KR100742950B1 - Baking hardening type cold rolled steel sheet having increased yield strength and process for producing the same - Google Patents

Baking hardening type cold rolled steel sheet having increased yield strength and process for producing the same Download PDF

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KR100742950B1
KR100742950B1 KR1020060040235A KR20060040235A KR100742950B1 KR 100742950 B1 KR100742950 B1 KR 100742950B1 KR 1020060040235 A KR1020060040235 A KR 1020060040235A KR 20060040235 A KR20060040235 A KR 20060040235A KR 100742950 B1 KR100742950 B1 KR 100742950B1
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윤정봉
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주식회사 포스코
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Abstract

Ti와 Nb의 복합계 IF강에서 미세한 (Mn,Cu)S석출물과 AlN석출물에 의해 항복강도와 면내이방성이 개선되는 냉연강판과 그 제조방법이 제공된다. Provided is a cold rolled steel sheet and its manufacturing method which improve yield strength and in-plane anisotropy by fine (Mn, Cu) S precipitates and AlN precipitates in a composite IF steel of Ti and Nb.

이 냉연강판은, 중량%로, C: 0.001-0.01%, Cu:0.01-0.2%, Mn:0.01-0.3%, S:0.005-0.08%, Al:0.1%이하, N:0.004-0.02%, P:0.2%이하, B:0.0001-0.002%, Ti:0.005~0.15%, Nb:0.002-0.04%, 나머지 Fe 및 기타 불가피한 불순물로 조성되고, The cold rolled steel sheet is, by weight, C: 0.001-0.01%, Cu: 0.01-0.2%, Mn: 0.01-0.3%, S: 0.005-0.08%, Al: 0.1% or less, N: 0.004-0.02%, P: 0.2% or less, B: 0.0001-0.002%, Ti: 0.005-0.15%, Nb: 0.002-0.04%, remaining Fe and other unavoidable impurities,

상기 Cu, Mn, S, Al, N, C, Ti, Nb가 Cu, Mn, S, Al, N, C, Ti, Nb is

Cu+Mn:0.05-0.4%, (Mn/55+Cu/63.5)/( S*/32):1-30, (Al/27)/( N*/14):1-10,Cu + Mn: 0.05-0.4%, (Mn / 55 + Cu / 63.5) / (S * / 32): 1-30, (Al / 27) / (N * / 14): 1-10,

Cs(solute carbon):5-30를 만족하고Cs (solute carbon): Meets 5-30

[여기서, S*=S-0.8x(Ti-0.8x(48/14)xN)x(32/48), [Where S * = S-0.8x (Ti-0.8x (48/14) xN) x (32/48),

N* =N-0.8x(Ti-0.8x(48/32)xS))x(14/48) , Cs=(C-Nbx12/93-Ti*x12/48)x10000, N * = N-0.8x (Ti-0.8x (48/32) xS)) x (14/48), Cs = (C-Nbx12 / 93-Ti * x12 / 48) x10000,

Ti*=Ti-0.8x((48/14)xN+(48/32)xS) 단, Ti*<0일 경우 Ti*=0으로 함] Ti * = Ti-0.8x (( 48/14) xN + (48/32) xS) If stage, Ti * <0 il referred to as Ti * = 0]

(Mn,Cu)S석출물과 AlN석출물의 평균크기가 0.2㎛이하로 이루어진다. The average size of the (Mn, Cu) S precipitates and AlN precipitates is less than 0.2 µm.

본 발명에서는 IF강에서 내식성을 위해 Cu를 첨가하는 기술 또는 Cu를 ε-Cu의 석출상으로 이용하는 기술과는 달리, Cu를 미세한 CuS석출물로 이용하면서 MnS석출물과 AlN석출물을 함께 이용하는 것이다. In the present invention, unlike the technique of adding Cu for corrosion resistance in IF steel or the technique of using Cu as the precipitated phase of ε-Cu, MnS precipitate and AlN precipitate are used together while using Cu as a fine CuS precipitate.

소부경화형, 자동차소재, (Mn,Cu)S석출물, AlN석출물, 면내이방성, 항복강도 Stiffening hardening type, automotive material, (Mn, Cu) S precipitate, AlN precipitate, in-plane anisotropy, yield strength

Description

항복강도가 우수한 소부경화형 냉연강판과 그 제조방법{BAKING HARDENING TYPE COLD ROLLED STEEL SHEET HAVING INCREASED YIELD STRENGTH AND PROCESS FOR PRODUCING THE SAME}Baking HARDENING TYPE COLD ROLLED STEEL SHEET HAVING INCREASED YIELD STRENGTH AND PROCESS FOR PRODUCING THE SAME}

일본 공개특허공보 1994-240365호 Japanese Unexamined Patent Publication No. 1994-240365

일본 공개특허공보 1995-216460호 Japanese Unexamined Patent Publication No. 1995-216460

본 발명은 자동차, 가전제품 등의 소재로 사용되는 소부경화형 냉연강판에 관한 것으로, 보다 상세하게는 Ti와 Nb의 복합계 IF강에서 미세한 (Mn,Cu)S석출물과 AlN석출물에 의해 항복강도와 면내이방성이 개선되는 냉연강판과 그 제조방법에 관한 것이다. The present invention relates to a hardened hardened cold rolled steel sheet used as a material for automobiles, home appliances, and more particularly, to yield strength by fine (Mn, Cu) S precipitates and AlN precipitates in a composite IF steel of Ti and Nb. It relates to a cold-rolled steel sheet and a manufacturing method for improving the in-plane anisotropy.

자동차 등의 외판소재에는 내덴트성을 높이기 위해 소부경화형 냉연강판이 사용되고 있다. 소부경화형 냉연강판은 강판중에 적정량의 고용탄소를 잔존시키고, 프레스 성형시에 생성된 전위를 도장소부시의 열을 이용하여 고용탄소로 고착하여 항복점을 높인 강이다.In addition, the hardening type cold rolled steel sheet is used for exterior materials such as automobiles in order to increase dent resistance. The hardened hardened cold rolled steel is a steel in which an appropriate amount of solid solution carbon remains in the steel sheet and the potential generated during press molding is fixed to solid solution carbon using heat from the coating furnace to increase the yield point.

소부경화형 냉연강판에는 상소둔재인 Al-Killed강과 IF강(Interstitial Free Steel)이 있다. There are Al-Killed steel and IF steel (Interstitial Free Steel).

상소둔재인 Al-Killed 강의 경우에는 적은 양의 고용탄소가 잔존하고 있어 내시효특성을 확보하면서 소부처리 후 10-20MPa 정도의 소부경화능을 가진다. 상소둔재의 경우에는 소부처리 후 상승하는 항복강도가 낮고, 장시간 소둔하므로 생산성이 낮은 단점이 있다. In the case of Al-Killed steel, which is an ordinary annealing material, a small amount of dissolved carbon remains, and it has a hardening hardening capacity of about 10-20 MPa after the calcination treatment while securing aging characteristics. In the case of the annealing material, the yield strength rising after the baking treatment is low, and there is a disadvantage in that the productivity is low because it is annealed for a long time.

IF강은 Ti, Nb을 첨가하여 강중에 고용된 탄소 또는 질소를 완전히 석출하여 성형성을 향상시킨 강종으로서, 이 IF강에 소부경화특성을 부여한 것이 소부경화형 IF강이다. 소부경화형 IF강은 Ti 또는 Nb의 첨가량과 탄소의 첨가량을 제어하여 적당한 양의 탄소를 강중에 잔존하게 하여 소부경화특성을 부여한 것이다. 이와 관련된 기술로는 일본 공개특허공보 1994-240365호와 1995-216460호가 있다.IF steel is a steel grade which adds Ti and Nb to improve the formability by completely depositing carbon or nitrogen dissolved in steel, and it is the hardening hardening IF steel that gives the hardening hardening characteristic to the IF steel. The baking hardening type IF steel controls the adding amount of Ti or Nb and the adding amount of carbon so that an appropriate amount of carbon remains in the steel to give the baking hardening characteristic. As related technologies, there are Japanese Patent Application Laid-open Nos. 1994-240365 and 1995-216460.

일본 공개특허공보 1994-240365호는 소부경화형 IF강에서 내식성을 확보하기 위하여 Cu와 P를 복합 첨가하고 있다. Japanese Laid-Open Patent Publication No. 1994-240365 combines Cu and P in order to secure corrosion resistance in a hardened type IF steel.

일본 공개특허공보 1995-216340호는 내식성을 확보하기 위해 Cu와 P를 복합첨가한 소부경화형 IF강에서 고용C를 TiC로 고정할 수 없는 정도의 미량 Ti를 첨가하고 필요에 따라 Nb를 첨가하면서 열연조건을 제어하면 우수한 심교성이 얻어진다고 제안하고 있다. Japanese Laid-Open Patent Publication No. 1995-216340 discloses hot rolling while adding a small amount of Ti to the extent that the solid solution C cannot be fixed to TiC in a small hardening type IF steel including a combination of Cu and P and Nb as necessary to secure corrosion resistance. It is proposed that excellent control of depth can be obtained by controlling the conditions.

