material for automobiles should show resistance to yield characteristics in order to improve dimensional precision during molding. At the same time, in order to secure aging resistance for more than one year, it is preferable to secure a hard phase (Martensite) fraction of 2.0% or more. Therefore, the present invention includes a method for manufacturing a steel type containing 2.0% or more of martensitic structure in a ferrite matrix.
나아가, 본 발명의 일 실시예에 따른 합금화 용융아연도금 강판은 상술한 냉연 강판의 표면에 합금화 용융아연도금층을 더 포함하는 강판이다. 상기 합금화 용융아연도금층의 감마(Γ)상은 두께가 0.7 ㎛ 이하일 수 있으며, 상기 합금화 용융아연도금층의 HCI(Hat-bead Contrast Index) 지수는 120 이하일 수 있다. Furthermore, the hot-dip galvanized steel sheet according to an embodiment of the present invention is a steel sheet further comprising an alloyed hot-dip galvanized layer on the surface of the cold-rolled steel sheet. The gamma (Γ) phase of the alloying hot-dip galvanizing layer may have a thickness of 0.7 μm or less, and a Hat-bead Contrast Index (HCI) index of the alloying hot-dip galvanizing layer may be 120 or less.
HCI는 Hat-bead Contrast Index를 의미하며, 시험 후 파편의 박리양이 많을수록 값이 높으며, 반대로 박리양이 적을수록 값이 낮다. HCI 지수가 높을수록 도금성이 열위하며, HCI 지수가 낮을수록 도금층이 우수하다. HCI stands for Hat-bead Contrast Index, and after the test, the larger the amount of delamination of the fragments, the higher the value. The higher the HCI index, the worse the plating property, and the lower the HCI index, the better the plating layer.
도 2는 본 발명의 일 실시예에 따르는 합금화 용융아연도금 강판의 도금특성인 HCI 지수를 도출하기 위한 시험법 기준 및 시험평가 방법을 도해하는 도면이다.2 is a diagram illustrating a test method standard and test evaluation method for deriving an HCI index, which is a plating characteristic of an alloyed hot-dip galvanized steel sheet according to an embodiment of the present invention.
도 2의 (a)는 HCI 지수를 도출하기 위한 드로잉 공정을 도해하는 바, 클램핑 포스(clamping force)는 30kN이며, 펀치 스피드(punch speed)는 300mm/s이며, 도로잉 높이(drawing height)는 65mm인 시험법 기준을 적용하였다. 도 2의 (b)는 HCI 지수를 도출하기 위한 시험평가 방법을 도해하는 바, 유색으로 음영된 부분을 테이핑하고 HCI로 도금 박리성을 평가한다. 즉, 도금의 접합력 및 도금박리성을 평가하는 지수인 HCI는 도 2와 같은 도금테스트 (HAT)를 기반으로 작성한 도금 박리 지수를 의미한다. HCI 지수에 대한 상세한 설명은 하기의 논문을 참조할 수 있다. Figure 2 (a) illustrates the drawing process for deriving the HCI index, the clamping force (clamping force) is 30 kN, the punch speed (punch speed) is 300 mm / s, the drawing height (drawing height) is A test method standard of 65 mm was applied. Figure 2 (b) illustrates a test evaluation method for deriving the HCI index, taping the colored shaded portion and evaluating the plating peelability with HCI. That is, HCI, which is an index for evaluating adhesion and plating peelability of plating, refers to a plating peeling index prepared based on a plating test (HAT) as shown in FIG. 2 . For a detailed description of the HCI index, refer to the following paper.
논문: Park, H., Jeong, Y., Lee, K. et al. Correlation of Interface Microstructural Features with the Adhesive Bonding Strength of Galvannealed Interstitial-Free Steel. Met. Mater. Int. (2020). Papers: Park, H., Jeong, Y., Lee, K. et al. Correlation of Interface Microstructural Features with the Adhesive Bonding Strength of Galvannealed Interstitial-Free Steel. Met. Mater. Int. (2020).
냉연 강판 및 합금화 용융아연도금 강판의 제조 방법Manufacturing method of cold rolled steel sheet and alloyed hot-dip galvanized steel sheet
도 3은 본 발명의 일 실시예에 따르는 냉연 강판 및 합금화 용융아연도금 강판의 제조 방법을 도해하는 순서도이다. 3 is a flowchart illustrating a method of manufacturing a cold-rolled steel sheet and an alloyed hot-dip galvanized steel sheet according to an embodiment of the present invention.
