KR20020044241A - A method for manufacturing high strength cold rolled steel sheet with excellent workability - Google Patents

A method for manufacturing high strength cold rolled steel sheet with excellent workability Download PDF

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KR20020044241A
KR20020044241A KR1020000073231A KR20000073231A KR20020044241A KR 20020044241 A KR20020044241 A KR 20020044241A KR 1020000073231 A KR1020000073231 A KR 1020000073231A KR 20000073231 A KR20000073231 A KR 20000073231A KR 20020044241 A KR20020044241 A KR 20020044241A
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steel sheet
cold rolled
steel
rolled steel
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KR100481364B1 (en
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진광근
홍영광
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이구택
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
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—Cold rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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

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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

PURPOSE: A method for manufacturing a high strength cold rolled steel sheet with excellent workability and secondary working brittleness resistance is provided. Obtained cold rolled steel sheet by this method has a tensile strength of 35 to 40 kgf/mm¬2. CONSTITUTION: The method for manufacturing a high strength cold rolled steel sheet with excellent workability includes the steps of finish hot rolling a steel sheet comprising C 0.02-0.20 wt.%, Mn 0.3-1.5 wt.%, P 0.02-0.05 wt.%, S 0.02 wt.% or less, N 0.0030 wt.% or less, B 0.0005-0.003 wt.%, Mo 0.02-0.1 wt.%, sol-Al 0.1 wt.% or less, a balance of Fe and other inevitable impurities in the temperature range of Ar3 to Ar3+50°C; coiling the hot rolled steel sheet in the temperature range of 600 to 680°C; pickling and cold rolling; and annealing the cold rolled steel sheet in the temperature range of 760 of 850°C for less than 3 minutes. Additionally, the high strength cold rolled steel sheet is added with Nb 0.003-0.01 wt.%.

Description

가공성이 우수한 고강도 냉연강판의 제조방법{A METHOD FOR MANUFACTURING HIGH STRENGTH COLD ROLLED STEEL SHEET WITH EXCELLENT WORKABILITY}Manufacturing method of high strength cold rolled steel sheet with excellent workability {A METHOD FOR MANUFACTURING HIGH STRENGTH COLD ROLLED STEEL SHEET WITH EXCELLENT WORKABILITY}

본 발명은 자동차의 외판재 및 구조부재(member종류), 또는 용융아연도금강판용 원판으로 사용되는 고강도 냉연강판의 제조방법에 관한 것으로, 보다 상세하게는 강 성분을 조정하여 인장강도를 확보함은 가공성 및 내2차 가공취성을 개선한 인장강도 35~50Kgf/㎟급 자동차용 고강도 냉연강판의 제조방법에 관한 것이다.The present invention relates to a method for manufacturing a high strength cold rolled steel sheet used as an outer plate of a vehicle and a structural member (member type), or a disc for hot-dip galvanized steel sheet, and more particularly, to adjust the steel component to secure tensile strength. And a method of manufacturing a high strength cold rolled steel sheet for automobiles having a tensile strength of 35 to 50 Kgf / mm 2 with improved secondary work brittleness.

종래 자동차용 고강도 냉연강판은, 저탄소강에 Mn, Si, P 등의 고용강화 원소를 첨가하는 고용강화강, Ti 또는 Nb 등의 석출강화 원소를 첨가하는 석출강화강으로 제조되었다.Conventionally, high-strength cold rolled steel sheets for automobiles have been made of low-carbon steels, solid solution-strengthened steels such as Mn, Si, and P, and precipitation-reinforced steels, such as Ti and Nb.

상기 고용강화강을 제조하는 방법에 관한 기술로서, 일본 특개평6-108202에서는 P을 기본으로 하고 Mn, Si을 복합첨가하였고, 용융아연도금원판인 경우에는 Si을 첨가하지 않았다. 그러나, 이 강에서는 P의 양에 의해 인장강도가 확보되기 때문에, 인장강도를 높이기 위해서는 P의 첨가량을 증가해야 하는데, P의 첨가량이 증가하면 내2차 가공취성이 나쁘고 용융아연의 합금화를 저해하는 원인으로 작용한다.As a technique relating to the method of manufacturing the above-described solid solution steel, Japanese Patent Laid-Open No. Hei 6-108202 is based on P, and Mn and Si are compositely added. However, in this steel, the tensile strength is secured by the amount of P. Therefore, in order to increase the tensile strength, the amount of P added must be increased. When the amount of P is increased, the secondary work brittleness is poor and it inhibits the alloying of molten zinc. Act as a cause.