상기한 선행기술들은 소부경화형 IF강에서 내식성을 확보하기 위해 Cu를 0.05-1.0%의 범위로 하나 실제 Cu를 0.2%이상으로 과량 첨가하는 강이다. 이들은 면내이방성에 대한 검토가 없다. 면내이방성이 낮으면 가공시 주름 발생이 적어지고 가공후에는 귀(ear) 발생이 적은 장점이 있다. 또한, 상기 선행기술들에서는 항복비(항복강도/인장강도)가 그리 높지 않다. 동일강도 대비 항복강도가 더 높으면 강판의 두께를 줄일 수 있어 경량화 효과가 있다. 선행기술들에서 항복비가 그나마 높은 강종은 P의 함량과 Cu의 함량이 높게 설계된 성분계이다. P의 함량이 높으면 도금성이 좋지 않고, Cu의 함량이 높으면 제조원가가 높아진다. The above prior arts are steels in which Cu is added in an amount of 0.05-1.0% but actually 0.2% or more, in order to secure corrosion resistance in the hardening type IF steel. They do not have a review of in-plane anisotropy. When the in-plane anisotropy is low, wrinkles are less generated during processing, and there is less advantage of generating ears after processing. In addition, the yield ratio (yield strength / tensile strength) is not very high in the prior arts. If the yield strength is higher than the same strength, the thickness of the steel sheet can be reduced, thereby reducing the weight. Steel grades with high yield ratios in the prior arts are component systems designed with high P content and Cu content. If the content of P is high, the plating property is not good. If the content of Cu is high, the production cost is high.

본 발명은 소부경화형 IF강에서 (Mn,Cu)S석출물과 AlN석출물에 의해 항복강도를 증진하면서 면내이방성을 낮출 수 있는 냉연강판과 그 제조방법을 제공하는데 그 목적이 있다. An object of the present invention is to provide a cold-rolled steel sheet and a method of manufacturing the same, which can lower in-plane anisotropy while improving yield strength by (Mn, Cu) S precipitates and AlN precipitates in a small hardening type IF steel.

상기 목적을 달성하기 위한 본 발명의 냉연강판은, Cold rolled steel sheet of the present invention for achieving the above object,

중량%로, C: 0.001-0.01%, Cu:0.01-0.2%, Mn:0.01-0.3%, S:0.005-0.08%, Al:0.1%이하, N:0.004-0.02%, P:0.2%이하, B:0.0001-0.002%, Ti:0.005~0.15%, Nb:0.002-0.04%, 나머지 Fe 및 기타 불가피한 불순물로 조성되고, By weight%, C: 0.001-0.01%, Cu: 0.01-0.2%, Mn: 0.01-0.3%, S: 0.005-0.08%, Al: 0.1% or less, N: 0.004-0.02%, P: 0.2% or less , B: 0.0001-0.002%, Ti: 0.005-0.15%, Nb: 0.002-0.04%, remaining Fe and other inevitable impurities,

상기 Cu, Mn, S, Al, N, C, Ti, Nb가 Cu, Mn, S, Al, N, C, Ti, Nb is

Cu+Mn:0.05-0.4%, (Mn/55+Cu/63.5)/( S*/32):1-30, (Al/27)/( N*/14):1-10,Cu + Mn: 0.05-0.4%, (Mn / 55 + Cu / 63.5) / (S * / 32): 1-30, (Al / 27) / (N * / 14): 1-10,

Cs(solute carbon):5-30를 만족하고Cs (solute carbon): Meets 5-30

[여기서, S*=S-0.8x(Ti-0.8x(48/14)xN)x(32/48), [Where S * = S-0.8x (Ti-0.8x (48/14) xN) x (32/48),

N* =N-0.8x(Ti-0.8x(48/32)xS))x(14/48) , Cs=(C-Nbx12/93-Ti*x12/48)x10000, N * = N-0.8x (Ti-0.8x (48/32) xS)) x (14/48), Cs = (C-Nbx12 / 93-Ti * x12 / 48) x10000,

Ti*=Ti-0.8x((48/14)xN+(48/32)xS) 단, Ti*<0일 경우 Ti*=0으로 함] Ti * = Ti-0.8x (( 48/14) xN + (48/32) xS) If stage, Ti * <0 il referred to as Ti * = 0]

(Mn,Cu)S석출물과 AlN석출물의 평균크기가 0.2㎛이하로 이루어진다.The average size of the (Mn, Cu) S precipitates and AlN precipitates is less than 0.2 µm.

본 발명에서 Al:0.1%이하의 조건에서, N:0.004%초과-0.02%이하, 바람직하게는 N:0.0041-0.02%, 보다 바람직하게는 N:0.005-0.02%의 조건에서 Al과 N이 (Al/27)/( N*/14):1-10의 조건을 만족하도록 하여 평균 크기 0.2㎛이하의 AlN의 석출물이 분포하도록 한다. In the present invention, Al and N are less than N: 0.004% and less than -0.02%, preferably N: 0.0041-0.02%, more preferably N: 0.005-0.02%, under Al: 0.1% or less. Al / 27) / (N * / 14): 1-10 is satisfied so that precipitates of AlN having an average size of 0.2 μm or less are distributed.

본 발명에서 석출물은 1X106개/mm2 이상, 보다 바람직하게는 1X107개/mm2 이상이 바람직하다. In the present invention, the precipitate is preferably 1 × 10 6 / mm 2 or more, more preferably 1 × 10 7 / mm 2 or more.

본 발명의 냉연강판은 성분설계에 따라 280MPa급의 연질냉연강판과 340MPa이상의 고강도 냉연강판의 특성을 갖는다. The cold rolled steel sheet of the present invention has the characteristics of a soft cold rolled steel sheet of 280MPa grade and high strength cold rolled steel sheet of 340MPa or more according to the component design.

상기한 성분계에서 P의 함량은 0.015%이하로 하면 280MPa급의 연질냉연강판이 얻어 진다. 이 냉연강판에다 고용강화원소인 Si, Cr의 1종 또는 2종이 추가로 함유되거나 P의 함량이 0.015~0.2%로 하면 340MPa이상의 고강도 특성이 확보된다. P가 단독으로 함유되는 고강도 강의 경우에는 P의 함량은 0.03~0.2%가 바람직하다. Si의 경우에는 0.1-0.8%, Cr의 경우에는 0.2-1.2%가 바람직하다. Si과 Cr의 1종이상 함유되는 경우에 P의 함량은 0.2%이하의 범위에서 다양하게 설계될 수 있다. If the content of P in the above component system is 0.015% or less, a 280 MPa grade soft cold rolled steel sheet is obtained. The cold rolled steel sheet further contains one or two of the solid solution strengthening elements Si and Cr, or when the P content is 0.015 to 0.2%, high strength characteristics of 340 MPa or more are secured. In the case of high strength steel containing P alone, the content of P is preferably 0.03 to 0.2%. 0.1-0.8% for Si and 0.2-1.2% for Cr are preferred. In the case of containing at least one of Si and Cr, the content of P may be variously designed in the range of 0.2% or less.

본 발명의 냉연강판에서 가공성을 보다 개선하고자 한다면 Mo을 0.01~0.2%추가로 포함할 수 있다. If you want to improve the workability in the cold rolled steel sheet of the present invention may further comprise Mo 0.01 ~ 0.2%.

상기한 냉연강판의 제조방법은, 본 발명의 성분계를 만족하는 슬라브를 1100℃이상의 온도로 재가열한 후 마무리 압연온도를 Ar3변태점 이상으로 하여 열간압연하고 300℃/min이상의 속도로 냉각하고 700℃이하의 온도에서 권취한 다음, 냉간 압연하고, 연속소둔하는 것이다. In the method for producing a cold rolled steel sheet, the slab that satisfies the component system of the present invention is reheated to a temperature of 1100 ° C. or higher, and then hot-rolled at a finish rolling temperature of Ar 3 or higher and cooled at a speed of 300 ° C./min or higher, and 700 ° C. After winding up at the following temperature, it cold-rolls and continuously anneales.

이하, 본 발명을 상세히 설명한다. Hereinafter, the present invention will be described in detail.

본 발명에서 (Mn,Cu)S석출물은 MnS석출물, CuS석출물 또는 Mn과 Cu의 복합 석출물을 포함하는 표현이다. In the present invention, (Mn, Cu) S precipitate is an expression including MnS precipitate, CuS precipitate or a composite precipitate of Mn and Cu.

본 발명은 소부경화형 IF강에 미세한 (Mn,Cu)S석출물과 AlN석출물이 확보되면 결정 립이 미세하게 되어 항복강도가 증진되고 면내이방성지수가 낮아져 가공성이 개선된다는 연구결과에 기초하여 완성된 것이다.The present invention is completed based on the results of the study that when the (Mn, Cu) S precipitate and AlN precipitate are secured in the small hardening type IF steel, the grains become fine and the yield strength is enhanced and the in-plane anisotropy index is lowered to improve the workability. .

IF강에서 Cu는 내식성 향상원소로 주로 이용되고 있으며, 실제 그 첨가량은 0.2%이상이다. 또는, Cu를 ε-Cu의 석출상으로 이용하는 기술은 알려져 있다. Cu is mainly used as an element to improve corrosion resistance in IF steel, and the amount of addition is actually 0.2% or more. Or the technique which uses Cu as a precipitated phase of (epsilon) -Cu is known.

