KR101042434B1 - A cold rolledsteel sheet and method for manufacturing the same - Google Patents
A cold rolledsteel sheet and method for manufacturing the same Download PDFInfo
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- KR101042434B1 KR101042434B1 KR1020080103409A KR20080103409A KR101042434B1 KR 101042434 B1 KR101042434 B1 KR 101042434B1 KR 1020080103409 A KR1020080103409 A KR 1020080103409A KR 20080103409 A KR20080103409 A KR 20080103409A KR 101042434 B1 KR101042434 B1 KR 101042434B1
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Abstract
본 발명은 탄소와 질소를 고용원소로 이용하여 소부경화성과 상온 내시효성이 우수한 냉연강판을 제조할 수 있도록 한 냉연강판의 제조방법에 관한 것이다.The present invention relates to a method for manufacturing a cold rolled steel sheet, which is capable of producing a cold rolled steel sheet having excellent hardening hardening and room temperature aging resistance using carbon and nitrogen as solid solutions.
본 발명에 따른 냉연강판의 제조방법은, 중량 %로, 탄소(C) 0 초과 0.005% 이하, 질소(N) 0.002~0.005%, 망간(Mn) 0.1 ~ 1.0%, 인(P) 0.005 ~ 0.1%, 니오븀(Nb)0.015 ~ 0.04%, 규소(Si) 0 초과 0.3%이하, 황(S) 0 초과 0.02% 이하 , 알루미늄(Al) 0.001 ~ 0.03%을 첨가하고, Nb/C 원자비를 1이상, Al/N 원자비를 0.5 ~ 1.5로 조절하며, 나머지 잔부가 철(Fe)과 강의 제조시 불가피하게 함유되는 원소를 포함한 강을 오스테나이트 영역의 온도인 1150~1300℃에서 균질화 처리한 후에, 마무리 열간 압연할 시에 Ar₃변태점 직상인 890~950℃에서 압연하여 열연 강판으로 제조하고, 이어서 450~650℃의 온도 범위에서 열연 권취한 다음에, 권취된 열연 강판을 냉간 압하율 40~80%로 압연하고, 소둔을 750~880℃ 사이에서 실시한다.Method for producing a cold rolled steel sheet according to the present invention, in weight%, carbon (C) more than 0 0.005% or less, nitrogen (N) 0.002 ~ 0.005%, manganese (Mn) 0.1 ~ 1.0%, phosphorus (P) 0.005 ~ 0.1 %, Niobium (Nb) 0.015 to 0.04%, silicon (Si) above 0 and 0.3% or less, sulfur (S) above 0 and 0.02% or less, aluminum (Al) 0.001 to 0.03%, and the Nb / C atomic ratio is 1 As described above, the Al / N atomic ratio is adjusted to 0.5 to 1.5, and the remainder is homogenized at 1150 to 1300 ° C., which is the temperature of the austenitic region, of steel containing iron (Fe) and elements which are inevitably contained in the production of steel. In the final hot rolling, the steel sheet was rolled at 890 to 950 ° C., which is directly above the Ar₃ transformation point, to be produced as a hot rolled steel sheet, and then hot rolled at a temperature range of 450 to 650 ° C., and then the wound hot rolled steel sheet was cold rolled down to 40 to 80 degrees. It rolls at% and performs annealing between 750-880 degreeC.
이에 따르면 본 발명은 탄소와 질소를 고용원소로 이용하기 위해 니오븀, 알루미늄 등과 같은 합금원소의 첨가량을 조절하고 열처리 온도를 저온 소둔과 저온 권취 과정을 통해 제조함으로써, 상온 내시효성과 소부경화성이 우수한 냉연강판을 제조할 수 있는 유용한 효과를 갖는다.According to the present invention by controlling the amount of alloying elements such as niobium, aluminum, etc. in order to use carbon and nitrogen as the solid solution element, and manufacturing the heat treatment temperature through low temperature annealing and low temperature winding process, cold rolling excellent in room temperature aging resistance and hardening hardenability It has a useful effect to produce a steel sheet.
Description
본 발명은 자동차의 문 또는 후드(hood), 트렁크(trunk lid)와 같은 외판재에 적용하는 냉연강판의 제조방법에 관한 것으로, 보다 상세하게는 저탄소강에 고용원소의 탄소와 질소를 고착하기 위한 니오븀(Nb)과 알루미늄(Al)의 첨가량을 조절하고, 강의 강도를 조절하기 위해서 망간(Mn), 인(P) 첨가량을 적절하게 조절함으로써 우수한 상온 내시효성 및 소부경화성을 갖도록 함과 아울러, 외판재로서 필요한 항복강도와 도장 열처리후 최종 제품에서 높은 항복강도를 유지할 수 있도록 한 냉연강판의 제조방법에 관한 것이다. The present invention relates to a method for manufacturing a cold rolled steel sheet applied to an outer plate such as a door, a hood, a trunk lid of a vehicle, and more particularly, to fix carbon and nitrogen of solid elements in low carbon steel. By controlling the addition amount of niobium (Nb) and aluminum (Al), and appropriately adjusting the amount of manganese (Mn) and phosphorus (P) to control the strength of the steel, it has excellent room temperature resistance and baking hardening, The present invention relates to a method for producing a cold rolled steel sheet which is capable of maintaining a high yield strength in a final product after heat treatment and coating heat treatment required as a sheet material.
최근 자동차용 냉연강판은 자동차 경량화에 의한 연비향상과 차체의 경량화를 목적으로 하는 고강도화가 요구되며, 그외에도 충분한 항복강도,인장강도, 양호한 프레스 성형성, 스폿 용접성, 피로특성 및 도장내식성등이 요구된다.In recent years, cold rolled steel sheets for automobiles are required to improve fuel efficiency by reducing the weight of automobiles and to increase their strength to reduce the weight of the vehicle body.In addition, sufficient yield strength, tensile strength, good press formability, spot weldability, fatigue characteristics and paint corrosion resistance are required. do.