도 3을 참조하면, 본 발명의 일 실시예에 따르는 냉연 강판의 제조 방법은 (a) 탄소(C) : 0.01 ~ 0.06중량%, 망간(Mn) : 1.0 ~ 2.5중량%, 황(S) : 0 초과 0.01중량% 이하, 인(P) : 0 초과 0.08중량% 이하, 실리콘(Si) : 0.01 ~ 0.07중량%, 알루미늄(Al) : 0.01 ~ 1.0중량%, 크롬(Cr) : 0 초과 1.5중량% 이하, 몰리브덴(Mo): 0 초과 0.5중량% 이하, 크롬(Cr) 및 몰리브덴[Mo] : 0.3중량%≤[Cr]+0.3[Mo]≤1.5중량% 이 되도록 크롬(Cr) 및 몰리브덴 (Mo) 중 적어도 1종 이상을 포함하며 나머지 철(Fe)과 불가피한 불순물로 이루어진 강재를 제공하는 단계(S100); (b) 상기 강재를 재가열온도(SRT) : 1150 ~ 1300℃, 마무리압연온도(FDT) : 820 ~ 920℃, 권취온도(CT) : 560 ~ 700℃인 조건으로 열간 압연하는 단계(S200); (c) 상기 강재를 55 ~ 75%의 압하율로 냉간 압연하는 단계(S300); 및 (d) 상기 강재를 760 ~ 840℃에서 소둔 공정하는 단계(S400); 를 포함한다. Referring to FIG. 3 , the method for manufacturing a cold-rolled steel sheet according to an embodiment of the present invention includes (a) carbon (C): 0.01 to 0.06 wt%, manganese (Mn): 1.0 to 2.5 wt%, sulfur (S): More than 0 and less than 0.01 wt%, Phosphorus (P): More than 0 and less than or equal to 0.08 wt%, Silicon (Si): 0.01 to 0.07 wt%, Aluminum (Al): 0.01 to 1.0 wt%, Chromium (Cr): More than 0 to 1.5 wt% % or less, molybdenum (Mo): more than 0 and 0.5 wt% or less, chromium (Cr) and molybdenum [Mo]: 0.3 wt% ≤ [Cr] + 0.3 [Mo] ≤ 1.5 wt% so that chromium (Cr) and molybdenum ( Mo) comprising at least one or more of providing a steel material comprising the remaining iron (Fe) and unavoidable impurities (S100); (b) the reheating temperature (SRT) of the steel: 1150 ~ 1300 ℃, finish rolling temperature (FDT): 820 ~ 920 ℃, winding temperature (CT): hot rolling under the conditions of 560 ~ 700 ℃ (S200); (c) cold rolling the steel at a reduction ratio of 55 to 75% (S300); And (d) annealing the steel material at 760 ~ 840 ℃ (S400); includes
열간 압연하는 단계(S200)에서, 슬라브 강재를 재가열온도(SRT) : 1150 ~ 1300℃로 가열하여 주조 시 편석된 성분 및 석출물을 재고용 시킨다. 나아가, 마무리압연온도(FDT) : 820 ~ 920℃ 범위에서 열간 압연을 마무리 한다. 사상압연 온도가 820℃ 미만일 경우 상변화에 의해 압연성이 저하되며, 920℃를 초과하면 결정립이 조대해져, 이에 따라 강도 및 항복비 특성이 열화되므로 920℃이하에서 실시한다. 또한, 권취온도(CT)가 700℃를 초과할 경우에는 조대립의 형성으로 항복비가 감소하고 강도가 저하되며, 권취온도가 560℃ 미만으로 저온일 경우에는 조직이 미세하게 되어 강도와 인성은 증가할 수 있으나, 연신율을 충족하기 어렵다.In the hot rolling step (S200), the slab steel is heated to a reheating temperature (SRT): 1150 ~ 1300 ℃ to re-dissolve segregated components and precipitates during casting. Further, finish rolling temperature (FDT): finish hot rolling in the range of 820 ~ 920 ℃. When the finishing rolling temperature is less than 820°C, the rolling property is reduced due to a phase change, and when it exceeds 920°C, the grains become coarse, and thus the strength and yield ratio characteristics deteriorate. In addition, when the coiling temperature (CT) exceeds 700 ℃, the yield ratio decreases and the strength decreases due to the formation of coarse grains. However, it is difficult to satisfy the elongation rate.