한편, 상기 석출강화강을 제조하는 방법에 관한 기술로서, 일본특개소62-56209에서는 고용강화강에 비해 Mn, P 또는 Si과 같은 원소의 첨가량을 줄이는 대신 강도상승효과가 큰 Ti 또는 Nb 탄화물을 형성시켜 인장강도를 확보하였다. 그러나, 이 경우 석출물에 의한 강도 상승효과가 현저하고 P의 첨가량을 줄여서 내2차 가공취성은 우수하지만, 석출물에 의하여 항복강도가 높고 연신율이 낮아 가공성이 떨어지는 단점이 있다.On the other hand, as a technique for manufacturing the precipitation-reinforced steel, Japanese Patent Laid-Open No. 62-56209, instead of reducing the amount of addition of elements such as Mn, P, or Si compared to solid-state tempered steel, Ti or Nb carbide having a large strength increase effect It was formed to secure the tensile strength. However, in this case, the strength synergistic effect by the precipitate is remarkable and the secondary work brittleness is excellent by reducing the amount of P added, but the yield has a disadvantage in that the yield strength is high and the elongation is low due to the precipitate.

최근에는 상기한 바와 같은 두 강종의 특성을 조합하여, 고용강화 원소인 Mn과 P의 첨가량을 줄이고 Nb을 0.02%첨가함으로써 가공성과 내2차 가공취성을 개선한 강이 제조되고 있다. 그러나, 이 강의 경우도 강도확보가 주로 니오비움 탄화물에 의하여 얻어지기 때문에, 가공성 개선이 고용강화강에 비하여 낮은 단점이 있다.Recently, by combining the characteristics of the two types of steel as described above, by reducing the addition amount of Mn and P as the solid solution strengthening element and by adding 0.02% Nb, steel has been produced to improve workability and secondary work brittleness. However, even in this steel, since strength is obtained mainly by niobium carbide, workability improvement is lower than that of solid solution hardened steel.

이에, 본 발명의 발명자들은 상기와 같은 요구에 대응하기 위하여 연구와 실험을 행하고, 그 결과에 근거하여 본 발명을 제안하게 된 것으로, 본 발명은 강중 Mn, P, B, Mo, 및 선택적으로 Nb을 첨가함으로써, 35~50Kgf/㎟의 인장강도를 확보하고 가공성 및 내2차 가공취성을 개선할 수 있는 고강도 냉연강판의 제조방법을 제공함에 그 목적이 있다.Accordingly, the inventors of the present invention have conducted research and experiments in order to respond to the above demands, and have proposed the present invention based on the results, and the present invention provides Mn, P, B, Mo, and optionally Nb in steel. It is an object of the present invention to provide a method for producing a high strength cold rolled steel sheet which can secure a tensile strength of 35 to 50 Kgf / mm 2 and improve workability and secondary work brittleness.

상기한 목적을 달성하기 위한 본 발명은,The present invention for achieving the above object,

중량%로, C:0.02~0.20%, Mn:0.3∼1.5%, P:0.02∼0.05%, S:0.02%이하, N:0.0030%이하, B:0.0005~0.003%, Mo:0.02~0.1%, 산가용Al:0.1%이하, 잔부 Fe 및 기타 불가피한 불순물로 조성된 강을 Ar3이상 Ar3+50℃ 이하의 온도에서 열간압연을 마무리하고, 600~680℃에서 권취한 후 산세 및 냉간압연하고, 760~850℃의 온도에서 3분이내로 소둔하는 것을 포함하여 이루어지는 가공성이 우수한 고강도 냉연강판의 제조방법에 관한 것이다.By weight%, C: 0.02-0.20%, Mn: 0.3-1.5%, P: 0.02-0.05%, S: 0.02% or less, N: 0.0030% or less, B: 0.0005-0.003%, Mo: 0.02-0.1% , The acid-soluble Al: 0.1% or less, the remainder Fe and other inevitable impurities, the steel is hot rolled at a temperature of Ar 3 or more Ar 3 +50 ℃ or less, wound up at 600 ~ 680 ℃, pickling and cold rolling The present invention relates to a method for producing a high strength cold rolled steel sheet having excellent workability, including annealing within 3 minutes at a temperature of 760 to 850 ° C.

또한, 본 발명에서는 상기한 강 성분 중 0.003~0.01%의 Nb을 추가로 함유시킬 수 있다.Moreover, in this invention, 0.003 to 0.01% of Nb can be contained further in said steel component.

