KR100435466B1 - A method for manufacturing p added extra low carbon cold rolled steel sheet with superior deep drawability - Google Patents

A method for manufacturing p added extra low carbon cold rolled steel sheet with superior deep drawability Download PDF

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KR100435466B1
KR100435466B1 KR10-1999-0059644A KR19990059644A KR100435466B1 KR 100435466 B1 KR100435466 B1 KR 100435466B1 KR 19990059644 A KR19990059644 A KR 19990059644A KR 100435466 B1 KR100435466 B1 KR 100435466B1
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steel
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cold rolled
low carbon
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KR20010062900A (en
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진광근
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주식회사 포스코
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
    • C21D8/0436—Cold rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
    • C21D8/0426—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
    • C21D8/0463—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment following hot rolling
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Sheet Steel (AREA)

Abstract

본 발명은 극저탄소강판의 제조방법에 관한 것으로, Ti의 함량을 높여 강중 고용 Ti의 양을 증가시키고, 열간압연 후 계단식냉각을 실시함으로써, 생산성 및 재질 향상이 뛰어나고 딥 드로잉성이 우수한 P첨가 극저탄소냉연강판을 제조하는데, 목적이 있다.The present invention relates to a method for manufacturing an ultra low carbon steel sheet, by increasing the content of Ti to increase the amount of solid solution Ti in the steel, and by performing stepwise cooling after hot rolling, it is excellent in productivity and material improvement and excellent P drawing pole To produce a low carbon cold rolled steel sheet, there is a purpose.

본 발명은 냉연강판의 제조방법에 있어서,The present invention is a method for manufacturing a cold rolled steel sheet,

중량%로 C:0.005% 이하, Si:0.02% 이하, Mn:1.0% 이하, P:0.02~0.10%, S:0.005% 이하, N:0.002% 이하, sol.Al:0.01~0.04%, Ti:0.05~0.15%, Nb:0.005% 이하, 6.5N%+3S%≤Zr≤0.03%, 잔부 Fe 및 기타 불가피한 불순물로 조성된 강 슬라브를 910℃ 이상의 마무리압연온도 조건으로 열간압연하여 열연판을 제조한 후, 30~70℃/초의 냉각속도로 680~720℃까지 급냉한 다음 630~650℃까지 5~10초 동안 공냉한 후 급냉하고, 550~600℃의 온도범위에서 권취한 후 냉간압연하고, 780~850℃의 온도에서 30초~3분간 연속소둔한 다음 냉각하는 것을 특징으로 하는 딥드로잉성이 우수한 P첨가 극저탄소강의 제조방법을 그 기술적 요지로 한다.C: 0.005% or less, Si: 0.02% or less, Mn: 1.0% or less, P: 0.02 to 0.10%, S: 0.005% or less, N: 0.002% or less, sol.Al: 0.01 to 0.04%, Ti : 0.05 ~ 0.15%, Nb: 0.005% or less, 6.5N% + 3S% ≤Zr≤0.03%, steel slab composed of balance Fe and other unavoidable impurities is hot rolled at the finish rolling temperature of 910 ℃ or higher After manufacturing, it is quenched to 680 ~ 720 ℃ at a cooling rate of 30 ~ 70 ℃ / second, and then cooled by air for 5 ~ 10 seconds to 630 ~ 650 ℃, then quenched, and then cold rolled at a temperature range of 550 ~ 600 ℃. In addition, a method of manufacturing P-added ultra-low carbon steel having excellent deep drawing properties, which is continuously annealed for 30 seconds to 3 minutes at a temperature of 780 to 850 ° C. and then cooled, has the technical gist of the present invention.

Description

딥드로잉성이 우수한 Ｐ첨가 극저탄소 냉연강판의 제조방법{A METHOD FOR MANUFACTURING P ADDED EXTRA LOW CARBON COLD ROLLED STEEL SHEET WITH SUPERIOR DEEP DRAWABILITY}Manufacturing method of P-added ultra low carbon cold rolled steel sheet with excellent deep drawing property {A METHOD FOR MANUFACTURING P ADDED EXTRA LOW CARBON COLD ROLLED STEEL SHEET WITH SUPERIOR DEEP DRAWABILITY}

본 발명은 자동차의 차체 경량화에 사용되는 고강도 냉연강판에 관한 것으로서, 보다 상세하게는 인 첨가 극저탄소강에 다량의 Ti을 첨가하고 계단식냉각을 적용함으로써 우수한 딥 드로잉성을 제공할 수 있는 P첨가 극저탄소 냉연강판을 제조하는 방법에 관한 것이다.The present invention relates to a high-strength cold-rolled steel sheet used to reduce the weight of automobiles, and more particularly, by adding a large amount of Ti to phosphorus-added ultra low carbon steel and applying stepwise cooling, P-added poles can be provided with excellent deep drawing properties. It relates to a method for producing a low carbon cold rolled steel sheet.