냉간 압연하는 단계(S300)에서, 냉간 압하율이 55% 미만일 경우 균질한 미세조직을 얻기 어렵고, 재결정이 지연된다. 또한 냉간 압하율이 75%를 초과할 경우 냉연 부하가 증가하므로 냉간 압하율은 55 ~ 75%로 관리함이 바람직하다.In the cold rolling step (S300), when the cold rolling reduction is less than 55%, it is difficult to obtain a homogeneous microstructure, and recrystallization is delayed. In addition, when the cold rolling reduction exceeds 75%, the cold rolling load increases, so it is desirable to manage the cold rolling reduction at 55 to 75%.
소둔 공정하는 단계(S400)에서, 강재의 강도 및 저항복비 특성 및 내시효성을 확보하는 공정으로 인장강도 340MPa 이상을 확보하기 위하여 2 ~ 10% 대의 마르텐사이트 분율을 목표로 한다. 소둔 공정은 마르텐사이트 형성을 위해 이상분리를 하는 공정으로 냉연 설비 특성에 따라 최종 마르텐사이트 분율 2 ~ 10%를 확보하기 위해 760 ~ 840℃ 이내 범위에서 실시한다.In the step (S400) of the annealing process, a martensite fraction of 2 to 10% is targeted in order to secure a tensile strength of 340 MPa or more as a process of securing the strength and resistance to yield ratio characteristics and aging resistance of the steel material. The annealing process is a process of abnormal separation to form martensite, and it is carried out within the range of 760 to 840°C to secure a final martensite fraction of 2 to 10% depending on the characteristics of the cold rolling facility.
본 발명의 일 실시예에 따르는 합금화 용융아연도금 강판의 제조 방법은 단계(S100) 내지 단계(S400)를 수행하여 구현된 냉연 강판에 합금화 용융아연도금층을 형성하는 단계(S500)를 더 포함할 수 있다. The method of manufacturing an alloyed hot-dip galvanized steel sheet according to an embodiment of the present invention may further include the step (S500) of forming an alloyed hot-dip galvanizing layer on the cold-rolled steel sheet implemented by performing steps (S100) to (S400). have.
합금화 용융아연도금층을 형성하는 단계(S500)에서, 합금화 열처리 온도는 450 ~ 550℃로 실시하며, 합금화 열처리 이후, -20℃/sec.로 250℃ 이하의 온도로 급냉하여 마르텐사이트 조직을 만든다. In the step of forming the alloying hot-dip galvanizing layer (S500), the alloying heat treatment temperature is carried out at 450 ~ 550 ℃, after the alloying heat treatment, quenching to a temperature of 250 ℃ or less at -20 ℃ / sec. to make a martensitic structure.
도금층을 형성한 후에, 형상 제어 및 표면 품질 향상을 위해 조질 압연을 수행할 수 있다. 조질 압연이 과다할 경우 항복강도 및 항복비가 증가하기 때문에 압하율을 1.0% 이하로 제한할 수 있다. After forming the plating layer, temper rolling may be performed for shape control and surface quality improvement. If the temper rolling is excessive, the reduction ratio can be limited to 1.0% or less because the yield strength and yield ratio increase.
실험예Experimental example
이하, 본 발명의 이해를 돕기 위해 바람직한 실험예를 제시한다. 다만, 다음의 실험예는 본 발명의 이해를 돕기 위한 것일 뿐, 본 발명이 다음의 실험예에 의해 한정되는 것은 아니다. Hereinafter, preferred experimental examples are presented to help the understanding of the present invention. However, the following experimental examples are only for helping understanding of the present invention, and the present invention is not limited by the following experimental examples.
표 1은 본 발명의 실험예의 시편의 주요 성분, 기계적 특성 및 표면 특성을 나타낸 것이다. Table 1 shows the main components, mechanical properties and surface properties of the specimens of the experimental examples of the present invention.