일반적으로 강판은 강도와 성형성이 서로 상반되는 특징으로 나타나는 것이 통상적이지만, 양 특성을 만족하는 강으로는 복합조직 강판과 소부경화형 강판이 있다.In general, the steel sheet is usually represented by the characteristics of the strength and formability are opposite to each other, the steel that satisfies both characteristics is a composite steel sheet and a hardened steel sheet.
그중 복합조직 강판은 인장강도가 40Kgf/㎟급 이상으로 높은 인장강도에 비해 성형성이 저하될 뿐만 아니라, 망간, 크롬등의 합금원소의 과다 첨가로 인해 제조시 원가 상승을 초래한다.Among them, the composite steel sheet has a tensile strength of 40 Kgf /
또한, 소부경화형 강판은 인장강도 40Kgf/㎟급 이하인 강에서 프레스 성형시 연질강판에 가까운 항복강도를 가지므로 연성이 우수하며 프레스 성형후 도장소부 처리시 항복강도가 상승하는 강의 특성을 갖는다.In addition, the hardened hardened steel sheet has a yield strength close to the soft steel sheet during press forming in a steel having a tensile strength of 40 Kgf /
소부경화는 강중에 고용된 침입형 원소인 탄소나 질소가 변형과정에서 생성된 전위를 고착하여 발생하는 일종의 변형시효를 이용한 것으로 고용탄소 및 질소가 증가하면 소부경화량은 증가하나 고용원소의 과다로 인해 상온시효를 수반하여 성형성의 악화를 초래하게 되므로 고용원소의 제어가 중요하다.Baking hardening is a type of strain aging that occurs when carbon or nitrogen, an invasive element dissolved in steel, adheres to the potential generated during the deformation process. Therefore, control of the employment element is important because it leads to deterioration of moldability with room temperature aging.
종래의 자동차 외판재용 강판은 극저탄소 알루미늄 킬드강에 티타늄(Ti) 또는니오븀(Nb)의 첨가량을 적절히 조절하여 강중에 존재하는 고용탄소의 양을 조절하여 소부경화능을 확보하고, 고용강화원소인 인(P), 망간(Mn), 실리콘(Si)등을 첨가하여 항복강도를 확보하여 제조하여 왔다. The conventional steel sheet for automotive exterior materials is appropriately adjusted the amount of titanium (Ti) or niobium (Nb) added to the ultra-low carbon aluminum-kilted steel to adjust the amount of solid solution carbon present in the steel to secure the hardening hardening ability, Phosphorus (P), manganese (Mn), silicon (Si) and the like have been added to secure the yield strength.
기존 소부경화강을 형성하기 위해 티타늄을 첨가하여 잔류하는 고용탄소량을 제어하는 방법은 티타늄이 질소(N), 황(S), 탄소(C)등 다양한 원소와 강중에서 결합하기 때문에 최종 소부경화능에 미치는 고용탄소량이 크게 변화하여 재질편차가 심할 우려가 있다. The method of controlling the amount of solid solution remaining by adding titanium to form existing hardened hardened steel is because the final bond hardened because titanium combines with various elements such as nitrogen (N), sulfur (S), and carbon (C) in steel. There is a possibility that the material deviation may be severe due to the large change in the amount of carbon employed.
한편,소부경화강을 형성하는 다른 예로, 니오븀(Nb)을 첨가하여 잔류하는 고용탄소량을 제어하는 방법은 고온소둔을 필요로 하기 때문에 소둔조건에 따라서 재 질편차가 심하고, 용융도금재 제조시 도금품질이 나빠질 우려가 있었다. 그리고 기존의 고용탄소를 이용하여 소부경화능을 확보하는 방법은 탄소의 확산속도가 빠르기 때문에 시효보증기간을 장시간 확보하기 어려운 단점이 있다.On the other hand, as another example of forming hardened steel, the method of controlling the amount of solid solution carbon remaining by adding niobium (Nb) requires high temperature annealing, so the material deviation is severe depending on the annealing conditions, There was a fear that the plating quality deteriorated. In addition, the method of securing hardening hardening capacity using the existing solid carbon has a disadvantage in that it is difficult to secure the aging guarantee period for a long time because the carbon diffusion speed is high.
즉, 종래 소부경화강은 고용탄소를 강중에 잔류시켜 소부경화능을 확보할 경우, 탄소가 상온에서 확산이 빠르기 때문에 소부경화능이 높은 반면에 상온 내시효성이 저하되는 단점을 갖는다.That is, the conventional hardened hardened steel has a disadvantage in that when the solid hardened carbon is retained in the steel to secure the hardened hardening ability, the hardening hardening ability is high and the room temperature aging resistance is lowered because the carbon is rapidly diffused at room temperature.
또한, 고용질소일 경우에는 알루미늄 탈산강에서 일반적인 권취공정에서 대부분 AlN으로 석출되거나, 티타늄을 첨가한 강의 경우에는 고온에서 TiN 으로 석출되기 때문에 소부 경화에 필요한 고용원소로 이용할 수 없는 단점이 있었다.In addition, in the case of solid solution nitrogen, most of the aluminum deoxidized steel is precipitated as AlN in a general winding process, or in the case of titanium-added steel, because it is precipitated as TiN at a high temperature, there is a disadvantage in that it cannot be used as a solid element required for baking.
또한 소부경화능을 확보하기 위한 기술로, 탄소함량이 0.01% 이상인 저탄소강의 경우에 고온소둔을 통해 고용탄소를 제거하고 알루미늄 첨가로 고용질소를 제어한 사례가 있다. 하지만 고온소둔은 제어조건에 따라 부위별 재질편차가 심하고 소둔 후에도 고용탄소가 완전히 제거되지 않는 단점이 있다. In addition, as a technique for securing the bake hardening ability, in the case of low carbon steel having a carbon content of 0.01% or more, there is a case in which the solid solution nitrogen is removed by high temperature annealing and aluminum is added. However, high temperature annealing has a disadvantage in that the material deviation of each part is severe according to the control conditions and that the dissolved carbon is not completely removed even after annealing.