자동차용 고강도 냉연강판은, 강화원소로 P를 주로 이용하고 탄소를 석출시키기 위해 Ti을 사용하여 제조되는데, 종래에는 Ti,Nb 또는 Ti+Nb를 첨가하는데 있어서 FeTiP의 대량석출을 억제하고 고용탄소를 석출시키기 위하여 Ti양을 0.05%이하로 하고, 열간압연한 후 일정속도로 냉각한 다음 마지막 단계에서 권취온도를 600~650℃로 제어하여 제조하였다. 이 때, 탄소가 석출하는 과정에서 P가 FeTiP의인화물로 석출하여 드로잉성이 저하하는 문제가 있어서, 성형이 복잡한 부품의 가공에 적용되지 못하고 있다.High strength cold rolled steel sheets for automobiles are manufactured using P mainly as a reinforcing element and Ti to precipitate carbon. Conventionally, in order to add Ti, Nb or Ti + Nb, it is possible to suppress the large precipitation of FeTiP and In order to precipitate, the Ti amount was 0.05% or less, hot-rolled and cooled at a constant speed, and then the winding temperature was controlled to 600-650 ° C. in the last step. At this time, P is precipitated as a phosphide of FeTiP in the process of depositing carbon, and the drawing property is deteriorated, and thus it is not applied to the processing of a component having a complicated molding.

딥 드로잉성이 우수한 극저탄소 고강도 냉연강판으로 공지된 기술로는 일본특허 공개공보92-000957호 및 일본특허 공개공보94-57372호 등이 있는데, 이들 방법에서는 탄소함량이 50ppm이하인 알루미늄 킬드 극저탄소강에 Mn, Si, P 등의 고용강화 원소를 첨가하여 강도와 드로잉성을 확보하고 있으나, 랭크포드값이 2.0이하로 비교적 낮다.Known techniques for ultra low carbon high strength cold rolled steel with excellent deep drawing properties include Japanese Patent Application Laid-Open No. 92-000957 and Japanese Patent Application Publication No. 94-57372. In these methods, aluminum-killed ultra-low carbon steel having a carbon content of 50 ppm or less. The addition of solid solution strengthening elements such as Mn, Si, and P to secure the strength and drawability, but the Rankford value is relatively low, 2.0 or less.

한편, 최근에는 0.02%Ti-0.02%Nb첨가 극저탄소강에 1.4%Mn을 첨가하고 350℃정도의 저온에서 권취하여 열연단계에서 FeTiP석출물의 석출을 억제하고 냉연후에는 연속소둔과 같은 급속가열소둔을 하는 방법(철과강,1990,p.422)이 있다. 그러나, 이 방법에서도 역시 드로잉성이 낮은 문제점이 있다.On the other hand, recently added 1.4% Mn to 0.02% Ti-0.02% Nb addition ultra low carbon steel and wound at a low temperature of about 350 ° C to suppress the precipitation of FeTiP precipitates in the hot rolling step, and rapid heating annealing such as continuous annealing after cold rolling (Steel and Steel, 1990, p. 422). However, this method also has a problem of low drawability.

또한, 열연판의 결정립이 미세하면 딥 드로잉성이 개선되므로, 종래에는 IF강의 열연판의 결정립을 미세화하기 위해서 마무리압연 마지막 단계에서 가속냉각을 하는 방법이 제시되기도 하였다. 그러나, 이 경우 압연판의 치수나 온도를 측정하는 계측기의 수증기 오염을 유발하는 문제점이 있다.In addition, since the deep drawing property is improved when the grains of the hot rolled sheet are fine, conventionally, a method of accelerated cooling at the final stage of finishing rolling has been proposed in order to refine the grains of the hot rolled sheet of IF steel. However, in this case, there is a problem that causes water vapor contamination of the measuring instrument for measuring the dimensions and the temperature of the rolled sheet.