(wt%)Si
(wt%)
(wt%)Cr
(wt%)
(wt%)Al
(wt%)
(MPa)YP
(MPa)
(MPa)ts
(MPa)
(%)EL
(%)
표 1을 참조하면, 실시예1, 실시예2 및 실시예3은 탄소(C) : 0.01 ~ 0.06중량%, 망간(Mn) : 1.0 ~ 2.5중량%, 황(S) : 0 초과 0.01중량% 이하, 인(P) : 0 초과 0.08중량% 이하, 실리콘(Si) : 0.01 ~ 0.07중량%, 알루미늄(Al) : 0.01 ~ 1.0중량%, 크롬(Cr) : 0 초과 1.5중량% 이하, 몰리브덴(Mo): 0 초과 0.5중량% 이하, 크롬(Cr) 및 몰리브덴[Mo] : 0.3중량%≤[Cr]+0.3[Mo]≤1.5중량% 이 되도록 크롬(Cr) 및 몰리브덴 (Mo) 중 적어도 1종 이상을 포함하며 나머지 철(Fe)로 이루어진 조성범위를 만족한다. 나아가, 하기 수식1을 만족한다. Referring to Table 1, Examples 1, 2 and 3 are carbon (C): 0.01 to 0.06% by weight, manganese (Mn): 1.0 to 2.5% by weight, sulfur (S): more than 0 0.01% by weight or less, phosphorus (P): more than 0 0.08 wt% or less, silicon (Si): 0.01 to 0.07 wt%, aluminum (Al): 0.01 to 1.0 wt%, chromium (Cr): more than 0 to 1.5 wt% or less, molybdenum ( Mo): greater than 0 and 0.5 wt% or less, chromium (Cr) and molybdenum [Mo]: at least 1 of chromium (Cr) and molybdenum (Mo) so that 0.3 wt% ≤ [Cr] + 0.3 [Mo] ≤ 1.5 wt % It includes more than one species and satisfies the composition range of the remaining iron (Fe). Further, Equation 1 below is satisfied.
수식1 : 4 ≤ 140 * [Si] - 1.7 * [Cr] + 12 * [Al] ≤ 14.8Equation 1: 4 ≤ 140 * [Si] - 1.7 * [Cr] + 12 * [Al] ≤ 14.8
(단, [Si], [Cr] 및 [Al]은 상기 강재에서 각각 실리콘(Si), 크롬(Cr) 및 알루미늄(Al)의 중량%에 해당함)(However, [Si], [Cr] and [Al] correspond to the weight percent of silicon (Si), chromium (Cr) and aluminum (Al) in the steel, respectively)
이 경우, 실시예1, 실시예2 및 실시예3에 따른 냉연 강판은 항복강도(YS) : 300MPa 이하, 인장강도 (TS) : 340MPa 이상, 연신율(EL) : 30% 이상, 항복비(YR) : 0.65 이하인 기계적 특성을 만족한다. 구체적으로, 실시예1, 실시예2 및 실시예3에 따른 냉연 강판은 항복강도(YS) : 190 ~ 300MPa, 인장강도 (TS) : 340 ~ 530MPa, 연신율(EL) : 30 ~ 40%, 항복비(YR) : 0.45 ~ 0.65일 수 있다. In this case, the cold-rolled steel sheets according to Examples 1, 2 and 3 have yield strength (YS): 300 MPa or less, tensile strength (TS): 340 MPa or more, elongation (EL): 30% or more, yield ratio (YR) ): satisfies the mechanical properties of 0.65 or less. Specifically, the cold rolled steel sheets according to Examples 1, 2 and 3 have yield strength (YS): 190 to 300 MPa, tensile strength (TS): 340 to 530 MPa, elongation (EL): 30 to 40%, yield Ratio (YR): may be 0.45 to 0.65.
또한, 실시예1, 실시예2 및 실시예3에 따른 합금화 용융아연도금 강판은 합금화 용융아연도금층의 감마(Γ)상 두께가 0.7 ㎛ 이하, 합금화 용융아연도금층의 HCI(Hat-bead Contrast Index) 지수가 120 이하인 표면 특성을 만족하여 도금 박리 없이 양호함을 확인할 수 있다.In addition, the alloyed hot-dip galvanized steel sheets according to Examples 1, 2 and 3 had a gamma (Γ) phase thickness of 0.7 μm or less of the alloyed hot-dip galvanized layer, and a Hat-bead Contrast Index (HCI) of the alloyed hot-dip galvanized layer. It can be confirmed that the index satisfies the surface characteristics of 120 or less, and thus good without plating peeling.
이와 달리, 비교예1 내지 비교예4는 상기 수식1을 하회하여 만족하지 못한다. 이 경우, 비교예1 내지 비교예4에 따른 합금화 용융아연도금 강판은 합금화 용융아연도금층의 감마(Γ)상 두께가 0.7 ㎛ 이하를 만족하지 못하며, 합금화 용융아연도금층의 HCI(Hat-bead Contrast Index) 지수가 120 이하를 만족하지 못하며, 도금 박리 현상이 나타남을 확인할 수 있다. On the other hand, Comparative Examples 1 to 4 are not satisfied by less than Equation 1 above. In this case, in the alloyed hot-dip galvanized steel sheets according to Comparative Examples 1 to 4, the gamma (Γ) phase thickness of the alloyed hot-dip galvanized layer did not satisfy 0.7 μm or less, and the Hat-bead Contrast Index (HCI) of the alloyed hot-dip galvanized layer was ) index does not satisfy 120 or less, and it can be seen that plating peeling occurs.