이 경우 티타늄과 니오븀을 첨가하여 고용탄소를 제거하더라도 NbC와 TiC의 관리가 제어되지 않으면 잔류 고용탄소로 인하여 성형성이 저하되고 상온 내시효성이 안정적으로 확보되지 않는 단점이 있다. In this case, even if the removal of the solid solution carbon by adding titanium and niobium, if the management of NbC and TiC is not controlled, there is a disadvantage that the moldability is lowered due to the residual solid solution carbon and the room temperature aging resistance is not stably secured.
본 발명은 상기한 제반문제점을 감안하여 이를 해결하고자 제안된 것으로, 그 목적은 탄소와 질소를 고착하기 위한 니오븀(Nb)과 알루미늄(Al)의 첨가량을 조절하고, 강의 강도를 조절하기 위해서 망간(Mn), 인(P) 첨가량을 적절하게 조절함과 아울러, 저온 소둔과 저온 권취 공정을 통해 제조함으로써 외판재로서 필요한 항복강도와 도장 열처리후 최종 제품에서 높은 항복강도를 유지하여 내덴트(dent)성이 우수한 냉연강판의 제조방법을 제공하는 데 있다.The present invention has been proposed in view of the above-mentioned problems, and its object is to adjust the amount of niobium (Nb) and aluminum (Al) to fix carbon and nitrogen, and to adjust the strength of steel (manganese) Mn) and phosphorus (P) addition amount is appropriately controlled and manufactured through low temperature annealing and low temperature winding process to maintain the yield strength required as an outer plate material and high yield strength in the final product after coating heat treatment. It is to provide a method for producing a cold rolled steel sheet having excellent properties.
상기한 목적을 달성하기 위한 본 발명은 중량 %로, 탄소(C) 0 초과 0.005% 이하, 질소(N) 0.002 ~ 0.005%, 망간(Mn) 0.1 ~ 1.0%, 인(P) 0.005 ~ 0.1%, 니오븀(Nb) 0.015 ~ 0.04%, 규소(Si) 0 초과 0.3%이하, 황(S) 0 초과 0.02% 이하 , 알루미늄(Al) 0.001 ~ 0.03%을 첨가하고,The present invention for achieving the above object in terms of weight%, carbon (C) more than 0 0.005% or less, nitrogen (N) 0.002 ~ 0.005%, manganese (Mn) 0.1 ~ 1.0%, phosphorus (P) 0.005 ~ 0.1% , Niobium (Nb) 0.015 to 0.04%, silicon (Si) 0 to 0.3% or less, sulfur (S) 0 to 0.02% or less, aluminum (Al) 0.001 to 0.03%, and
Nb/C 원자비를 1이상, Al/N 원자비를 0.5 ~ 1.5로 조절하고, 나머지 잔부가 철(Fe)과 강의 제조시 불가피하게 함유되는 원소를 포함한 강을 1150 ~ 1300℃에서 균질화 처리 후 마무리 열간압연온도를 Ar₃변태점 직상인 890 ~ 950℃로 하며, After adjusting the Nb / C atomic ratio to 1 or more and the Al / N atomic ratio to 0.5 to 1.5, the homogeneous treatment at 1150 to 1300 ° C. for the steel containing the remaining balance inevitably contained in the production of iron (Fe) and steel. Finish hot rolling temperature is 890 ~ 950 ℃, which is directly above Ar₃ transformation point,
상기 열간 압연된 열연강판을 열연 권취하고, 상기 열연강판을 냉간압하율을 40 ~ 80%로 하여 냉간압연하는 것을 특징으로 한다.The hot rolled hot rolled steel sheet is hot rolled, and the hot rolled steel sheet is cold rolled with a cold reduction ratio of 40 to 80%.
또한, 상기 냉간 압연후에 750 ~ 880℃의 온도 범위에서 소둔 처리하는 것이다.Further, after the cold rolling, the annealing treatment is performed at a temperature range of 750 to 880 ° C.
그리고 상기 열연권취는 450 ~ 650℃의 온도범위에서 실시하는 것이 바람직하다.And the hot rolled winding is preferably carried out in a temperature range of 450 ~ 650 ℃.
본 발명의 다른 특징적인 요소로는 중량 %로, 탄소(C) 0 초과 0.005% 이하, 질소(N) 0.002~0.005%, 망간(Mn) 0.1 ~ 1.0%, 인(P) 0.005 ~ 0.1%, 니오븀(Nb) 0.015 ~ 0.04%, 규소(Si) 0 초과 0.3%이하, 황(S) 0 초과 0.02% 이하 , 알루미늄(Al) 0.001 ~ 0.03%을 첨가하고,Other characteristic elements of the present invention are by weight%, carbon (C) greater than 0 and 0.005% or less, nitrogen (N) 0.002 to 0.005%, manganese (Mn) 0.1 to 1.0%, phosphorus (P) 0.005 to 0.1%, Niobium (Nb) 0.015 to 0.04%, silicon (Si) above 0 and 0.3% or less, sulfur (S) above 0 and 0.02% or less, aluminum (Al) 0.001 and 0.03%, and
Nb/C 원자비를 1이상, Al/N 원자비를 0.5 ~ 1.5로 조절하고, 나머지 잔부가 철(Fe)과 강의 제조시 불가피하게 함유되는 원소를 포함한 강으로 이루어진 냉연강판을 특징으로 한다. The Nb / C atomic ratio is adjusted to 1 or more, and the Al / N atomic ratio is adjusted to 0.5 to 1.5, and the remainder is characterized by a cold rolled steel sheet made of steel containing iron (Fe) and elements which are inevitably contained in the production of steel.