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

본 발명의 발명자들은, 고강도 냉연강판에서 가공성 및 내2차 가공취성을 향상시키는 방법에 관한 연구 및 실험을 통해 본 발명을 완성시킨 것으로, 강중 B을 첨가하여 BN을 형성시킴으로써 가공성을 향상시키고, P 또는 선택적으로 첨가되는 Nb의 함량을 줄여 내2차 가공취성을 확보하며, 또한 Mo을 첨가하여 강도를 보완하도록 하였다.The inventors of the present invention have completed the present invention through research and experiment on a method for improving workability and secondary work brittleness in high strength cold rolled steel sheet, and improve the workability by adding B in steel to form BN, Alternatively, by selectively reducing the content of Nb added to ensure the secondary processing brittleness, and also added Mo to complement the strength.

이하, 강 성분 및 제조조건에 대하여 설명한다.Hereinafter, a steel component and manufacturing conditions are demonstrated.

C는 강도를 증가시키는 원소로서, 그 함량이 0.02%미만이면 강도 상승효과가작을 뿐 아니라, 제강과정에서 2차 정련을 실시해야 하기 때문에 제조비용이 상승하는 문제가 있고, 0.20%이상이면 제강과정에서 슬라브의 균열이 발생하여 제품실수율을 저하시키며 제조과정에서 베이나이트와 같은 경질의 조직을 형성하여 가공성을 떨어뜨린다. 따라서, 상기 C의 함량은 0.02~0.20%로 설정하는 것이 바람직하다.C is an element that increases the strength. If the content is less than 0.02%, the strength increase effect is not only small, but the manufacturing cost increases because the secondary refining should be performed during the steelmaking process. The crack of slab occurs in the product, which lowers the product yield rate, and in the manufacturing process, forms a hard structure such as bainite, thereby degrading workability. Therefore, the content of C is preferably set to 0.02 to 0.20%.

Mn은 고용강화에 의해 강도를 향상시키는 원소로서, 그 함량이 0.3%미만이면 강화 효과가 너무 작고 1.5%이상이면 제조공정에서 냉각과정중 베이나이트와 같은 급냉조직을 형성하여 가공성을 나쁘게 하기 때문에, 0.3~1.5%로 첨가하는 것이 바람직하다.Mn is an element that improves strength by solid solution strengthening. If the content is less than 0.3%, the reinforcing effect is too small, and if it is more than 1.5%, Mn forms a quench structure such as bainite during the cooling process in the manufacturing process, thereby deteriorating workability. It is preferable to add in 0.3 to 1.5%.

P은 고용강화가 매우 큰 원소로서, 그 함량이 0.02% 미만이면 첨가효과가 작고 0.05%이상이면 연신율과 내2차 가공취성이 저하하기 때문에, 0.02~0.05%로 제한하는 것이 바람직하다.P is an element having a very high solid solution strengthening. If the content is less than 0.02%, the effect of addition is small, and if it is 0.05% or more, the elongation and secondary work brittleness are lowered, so it is preferable to limit it to 0.02 to 0.05%.

S은 열연강판의 적열취성을 유발하여 제품의 실수율을 떨어뜨리는 원소로서, Mn과 결합해 MnS로 되어 적열취성의 발생이 방지되지만, 그 함량이 0.02%보다 많으면 가공성을 저하시키기 때문에, 상한을 0.02%로 제한하는 것이 바람직하다.S is an element that induces hot brittle brittleness of a hot rolled steel sheet and lowers the real error rate of the product. S is combined with Mn to form MnS to prevent hot brittleness. However, if the content is more than 0.02%, the workability decreases. It is desirable to limit to%.

N는 철 원자사이에 존재하여 강도를 높이고 연신율을 낮추는 원소이기 때문에, 본 발명에서는 B을 첨가하여 BN의 형태로 석출시킴으로써 가공성을 해치지 않도록 하였다. 그러나, 상기 N의 함량이 너무 많으면 필요로 하는 B의 양이 증가하기 때문에, 0.0030%이하로 제한하는 것이 바람직하다.Since N is an element that exists between iron atoms to increase strength and lower elongation, in the present invention, B is added to precipitate in the form of BN so as not to impair workability. However, if the content of N is too high, the amount of B required is increased, so it is preferable to limit it to 0.0030% or less.