또한, 비교예5는 실리콘(Si) : 0.01 ~ 0.07중량%의 조성범위를 만족하지 못하며, 상기 수식1을 상회하여 만족하지 못한다. 이 경우, 비교예5에 따른 냉연 강판은 항복강도(YS) : 300MPa 이하인 기계적 특성을 만족하지 못하여, 미도금 현상이 발생함을 확인할 수 있다. In addition, Comparative Example 5 does not satisfy the composition range of silicon (Si): 0.01 to 0.07% by weight, and exceeds Equation 1, and is not satisfied. In this case, the cold-rolled steel sheet according to Comparative Example 5 did not satisfy the mechanical properties of the yield strength (YS): 300 MPa or less, so it could be confirmed that the non-plating phenomenon occurred.
이상에서 설명한 본 발명의 기술적 사상이 전술한 실시예 및 첨부된 도면에 한정되지 않으며, 본 발명의 기술적 사상을 벗어나지 않는 범위 내에서 여러 가지 치환, 변형 및 변경이 가능하다는 것은, 본 발명의 기술적 사상이 속하는 기술분야에서 통상의 지식을 가진 자에게 있어 명백할 것이다.The technical spirit of the present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it is the technical spirit of the present invention that various substitutions, modifications and changes are possible within the scope without departing from the technical spirit of the present invention. It will be apparent to those of ordinary skill in the art to which this belongs.
Claims (10)
항복강도(YS) : 300MPa 이하, 인장강도 (TS) : 340MPa 이상, 연신율(EL) : 30% 이상, 항복비(YR) : 0.65 이하인,
냉연 강판.Carbon (C): 0.01 to 0.06 wt%, Manganese (Mn): 1.0 to 2.5 wt%, Sulfur (S): More than 0 and less than 0.01 wt%, Phosphorus (P): More than 0 and less than or equal to 0.08 wt%, Silicon (Si) : 0.01 to 0.07 wt%, aluminum (Al): 0.01 to 1.0 wt%, chromium (Cr): more than 0 and less than 1.5 wt%, molybdenum (Mo): more than 0 and less than 0.5 wt%, chromium (Cr) and molybdenum [Mo] ]: contains at least one of chromium (Cr) and molybdenum (Mo) so that 0.3 wt% ≤ [Cr] + 0.3 [Mo] ≤ 1.5 wt %, and consists of the remaining iron (Fe) and unavoidable impurities,
Yield strength (YS): 300 MPa or less, Tensile strength (TS): 340 MPa or more, Elongation (EL): 30% or more, Yield ratio (YR): 0.65 or less,
cold rolled steel sheet.
하기 수식1을 만족하는,
냉연 강판.
수식1 : 4 ≤ 140 * [Si] - 1.7 * [Cr] + 12 * [Al] ≤ 14.8
(여기에서, [Si], [Cr] 및 [Al]은 상기 냉연 강판에서 각각 실리콘(Si), 크롬(Cr) 및 알루미늄(Al)의 중량%에 해당함)The method of claim 1,
Satisfying Equation 1 below,
cold rolled steel sheet.
Equation 1: 4 ≤ 140 * [Si] - 1.7 * [Cr] + 12 * [Al] ≤ 14.8
(Here, [Si], [Cr] and [Al] correspond to the weight % of silicon (Si), chromium (Cr) and aluminum (Al) in the cold-rolled steel sheet, respectively)
최종 미세 조직은 페라이트와 마르텐사이트를 포함하되, 상기 페라이트 기지에 상기 마르텐사이트 조직을 2 ~ 10%의 비율로 함유하는 것을 특징으로 하는,
냉연 강판.The method of claim 1,
The final microstructure includes ferrite and martensite, characterized in that the martensite structure is contained in the ferrite matrix in a ratio of 2 to 10%,
cold rolled steel sheet.
합금화 용융아연도금 강판.Claims 1 to 3, characterized in that it further comprises an alloyed hot-dip galvanizing layer on the surface of the cold-rolled steel sheet according to any one of claims 1 to 3,
Alloyed hot-dip galvanized steel sheet.