본 발명은 탄소와 질소를 고용원소로 이용하여 소부경화성과 상온 내시효성이 우수한 냉연강판을 제조하도록 한 것인 바, 이에 따르면 본 발명은 탄소와 질소를 고용원소로 이용하기 위해 니오븀, 알루미늄 등과 같은 합금원소의 첨가량을 조절하고 열처리 온도를 저온 소둔과 저온 권취 과정을 통해 제조함으로써, 상온 내시효성과 소부경화성이 우수한 냉연강판을 제조할 수 있는 유용한 효과를 갖는다.The present invention is to produce a cold rolled steel sheet having excellent hardening hardening and room temperature aging resistance using carbon and nitrogen as a solid solution element, according to the present invention to use carbon and nitrogen as a solid element such as niobium, aluminum By controlling the addition amount of the alloying element and the heat treatment temperature is prepared through the low temperature annealing and low temperature winding process, it has a useful effect that can produce a cold rolled steel sheet excellent in room temperature aging resistance and baking hardening.
또한, 본 발명은 고용탄소를 최대한 억제하여 소부경화에서의 탄소의 영향을 차단하므로 불균일 가공이 방지되고 상온 내시효성이 보증되어 시효보증기간이 장기간 확보되는 유용한 효과를 갖는다. In addition, the present invention has the useful effect of preventing the non-uniform processing and the shelf-life aging resistance is ensured for a long time by preventing the effect of the carbon in the hardening hardening by inhibiting the solid solution carbon as much as possible.
또한, 본 발명은 망간의 함량을 낮추므로 가공성 및 스폿 용접성이 향상된다. 그리고 망간의 함량을 낮춤에 의해 발생되는 강판의 강도저하는 석출물 및 고 용질소의 제어를 통한 소부경화를 통해 확보되도록 하였다. 따라서 자동차용 외판재에 안정적으로 사용할 수 있는 유용한 효과가 있다. In addition, the present invention lowers the content of manganese, thereby improving workability and spot weldability. In addition, the decrease in strength of the steel sheet produced by lowering the content of manganese was ensured through hardening of the bake through control of precipitates and solid nitrogen. Therefore, there is a useful effect that can be used stably in the exterior plate material for cars.
이하, 본 발명의 바람직한 실시예를 첨부된 도면을 참조하여 상세히 설명하기로 한다.Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
본 발명에 따른 냉연강판 및 그의 제조방법은, 중량 %로, 탄소(C) 0 초과 0.005% 이하, 질소(N) 0.002 ~ 0.005%, 망간(Mn) 0.1 ~ 1.0%, 인(P) 0.005 ~ 0.1%, 니오븀(Nb) 0.015 ~ 0.04%, 규소(Si) 0 초과 0.3% 이하, 황(S) 0 초과 0.02% 이하 , 알루미늄(Al) 0.001 ~ 0.03%을 첨가하고, Nb/C 원자비를 1이상, Al/N 원자비를 0.5 ~ 1.5로 조절하며, 나머지 잔부가 철(Fe)과 강의 제조시 불가피하게 함유되는 원소를 포함한 강을 오스테나이트 영역의 온도인 1150~1300℃에서 균질화 처리한 후에, 마무리 열간 압연할 시에 Ar₃변태점 직상인 890~950℃에서 압연하여 열연 강판으로 제조하고, 이어서 450~650℃의 온도 범위에서 열연 권취한 다음에, 권취된 열연 강판을 냉간 압하율 40~80%로 압연하고, 소둔을 750~880℃ 사이에서 실시한다.Cold rolled steel sheet according to the present invention and its manufacturing method, in weight%, carbon (C) more than 0 0.005% or less, nitrogen (N) 0.002 ~ 0.005%, manganese (Mn) 0.1 ~ 1.0%, phosphorus (P) 0.005 ~ 0.1%, niobium (Nb) 0.015 to 0.04%, silicon (Si) above 0 and 0.3% or less, sulfur (S) above 0 and 0.02% or less, aluminum (Al) 0.001 to 0.03%, and the Nb / C atomic ratio At least 1, the Al / N atomic ratio is adjusted to 0.5 to 1.5, and the remainder is homogenized at 1150 to 1300 ° C., which is the temperature of the austenitic region, of steel containing iron (Fe) and elements which are inevitably contained in the production of steel. Subsequently, during finish hot rolling, the steel sheet was rolled at a temperature of 890 to 950 ° C., which is directly above the Ar 3 transformation point, to be produced as a hot rolled steel sheet, and then hot rolled at a temperature range of 450 to 650 ° C., and then the wound hot rolled steel sheet was 40 to 40 It rolls at 80% and performs annealing between 750-880 degreeC.
이후에, 합금화 용융도금라인에서 갈바륨이나 아연도금하는 과정에서 460℃의 온도에서 용융도금하고, 460~560℃의 온도에서 합금화 처리를 실시하여 용융도금 강판을 제조할 수 있다.Subsequently, in the process of galvalume or zinc plating in the alloying hot-dip plating line, the hot-dip galvanizing at a temperature of 460 ℃, and the alloying treatment at a temperature of 460 ~ 560 ℃ can be produced a hot-dip steel sheet.
이때, 소둔 처리후 400℃의 온도에서 과시효 처리하는 것이 바람직하지만, 저온 소둔으로 인해 생략되어도 무방할 것이다.At this time, it is preferable to overage at a temperature of 400 ° C. after the annealing treatment, but it may be omitted due to low temperature annealing.
앞의 도금 온도 460℃는 공지의 용융조 내의 온도이므로, 온도 범위를 정확 하게 지정하지 않는 것이 바람직하다.Since the previous plating temperature of 460 ° C is a temperature in a known melting bath, it is preferable not to specify the temperature range accurately.
상기한 열연 권취 단계에서 450℃ 이하로 낮을 경우에는 슬라브 재가열 공정에서 질소가 AlN으로 결합되기 때문에 질소에 의한 소부경화능 확보가 어렵게 된다.When the temperature is lower than 450 ° C. in the hot rolling step, it is difficult to secure the bake hardening ability by nitrogen because nitrogen is bonded to AlN in the slab reheating process.