그러나, IF강에서 미세한 CuS석출물과 함께 MnS석출물을 확보하여 결정립 미세화를 도모하는 기술은 알려져 있지 않다. 또한, N은 불순물로서 Ti나 Al에 의해 TiN, AlN으로 고정하는 관점에서 관리하고 있다. 이는 N을 최대한 낮추려고 노력하거나 또는 N을 석출하여 고정하나 이는 조대한 석출물로 분포하게 되는 것이다. 이러한 기술들은 미세한 AlN석출물이 다량 분포할 때 강에 긍정적인 영향에 대한 인식이 부족한 것이다. However, there is no known technique for achieving grain refinement by securing MnS precipitates together with fine CuS precipitates in the IF steel. In addition, N is managed from the viewpoint of fixing TiN and AlN by Ti or Al as impurities. Either try to lower N as much as possible, or settle and fix N, but it will be distributed as a coarse precipitate. These techniques lack awareness of the positive effects on the steel when large amounts of fine AlN precipitates are distributed.

Ti와 Nb의 복합계 IF강에서 (Mn,Cu)S석출물과 AlN석출물을 확보하기 위해서는 (Mn,Cu)S로 석출되는 S와 AlN으로 석출되는 N를 확보하여야 한다. IF강에서 Ti는 C, N, S와 반응하여 TiC, TiN, Ti(C,N), Ti4C2S2 등으로 석출되므로, S가 (Mn,Cu)S로, N은 AlN으로 석출될 수 있도록 제반성분의 관리가 요구된다. In order to secure (Mn, Cu) S and AlN precipitates in the composite IF steel of Ti and Nb, S and N precipitated as (Mn, Cu) S must be secured. In the IF steel, Ti reacts with C, N, and S to precipitate TiC, TiN, Ti (C, N), Ti 4 C 2 S 2, etc., so that S is (Mn, Cu) S and N is AlN. Management of all ingredients is required to be possible.

(Mn,Cu)S석출물과 AlN석출물은 결정립을 미세하게 한다. 결정립이 미세하게 되면, Ti에 의해 석출하지 않은 고용탄소는 결정립내 보다 결정립계에 더 많이 존재하게 된다. 이에 따라, 상온 비시효특성이 확보되면서 소부경화특성을 개선하게 되는 것이다. 결정립내에 잔존하는 고용탄소는 이동이 비교적 자유롭기 때문에 가동전위와 결합하여 상온시효특성에 영향을 미치게 된다. 이에 반해, 결정립계나 석출물의 주변과 같이 보다 안정된 위치에 편석하는 고용탄소는 도장소부처리와 같은 고온에서 활성화되어 소부경화특성에 영향을 주게 된다. 이와 같이, 결정립내의 고용탄소량이 줄어든다는 것은 보다 안정된 위치 즉, 결정립계나 미세한 석출물들의 주변에서 탄소가 존재하여 소부경화특성에 영향을 미친다는 것이다.(Mn, Cu) S precipitates and AlN precipitates are fine grains. When the grains become fine, more dissolved carbon not precipitated by Ti is present in the grain boundaries than in the grains. Accordingly, while the room temperature non-aging characteristics are secured, the baking hardening characteristics are improved. The dissolved carbon remaining in the grains is relatively free to move, which affects the aging characteristics in combination with the operating potential. On the other hand, solid solution carbon segregating at a more stable position, such as grain boundaries or precipitates, is activated at high temperatures such as coating baking treatment, thereby affecting the baking hardening characteristics. As such, the decrease in the amount of solid solution carbon in the grains means that carbon exists in a more stable position, that is, around grain boundaries or fine precipitates, thereby affecting the hardening characteristic.

본 발명에 따라 미세하게 분포하는 (Mn,Cu)S석출물과 AlN석출물들은 석출강화에 의한 항복강도의 상승과 강도-연성 밸런스 특성의 개선 그리고, 면내이방성 지수에도 긍정적인 영향을 미친다. 이를 위해서는 (Mn,Cu)S석출물과 AlN석출물이 미세하게 분포하여야 하면, 이는 Cu, Mn, Ti, C, N, S, Al 의 함량 및 이들의 성분비 조건 그리고, 제조조건 특히, 열간압연이 끝난 후 냉각속도가 영향을 미친다. The finely distributed (Mn, Cu) S precipitates and AlN precipitates according to the present invention have a positive effect on the increase in yield strength and the strength-ductility balance characteristics and the in-plane anisotropy index. For this purpose, (Mn, Cu) S precipitates and AlN precipitates should be finely distributed, which means that the content of Cu, Mn, Ti, C, N, S, Al and their component ratio conditions, and manufacturing conditions, in particular, hot rolling The cooling rate then affects.

먼저, 기본성분이 되는 C, Cu, Mn, S, Al, P, N, B, Ti에 대해 설명한다. First, C, Cu, Mn, S, Al, P, N, B, Ti serving as basic components will be described.

탄소(C)의 함량은 0.001-0.01%가 바람직하다.The content of carbon (C) is preferably 0.001-0.01%.

탄소(C)의 함량이 0.001%미만일 경우 소부경화량이 적고, 0.01%초과의 경우에는 성형성이 저하된다. 탄소의 함량이 높아질수록 소부경화량은 커진다. 이를 고려할 때 보다 바람직하게는 탄소(C)함량은 0.003-0.01%, 또는 0.005-0.01%로 하는 것이다. If the content of carbon (C) is less than 0.001%, the amount of hardening of baking is small, and if it is more than 0.01%, moldability is lowered. The higher the carbon content, the larger the hardened portion. Considering this, the carbon (C) content is more preferably 0.003-0.01%, or 0.005-0.01%.

구리(Cu)의 함량은 0.01~0.2%가 바람직하다.The content of copper (Cu) is preferably 0.01 to 0.2%.

Cu는 미세한 CuS석출물을 형성하여 결정립을 미세하게 하여 면내이방성 지수를 낮추고 석출강화에 의해 항복강도를 증진시킨다. 이를 위해서는 Cu의 함량이 0.01%이상 되어야 미세하게 석출할 수 있고 0.2%초과하면 조대하게 석출한다. 바람직한 Cu의 함량은 0.03-0.2%로 하는 것이다. Cu forms fine CuS precipitates to finer grains, lowering the in-plane anisotropy index and enhancing yield strength by precipitation strengthening. For this purpose, the Cu content must be more than 0.01% to precipitate finely, and when it exceeds 0.2%, it is coarsened. Preferable Cu content is 0.03-0.2%.

망간(Mn)의 함량은 0.01-0.3%가 바람직하다. The content of manganese (Mn) is preferably 0.01-0.3%.

망간은 강중 고용상태의 황을 MnS로 석출하여 고용 황에 의한 적열취성(Hot shortness)을 방지하거나 고용강화원소로 알려져 있다. 이러한 기술적 관점에서는 망간의 함량을 높게 첨가하는 것이 일반적이다. 그러나, 본 발명에서는 망간의 함량을 낮추면서 황의 함량을 적절해지는 경우에 MnS가 매우 미세하게 석출되어 결정립 미세화에 의해 소성이방성, 면내이방성의 특성을 개선하고 석출강화에 의해 항복강도의 특성을 개선한다는 연구결과에 기초하여 망간의 함량을 0.3%이하로 한다. 이러한 특성을 확보하기 위해서는 망간의 함량이 0.01%이상이 되어야 하는데, 그 함량이 0.01%미만의 경우에는 고용 상태로 잔존하는 황의 함량이 많기 때문에 적열취성이 발생할 수 있으며, 망간의 함량이 0.3% 초과의 경우에는 망간의 함량이 높아 조대한 MnS석출물이 생성되어 강도확보가 곤란해 진다. Manganese is known as MnS to prevent hot shortness caused by solid sulfur by precipitating sulfur in solid state in steel. From this technical point of view, it is common to add a high content of manganese. However, in the present invention, when the sulfur content is appropriate while lowering the content of manganese, MnS precipitates very finely, thereby improving the properties of plastic anisotropy and in-plane anisotropy by grain refinement and improving the yield strength by precipitation strengthening. Based on the results of the study, the content of manganese should be less than 0.3%. In order to secure these characteristics, the content of manganese should be 0.01% or more. If the content is less than 0.01%, red brittleness may occur due to the large amount of sulfur remaining in the solid state, and the content of manganese exceeds 0.3%. In the case of, the content of manganese is high and coarse MnS precipitates are formed, making it difficult to secure strength.

황(S)의 함량은 0.005-0.08%가 바람직하다.The content of sulfur (S) is preferably 0.005-0.08%.

황(S)은 Cu와 반응하여 미세한 (Mn,Cu)S의 석출물을 형성한다. 이러한 S의 함량이 0.005%미만의 경우에는 상기한 석출물의 석출량이 적을 뿐만 아니라 석출되는 석출물의 숫자가 매우 적다. 황의 함량이 0.08% 초과의 경우에는 고용된 황의 함량이 많아 연성 및 성형성이 크게 낮아지며, 적열취성의 우려가 있기 때문이다. Sulfur (S) reacts with Cu to form fine (Mn, Cu) S precipitates. When the content of S is less than 0.005%, not only the amount of precipitates precipitated is small but also the number of precipitates precipitated is very small. If the content of sulfur is more than 0.08%, the content of the solid solution of sulfur is so high that the ductility and formability is greatly lowered, there is a fear of red brittleness.

알루미늄(Al)의 함량은 0.1%이하가 바람직하다.The content of aluminum (Al) is preferably 0.1% or less.