이에, 본 발명자는 상기와 같은 문제점을 해결하기 위하여 연구와 실험을 거듭하고 그 결과에 근거하여 본 발명을 제안하게 된 것으로, 본 발명은 Ti의 함량을높여 강중 고용 Ti의 양을 증가시키고, 열간압연 후 계단식냉각을 실시함으로써, 생산성 및 재질 향상이 뛰어나고 딥 드로잉성이 우수한 P첨가 극저탄소냉연강판을 제조하는데, 그 목적이 있다.Accordingly, the present inventors have repeatedly conducted research and experiments to solve the above problems, and suggest the present invention based on the results. The present invention increases the amount of solid solution Ti in steel by increasing the content of Ti and hot. By carrying out the step cooling after rolling, to produce a P-added ultra-low carbon cold rolled steel sheet excellent in productivity and material improvement and excellent deep drawing property, the purpose is.

도1은 본 발명과 종래의 냉각방법을 비교한 냉각곡선1 is a cooling curve comparing the present invention and the conventional cooling method

본 발명은 극저탄소 냉연강판의 제조방법에 있어서,The present invention provides a method for producing an ultra low carbon cold rolled steel sheet,

중량%로 C:0.005% 이하, Si:0.02% 이하, Mn:1.0% 이하, P:0.02~0.10%, S:0.005% 이하, N:0.002% 이하, sol.Al:0.01~0.04%, Ti:0.05~0.15%, Nb:0.005% 이하, 6.5N%+3S%≤Zr≤0.03%, 잔부 Fe 및 기타 불가피한 불순물로 조성된 강 슬라브를 910℃ 이상의 마무리압연온도 조건으로 열간압연하여 열연판을 제조한 후, 30~70℃/초의 냉각속도로 680~720℃까지 급냉한 다음 630~650℃까지 5~10초 동안 공냉한 후 급냉하고, 550~600℃의 온도범위에서 권취한 후 냉간압연하고, 780~850℃의 온도에서 30초~3분간 연속소둔한 다음, 냉각하는 것을 특징으로 하는 딥드로잉성이 우수한 P첨가 극저탄소강의 제조방법에 관한 것이다.C: 0.005% or less, Si: 0.02% or less, Mn: 1.0% or less, P: 0.02 to 0.10%, S: 0.005% or less, N: 0.002% or less, sol.Al: 0.01 to 0.04%, Ti : 0.05 ~ 0.15%, Nb: 0.005% or less, 6.5N% + 3S% ≤Zr≤0.03%, steel slab composed of balance Fe and other unavoidable impurities is hot rolled at the finish rolling temperature of 910 ℃ or higher After manufacturing, it is quenched to 680 ~ 720 ℃ at a cooling rate of 30 ~ 70 ℃ / second, and then cooled by air for 5 ~ 10 seconds to 630 ~ 650 ℃, then quenched, and then cold rolled at a temperature range of 550 ~ 600 ℃. The present invention relates to a method for producing P-added ultra low carbon steel having excellent deep drawing properties, which is subsequently annealed at a temperature of 780 ° C. to 850 ° C. for 30 seconds to 3 minutes.

이하, 본 발명에 대하여 설명한다.EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

상기 C는 탄화물로 존재하지 않고 고용탄소로 존재하면 드로잉성을 저해하는 작용을 하기 때문에, 그 함량은 0.005% 이하로 제한하는 것이 바람직하다.Since C does not exist as a carbide but as a solid solution of carbon, it inhibits the drawing property, so the content thereof is preferably limited to 0.005% or less.

상기 Si는 강중에 산화물로 작용하여 연성을 저해하기 때문에, 0.02% 이하로제한하는 것이 바람직하다.Since said Si acts as an oxide in steel and inhibits ductility, it is preferable to limit it to 0.02% or less.

상기 Mn은 강도를 증가시키고, 강중 고용탄소가 존재하지 않으면 드로잉성에 영향을 미치지 않기 때문에 1.0% 까지 첨가될 수 있다. 그러나, 1.0%보다 과잉 첨가될 경우에는 Mn에 의한 소입성 증가로 열간압연후 베이나이틱 페라이트가 형성됨으로써 드로잉성을 저하시키므로, 그 함량은 1.0% 미만으로 제한하는 것이 바람직하다.The Mn increases the strength and may be added up to 1.0% because it does not affect the drawability without the presence of solid solution carbon in the steel. However, when added in excess of 1.0%, since bainitic ferrite is formed after hot rolling due to an increase in the hardenability by Mn, the drawing property is lowered. Therefore, the content is preferably limited to less than 1.0%.