이와 반대로, 권취온도가 650℃보다 높을 경우에는 소부경화능이 급격히 감소하게 되므로, 열연 권취 온도를 450~650℃로 제한하는 것이 바람직하다.On the contrary, when the coiling temperature is higher than 650 ° C., the baking hardening capacity is drastically reduced, so it is preferable to limit the hot rolled coiling temperature to 450 to 650 ° C.
또한, 본 발명의 합금조성은 고용탄소를 최대한 억제하기 위하여 탄소함량이 0.005wt% 이하인 극저탄소강을 사용한다. 이는 원강에서부터 탄소함량을 낮춰 고용질소만으로 강의 소부경화를 제어한다. In addition, the alloy composition of the present invention uses ultralow carbon steel having a carbon content of 0.005 wt% or less in order to suppress the solid solution carbon as much as possible. It lowers carbon content from raw steel to control the hardening of the steel with only solid nitrogen.
소부경화능을 달성하기에는 질소만으로 제어하는 경우 탄소보다 유리하다. 이는 질소가 탄소보다 강 중에서 확산속도가 느리므로 상온 내시효성 측면에서 유리하기 때문이다. 여기서, 상온 내시효는 시간에 따라 강판의 재질이 바뀌는 것을 의미하며, 소부경화강은 철강사에서 자동차사로 공급된 후에도 오랜시일이 지난 후 사용이 되기 때문에 상온 내시효성이 보증되어야 한다. It is more advantageous than carbon when controlling only with nitrogen to achieve the small hardening ability. This is because nitrogen has a slower diffusion rate in steel than carbon, which is advantageous in terms of room temperature aging resistance. Here, the room temperature aging means that the material of the steel sheet changes with time, and since the hardened hardened steel is used after a long time after being supplied from the steel company to the automobile company, the room temperature aging resistance should be guaranteed.
그리고 미량의 잔류 고용탄소는 Nb/C 원자비를 조절하여 최대한 제거한다. 이를 위해 Nb/C 원자비는 1이상으로 조절한다. 이는 강 중의 고용탄소를 모두 NbC의 석출물로 석출하여 고용질소만이 강 중에 존재하도록 한다. 그에 따라 소부경화시 고용탄소의 영향이 차단된다.And trace amounts of residual dissolved carbon are removed as much as possible by controlling the Nb / C atomic ratio. For this purpose, the Nb / C atomic ratio is adjusted to 1 or more. This precipitates all of the dissolved carbon in the river as a precipitate of NbC so that only solid nitrogen exists in the river. As a result, the effects of carbon employment are blocked when baking.
고용질소는 질소와 석출물을 형성하는 알루미늄에 의해 제어된다. 고용질소도 적정하게 제어되지 않을 경우 상온 내시효성 및 성형성 저하 문제를 수반한다. 고용질소를 제어하기 위한 Al/N 원자비는 0.5 ~ 1.5로 조절한다. 이는 Al/N 원자비가 0.5 미만이면 상온 내시효성이 안정적으로 확보되지 못하고, 1.5를 초과하면 적정한 고용질소가 확보되지 않아 소부경화능이 저하되기 때문이다.Solid nitrogen is controlled by aluminum, which forms precipitates with nitrogen. Solid nitrogen is also accompanied by problems of room temperature aging resistance and moldability if not properly controlled. The Al / N atomic ratio to control the solid solution nitrogen is adjusted to 0.5 ~ 1.5. This is because when the Al / N atomic ratio is less than 0.5, room temperature aging resistance is not stably secured, and when the Al / N atomic ratio is more than 1.5, proper solid solution nitrogen is not secured, and thus the hardening hardening ability is lowered.
또한, 본 발명의 합금조성은 가공성 및 스폿 용접성을 악화시키는 원소인 망간 함량을 낮추어 가공성 및 스폿 용접성을 향상시킨다. 이때, 망간 함량을 낮춤에 의해 발생되는 냉연강판의 강도저하는 NbC와 AlN 석출경화를 통한 조직균일 및 미세화를 통해 보강된다. In addition, the alloy composition of the present invention lowers the manganese content, which is an element deteriorating workability and spot weldability, thereby improving workability and spot weldability. At this time, the decrease in strength of the cold rolled steel sheet produced by lowering the manganese content is reinforced through tissue uniformity and refinement through NbC and AlN precipitation hardening.
본 발명의 냉연강판에 함유되는 성분들에 대한 설명은 중량 %(이하에서는 %라 함)을 기준으로 설명하면 다음과 같다.Description of the components contained in the cold rolled steel sheet of the present invention will be described based on weight% (hereinafter referred to as%).
1.탄소(C): 0 초과 0.005 % 이하1.Carbon (C): more than 0 and less than 0.005%
탄소(C)의 양이 0.005% 이상이 되면, 탄소를 고착시키기 위한 니오븀(Nb)의 양이 증가하여 강의 제조비용이 증가할 뿐만 아니라, 강의 가공성이 감소한다. When the amount of carbon (C) is 0.005% or more, the amount of niobium (Nb) for fixing carbon is increased to increase the manufacturing cost of the steel and decrease the workability of the steel.
또한, 니오븀에 의한 탄소의 고착이 충분하지 못할 경우 탄소에 의한 시효현상이 빠르게 진행되어 강의 상온 내시효성을 감소시킬 수 있다. 따라서 탄소의 첨가량을 0.005%이하로 제한한다. In addition, when the carbon is not sufficiently adhered by niobium, the aging phenomenon due to carbon proceeds rapidly, thereby reducing the room temperature aging resistance of the steel. Therefore, the amount of carbon added is limited to 0.005% or less.