Al은 N과 미세한 AlN석출물을 형성하여 결정립미세화와 더불어 석출강화에 의해 항복강도를 증진시킨다. 이를 위해 0.1%까지 첨가한다. Al의 함량이 0.1%초과되는 경우에는 고용상태의 Al의 함량이 많아 연성이 저하될 우려가 있다. Al forms fine AlN precipitates with N to enhance yield strength by grain refinement and precipitation strengthening. To this end, add up to 0.1%. When the Al content is more than 0.1%, there is a fear that the ductility decreases because the Al content is high in solid solution.

질소(N)의 함량은 0.004%초과-0.02%이하가 바람직하다. 보다 바람직하게는 0.005-0.02%로 하는 것이다. The content of nitrogen (N) is preferably more than 0.004% -0.02% or less. More preferably, it is 0.005-0.02%.

N함량이 0.004%미만의 경우에는 석출되는 AlN의 숫자가 적어 결정립미세화 및 석출강화의 효과가 적으며, 0.02%를 초과할 경우는 고용질소에 의한 시효보증이 곤란하므로 0.02%이하로 하는 것이 바람직하다. If the content of N is less than 0.004%, the number of precipitated AlN is small, so the effect of grain refinement and strengthening of precipitation is small. If it exceeds 0.02%, it is difficult to guarantee the aging by solid nitrogen, so it should be less than 0.02%. Do.

인(P)의 함량은 0.2%이하가 바람직하다. The content of phosphorus (P) is preferably 0.2% or less.

인은 고용강화효과가 높으면서 r값의 저하가 적은 원소로서 본 발명에 따라 석출물을 제어하는 강에서 고강도를 보증한다. 280Mpa급의 강도가 요구되는 강종에서 P의 함량은 0.015%이하로 하는 것이 좋다. 340Mpa급 이상의 고강도 강에서는 0.016~0.2%로 하는 것이 좋다. 이러한 P의 함량이 0.2% 초과의 경우에는 연성이 저 하하여 상한 값을 0.2%로 제한하는 것이 바람직하다. 본 발명에서 Si, Cr이 첨가되는 경우에는 P의 함량을 0.2%이하의 범위로 하면서 다양한 강도의 설계가 가능하다. Phosphorus is an element having a high solid solution strengthening effect and a small decrease in r value, and guarantees high strength in steels for controlling precipitates according to the present invention. In steel grades requiring strength of 280 Mpa, the content of P should be less than 0.015%. For high strength steel of 340Mpa or higher, it is recommended to set it as 0.016 ~ 0.2%. If the content of P is more than 0.2%, it is preferable that the ductility is lowered so as to limit the upper limit to 0.2%. When Si and Cr are added in the present invention, the P content can be designed in various strengths while keeping the content of P or less within 0.2%.

보론(B)의 함량은 0.0001~0.002%가 바람직하다.The content of boron (B) is preferably 0.0001 to 0.002%.

보론은 2차가공취성을 방지하기 위해 첨가하는데 이를 위해 보론의 함량이 0.0001%이상인 것이 바람직하다. 보론의 함량이 0.002%를 초과하면 오무림 가공성(deep drawing)이 크게 저하될 수 있다. Boron is added to prevent secondary processing brittleness. For this purpose, the boron content is preferably 0.0001% or more. If the boron content exceeds 0.002%, deep drawing may be greatly degraded.

티타늄(Ti)의 함량은 0.005~0.15%로 하는 것이다. The content of titanium (Ti) is to be 0.005 ~ 0.15%.

티타늄은 비시효성 확보 및 성형성 향상을 목적으로 첨가하는데 티타늄은 강력한 탄화물 생성 원소로 강중에 첨가되어 TiC석출물을 석출시켜 고용 상태의 탄소를 석출하므로써 비시효성을 확보한다. 티타늄의 첨가량이 0.005%미만의 경우 TiC석출물의 석출량이 너무 적어 집합조직의 발달이 적어 오무림 가공성을 개선하는 효과가 거의 없다. Ti가 0.15%초과할 경우 TiC석출물의 크기 너무 커 결정립미세화 효가가 감소되어 면내이방성지수가 높아지며 항복강도도 저하하고 도금특성이 크게 저하한다. Titanium is added for the purpose of securing inaging and improving moldability. Titanium is a strong carbide-generating element and is added to steel to precipitate TiC precipitates to precipitate insoluble solids. If the addition amount of titanium is less than 0.005%, the precipitation amount of TiC precipitate is too small, and there is little effect of improving the processability of the soil because of less development of the texture. If Ti exceeds 0.15%, the TiC precipitates are too large to reduce the grain refining efficiency, resulting in an increase in in-plane anisotropy, lowering the yield strength and greatly degrading the plating properties.

니오븀(Nb)의 함량은 0.002~0.04%가 바람직하다.The content of niobium (Nb) is preferably 0.002 to 0.04%.

Nb은 비시효성 확보 및 성형성 향상을 목적으로 첨가한다. Nb은 강력한 탄화물 생 성 원소로 강중에 첨가되어 NbC석출물을 석출시킨다. 또한 NbC석출물은 소둔중 집합조직을 발달하여 오무림 가공성을 크게 향상하는 효과가 있다. Nb의 첨가량이 0.002%이하의 경우 NbC석출물의 석출량이 너무 적어 집합조직의 발달이 적어 오무림 가공성을 개선하는 효과가 거의 없다. Nb가 0.04%초과할 경우 NbC석출물의 양이 너무 많아 오무림가공성 및 연신율이 낮아져 성형성이 크게 저하할 수 있다.Nb is added for the purpose of ensuring inaging and improving moldability. Nb is a strong carbide-forming element that is added to steel to precipitate NbC precipitates. In addition, NbC precipitates have an effect of greatly improving the processing ability of the soil by developing the aggregated structure during annealing. If the amount of Nb added is less than 0.002%, the amount of precipitation of NbC precipitates is so small that there is little development of aggregates, and thus there is little effect of improving Omrim processability. When Nb exceeds 0.04%, the amount of NbC precipitates is too high, resulting in low rimability and low elongation, which may significantly reduce moldability.

본 발명에서는 냉연강판에 미세한 (Mn,Cu)S석출물과 AlN석출물을 확보하면서 적량의 고용탄소를 확보하기 위한 관점에서 Ti, Nb, S, C, N, Cu, Mn, Al의 성분비를 제어하는데 특징이 있다. IF강에서 Ti은 TiC, TiN, TiS, Ti(C,N), Ti4C2S2등의 석출물을 석출하는 것으로 알려져 있고, 이러한 석출물을 활용하기 위하여 Ti, S, C, N의 성분관계를 제어하고 있다. 그러나 본 발명에서는 (Mn,Cu)S석출물과 AlN석출물을 확보하면서 적량의 고용탄소를 확보하기 위하여, Ti, Nb, S, C, N, Cu, Mn, Al의 관계를 관리한다.In the present invention, to control the component ratios of Ti, Nb, S, C, N, Cu, Mn, Al from the viewpoint of securing an appropriate amount of solid carbon while securing fine (Mn, Cu) S precipitates and AlN precipitates in the cold rolled steel sheet There is a characteristic. In IF steel, Ti is known to precipitate precipitates such as TiC, TiN, TiS, Ti (C, N), Ti 4 C 2 S 2, and the composition of Ti, S, C, and N in order to utilize these precipitates. Is controlling. However, in the present invention, the relationship between Ti, Nb, S, C, N, Cu, Mn, and Al is managed in order to secure an appropriate amount of dissolved carbon while securing (Mn, Cu) S precipitates and AlN precipitates.

[관계식 1][Relationship 1]

Mn+Cu:0.05-0.4%Mn + Cu: 0.05-0.4%

[관계식 2][Relationship 2]

(Mn/55+Cu/63.5)/( S*/32):1-30, (Mn / 55 + Cu / 63.5) / (S * / 32): 1-30,

여기서, S*=S-0.8x(Ti-0.8x(48/14)xN)x(32/48)임Where S * = S-0.8x (Ti-0.8x (48/14) xN) x (32/48)

[관계식 3][Relationship 3]

(Al/27)/( N*/14):1-10, (Al / 27) / (N * / 14): 1-10,

여기서, N* =N-0.8x(Ti-0.8x(48/32)xS))x(14/48)Where N * = N-0.8x (Ti-0.8x (48/32) xS)) x (14/48)

[관계식 4][Relationship 4]

Cs(solute carbon):5-30Cs (solute carbon): 5-30

여기서, Cs=(C-Nbx12/93-Ti*x12/48)x10000, Where Cs = (C-Nbx12 / 93-Ti * x12 / 48) x10000,

Ti*=Ti-0.8x((48/14)xN+(48/32)xS)임Ti * = Ti-0.8x ((48/14) xN + (48/32) xS)

Ti*가 음의 값일 경우는 0으로 한다.If Ti * is negative, set it to 0.

상기 관계식에서 Cu, Mn, S, Ti, Nb, C, N, Al은 중량%이다. In the above relation Cu, Mn, S, Ti, Nb, C, N, Al is the weight percent.

관계식 1과 2는 미세한 (Mn,Cu)S의 석출물을 얻기 위한 것이다. Equations 1 and 2 are for obtaining a fine (Mn, Cu) S precipitate.

미세한 (Mn,Cu)S의 석출물을 충분히 얻기 위해서는 Mn과 Cu의 총합이 0.05%이상이어야 하며, 0.4% 초과의 경우에는 (Mn,Cu)S의 석출물이 조대해진다. In order to sufficiently obtain fine precipitates of (Mn, Cu) S, the sum of Mn and Cu should be 0.05% or more, and if more than 0.4%, precipitates of (Mn, Cu) S are coarse.