상기 합금화 용융아연도금층의 감마(Γ)상은 두께가 0.7 ㎛ 이하인 것을 특징으로 하는,
합금화 용융아연도금 강판.5. The method of claim 4,
The gamma (Γ) phase of the alloying hot-dip galvanizing layer is characterized in that the thickness is 0.7 ㎛ or less,
Alloyed hot-dip galvanized steel sheet.
상기 합금화 용융아연도금층의 HCI(Hat-bead Contrast Index) 지수는 120 이하인 것을 특징으로 하는,
합금화 용융아연도금 강판.5. The method of claim 4,
The HCI (Hat-bead Contrast Index) index of the alloyed hot-dip galvanized layer is characterized in that 120 or less,
Alloyed hot-dip galvanized steel sheet.
(b) 상기 강재를 재가열온도(SRT) : 1150 ~ 1300℃, 마무리압연온도(FDT) : 820 ~ 920℃, 권취온도(CT) : 560 ~ 700℃인 조건으로 열간 압연하는 단계;
(c) 상기 강재를 55 ~ 75%의 압하율로 냉간 압연하는 단계; 및
(d) 상기 강재를 760 ~ 840℃에서 소둔 공정하는 단계; 를 포함하는,
냉연 강판의 제조 방법.(a) Carbon (C): 0.01 to 0.06 wt%, Manganese (Mn): 1.0 to 2.5 wt%, Sulfur (S): More than 0 and less than 0.01 wt%, Phosphorus (P): More than 0 and less than or equal to 0.08 wt%, Silicon (Si): 0.01 to 0.07% by weight, aluminum (Al): 0.01 to 1.0% by weight, chromium (Cr): more than 0 and 1.5% by weight or less, molybdenum (Mo): more than 0 to 0.5% by weight or less, chromium (Cr) and Molybdenum [Mo]: contains at least one of chromium (Cr) and molybdenum (Mo) so that 0.3 wt% ≤ [Cr] + 0.3 [Mo] ≤ 1.5 wt %, and the remaining iron (Fe) and unavoidable impurities providing steel;
(b) the reheating temperature (SRT) of the steel: 1150 ~ 1300 ℃, finish rolling temperature (FDT): 820 ~ 920 ℃, winding temperature (CT): hot rolling under the conditions of 560 ~ 700 ℃;
(c) cold rolling the steel at a reduction ratio of 55 to 75%; and
(d) annealing the steel material at 760 ~ 840 ℃; containing,
A method for manufacturing a cold rolled steel sheet.
상기 강재는 하기 수식1을 만족하는,
냉연 강판의 제조 방법.
수식1 : 4 ≤ 140 * [Si] - 1.7 * [Cr] + 12 * [Al] ≤ 14.8
(여기에서, [Si], [Cr] 및 [Al]은 상기 강재에서 각각 실리콘(Si), 크롬(Cr) 및 알루미늄(Al)의 중량%에 해당함)8. The method of claim 7,
The steel material satisfies the following Equation 1,
A method for manufacturing a cold rolled steel sheet.
Equation 1: 4 ≤ 140 * [Si] - 1.7 * [Cr] + 12 * [Al] ≤ 14.8
(Here, [Si], [Cr] and [Al] correspond to the weight percent of silicon (Si), chromium (Cr) and aluminum (Al) in the steel, respectively)
상기 (a) 내지 (d) 단계를 수행한 후 항복강도(YS) : 300MPa 이하, 인장강도 (TS) : 340MPa 이상, 연신율(EL) : 30% 이상, 항복비(YR) : 0.65 이하인 것을 특징으로 하는,
냉연 강판의 제조 방법.8. The method of claim 7,
After performing steps (a) to (d), yield strength (YS): 300 MPa or less, tensile strength (TS): 340 MPa or more, elongation (EL): 30% or more, yield ratio (YR): 0.65 or less to do,
A method for manufacturing a cold rolled steel sheet.
상기 합금화 용융아연도금층을 형성하기 위한 합금화 열처리 온도는 450 ~ 550℃인 것을 특징으로 하는,
합금화 용융아연도금 강판의 제조 방법.10. The method of any one of claims 7 to 9, further comprising the step of forming an alloyed hot-dip galvanizing layer on the cold-rolled steel sheet implemented by the method,
The alloying heat treatment temperature for forming the alloying hot-dip galvanizing layer is characterized in that 450 ~ 550 ℃,
A method for manufacturing an alloyed hot-dip galvanized steel sheet.
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