2. 규소(Si) : 0 초과 0.3%이하2. Silicon (Si): more than 0 and less than 0.3%
규소(Si)는 강종에 고용으로 존재하는 탄소의 활동도를 증가시켜 상온 내시 효성을 나쁘게 하고, 도금시 도금품질을 크게 저하시킨다. 그리고 첨가량이 증가할수록 고용강화효과에 의해서 강도는 증가하지만 그에 따른 연성의 감소가 일어나므로 규소의 상한첨가량을 0.3%로 제한한다Silicon (Si) increases the activity of carbon present in solid solution in steel grades, thereby deteriorating the aging resistance at room temperature and greatly reducing the plating quality during plating. As the added amount increases, the strength increases due to the solid solution effect, but the ductility decreases, so the upper limit of silicon is limited to 0.3%.
3. 망간(3. Manganese MnMn ) : 0.1~1.0%): 0.1 ~ 1.0%
망간(Mn)은 강중에 고용상태로 존재하여 강의 강도를 증가시키는 기능을 갖지만, 첨가량이 1.0% 이상이 되면 강의 연성이 크게 감소하므로 망간의 상한 첨가량을 1.0%로 한다. 그러나 강중에 망간이 첨가되지 않으면 강중에 존재하는 황에 의한 고온취성이 일어날수 있어 망간의 하한 첨가량을 0.1%로 제한하는 것이 바람직하다. Manganese (Mn) exists in solid solution in the steel and has a function of increasing the strength of the steel, but when the amount added is more than 1.0%, the ductility of the steel is greatly reduced, so the upper limit of manganese is 1.0%. However, if manganese is not added to the steel, high temperature brittleness may occur due to sulfur present in the steel, so the lower limit of the amount of manganese is preferably limited to 0.1%.
4. 인(P) : 0.005~0.1%4. Phosphorus (P): 0.005 ~ 0.1%
인(P)은 강중에 고용상태로 존재하여 강의 강도를 증가시키는 기능을 갖는다. 다만, 첨가량이 0.1% 이상이 되면 강의 연성이 크게 감소하고, 용접성이 크게 저하되므로 인의 상한 첨가량을 0.1%로 한다. 하지만 강중에 망간이 첨가되지 않으면 강의 충분한 강도확보가 어렵기 때문에, 인의 하한 첨가량을 0.005%로 제한하는 것이 바람직하다. Phosphorus (P) is in solid solution in the steel and has a function of increasing the strength of the steel. However, when the added amount is 0.1% or more, the ductility of the steel is greatly reduced, and the weldability is greatly reduced, so the upper limit of phosphorus is made 0.1%. However, if manganese is not added to the steel, it is difficult to secure sufficient strength of the steel. Therefore, it is preferable to limit the minimum amount of phosphorus added to 0.005%.
5. 니오븀(5. Niobium ( NbNb ) : 0.015~0.04%): 0.015 ~ 0.04%
니오븀(Nb)은 강중에 고용상태로 존재하는 탄소를 고착하기 위하여 첨가한 다. 강중에 고용탄소로 존재하는 고용탄소는 냉연집합조직형성을 저해하여 강의 가공성을 감소시킨다. 그리고 고용상태로 존재하는 탄소가 있을 경우 탄소의 빠른 확산에 의해서 상온 내시효성을 열화시키므로 고용탄소를 고착하기 위한 충분한 양의 니오븀이 필요하다. 첨가가 필요한 니오븀의 양은 Nb/C의 원자량이 1이상이 되도록 첨가하여야 되는데, 탄소의 첨가량을 고려하여 하한은 0.015%, 상한은 0.04%로 제한하였다.Niobium (Nb) is added to fix carbon in solid solution in steel. Solid carbon, which is present as solid carbon in the steel, inhibits the formation of cold-rolled aggregates and reduces the workability of the steel. In addition, if carbon exists in solid solution, niobium is required in sufficient amount to fix solid carbon because it deteriorates room temperature aging resistance by rapid diffusion of carbon. The amount of niobium that needs to be added should be added so that the atomic weight of Nb / C is 1 or more. In consideration of the amount of carbon added, the lower limit is limited to 0.015% and the upper limit is 0.04%.
6. 질소(N) : 0.002~0.005% 6. Nitrogen (N): 0.002 ~ 0.005%
일반적으로 질소(N)는 강중에 불가피하게 첨가되는 원소이지만 본 발명에서는 이 질소를 이용하여 소부경화능을 제어하기 때문에 첨가량을 조절할 필요가 있다. 첨가량이 너무 적으면 질소에 의한 소부경화능을 확보할 수 없고, 너무 많게 되면 질소에 의한 소부경화능은 충분히 확보할 수 있지만, 고용질소에 의한 시효현상이 발생할 수 있고 가공성이 감소할 수 있으므로 질소의 첨가량을 0.002~0.005%로 한다. In general, nitrogen (N) is an element that is inevitably added to steel, but in the present invention, since the baking hardening ability is controlled using this nitrogen, the amount of addition needs to be adjusted. If the addition amount is too small, the baking hardening capacity by nitrogen cannot be secured. If the adding amount is too high, the baking hardening capacity by nitrogen can be sufficiently secured, but the aging phenomenon by solid solution nitrogen may occur and the workability may be reduced. The addition amount of is set to 0.002 to 0.005%.
7. 알루미늄(7. Aluminum ( AlAl ) : 0.001 ~ 0.03% ): 0.001 ~ 0.03%
알루미늄(Al)은 강의 탈산을 위하여 첨가되기도 하지만 본 발명에서는 질소와 결합하여 소부경화능을 제어하는데 이용한다. 알루미늄의 첨가량이 0.001% 미만이 되면 탈산기능이 저하되어 강중에 산소가 존재하게 되어 제강시 망간, 실리콘 등의 산화물 형성원소가 첨가될 경우 망간산화물, 실리콘 산화물등을 형성하기 때 문에 망간, 실리콘 등의 성분제어가 힘들게 된다. 그러나 알루미늄의 양이 0.03% 이상이 되면 필요이상으로 첨가되어 강중에 존재하는 질소와 반응하여 질화 알루미늄(AlN) 석출물을 형성하기 때문에 질소에 의한 소부경화능을 얻을 수 없다. 따라서 알루미늄의 상한 첨가량을 0.03% 로 제한한다. Aluminum (Al) may be added for deoxidation of steel, but in the present invention, it is used to control the baking hardening ability by combining with nitrogen. When the amount of aluminum added is less than 0.001%, the deoxidation function is deteriorated and oxygen is present in the steel. When the oxide forming elements such as manganese and silicon are added during steelmaking, manganese oxide and silicon oxide are formed. Control of components, etc. becomes difficult. However, when the amount of aluminum is more than 0.03%, it is added more than necessary to react with nitrogen present in the steel to form aluminum nitride (AlN) precipitates, so it is not possible to obtain the small hardening ability by nitrogen. Therefore, the upper limit of the addition amount of aluminum is limited to 0.03%.