관계식 2에서 S*은 총S의 함량에서 Mn과 Cu와 반응하는 S의 함량을 나타내는 것으로, 미세한 (Mn,Cu)S석출물을 확보하도록 하기 위해서 관계식 2의 값이 1-30을 만족하는 것이 바람직하다. 관계식 2의 값이 1이상이 되어야 유효한 (Mn,Cu)S석출물이 석출하게 되며, 30초과의 경우에는 (Mn,Cu)S석출물이 조대하여 가공성과 항복강도의 특성이 좋지 않다. In relation 2, S * represents the amount of S reacting with Mn and Cu in the total S content. In order to secure fine (Mn, Cu) S precipitates, the value of relation 2 satisfies 1-30. Do. When the value of relation 2 is greater than or equal to 1, effective (Mn, Cu) S precipitates are precipitated, and in the case of more than 30, (Mn, Cu) S precipitates are coarse, resulting in poor workability and yield strength.

관계식 3에서 N*은 총N의 함량에서 Ti와 반응하지 않는 N의 함량을 나타내는 것으로, 미세한 AlN석출물을 확보하도록 하기 위해서 관계식 3의 값이 1-10을 만족하는 것이 바람직하다. 관계식 3의 값이 1이상이 되어야 유효한 AlN석출물이 석출하게 되며, 10초과의 경우에는 AlN석출물이 조대하여 가공성과 항복강도의 특성이 좋지 않다. 보다 바람직하게는 관계식 2의 값이 1-7를 만족하는 것이다. In relation 3, N * represents the content of N that does not react with Ti in the total content of N. In order to secure fine AlN precipitates, the value of relation 3 preferably satisfies 1-10. When the value of relation 3 is greater than or equal to 1, effective AlN precipitates are precipitated, and in the case of more than 10, AlN precipitates are coarse, resulting in poor workability and yield strength. More preferably, the value of relation 2 satisfies 1-7.

관계식 4에서 Ti*은 총Ti의 함량에서 N, S와 반응하고 남은 Ti의 함량을 나타내는 것으로, Ti*가 음의값일경우는 0으로 하는데 이는 Ti*가 음의 값이 되는 경우는 고용 N과 S를 석출하기에도 Ti가 모자라는 것을 의미하는 것으로 고용 C가 새로 생성되는 것은 아니므로 그 값을 0으로 하는 것이 당연하다. 상기 Cs는 TiC와 NbC로 석출되지 않은 고용탄소의 함량을 나타내는 것이다. 즉, Cs(solute carbon)가 5-30을 만족하여야 한다. 관계식 4에서 계산되는 Cs 즉, 고용탄소의 함량 단위는 ppm이 된다.In equation 4 Ti * is in the content of total Ti represents the content of N, S and the reaction and the rest of Ti, Ti * is the case if a value of the negative, which for a 0 Ti * is the value of the negative solute N and It means that Ti is not enough even to precipitate S, and it is natural to set the value to 0 since no new employment C is created. The Cs represents the content of solid solution carbon not precipitated with TiC and NbC. That is, Cs (solute carbon) should satisfy 5-30. The unit of content of Cs, ie, the solid solution carbon, calculated in Equation 4 is ppm.

Cs값이 5ppm이상 되어야 소부경화량을 확보할 수 있으며, 30ppm을 초과할 경우에는 고용탄소의 함량이 높아서 비시효성을 확보하기 어렵다. If the Cs value is 5ppm or more, it is possible to secure the hardening of the baking. If it exceeds 30ppm, it is difficult to secure the non-aging due to the high content of solid solution carbon.

본 발명의 성분계에서 석출물은 미세하게 분포할수록 유리한데, 바람직하게는 (Mn,Cu)S석출물과 AlN석출물의 평균크기가 0.2㎛이하이다. 본 발명의 연구결과에 따르면 석출물의 평균크기가 0.2㎛ 초과의 경우에는 특히 강도가 낮아지고, 면내이 방성지수가 좋지 않다. In the component system of the present invention, the finer the distribution, the more advantageous. Preferably, the average size of (Mn, Cu) S precipitates and AlN precipitates is 0.2 µm or less. According to the results of the present invention, especially when the average size of the precipitate is more than 0.2㎛, the strength is low, the in-plane isotropic index is not good.

나아가, 본 발명의 성분계에는 0.2㎛이하의 석출물이 다량 분포하는데, 그 분포수는 특별히 제한하지는 않는다. 석출물의 분포수가 많아질수록 좋은데, 바람직하게는 석출물의 분포수가 mm2당 1X106개 이상, 보다 바람직하게는 1X107개/mm2 이상이다. 석출물의 분포수가 많아지면 소성이방성지수가 더욱 높아지고 면내이방성지수는 낮아져 가공성이 크게 개선된다. 일반적으로 소성이방성지수가 높아지면 면내이방성지수는 올라가서 가공성 측면에서 소성이방성지수를 높이는데 한계가 있다는 점을 감안할 때, 석출물의 분포수에 따라 소성이방성지수와 면내이방성지수의 특이한 변화는 주목할 만 하다. Furthermore, although the precipitate of 0.2 micrometer or less is distributed in a large amount in the component system of this invention, the distribution number is not specifically limited. The larger the number of distribution of precipitates, the better. Preferably, the number of distribution of precipitates is at least 1 × 10 6 per mm 2 , more preferably at least 1 × 10 7 / mm 2 . The larger the distribution of precipitates, the higher the plastic anisotropy index and the lower in-plane anisotropy index are. In general, when the plastic anisotropy index increases, the in-plane anisotropy index rises and there is a limit to increasing the plastic anisotropy index in terms of processability. .

본 발명에서는 340MPa급 이상의 고강도 강판으로 적용하는 경우에는 상기 P와 같은 고용강화원소 즉, P, Si, Cr의 1종 또는 2종이상을 첨가할 수 있다. P에 대해서는 상술한 바, 중복기재는 생략한다. In the present invention, when applied to a high-strength steel sheet of 340 MPa grade or more, one or two or more solid solution strengthening elements such as P, that is, P, Si, and Cr may be added. As described above with respect to P, redundant descriptions are omitted.

실리콘(Si)의 함량은 0.1-0.8%가 바람직하다.The content of silicon (Si) is preferably 0.1-0.8%.

Si은 고용강화효과가 높으면서 연신율의 저하가 낮은 원소로 본 발명에 따라 석출물을 제어하는 강에서 고강도를 보증한다. Si의 함량이 0.1%이상 되어야 강도를 확보할 수 있으며, 0.8%초과의 경우에는 연성이 저하한다. Si is an element having a high solid solution strengthening effect and a low drop in elongation, which ensures high strength in steels for controlling precipitates according to the present invention. When the content of Si is more than 0.1% to secure the strength, in the case of more than 0.8% ductility is reduced.

크롬(Cr)의 함량은 0.2~1.2%가 바람직하다.The content of chromium (Cr) is preferably 0.2 to 1.2%.

Cr은 고용강화효과가 높으면서 2차가공취성온도를 낮추며 Cr탄화물에 의해 시효지수를 낮추는 원소로서, 본 발명에 따라 석출물을 제어하는 강에서 고강도를 보증하며 면내이방성 지수도 낮게 한다. Cr의 함량이 0.2%이상 되어야 강도를 확보할 수 있으며, 1.2% 초과의 경우에는 연성이 저하한다.Cr is an element that lowers the secondary brittleness temperature and decreases the aging index by Cr carbide while having a high solid-solution strengthening effect, and assures high strength in steels for controlling precipitates according to the present invention and also lowers in-plane anisotropy index. The Cr content is more than 0.2% to secure the strength, in the case of more than 1.2% ductility is reduced.

본 발명의 냉연강판에서 몰리브덴(Mo)이 추가로 첨가될 수 있다. In the cold rolled steel sheet of the present invention, molybdenum (Mo) may be further added.

몰리브덴(Mo)의 함량은 0.01~0.2%가 바람직하다.The content of molybdenum (Mo) is preferably 0.01 to 0.2%.

Mo은 소성이방성지수를 높이는 원소로서 첨가되는데, 그 함량이 0.01%이상 되어야 소성이방성지수가 커지며, 0.2%를 초과하면 소성이방성지수는 더 이상 커지지 않고 열간취성을 일으킬 우려가 있다. Mo is added as an element to increase the plastic anisotropy index, the content of the plastic anisotropy index is increased when the content is more than 0.01%, if the content exceeds 0.2%, the plastic anisotropy index is no longer increased and there is a risk of causing hot brittleness.

[냉연강판의 제조방법][Manufacturing method of cold rolled steel sheet]

본 발명은 상기한 강조성을 만족하는 강을 열간압연과 냉간압연을 통해 냉간압연판에 (Mn,Cu)S석출물과 AlN석출물의 평균크기가 0.2㎛ 이하를 만족하도록 하는데 특징이 있다. 냉간압연판에서 (Mn,Cu)S석출물과 AlN석출물의 평균 크기는 성분설계와 함께 재가열온도, 권취온도 등의 제조공정에 영향을 받으나 특히 열간압연후의 냉각속도에 직접적인 영향을 받는다. The present invention is characterized by satisfying the average size of (Mn, Cu) S precipitates and AlN precipitates in a cold rolled sheet through hot rolling and cold rolling. The average size of (Mn, Cu) S precipitates and AlN precipitates in the cold rolled plate is influenced by the design process such as reheating temperature and winding temperature together with the component design, but especially by the cooling rate after hot rolling.