상기 P은 첨가량에 비해 고용강화 효과가 가장 우수한 원소로, 가격이 저렴하기 때문에 합금비용이 낮은 장점을 가지고 있다. 그러나, 극저탄소강에서 탄소를 석출시키기 위해 첨가하는 Ti과 결합하여 FeTiP를 형성하면 소둔시 재결정온도를 상승시켜 드로잉성과 연성을 저하시키는 문제가 있다. 따라서, 본 발명에서는 냉각방법과 권취온도를 제어하여 FeTiP석출을 억제하는 강화원소로 P이 첨가된다. 그러나, 그 함량이 0.10%를 초과하면 점용접성을 해치므로, 0.10% 이하로 제한하는 것이 바람직하다.The P is an element having the highest solid solution strengthening effect compared to the added amount, and has an advantage of low alloy cost because of low price. However, when FeTiP is formed by combining with Ti added to precipitate carbon in the ultra low carbon steel, there is a problem in that the recrystallization temperature is increased during annealing, thereby degrading the drawability and ductility. Therefore, in the present invention, P is added as a reinforcing element that suppresses FeTiP precipitation by controlling the cooling method and the winding temperature. However, if the content exceeds 0.10%, the spot weldability is impaired, so it is preferable to limit it to 0.10% or less.

상기 S은 강중에서 Zr와 결합하여 황화물을 만드는 원소로, 그 함량이 0.005%까지는 Zr4C2S2의 석출물을 형성하여 드로잉성을 증가시키지만, 0.005%를 초과하는 경우에는 ZrS로 석출하여 드로잉성에 영향을 미치지 않는다. 따라서, 본 발명에서는 드로잉성 개선을 위해, 그 함량을 0.005% 이하로 설정하는 것이바람직하다.S is an element that forms sulfides by combining with Zr in steel, and the content of Zr 4 C 2 S 2 forms precipitates up to 0.005% to increase the drawability, but when it exceeds 0.005%, it is precipitated as ZrS and drawn. Does not affect sex Therefore, in the present invention, in order to improve the drawing property, it is preferable to set the content to 0.005% or less.

상기 N는 강중 Ti, Zr 등과 결합하여 연성을 저하시키기 때문에, 0.002% 이하로 제한하는 것이 바람직하다.Since N combines with Ti, Zr, etc. in steel to reduce ductility, it is preferable to limit the content to 0.002% or less.

상기 Al은 그 함량이 0.01% 미만인 경우에는 주편터짐이 발생하고, 반면에 0.04%를 초과하면 경제성을 해치므로, 그 함량은 0.01~0.04%로 설정하는 것이 바람직하다.When the Al content is less than 0.01% cast iron burst occurs, on the other hand, if the content exceeds 0.04% impairs the economic efficiency, the content is preferably set to 0.01 ~ 0.04%.

상기 Ti은 강중 탄소와 결합하여 탄화물을 형성하거나 다량으로 첨가하면 고용 Ti으로 존재하여 드로잉성을 증가시키지만, 반대로 인화물(FeTiP)을 형성하면 드로잉성을 감소시킨다. 탄화물과 인화물의 형성은 압연후 냉각과정과 권취과정에서 이루어지기 때문에, 열연후 냉각 및 권취조건을 제어하여 탄화물은 석출시키고 인화물은 형성되지 않도록 하였다. 따라서, 상기 Ti의 함량은 탄소와 결합하고 고용 Ti을 0.03% 이상이 되도록 하기 위해서 0.05%이상으로 해야한다. 그러나, Ti이 너무 많이 첨가되면 연주공정에서 산화물(TiO2)가 형성되고 노즐에 부착되어 작업성을 저하시키기 때문에, 그 함량은 0.05~0.15%로 제한하는 것이 바람직하다.When Ti is combined with carbon in steel to form carbides or when added in a large amount, Ti exists as solid solution Ti to increase the drawability, whereas on the contrary, when TiO is formed, the drawability is reduced. Since the formation of carbide and phosphide is carried out during cooling and winding after rolling, the cooling and winding conditions after hot rolling were controlled to precipitate carbide and prevent phosphide from forming. Therefore, the content of Ti should be 0.05% or more in order to bond with carbon and make the solid solution Ti more than 0.03%. However, when too much Ti is added, oxides (TiO 2 ) are formed in the reproducing process and adhere to the nozzles, thereby degrading workability. Therefore, the content is preferably limited to 0.05 to 0.15%.