그외에도, 황(S)은 일반적으로 강의 제조시 불가피하게 함유되는 원소이므로 그 첨가범위를 0.02%이하로 제한한다.In addition, since sulfur (S) is generally an element that is inevitably contained in the production of steel, the addition range is limited to 0.02% or less.
아래의 표 1은 각각의 성분 요소가 다른 본 발명의 실시예와 비교예를 나타낸 것이다.Table 1 below shows examples and comparative examples of the present invention in which each component element is different.
[표 1]TABLE 1
번호River
number
상기한 표 1에서의 비교예와 본 발명의 실시예는 용해된 강의 강괴를 1250℃의 가열로에서 두시간 유지한 후에 열간압연을 시행한 것으로서, 열간압연의 마무리 온도는 900℃이며, 열연 권취 온도는 560℃이고, 냉간 압하율을 70%로 하여 냉간압연을 실시하되, The comparative example and the embodiment of the present invention described in Table 1 were subjected to hot rolling after maintaining the molten steel ingot in a heating furnace at 1250 ° C. for two hours, and the finishing temperature of hot rolling was 900 ° C. Is 560 ℃, cold rolling is carried out with a cold reduction rate of 70%,
냉간압연된 시편의 소둔 온도를 800℃로 하고, 냉각속도를 -3℃/sec로 냉각하여 연속 소둔을 하고, 연속 소둔이 끝난 시편을 만능인장 시험기를 이용하여 인장시험을 한 것이다.The annealing temperature of the cold rolled specimen was 800 ° C., the cooling rate was cooled to −3 ° C./sec, followed by continuous annealing, and the tensile annealing test was performed using a universal tensile tester.
아래의 표 2는 표 1의 실시예와 비교예의 열처리 조건 또는 제조조건에 따른 기계적 성질 변화를 나타낸 것이다.Table 2 below shows the change in mechanical properties according to the heat treatment conditions or manufacturing conditions of the Examples and Comparative Examples of Table 1.
[표 2]TABLE 2
번호River
number
비 고
Remarks
(MPa)Yield strength
(MPa)
(MPa)The tensile strength
(MPa)
(%)Elongation
(%)
(MPa)BH
(MPa)
(MPa)AI
(MPa)
상기한 표2에 표시된 바와 같이, 시료번호 1~4번은 본 발명의 실시예에 해당하며, 인장강도가 270~360MPa 이고, 연신율은 38~47% 이며, 소부경화강 33~40MPa이고, 시효지수는 30 이하로 고강도강이면서 우수한 연성을 유지함과 아울러, 높은 소부경화능을 가지면서도 상온 내시효성이 우수한 특성을 보이고 있다.As shown in Table 2, Sample No. 1 to 4 corresponds to the embodiment of the present invention, the tensile strength is 270 ~ 360MPa, the elongation is 38 ~ 47%, the hardening hardened steel 33 ~ 40MPa, the aging index Has a high strength steel of 30 or less and maintains excellent ductility, and exhibits excellent aging resistance at room temperature while having high bake hardening ability.
한편 5,6,8번 비교예는 Al의 첨가량이 높아 권취공정에서 낮은 권취 온도로 실시하였음에도 불구하고 알루미늄이 질소를 고착하여 충분한 소부경화능을 확보할 수 없게 된다.On the other hand, in Comparative Examples Nos. 5, 6 and 8, although Al was added at a low winding temperature in the winding process, aluminum did not secure sufficient baking hardening capacity due to the fixation of nitrogen.
또, 7번 비교예는 니오븀이 첨가되지 않아서 강중에 고용상태로 존재하는 탄소의 량이 많아 소부경화능은 높지만 상온 내시효성이 낮아지게 된다.In Comparative Example 7, niobium is not added, so the amount of carbon present in solid solution in the steel is high, so that the hardening hardening ability is high, but the room temperature aging resistance is low.
도 1은 상기한 비교예들과 실시예들중 각각 하나의 예(번호 1의 실시예,번호 5의 비교예)에서 열연 권취 온도에 따른 소부 경화값의 변화를 나타낸 그래프이고, 도 2는 소둔 온도에 따른 소부경화값의 변화를 나타낸 그래프이다.1 is a graph showing a change in the bake hardening value according to the hot-rolled winding temperature in each of the above-described comparative examples and examples (Example 1, Comparative Example 5), Figure 2 is annealing It is a graph showing the change of the baking hardening value with temperature.
도 1에서와 같이, 1번 실시예의 권취온도가 낮아짐에 따라 소부경화능이 증가하고, 특히 600℃ 이하에서 급격하게 소부경화능이 증가함을 알 수 있다.As shown in Figure 1, as the winding temperature of Example 1 is lowered, the baking hardening ability is increased, particularly, it can be seen that the baking hardening capacity rapidly increases below 600 ℃.
이는, 열연 권취온도가 낮아질 경우 AlN의 석출이 지연되기 때문에 고용상태의 질소가 많이 존재할 수 있기 때문이다.This is because the precipitation of AlN is delayed when the hot rolled winding temperature is lowered, so that a large amount of solid nitrogen may be present.