[열간압연조건][Hot Rolling Condition]

본 발명에서는 상기한 강조성을 만족하는 강을 재가열하여 열간압연한다. 재가열온 도는 1100℃이상이 바람직하다. 재가열온도가 1100℃미만의 경우에는 재가열온도가 낮아 연속주조중에 생성된 조대한 석출물들이 완전히 용해되지 않은 상태로 남아 있어 열간압연후에도 조대한 석출물이 많이 남아있기 때문이다.In the present invention, the steel that satisfies the above-mentioned emphasis is reheated and hot rolled. Reheating temperature is preferably 1100 ℃ or more. This is because when the reheating temperature is lower than 1100 ° C., the coarse precipitates generated during continuous casting remain completely insoluble due to the low reheating temperature, so that many coarse precipitates remain even after hot rolling.

열간압연은 마무리압연온도를 Ar3변태온도 이상의 조건에서 행하는 것이 바람직하다. 마무리압연온도가 Ar3변태온도 미만의 경우에는 압연립의 생성으로 가공성이 저하할 뿐만아니라 강도도 낮아지기 때문이다. Hot rolling is preferably carried out under the conditions of the finish rolling temperature higher than the Ar 3 transformation temperature. This is because when the finish rolling temperature is lower than the Ar 3 transformation temperature, not only the workability is reduced by the formation of the rolled grain but also the strength is lowered.

열간압연후 권취전 냉각속도는 300℃/min 이상으로 하는 것이 바람직하다. 본 발명에 따라 미세한 석출물을 얻기 위하여 그 성분비를 제어하더라도 냉각속도가 300℃/min 미만이면 석출물의 평균크기가 0.2㎛를 초과할 수 있다. 즉, 냉각속도가 빨라질수록 많은 수의 핵이 생성하여 석출물이 미세해지기 때문이다. 냉각속도가 빨라질수록 석출물의 크기가 미세해지므로 냉각속도의 상한을 제한할 필요는 없으나, 냉각속도가 1000℃/min 보다 빨라지더라도 석출물 미세화 효과가 더 이상 커지지 않으므로 냉각속도는 300~1000℃/min이 보다 바람직하다. It is preferable that the cooling rate before winding after hot rolling shall be 300 degreeC / min or more. Even if the component ratio is controlled to obtain a fine precipitate according to the present invention, if the cooling rate is less than 300 ° C / min, the average size of the precipitate may exceed 0.2 ㎛. In other words, as the cooling rate increases, a large number of nuclei are generated and the precipitate becomes fine. The faster the cooling rate, the finer the precipitate is, so it is not necessary to limit the upper limit of the cooling rate.However, even if the cooling rate is faster than 1000 ° C / min, the finer effect of the precipitate is no longer increased, so the cooling rate is 300 to 1000 ° C / min. This is more preferable.

[권취조건][Coiling condition]

상기와 같이 열간압연한 다음에는 권취를 행하는데, 권취온도는 700℃이하가 바람직하다. 권취온도가 700℃초과의 경우에는 석출물이 너무 조대하게 성장하여 강도 확보가 곤란하다.Winding is performed after hot rolling as above, but the winding temperature is preferably 700 ° C or lower. If the coiling temperature exceeds 700 ℃, precipitates grow too coarse to secure strength.

[냉간압연조건][Cold rolling condition]

냉간압연은 50~90%의 압하율로 행하는 것이 바람직하다. 냉간압하율이 50%미만의 경우에는 소둔재결정 핵생성양이 적기 때문에 소둔시 결정립이 너무 크게 성장하여 소둔 재결정립의 조대화로 강도 및 성형성이 저하한다. 냉간압하율이 90%초과의 경우에는 성형성은 향상되지만 핵생성 양이 너무 많아 소둔 재결정립은 오히려 너무 미세하여 연성이 저하한다. Cold rolling is preferably performed at a reduction ratio of 50 to 90%. If the cold reduction rate is less than 50%, the amount of nucleation of the annealing recrystallization is small, so that grains grow too large during annealing, resulting in a decrease in strength and formability due to coarsening of the annealing recrystallization grains. If the cold reduction ratio is more than 90%, the moldability is improved, but the nucleation amount is too high, so the annealing recrystallized grain is too fine to decrease the ductility.

[연속소둔][Continuous Annealing]

연속소둔 온도는 제품의 재질을 결정하는 중요한 역할을 한다. 본 발명에서는 700~900℃의 온도범위에서 행하는 것이 바람직하다. 연속소둔 온도가 700℃미만의 경우에는 재결정이 완료되지 않아 목표로 하는 연성 값을 확보할 수 없으며, 소둔온도가 900℃초과의 경우에는 재결정립의 조대화로 강도가 저하된다. 연속소둔시간은 재결정이 완료되도록 유지하는데, 약 10초이상이면 재결정이 완료된다. 바람직하게는 연속소둔시간을 10초~30분의 범위내로 하는 것이다,Continuous annealing temperature plays an important role in determining the material of the product. In this invention, it is preferable to carry out in the temperature range of 700-900 degreeC. If the continuous annealing temperature is less than 700 ° C., recrystallization is not completed and the target ductility value cannot be secured. If the annealing temperature is more than 900 ° C., the strength decreases due to coarsening of the recrystallized grains. The continuous annealing time keeps the recrystallization complete. If it is about 10 seconds or more, the recrystallization is completed. Preferably the continuous annealing time is in the range of 10 seconds to 30 minutes,

이하, 본 발명을 실시예를 통하여 보다 구체적으로 설명한다.Hereinafter, the present invention will be described in more detail with reference to Examples.

[실시예 1]Example 1

표 1의 강슬라브를 재가열하여 마무리열간압연하고 400℃/min 의 속도로 냉각하여 650℃에서 권취한 다음, 75%의 압하율로 냉간압연과 연속소둔처리하였다. 이때의 마무리압연온도는 Ar3변태점이상인 910℃이며, 연속소둔은 10℃/초의 속도로 830℃로 40초 동안 가열하여 행하였다. The steel slabs of Table 1 were reheated, hot rolled to finish, cooled to 400 ° C./min, wound up at 650 ° C., and then cold rolled and continuously annealed at a reduction rate of 75%. The finish rolling temperature of not less than Ar 3 transformation point is 910 ℃, continuous annealing was performed by heating for 40 seconds to 830 ℃ to 10 ℃ / second.

얻어진 소둔판은 기계적 특성을 조사하기 위해 ASTM규격(ASTM E-8 standard)에 의한 표준시편으로 가공하였다. 시편은 인장시험기(INSTRON사, Model 6025)를 이용하여 항복강도, 인장강도, 연신율, 소성이방성 지수(rm값), 면내이방성 지수(△r값) 및 시효평가지수를 측정하였다. 여기서 rm=(r0+2r45+r90)/4, △r=(r0-2r45+r90)/2이며, 시효평가지수는 소둔후 1.0% skin Pass압연한 시편을 100℃ X 2hr. 열처리후 측정된 항복점연신(Yield Point Elongation)율이다.The obtained annealing plate was processed into a standard specimen according to ASTM E-8 standard to investigate the mechanical properties. The specimen was measured for yield strength, tensile strength, elongation, plastic anisotropy index (r m value), in-plane anisotropy index (Δr value) and aging evaluation index using a tensile tester (INSTRON, Model 6025). Where r m = (r 0 + 2r 45 + r 90 ) / 4, △ r = (r 0 -2r 45 + r 90 ) / 2, and the aging evaluation index is 100 ° C for 1.0% skin pass-rolled specimen after annealing X 2hr. Yield point elongation rate measured after heat treatment.

소부경화특성은 시편에 2% 스트레인을 가한 후 170℃에서 20분간 열처리 후 항복강도를 측정하고, 측정된 항복강도 값에서 열처리전의 항복강도 값을 뺀 값을 BH값으로 한 것이다. The quench hardening properties were obtained by adding 2% strain to the specimen and measuring the yield strength after heat treatment at 170 ° C. for 20 minutes, and subtracting the yield strength value before heat treatment as the BH value.