B은 열간압연 공정에서 Al보다 먼저 N와 결합하여 BN을 형성함으로써 연신율을 향상시키고, 또한 P의 입계편석에 의한 내2차 가공취성을 억제하는 원소로서, 그 함량이 0.0005%미만이면 상기한 효과가 작고 0.003%이상이면 N와 경합하고 남은 양이 강의 조직을 경질화하고 소둔과정에서 재결정온도를 상승시켜 강도는 상승하지만 가공성을 해치기 때문에, 그 함량범위를 0.0005~0.003%로 설정하는 것이 바람직하다.B is an element that improves elongation by combining with N to form BN prior to Al in the hot rolling process and also suppresses secondary work brittleness due to grain boundary segregation of P. When the content is less than 0.0005%, Is small and more than 0.003%, the amount remaining after competing with N hardens the steel structure and increases the recrystallization temperature during the annealing process, thereby increasing the strength but impairing the workability. Therefore, it is preferable to set the content range to 0.0005 ~ 0.003%. .

Mo은 고용강화와 P의 편석에 의한 내2차 가공취성을 억제하는 원소로서, 그 함량이 0.02%미만이면 상기한 효과가 작고, 0.1%이상이면 합금비용이 상승하므로, 0.02~0.1%로 첨가하는 것이 바람직하다.Mo is an element that suppresses secondary work brittleness due to solid solution strengthening and segregation of P. If the content is less than 0.02%, the above-mentioned effect is small. It is desirable to.

산가용Al은 강중 탈산을 위하여 첨가되는데, 그 첨가량이 0.1%이상이면 제조원가가 상승하고 강판의 표면결함을 다량 발생시키므로, 상한을 0.1%로 제한하는 것이 바람직하다.Acid soluble Al is added for deoxidation in the steel. If the amount is 0.1% or more, the production cost increases and a large amount of surface defects of the steel sheet is generated. Therefore, the upper limit is preferably limited to 0.1%.

Nb은 본 발명에서 선택적으로 첨가되는 원소로서, 강중 C와 결합하여 NbC을형성함으로써 냉연강판의 강도를 향상시킨다. 그러나, 상기 NbC의 양이 너무 많으면 가공성이 크게 나빠지기 때문에, 상기 Nb의 함량은 0.003~0.01%로 첨가하는 것이 바람직하다.Nb is an element selectively added in the present invention, and combines with C in steel to form NbC to improve the strength of the cold rolled steel sheet. However, if the amount of NbC is too large, the workability is greatly deteriorated, so the content of Nb is preferably added at 0.003 to 0.01%.

상기와 같이 조성된 강 슬라브를 통상 1200℃정도에서 균질화 처리한 다음 열간압연하는데, 열간압연시 마무리 압연온도는 Ar3이상 Ar3+50℃이하로 설정하는 것이 바람직하다. 그 이유는, 상기 마무리 압연온도가 Ar3온도 미만이면 혼립이 생겨 가공성이 크게 감소하고, Ar3+50℃보다 높으면 열간압연 직후 결정립 성장속도가 증가하여 조대한 결정립이 얻어져 가공성이 열화되기 때문이다.The steel slab formed as described above is usually subjected to homogenization at about 1200 ° C. and then hot rolled, and the finish rolling temperature at the time of hot rolling is preferably set to Ar 3 to Ar 3 + 50 ° C. or less. The reason is that if the finish rolling temperature is less than the Ar 3 temperature, the mixture is formed and workability is greatly reduced. If the finish rolling temperature is higher than Ar 3 + 50 ° C., the grain growth rate is increased immediately after hot rolling, thereby obtaining coarse grains and degrading workability. to be.

그 후, 상기 열연판을 권취하는데, 그 온도가 600℃ 미만이면 석출물이 너무 미세화되어 가공성이 감소되고, 680℃ 이상이면 압연후 결정립 성장단계에서 결정립이 조대화되어 강도가 하락하고 또한 P이 입계에 편석하여 내2차 가공취성을 해치기 때문에, 600~680℃로 제한하는 것이 바람직하다.Thereafter, the hot rolled sheet is wound. If the temperature is less than 600 ° C., the precipitate becomes too fine and the workability is reduced. If the temperature is more than 680 ° C., the grains are coarsened in the grain growth step after rolling, and the strength decreases and P is grain boundary. In order to segregate in and impair secondary work brittleness, it is preferable to limit to 600-680 degreeC.