상기 Zr은 강 중 질소와 황을 고온에서 석출물로 고정시켜 슬라브 품질을 개선시키는 작용을 한다. 따라서, Zr은 최소한 강중 질소와 S를 제거할 수 있는 양을 초과하여 첨가해야 하는데, 일부분은 강중 탄소와 작용하게 하기 위하여 6.5N%+3S%≤Zr≤0.03%로 한정하는 것이 바람직하다. 상기 Zr의 함량이 6.5N%+3S% 미만이면 강중 N와 S을 완전하게 고정시킬 수 없으며, 0.03%를 초과하면 첨가에 따른 상기 효과가 포화된다.The Zr serves to improve the slab quality by fixing nitrogen and sulfur in the steel as precipitates at high temperatures. Therefore, Zr should be added at least in excess of the amount capable of removing nitrogen and S in the steel, and part of it is preferably limited to 6.5N% + 3S% ≦ Zr ≦ 0.03% in order to work with carbon in the steel. If the content of Zr is less than 6.5N% + 3S%, N and S in the steel cannot be completely fixed. If the content of Zr exceeds 0.03%, the effect of the addition is saturated.

상기 Nb는 강중에 고용되어 열연판의 결정립을 미세화시킴으로써 압연방향에 대하여 45도 방향의 드로잉성을 증대시키는 성분으로서, 그 함량이 0.005% 이하로 설정하는 것이 바람직한데, 그 이유는 그 함량이 0.005%를 초과하는 경우에는 재결정온도를 상승시켜 항복강도를 증가시키고 연신율을 저하시키기 때문이다.The Nb is a component that increases the drawability in the 45-degree direction with respect to the rolling direction by solidifying the steel grain in the steel sheet to refine the grains, and the content thereof is preferably set to 0.005% or less, because the content is 0.005. If it exceeds%, the recrystallization temperature is increased to increase the yield strength and lower the elongation.

상기와 같이 조성된 강 슬라브를 재가열한 후 열간압연하는데 있어서, 마무리압연 온도는 910℃ 이상인 것이 바람직하다. 그 이유는 상기 온도가 910℃보다 낮으면 압연변형을 받은 결정립의 재결정지연이 일어나 열연판조직상에서 등축립이 얻어지지 않고 (111)소둔집합조직의 발달이 억제되기 때문이다.In hot rolling after reheating the steel slab formed as described above, the finish rolling temperature is preferably 910 ° C or more. The reason is that when the temperature is lower than 910 ° C., recrystallization delay of the grains subjected to rolling deformation occurs, so that equiaxed grains are not obtained on the hot rolled sheet structure and development of the (111) annealing aggregate structure is suppressed.

이후, 상기 열연판을 냉각하여 권취하는데, 본 발명에서는 도1에 나타난 바와 같이, 상기 냉각방식을 계단식냉각으로 하고, 권취온도는 550~600℃로 설정하는 것이 바람직하다. 그 이유는 다음과 같다.Thereafter, the hot rolled sheet is cooled and wound. In the present invention, as shown in FIG. 1, the cooling method is stepwise cooling, and the winding temperature is preferably set to 550 to 600 ° C. The reason for this is as follows.

즉, 본 발명강과 같이 Ti함량이 높은 강을 종래의 방식으로 권취온도 제어지점까지 동일하게 냉각한 후 권취하면, 권취온도가 600℃이상인 경우에는 FeTiP가 석출하여 재결정온도가 상승하고 드로잉성과 연신율이 저하하는 문제가 있다. 반대로, 권취온도가 600℃보다 낮은 경우에는 열연판의 고용탄소가 잔류하여 드로잉성이 저하하여 권취온도설정이 어려운 문제점이 있다.That is, when the steel having a high Ti content as in the present invention is cooled to the winding temperature control point in the same manner as the conventional method and wound up, when the winding temperature is 600 ° C. or more, FeTiP precipitates to increase the recrystallization temperature and drawability and elongation are increased. There is a problem of deterioration. On the contrary, when the coiling temperature is lower than 600 ° C., there is a problem in that the solid solution carbon of the hot rolled sheet remains and the drawing property is lowered, so that the coiling temperature is difficult to set.

따라서, 본 발명에서는 압연후 680~720℃까지는 30~70℃/초의 냉각속도로 급냉하고, 다음 630~650℃까지는 5~10초 동안 공냉하고, 다시 급냉하여 550~600℃의 온도범위에서 권취하는 것이 바람직하다. 이와 같이 하면, 초기 급냉구간에서는 결정립이 미세화되고 공냉구간에서는 탄소가 석출되며, 600℃ 이하로 급냉하여 FeTiP의 석출을 억제함으로써, 고용Ti의 역할과 드로잉성을 현저히 증가시킬 수 있다.Therefore, in the present invention, after rolling, quenching is performed at a cooling rate of 30 to 70 ° C./sec to 680 to 720 ° C., followed by air cooling for 5 to 10 seconds to 630 to 650 ° C., followed by quenching again in a temperature range of 550 to 600 ° C. It is desirable to take In this way, crystal grains are refined in the initial quench section, carbon is precipitated in the air-cooled section, and the quenching is performed at 600 ° C. or lower to suppress the precipitation of FeTiP, thereby significantly increasing the role and drawability of solid solution Ti.