CC MnMn PP SS AlAl CuCu TiTi NbNb BB NN 기타Etc A1A1 0.00140.0014 0.110.11 0.0080.008 0.0080.008 0.0420.042 0.080.08 0.0090.009 0.0040.004 0.00070.0007 0.00720.0072 A2A2 0.00190.0019 0.080.08 0.00280.0028 0.0080.008 0.0360.036 0.110.11 0.0110.011 0.0040.004 0.00050.0005 0.0110.011 A3A3 0.00150.0015 0.090.09 0.0430.043 0.0070.007 0.0340.034 0.090.09 0.010.01 0.0030.003 0.00090.0009 0.0110.011 Si:0.09Si: 0.09 A4A4 0.00240.0024 0.110.11 0.0820.082 0.0090.009 0.0420.042 0.130.13 0.010.01 0.0040.004 0.00110.0011 0.0120.012 Si:0.12Si: 0.12 A5A5 0.00270.0027 0.080.08 0.110.11 0.0080.008 0.0670.067 0.120.12 0.0250.025 0.0060.006 0.00090.0009 0.00870.0087 Si:0.1Si: 0.1 A6A6 0.00250.0025 0.150.15 0.0370.037 0.0120.012 0.0730.073 0.140.14 0.020.02 0.0050.005 0.00090.0009 0.00720.0072 Si:0.11 Mo:0.087Si: 0.11 Mo: 0.087 A7A7 0.00220.0022 0.10.1 0.0370.037 0.0120.012 0.0410.041 0.130.13 0.0090.009 0.0040.004 0.00070.0007 0.0140.014 Si:0.13 Cr:0.31Si: 0.13 Cr: 0.31 A8A8 0.00130.0013 0.550.55 0.0440.044 0.0070.007 0.030.03 00 0.030.03 0.0120.012 0.00050.0005 0.00270.0027 A9A9 0.00450.0045 0.080.08 0.1210.121 0.0130.013 0.040.04 0.150.15 00 00 0.00080.0008 0.00180.0018

기타Etc Cu+MnCu + Mn (Mn/55+Cu/63.5)/(S*/32)(Mn / 55 + Cu / 63.5) / (S * / 32) (Al/27)/(N*/14)(Al / 27) / (N * / 14) CsCs 석출물의 평균크기 (㎛)Average size of precipitates (㎛) 석출물 수 (개/mm2)Number of precipitates (pcs / mm 2 ) A1A1 0.190.19 7.67.6 2.9672.967 1414 0.060.06 2.3X107 2.3 X 10 7 A2A2 0.190.19 5.65.6 1.7491.749 1919 0.060.06 2.9X107 2.9 X 10 7 A3A3 0.180.18 5.55.5 1.6591.659 1515 0.060.06 2.5X107 2.5 X 10 7 A4A4 0.240.24 6.16.1 1.7871.787 2424 0.050.05 4.2X107 4.2 X 10 7 A5A5 0.20.2 14.514.5 6.8036.803 2727 0.050.05 2.9X107 2.9 X 10 7 A6A6 0.290.29 13.313.3 6.4236.423 2525 0.050.05 3.1X107 3.1 X 10 7 A7A7 0.230.23 4.474.47 1.3931.393 2222 0.040.04 3.4X107 3.4 X 10 7 A8A8 0.550.55 -63-63 -6.65-6.65 -28-28 0.270.27 1.2X104 1.2 X 10 4 A9A9 0.230.23 7.817.81 3.8133.813 4545 0.060.06 9.5X105 9.5 X 10 5 S*=S-0.8x(Ti-0.8x(48/14)xN)x(32/48), N* =N-0.8x(Ti-0.8x(48/32)xS))x(14/48) , Cs=(C-Nbx12/93-Ti*x12/48)x10000, Ti*=Ti-0.8x((48/14)xN+(48/32)xS)S * = S-0.8x (Ti-0.8x (48/14) xN) x (32/48), N * = N-0.8x (Ti-0.8x (48/32) xS)) x (14 / 48), Cs = (C-Nbx12 / 93-Ti * x12 / 48) x10000, Ti * = Ti-0.8x ((48/14) xN + (48/32) xS)

시료번호Sample Number 기계적 성질Mechanical properties 비고Remarks 항복 강도 (MPa)Yield strength (MPa) 인장 강도 (MPa)Tensile strength (MPa) 연신율 (%)Elongation (%) 소성이방성 지수(rm)Plastic Anisotropy Index (r m ) 면내이방성 지수 (Δr)In-plane anisotropy index (Δr) 시효평가지수Aging Evaluation Index BH값(MPa)BH value (MPa) 2차가공취성 (DBTT-℃)2nd processing brittleness (DBTT- ℃) A1A1 192192 320320 4848 2.062.06 0.310.31 00 3737 -40-40 발명강Invention steel A2A2 211211 349349 4646 1.981.98 0.290.29 00 4848 -60-60 발명강Invention steel A3A3 221221 359359 4242 1.931.93 0.270.27 00 3333 -60-60 발명강Invention steel A4A4 252252 403403 3737 1.781.78 0.270.27 00 4545 -50-50 발명강Invention steel A5A5 321321 457457 3434 1.621.62 0.310.31 00 5858 -60-60 발명강Invention steel A6A6 234234 355355 4141 1.881.88 0.270.27 00 5151 -60-60 발명강Invention steel A7A7 222222 351351 4242 1.871.87 0.30.3 00 5151 -50-50 발명강Invention steel A8A8 189189 359359 4242 1.951.95 0.380.38 00 00 -50-50 비교강Comparative steel A9A9 336336 461461 2727 1.271.27 0.210.21 3.53.5 9696 -60-60 비교강Comparative steel

본 발명에서 상기 실시형태는 하나의 예시로서, 본 발명이 여기에 한정되는 것은 아니다. 본 발명의 특허청구범위에 기재된 기술적 사상과 실질적으로 동일한 구성을 갖고 동일한 작용효과를 이루는 것은 어떠한 것이어도 본 발명의 기술적 범위에 포함된다. In the present invention, the above embodiment is only one example, and the present invention is not limited thereto. Anything that has substantially the same configuration as the technical idea described in the claims of the present invention and achieves the same operation and effect is included in the technical scope of the present invention.

상술한 바와 같이, 본 발명은 소부경화형 IF강에 미세한 (Mn,Cu)S석출물과 AlN석출물을 분포시키는 것에 의해 결정립을 미세화시키고 이에 따라 면내이방성지수를 낮추고 또한, 석출강화에 의해 항복강도를 증진시키는 것이다.As described above, the present invention refines the grains by distributing fine (Mn, Cu) S precipitates and AlN precipitates in the small hardening IF steel, thereby lowering the in-plane anisotropy index and increasing yield strength by strengthening precipitation. It is to let.

Claims (10)