이로 인해 열연 권취공정에서 충분한 고용질소를 확보한 실시예 1,2,3,4에서는 도 2에서와 같이, 낮은 소둔온도에서도 충분한 소부 경화능을 확보할 수 있으므로 저온 소둔이 가능하게 된다. 소둔온도가 낮을수록 에너지가 절감되고 합금화 용융도금 특성이 향상된다. For this reason, in Examples 1, 2, 3, and 4, in which sufficient solid solution nitrogen is secured in the hot rolled winding process, as shown in FIG. 2, sufficient baking hardening ability can be ensured even at low annealing temperature, thereby enabling low temperature annealing. Lower annealing temperature saves energy and improves alloying hot-dip plating characteristics.
도 1은 본 발명에 따른 냉연강판의 제조방법에 의해 제조된 실시예와 다른 성분을 갖는 비교예를 대비한 것으로, 열연 권취 온도에 따른 소부 경화값의 변화를 나타낸 그래프.1 is a graph showing a change in the bake hardening value according to the hot-rolled coiling temperature, in contrast to the comparative example having a different component from the embodiment manufactured by the method for manufacturing a cold rolled steel sheet according to the present invention.
도 2는 본 발명 실시예와 비교예의 소둔 온도에 따른 소부경화값의 변화를 나타낸 그래프이다.2 is a graph showing the change in the bake hardening value according to the annealing temperature of the Examples and Comparative Examples of the present invention.
Claims (4)
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| DE112008001551T DE112008001551B4 (en) | 2007-10-29 | 2008-10-23 | A cold rolled steel sheet and process for its production |
| US12/602,764 US20100172788A1 (en) | 2007-10-29 | 2008-10-23 | Cold rolledsteel sheet and method for manufacturing the same |
| PCT/KR2008/006260 WO2009057911A1 (en) | 2007-10-29 | 2008-10-23 | A cold rolledsteel sheet and method for manufacturing the same |
| CN200880019601XA CN101680046B (en) | 2007-10-29 | 2008-10-23 | A cold rolledsteel sheet and method for manufacturing the same |
| JP2010511132A JP2010530030A (en) | 2007-10-29 | 2008-10-23 | Cold rolled steel sheet and method for producing the same |
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| JPH0525549A (en) * | 1991-07-22 | 1993-02-02 | Nippon Steel Corp | Production of cold rolled steel sheet excellent in baking hardenability |
| JP2002030383A (en) | 2000-07-11 | 2002-01-31 | Nippon Steel Corp | Hot dip galvanized steel sheet excellent in baking hardenability, powdering resistance and press formability and its production method |
| JP2002053933A (en) * | 2000-08-04 | 2002-02-19 | Nippon Steel Corp | Cold-rolled steel sheet or hot-rolled steel sheet having excellent hardenability in coating/baking and cold aging resistance, and its production method |
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| US3761324A (en) * | 1971-01-18 | 1973-09-25 | Armco Steel Corp | Columbium treated low carbon steel |
| US3847682A (en) * | 1972-11-14 | 1974-11-12 | Armco Steel Corp | Method of strengthening low carbon steel and product thereof |
| JP3140289B2 (en) * | 1994-04-08 | 2001-03-05 | 新日本製鐵株式会社 | Method for manufacturing high-strength cold-rolled steel sheet for automobiles that has excellent formability, has paint bake hardenability, and has little variation in paint bake hardenability in the width direction. |
| JP3596037B2 (en) * | 1994-08-01 | 2004-12-02 | Ｊｆｅスチール株式会社 | Manufacturing method of steel plate for can-making |
| JPH0892695A (en) * | 1994-09-29 | 1996-04-09 | Kawasaki Steel Corp | Steel sheet for two-piece can excellent in can making workability and flanging workability and its production |
| US5954896A (en) * | 1995-02-23 | 1999-09-21 | Nippon Steel Corporation | Cold rolled steel sheet and galvanized steel sheet having improved homogeneity in workability and process for producing same |
| KR100256371B1 (en) * | 1995-12-30 | 2000-05-15 | 이구택 | The method for resin coated cold sheet |
| JP4177478B2 (en) * | 1998-04-27 | 2008-11-05 | Ｊｆｅスチール株式会社 | Cold-rolled steel sheet, hot-dip galvanized steel sheet excellent in formability, panel shape, and dent resistance, and methods for producing them |
| JP3745496B2 (en) * | 1997-04-18 | 2006-02-15 | 新日本製鐵株式会社 | Manufacturing method of cold-rolled steel sheet and alloyed hot-dip galvanized steel sheet with excellent paint bake hardening performance |
| JP3353688B2 (en) * | 1998-02-24 | 2002-12-03 | 住友金属工業株式会社 | Cold rolled steel sheet for enamel and its manufacturing method |
| CN1174109C (en) * | 2002-09-20 | 2004-11-03 | 武汉钢铁(集团)公司 | Tagger steel strip for battery casing, and producing method thereof |
| JP4337764B2 (en) * | 2005-04-08 | 2009-09-30 | 住友金属工業株式会社 | High-strength cold-rolled steel sheet, hot-dip galvanized steel sheet, and production method thereof |
| JP4715496B2 (en) * | 2005-12-15 | 2011-07-06 | Ｊｆｅスチール株式会社 | Method for producing cold-rolled steel sheets with excellent strain aging resistance and small in-plane anisotropy |
| JP4900179B2 (en) * | 2007-10-11 | 2012-03-21 | Ｊｆｅスチール株式会社 | Manufacturing method of steel plate for can |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JPH0525549A (en) * | 1991-07-22 | 1993-02-02 | Nippon Steel Corp | Production of cold rolled steel sheet excellent in baking hardenability |
| JP2002030383A (en) | 2000-07-11 | 2002-01-31 | Nippon Steel Corp | Hot dip galvanized steel sheet excellent in baking hardenability, powdering resistance and press formability and its production method |
| JP2002053933A (en) * | 2000-08-04 | 2002-02-19 | Nippon Steel Corp | Cold-rolled steel sheet or hot-rolled steel sheet having excellent hardenability in coating/baking and cold aging resistance, and its production method |
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