상기 열연코일을 통상의 방법으로 산세한 후 냉간압연한 다음에는, 가공성을 부여하기 위하여 재결정온도 이상에서 소둔열처리를 실시한다. 이 때, 상기 냉연판 소둔은 760~850℃의 온도에서 통상 3분이내의 단시간으로 실시하는 것이 바람직하다. 즉, 상기 소둔온도가 760℃ 보다 낮으면 재결정이 완전하게 일어나지 못하여 가공성이 나쁘고 850℃ 보다 높으면 결정립 성장이 과다하게 일어나 강도가 크게 낮아지기 때문에 바람직하지 못하다.After the hot rolled coil is pickled by a conventional method and cold rolled, annealing heat treatment is performed at or above the recrystallization temperature to impart workability. At this time, it is preferable to perform the cold rolled sheet annealing at a temperature of 760 to 850 ° C for a short time usually within 3 minutes. In other words, when the annealing temperature is lower than 760 ° C, recrystallization does not occur completely, so that workability is poor, and when the annealing temperature is higher than 850 ° C, grain growth occurs excessively and the strength is greatly decreased.

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

(실시예)(Example)

하기 표 1과 같이 조성된 갖는 강 슬라브를 1200℃에서 1시간 가열하고 890℃에서 3mm두께로 마무리 열간압연한 다음 650℃로 냉각하고 이 온도에서 1시간 유지후 노냉하였다.The steel slab having the composition as shown in Table 1 was heated at 1200 ° C. for 1 hour, finished hot rolled at 890 ° C. at a thickness of 3 mm, cooled to 650 ° C., and maintained at this temperature for 1 hour.

이와 같이 하여 얻어진 열연판을 산세하고, 두께 1.2mm로 냉간압연한 뒤, 하기 표 2와 같이 소둔온도를 달리하여 50초간 소둔한 후 상온으로 냉각하였다.The hot rolled sheet thus obtained was pickled, cold rolled to a thickness of 1.2 mm, and then annealed for 50 seconds at different annealing temperatures as shown in Table 2, followed by cooling to room temperature.

그 후, 기계적 성질 및 내2차 가공취성을 측정하고, 그 결과를 하기 표 2에 나타내었는데, 여기서 내2차 가공취성은 드로잉비를 1.92로 하여 측정하였다.Thereafter, mechanical properties and secondary work brittleness were measured, and the results are shown in Table 2 below, where the second work brittleness was measured with a drawing ratio of 1.92.

구분division 화학성분(중량%)Chemical composition (% by weight) CC MnMn PP SS Sol.AlSol.Al NN BB MoMo NbNb 발명강1Inventive Steel 1 0.040.04 0.50.5 0.040.04 0.0050.005 0.40.4 0.0020.002 0.0010.001 0.050.05 －－ 발명강2Inventive Steel 2 0.070.07 0.90.9 0.040.04 0.0050.005 발명강3Invention Steel 3 0.140.14 0.60.6 0.040.04 0.0050.005 발명강4Inventive Steel 4 0.160.16 1.01.0 0.040.04 0.0050.005 발명강5Inventive Steel 5 0.030.03 0.30.3 0.030.03 0.0050.005 0.030.03 0.0050.005 발명강6Inventive Steel 6 0.060.06 0.60.6 0.030.03 0.0050.005 발명강7Inventive Steel 7 0.140.14 0.80.8 0.030.03 0.0050.005 비교강1Comparative Steel 1 0.090.09 0.90.9 0.100.10 0.010.01 0.0030.003 －－ －－ －－ 비교강2Comparative Steel 2 0.050.05 0.80.8 0.040.04 0.0050.005 0.020.02 비교강3Comparative Steel 3 0.070.07 0.70.7 0.010.01 0.0050.005 0.030.03

구분division 사용강종Steel grade used 제조조건Manufacture conditions 기계적 성질Mechanical properties 내2차가공취성(DBTT, ℃)Secondary processing brittleness (DBTT, ℃) 냉연판소둔온도(℃)Cold Rolled Annealing Temperature (℃) 항복강도(kg/㎟)Yield strength (kg / ㎡) 인장강도(kg/㎟)Tensile Strength (kg / ㎡) 연신율(%)Elongation (%) 발명재1Invention 1 발명강1Inventive Steel 1 810810 20.820.8 36.136.1 43.043.0 -90-90 발명재2Invention 2 발명강2Inventive Steel 2 810810 27.227.2 43.043.0 40.340.3 -85-85 발명재3Invention 3 780780 28.528.5 45.245.2 39.139.1 -80-80 발명재4Invention 4 830830 27.027.0 42.842.8 41.241.2 -85-85 발명재5Invention 5 발명강3Invention Steel 3 810810 30.830.8 46.546.5 36.536.5 -80-80 발명재6Invention 6 발명강4Inventive Steel 4 35.635.6 51.151.1 34.134.1 -70-70 발명재7Invention 7 발명강5Inventive Steel 5 21.521.5 36.736.7 42.142.1 -90-90 발명재8Invention Material 8 발명강6Inventive Steel 6 28.728.7 42.842.8 39.239.2 -90-90 발명재9Invention Material 9 발명강7Inventive Steel 7 35.335.3 51.051.0 36.836.8 -80-80 비교재1Comparative Material 1 비교강1Comparative Steel 1 830830 32.432.4 46.546.5 34.234.2 -30-30 비교재2Comparative Material 2 비교강2Comparative Steel 2 33.133.1 45.745.7 33.133.1 -50-50 비교재3Comparative Material 3 비교강3Comparative Steel 3 35.635.6 46.146.1 31.531.5 -70-70