그 다음, 냉간압연 및 연속소둔하는데, 상기 소둔온도는 780~850℃로 설정하는 것이 바람직하다. 그 이유는, 상기 온도가 780℃이상이면 (111)소둔집합조직이 형성 및 성장하여 드로잉성이 향상되지만, 850℃를 넘으면 판형상 및 통판성을 저해하는 문제가 있기 때문이다.Then, cold rolling and continuous annealing, the annealing temperature is preferably set to 780 ~ 850 ℃. The reason is that if the temperature is 780 ° C or higher, the (111) annealing aggregate structure is formed and grown, and the drawing property is improved.

한편, 이와 같은 연속소둔은 상기 소둔온도에서 30초~3분간 유지하여 실시하는 것이 바람직하다.On the other hand, it is preferable to perform such continuous annealing at the annealing temperature for 30 seconds to 3 minutes.

이하, 본 발명의 특징에 대하여 상세히 설명한다.Hereinafter, the features of the present invention will be described in detail.

본 발명은 강성분과 열연후 냉각 그리고 권취온도를 제어하여 P첨가 극저탄소강의 드로잉성을 향상시키는 방법에 관한 것으로, 저온권취를 함에도 불구하고 Ti, Zr첨가 및 냉각제어에 의해 고용탄소의 효과적인 석출, Ti 다량첨가에 따른 강중 고용 Ti의 효과, Nb, P첨가 및 냉각제어에 따른 결정립미세화 등으로, 소둔시 (111)집합조직을 가진 결정립의 성장을 촉진하여 드로잉성이 현저히 개선된 P첨가극저탄소강을 제조하는데 있다.The present invention relates to a method of improving the drawability of P-added ultra low carbon steel by controlling the steel composition, cooling after hot rolling, and winding temperature, and effective precipitation of solid solution carbon by addition of Ti, Zr and cooling despite the low temperature winding. P-added ultra-low carbon with significantly improved drawingability by promoting the growth of grains with (111) aggregation structure during annealing due to the effect of solid solution Ti in the steel due to the large amount of Ti, the addition of Nb, P, and micronization due to cooling control To manufacture steel.

이하, 실시예를 통하여 본 발명을 구체적으로 설명한다.Hereinafter, the present invention will be described in detail through examples.

(실시예)(Example)

하기 표1에 나타낸 조성을 가진 발명강 및 비교강 슬라브를 1200℃에서 1시간 가열하고, 920℃에서 마무리 열간압연하여 4mm 두께의 열연강판을 제조하고, 하기 표2와 같은 조건으로 열연강판을 냉각한 다음 열연판을 산세하여, 80%의 압하율로 두께 0.8mm까지 냉간압연하고 840℃에서 45초간 소둔한 다음, 650℃까지 서냉하고 400℃로 급냉하고 5분간 유지한 다음 상온까지 냉각하였다.The inventive steel and the comparative steel slab having the composition shown in Table 1 were heated at 1200 ° C. for 1 hour, hot rolled at 920 ° C. to produce a 4 mm thick hot rolled steel sheet, and the hot rolled steel sheet was cooled under the conditions shown in Table 2 below. The hot rolled sheet was then pickled, cold rolled to a thickness of 0.8 mm at 80% reduction rate, annealed at 840 ° C. for 45 seconds, slow cooled to 650 ° C., quenched at 400 ° C., held for 5 minutes, and then cooled to room temperature.

하기 표2에서 냉각방식 ①은 30℃/초의 냉각속도로 700℃까지 냉각하고 6초간 공냉하여 650℃가 되면 다시 30℃/초의 냉각속도로 580℃로 냉각하고 1시간 유지한 후 노냉처리하는 것이고, 냉각방식 ②는 열간압연후 30℃/초의 냉각속도로 620℃까지 냉각하여 1시간 유지한 후 노냉하는 것이다.In the following Table 2, the cooling method ① is cooled to 700 ° C. at a cooling rate of 30 ° C./sec and air cooled for 6 seconds to 650 ° C., and then cooled to 580 ° C. at a cooling rate of 30 ° C./second and maintained for 1 hour, followed by a furnace cooling treatment. , Cooling method ② is to cool down to 620 ℃ at 30 ℃ / sec.

상기한 바와 같이, 냉각방식을 달리하여 제조된 소둔판에 대하여 기계적 성질을 측정하고, 그 결과를 하기 표2 및 도1에 나타내었다.As described above, the mechanical properties of the annealing plate manufactured by different cooling methods were measured, and the results are shown in Table 2 and FIG. 1.