삭제delete 중량%로, C: 0.001-0.01%, Cu:0.01-0.2%, Mn:0.01-0.3%, S:0.005-0.08%, Al:0.1%이하, N:0.004-0.02%, P:0.2%이하, B:0.0001-0.002%, Ti:0.005~0.15%, Nb:0.002-0.04%, 나머지 Fe 및 기타 불가피한 불순물로 조성되고, By weight%, C: 0.001-0.01%, Cu: 0.01-0.2%, Mn: 0.01-0.3%, S: 0.005-0.08%, Al: 0.1% or less, N: 0.004-0.02%, P: 0.2% or less , B: 0.0001-0.002%, Ti: 0.005-0.15%, Nb: 0.002-0.04%, remaining Fe and other inevitable impurities, 상기 Cu, Mn, S, Al, N, C, Ti, Nb가 Cu, Mn, S, Al, N, C, Ti, Nb is Cu+Mn:0.05-0.4%, (Mn/55+Cu/63.5)/( S*/32):1-30, (Al/27)/( N*/14):1-10,Cu + Mn: 0.05-0.4%, (Mn / 55 + Cu / 63.5) / (S * / 32): 1-30, (Al / 27) / (N * / 14): 1-10, Cs(solute carbon):5-30를 만족하고Cs (solute carbon): Meets 5-30 [여기서, S*=S-0.8x(Ti-0.8x(48/14)xN)x(32/48), [Where S * = S-0.8x (Ti-0.8x (48/14) xN) x (32/48), N* =N-0.8x(Ti-0.8x(48/32)xS)x(14/48) , Cs=(C-Nbx12/93-Ti*x12/48)x10000, N * = N-0.8x (Ti-0.8x (48/32) xS) x (14/48), Cs = (C-Nbx12 / 93-Ti * x12 / 48) x10000, Ti*=Ti-0.8x((48/14)xN+(48/32)xS) 단, Ti*<0일 경우 Ti*=0으로 함] Ti * = Ti-0.8x (( 48/14) xN + (48/32) xS) If stage, Ti * <0 il referred to as Ti * = 0] (Mn,Cu)S석출물과 AlN석출물의 평균크기가 0.2㎛이하이며,The average size of (Mn, Cu) S precipitates and AlN precipitates is less than 0.2㎛, 상기 석출물수는 1X107개/mm2이상임을 특징으로 하는 항복강도가 우수한 소부경화형 냉연강판. The precipitated water hardening type cold rolled steel sheet excellent in yield strength, characterized in that 1X10 7 / mm 2 or more. 제 2항에 있어서, 상기 (Al/27)/( N*/14)는 1-7임을 특징으로 하는 항복강도가 우수한 소부경화형 냉연강판. 3. The hardened hardened cold rolled steel sheet having excellent yield strength according to claim 2, wherein (Al / 27) / (N * / 14) is 1-7. 제 2항에 있어서, 추가로 Si:0.1~0.8%, Cr:0.2~1.2%의 1종 또는 2종이 포함되는 것을 특징으로 하는 항복강도가 우수한 소부경화형 냉연강판. 3. The hardened hardened cold rolled steel sheet having excellent yield strength according to claim 2, further comprising one or two of Si: 0.1 to 0.8% and Cr: 0.2 to 1.2%. 제 2항 또는 제 4항에 있어서, 추가로 Mo이 0.01~0.2% 포함되는 것을 특징으로 하는 항복강도가 우수한 소부경화형 냉연강판. The hardened hardened cold rolled steel sheet according to claim 2 or 4, wherein Mo is contained in an amount of 0.01 to 0.2%. 삭제delete 중량%로, C: 0.001-0.01%, Cu:0.01-0.2%, Mn:0.01-0.3%, S:0.005-0.08%, Al:0.1%이하, N:0.004-0.02%, P:0.2%이하, B:0.0001-0.002%, Ti:0.005~0.15%, Nb:0.002-0.04%, 나머지 Fe 및 기타 불가피한 불순물로 조성되고, By weight%, C: 0.001-0.01%, Cu: 0.01-0.2%, Mn: 0.01-0.3%, S: 0.005-0.08%, Al: 0.1% or less, N: 0.004-0.02%, P: 0.2% or less , B: 0.0001-0.002%, Ti: 0.005-0.15%, Nb: 0.002-0.04%, remaining Fe and other inevitable impurities, 상기 Cu, Mn, S, Al, N, C, Ti, Nb가 Cu, Mn, S, Al, N, C, Ti, Nb is Cu+Mn:0.05-0.4%, (Mn/55+Cu/63.5)/( S*/32):1-30, (Al/27)/( N*/14):1-10,Cu + Mn: 0.05-0.4%, (Mn / 55 + Cu / 63.5) / (S * / 32): 1-30, (Al / 27) / (N * / 14): 1-10, Cs(solute carbon):5-30를 만족하는 슬라브를,Cs (solute carbon): Slabs satisfying 5-30, [여기서, S*=S-0.8x(Ti-0.8x(48/14)xN)x(32/48), [Where S * = S-0.8x (Ti-0.8x (48/14) xN) x (32/48), N* =N-0.8x(Ti-0.8x(48/32)xS)x(14/48) , Cs=(C-Nbx12/93-Ti*x12/48)x10000, N * = N-0.8x (Ti-0.8x (48/32) xS) x (14/48), Cs = (C-Nbx12 / 93-Ti * x12 / 48) x10000, Ti*=Ti-0.8x((48/14)xN+(48/32)xS) 단, Ti*<0일 경우 Ti*=0으로 함] Ti * = Ti-0.8x (( 48/14) xN + (48/32) xS) If stage, Ti * <0 il referred to as Ti * = 0] 1100℃이상의 온도로 재가열한 후 마무리 압연온도를 Ar3변태점 이상으로 하여 열간압연하고 300℃/min이상의 속도로 냉각하고 700℃이하의 온도에서 권취한 다음, 50~90%의 압하율로 냉간 압연하고, 700~900℃의 온도범위에서 10초~30분 동안 연속소둔하여 평균크기가 0.2㎛이하의 (Mn,Cu)S석출물과 AlN석출물이 1X107개/mm2이상 분포하는 항복강도가 우수한 소부경화형 냉연강판의 제조방법.After reheating to 1100 ℃ or higher, hot rolling with finishing rolling temperature above Ar 3 transformation point, cooling at 300 ℃ / min or higher, winding at temperature below 700 ℃, and cold rolling at 50 ~ 90% reduction rate It was continuously annealed for 10 seconds to 30 minutes in the temperature range of 700 ~ 900 ℃, and the yield strength of (Mn, Cu) S precipitates and AlN precipitates with an average size of less than 0.2㎛ was distributed more than 1 × 10 7 / mm 2. Method for producing a hardened hardened cold rolled steel sheet. 제 7항에 있어서, 상기 (Al/27)/( N*/14)는 1-7임을 특징으로 하는 항복강도가 우수한 소부경화형 냉연강판의 제조방법. 8. The method of claim 7, wherein (Al / 27) / (N * / 14) is 1-7. 제 7항에 있어서, 추가로 Si:0.1~0.8%, Cr:0.2~1.2%의 1종 또는 2종이 포함되는 것을 특징으로 하는 항복강도가 우수한 소부경화형 냉연강판의 제조방법. The method for producing a hardened hardened cold rolled steel sheet having excellent yield strength according to claim 7, further comprising one or two of Si: 0.1 to 0.8% and Cr: 0.2 to 1.2%. 제 7항 또는 제 9항에 있어서, 추가로 Mo이 0.01~0.2% 포함되는 것을 특징으로 하는 항복강도가 우수한 소부경화형 냉연강판의 제조방법.10. The method for producing a hardened hardened cold rolled steel sheet having excellent yield strength according to claim 7 or 9, wherein Mo is contained in an amount of 0.01 to 0.2%.
KR1020060040235A 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having increased yield strength and process for producing the same KR100742950B1 (en)

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KR1020050129240A KR100723180B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having good formability and process for producing the same
KR1020050130130A KR100723216B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having increased plastic anisotropy and process for producing the same
KR1020050129237A KR100723163B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having reduced plane anisotropy and process for producing the same
KR1020050129242A KR100723159B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having good formability and process for producing the same
KR1020050129236A KR100723164B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having good formability and process for producing the same
KR1020050129241A KR100723160B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having reduced plane anistropy and process for producing the same
KR1020050129239A KR100723181B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having good formability and process for producing the same
KR1020050130132A KR100742819B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having reduced plane anisotropy and process for producing the same
KR1020050129243A KR100723158B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having good formability and process for producing the same
KR1020050129238A KR100723182B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having increased plastic anistropy and process for producing the same
KR1020050129235A KR100723165B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having increased plastic anisotropy and process for producing the same
KR1020050130131A KR100742818B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having good formability and process for producing the same
KR1020060040224A KR100742941B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having good formability and process for producing the same
KR1020060040214A KR100742936B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040237A KR100742952B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having increased yield strength and process for producing the same
KR1020060040209A KR100742931B1 (en) 2005-05-03 2006-05-03 Non-aging type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040229A KR100742948B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having increased yield strength and process for producing the same
KR1020060040069A KR100742926B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040212A KR100742934B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040071A KR100742919B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040240A KR100742955B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040216A KR100742938B1 (en) 2005-05-03 2006-05-03 Non-aging type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040211A KR100742933B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having good formability and process for producing the same
KR1020060040235A KR100742950B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having increased yield strength and process for producing the same
KR1020060040213A KR100742935B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040207A KR100742929B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040226A KR100742944B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having reduced plane anisotropy and process for producing the same
KR1020060040215A KR100742937B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having reduced plane anisotropy and process for producing the same
KR1020060040206A KR100742917B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having reduced plane anisotropy and process for producing the same
KR1020060040236A KR100742951B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having good formability and process for producing the same
KR1020060040217A KR100742939B1 (en) 2005-05-03 2006-05-03 Non-aging type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040218A KR100742940B1 (en) 2005-05-03 2006-05-03 Non-aging type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040210A KR100742932B1 (en) 2005-05-03 2006-05-03 Non-aging type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040230A KR100742949B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having good formability and process for producing the same
KR1020060040070A KR100742927B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having good formability and process for producing the same
KR1020060040225A KR100742943B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040208A KR100742930B1 (en) 2005-05-03 2006-05-03 Non-aging type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040205A KR100742918B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040227A KR100742945B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040239A KR100742954B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040238A KR100742953B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040228A KR100742947B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having good formability and process for producing the same

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KR1020050129240A KR100723180B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having good formability and process for producing the same
KR1020050130130A KR100723216B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having increased plastic anisotropy and process for producing the same
KR1020050129237A KR100723163B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having reduced plane anisotropy and process for producing the same
KR1020050129242A KR100723159B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having good formability and process for producing the same
KR1020050129236A KR100723164B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having good formability and process for producing the same
KR1020050129241A KR100723160B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having reduced plane anistropy and process for producing the same
KR1020050129239A KR100723181B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having good formability and process for producing the same
KR1020050130132A KR100742819B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having reduced plane anisotropy and process for producing the same
KR1020050129243A KR100723158B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having good formability and process for producing the same
KR1020050129238A KR100723182B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having increased plastic anistropy and process for producing the same
KR1020050129235A KR100723165B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having increased plastic anisotropy and process for producing the same
KR1020050130131A KR100742818B1 (en) 2005-05-03 2005-12-26 Cold rolled steel sheet having good formability and process for producing the same
KR1020060040224A KR100742941B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having good formability and process for producing the same
KR1020060040214A KR100742936B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040237A KR100742952B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having increased yield strength and process for producing the same
KR1020060040209A KR100742931B1 (en) 2005-05-03 2006-05-03 Non-aging type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040229A KR100742948B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having increased yield strength and process for producing the same
KR1020060040069A KR100742926B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040212A KR100742934B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040071A KR100742919B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040240A KR100742955B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040216A KR100742938B1 (en) 2005-05-03 2006-05-03 Non-aging type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040211A KR100742933B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having good formability and process for producing the same

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KR1020060040213A KR100742935B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040207A KR100742929B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040226A KR100742944B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having reduced plane anisotropy and process for producing the same
KR1020060040215A KR100742937B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having reduced plane anisotropy and process for producing the same
KR1020060040206A KR100742917B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having reduced plane anisotropy and process for producing the same
KR1020060040236A KR100742951B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having good formability and process for producing the same
KR1020060040217A KR100742939B1 (en) 2005-05-03 2006-05-03 Non-aging type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040218A KR100742940B1 (en) 2005-05-03 2006-05-03 Non-aging type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040210A KR100742932B1 (en) 2005-05-03 2006-05-03 Non-aging type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040230A KR100742949B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having good formability and process for producing the same
KR1020060040070A KR100742927B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having good formability and process for producing the same
KR1020060040225A KR100742943B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040208A KR100742930B1 (en) 2005-05-03 2006-05-03 Non-aging type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040205A KR100742918B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040227A KR100742945B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040239A KR100742954B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040238A KR100742953B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet with high yield ratio and process for producing the same
KR1020060040228A KR100742947B1 (en) 2005-05-03 2006-05-03 Baking hardening type cold rolled steel sheet having good formability and process for producing the same

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JP (3) JP4954981B2 (en)
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