상기 표 2에 나타난 바와 같이, 본 발명강으로 제조된 발명재(1)~(9)는, 인장강도가 36.1~51.1Kgf/㎟이고, 가공성을 나타내는 연신율과 항복강도도 비교재와 동등 이상의 값을 갖으면서도, 내2차 가공취성이 모두 -70℃ 이하로 낮은 것을 알 수 있다.As shown in Table 2, the inventive materials (1) to (9) made of the present invention steel, the tensile strength is 36.1 ~ 51.1Kgf / mm2, the value of the elongation and yield strength showing the workability or more equivalent to the comparative material It can be seen that the secondary work brittle resistance is low at -70 ° C or lower, even though it has.

반면에, P이 다량첨가된 비교강(1), Nb이 다량 첨가된 비교강(2),(3)으로 제조된 비교재(1)~(3)은, 인장강도는 35~50Kgf/㎟의 수준이나, 가공성을 나타내는 연신율이 본 발명재와 동등 이하이고, 내2차 가공취성을 나타내는 DBTT도 -70℃이었다.On the other hand, the comparative materials (1) to (3) made of comparative steel (1), Pb added a large amount, Comparative steel (2), (3) added a large amount of P, the tensile strength is 35 ~ 50Kgf / mm2 The elongation which shows the level and processability of is equal to or less than this invention material, and DBTT which shows secondary work brittleness was also -70 degreeC.

상기한 바와 같은 본 발명에 의하면, 가공성 및 내2차 가공취성이 우수한 인장강도 35-50Kgf/㎟급 고강도 냉연강판을 용이하게 제조할 수 있기 때문에, 자동차의 차체경량화 및 안전성를 위한 부품용으로 적용될 수 있는 효과가 있는 것이다.According to the present invention as described above, since the high strength cold rolled steel sheet having a high tensile strength 35-50Kgf / mm2 excellent in machinability and secondary work brittleness can be easily manufactured, it can be applied for parts for automobile body weight reduction and safety It is effective.

Claims (2)

중량%로, C:0.02~0.20%, Mn:0.3∼1.5%, P:0.02∼0.05%, S:0.02%이하, N:0.0030%이하, B:0.0005~0.003%, Mo:0.02~0.1%, 산가용Al:0.1%이하, 잔부 Fe 및 기타 불가피한 불순물로 조성된 강을 Ar3이상 Ar3+50℃ 이하의 온도에서 열간압연을 마무리하고, 600~680℃에서 권취한 후 산세 및 냉간압연하고, 760~850℃의 온도에서 3분이내로 소둔하는 것을 포함하여 이루어지는 가공성이 우수한 고강도 냉연강판의 제조방법By weight%, C: 0.02-0.20%, Mn: 0.3-1.5%, P: 0.02-0.05%, S: 0.02% or less, N: 0.0030% or less, B: 0.0005-0.003%, Mo: 0.02-0.1% , The acid-soluble Al: 0.1% or less, the remainder Fe and other inevitable impurities, the steel is hot rolled at a temperature of Ar 3 or more Ar 3 +50 ℃ or less, wound up at 600 ~ 680 ℃, pickling and cold rolling And, a method for producing a high strength cold rolled steel sheet having excellent workability, including annealing within 3 minutes at a temperature of 760 ~ 850 ℃ 제 1항에 있어서, 상기 강 성분 중에는 0.003~0.01%의 Nb이 추가로 함유되는 것을 특징으로 하는 가공성이 우수한 고강도 냉연강판의 제조방법The method of manufacturing a high strength cold rolled steel sheet having excellent workability according to claim 1, wherein the steel component further contains 0.003 to 0.01% Nb.
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