강종Steel grade 성분함량(중량%)Ingredient Content (wt%) CC MnMn PP SS NN sol.Alsol.Al TiTi NbNb ZrZr 발명강1Inventive Steel 1 0.00260.0026 0.340.34 0.0350.035 0.0040.004 0.00190.0019 0.0310.031 0.0740.074 0.0030.003 0.0260.026 발명강2Inventive Steel 2 0.00310.0031 0.410.41 0.0740.074 0.0040.004 0.00170.0017 0.0320.032 0.0780.078 0.0250.025 발명강3Invention Steel 3 0.00230.0023 0.350.35 0.0910.091 0.0030.003 0.00180.0018 0.0290.029 0.0810.081 0.0300.030 발명강4Inventive Steel 4 0.00240.0024 0.690.69 0.0310.031 0.0040.004 0.00160.0016 0.0250.025 0.0820.082 0.0240.024 발명강5Inventive Steel 5 0.00250.0025 0.720.72 0.0690.069 0.0040.004 0.00190.0019 0.0390.039 0.0850.085 0.0250.025 발명강6Inventive Steel 6 0.00270.0027 0.670.67 0.0950.095 0.0050.005 0.00180.0018 0.0330.033 0.0790.079 0.0270.027 비교강7Comparative Steel 7 0.00310.0031 0.350.35 0.0670.067 0.0040.004 0.00190.0019 0.0350.035 0.0350.035 0.0050.005 0.0220.022 비교강8Comparative Steel 8 0.00290.0029 0.340.34 0.0740.074 0.0080.008 0.00170.0017 0.0280.028 0.0280.028 0.0100.010 －－ 비교강9Comparative Steel 9 0.00310.0031 0.400.40 0.0690.069 0.0080.008 0.00180.0018 0.0450.045 0.0450.045 －－

구분division 제조조건Manufacture conditions 기계적 성질Mechanical properties 냉각방식Cooling method 권취온도(℃)Winding temperature (℃) 소둔온도(℃)Annealing Temperature (℃) YS(kg/㎟)YS (kg / ㎡) TS(kg/㎟)TS (kg / ㎡) El(%)El (%) r값r value 발명재1Invention 1 발명강1Inventive Steel 1 ①① 580580 840840 18.218.2 33.133.1 43.143.1 2.452.45 비교재1Comparative Material 1 ②② 19.619.6 32.832.8 41.841.8 1.901.90 발명재2Invention 2 발명강2Inventive Steel 2 ①① 22.122.1 37.137.1 40.640.6 2.372.37 비교재2Comparative Material 2 ②② 23.523.5 36.636.6 38.438.4 1.791.79 발명재3Invention 3 발명강3Invention Steel 3 ①① 23.423.4 38.438.4 39.739.7 2.412.41 비교재3Comparative Material 3 ②② 25.025.0 37.137.1 37.637.6 1.811.81 발명재4Invention 4 발명강4Inventive Steel 4 ①① 20.320.3 35.435.4 42.842.8 2.432.43 비교재4Comparative Material 4 ②② 20.920.9 35.035.0 40.340.3 1.891.89 발명재5Invention 5 발명강5Inventive Steel 5 ①① 22.922.9 38.138.1 40.240.2 2.392.39 비교재5Comparative Material 5 ②② 24.024.0 37.937.9 38.438.4 1.821.82 발명재6Invention 6 발명강6Inventive Steel 6 ①① 25.125.1 41.541.5 38.738.7 2.302.30 비교재6Comparative Material 6 ②② 37.437.4 40.940.9 36.536.5 1.761.76 비교재7Comparative Material7 비교강7Comparative Steel 7 ①① 21.621.6 36.636.6 38.738.7 2.152.15 비교재8Comparative Material 8 ②② 620620 21.021.0 36.136.1 39.539.5 2.012.01 비교재9Comparative Material 9 비교강8Comparative Steel 8 ①① 21.721.7 36.836.8 38.838.8 1.931.93 비교재10Comparative Material 10 비교강9Comparative Steel 9 ②② 21.021.0 36.136.1 39.539.5 1.861.86

상기 표2에 나타난 바와 같이, 본 발명의 발명재(1)~(6)은 비교재(1)~(10)대비 인장강도 및 항복강도는 동등수준이고 특히 드로잉성(r값)이 현저하게 우수한 것을 알 수 있다. 그 이유는, 강성분에 Ti을 다량 함유시키고 열간압연후 계단식냉각방식을 적용하여, 강중에 고용탄소와 FeTiP의 석출물이 존재하지 않도록 하고, 결정립을 미세화시켜 소둔과정에서 (111)집합조직의 성장발달을 촉진시켰기 때문이다.As shown in Table 2, the inventive materials (1) to (6) of the present invention compared to the comparative materials (1) to (10), the tensile strength and the yield strength is the same level, especially the drawability (r value) is remarkably It can be seen that it is excellent. The reason is that the steel component contains a large amount of Ti, and hot rolling is applied to the stepwise cooling method so that precipitates of solid carbon and FeTiP do not exist in the steel, and the grains are refined to grow the (111) texture in the annealing process. Because it promoted development.

상기한 바와 같이, 본 발명은, Ti을 적절히 첨가하고 열간압연후 계단식냉각방식을 적용함으로써, 우수한 드로잉성 및 33~41kg/mm2의 인장강도를 갖는 P첨가 극저탄소강을 용이하게 제조하여, 자동차 차체의 경량화를 위한 심가공 부품의 고강도화를 이룰 수 있는 효과가 있는 것이다.As described above, the present invention, by appropriately adding Ti and applying a stepwise cooling method after hot rolling, the P-added ultra-low carbon steel having excellent drawing property and tensile strength of 33 ~ 41kg / mm 2 easily, It is an effect that can achieve a high strength of the deep-worked parts to reduce the weight of the automobile body.

Claims (2)

냉연강판의 제조방법에 있어서,In the manufacturing method of cold rolled steel sheet, 중량%로 C:0.005% 이하, Si:0.02% 이하, Mn:1.0% 이하, P:0.02~0.10%, S:0.005% 이하, N:0.002% 이하, sol.Al:0.01~0.04%, Ti:0.05~0.15%, Nb:0.005% 이하, 6.5N%+3S%≤Zr≤0.03%, 잔부 Fe 및 기타 불가피한 불순물로 조성된 강 슬라브를 910℃ 이상의 마무리압연온도 조건으로 열간압연하여 열연판을 제조한 후, 30~70℃/초의 냉각속도로 680~720℃까지 급냉한 다음 630~650℃까지 5~10초 동안 공냉한 후 급냉하고, 550~600℃의 온도범위에서 권취한 후 냉간압연하고, 780~850℃의 온도에서 30초~3분간 연속소둔한 다음 냉각하는 것을 특징으로 하는 딥드로잉성이 우수한 P첨가 극저탄소 냉연강판의 제조방법.C: 0.005% or less, Si: 0.02% or less, Mn: 1.0% or less, P: 0.02 to 0.10%, S: 0.005% or less, N: 0.002% or less, sol.Al: 0.01 to 0.04%, Ti : 0.05 ~ 0.15%, Nb: 0.005% or less, 6.5N% + 3S% ≤Zr≤0.03%, steel slab composed of balance Fe and other unavoidable impurities is hot rolled at the finish rolling temperature of 910 ℃ or higher After manufacturing, it is quenched to 680 ~ 720 ℃ at a cooling rate of 30 ~ 70 ℃ / second, and then cooled by air for 5 ~ 10 seconds to 630 ~ 650 ℃, then quenched, and then cold rolled at a temperature range of 550 ~ 600 ℃. And, a method for producing P-added ultra-low carbon cold rolled steel sheet excellent in deep drawing, characterized in that the cooling after continuous annealing for 30 seconds to 3 minutes at a temperature of 780 ~ 850 ℃. 삭제delete
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JPS5825435A (en) * 1981-08-05 1983-02-15 Kawasaki Steel Corp Manufacture of deep drawing cold rolling steel plate which is excellent in surface quality and state by continuous annealing
JPS61276930A (en) * 1985-05-31 1986-12-06 Kawasaki Steel Corp Production of cold rolled dead soft steel sheet having good elongation and deep drawability
JPS61276927A (en) * 1985-05-31 1986-12-06 Kawasaki Steel Corp Production of cold rolled steel sheet having good deep drawability

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Publication number Priority date Publication date Assignee Title
JPS5825435A (en) * 1981-08-05 1983-02-15 Kawasaki Steel Corp Manufacture of deep drawing cold rolling steel plate which is excellent in surface quality and state by continuous annealing
JPS61276930A (en) * 1985-05-31 1986-12-06 Kawasaki Steel Corp Production of cold rolled dead soft steel sheet having good elongation and deep drawability
JPS61276927A (en) * 1985-05-31 1986-12-06 Kawasaki Steel Corp Production of cold rolled steel sheet having good deep drawability

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