KR101048061B1 - Manufacturing method of low temperature annealing precipitation hardening type high strength steel sheet - Google Patents

Manufacturing method of low temperature annealing precipitation hardening type high strength steel sheet Download PDF

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KR101048061B1
KR101048061B1 KR1020030091534A KR20030091534A KR101048061B1 KR 101048061 B1 KR101048061 B1 KR 101048061B1 KR 1020030091534 A KR1020030091534 A KR 1020030091534A KR 20030091534 A KR20030091534 A KR 20030091534A KR 101048061 B1 KR101048061 B1 KR 101048061B1
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steel
steel sheet
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strength
annealing
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KR20050059818A (en
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한상호
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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
    • C21D8/0221—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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—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
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0273—Final recrystallisation annealing
    • C—CHEMISTRY; METALLURGY
    • 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

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical 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 자동차용 멤버류 등의 구조부재로 사용될 수 있도록 항복강도 380MPa 이상 확보 가능하며 항복비가 80% 이상인 고강도의 제조 방법에 관한 것이다.The present invention relates to a high strength manufacturing method capable of securing a yield strength of 380 MPa or more and yield ratio of 80% or more so that it can be used as a structural member such as automobile members.

본 발명에 의하면 중량 %로 C:0.07~0.12%, Mn:0.8~1.2%, P:0.001~0.02%, S:0.001~0.005%, N:0.001~0.003%, Si:0.001~0.1%, 산가용 Al:0.03~0.07%, Ti:0.03~0.06%, Nb:0.03~0.06%, V:0.02~0.04%, Mo:0.001~0.1% 및 잔부는 Fe 와 기타 불가피한 불순물로 구성되는 강을 Ar3변태점 이상에서 열간압연을 종료하고, 550~650 ℃의 온도 범위에서 권취를 행하는 단계, 통상 조건의 산세 및 55% 이상의 압하율로 냉간압연을 행하는 단계 및 연속 소둔로 또는 합금화 용융 도금 연속로에서 800~820 ℃의 온도 범위로 재결정 소둔을 행하는 단계로 구성된 고강도 강판의 제조 방법이 제공된다.According to the present invention, in weight% C: 0.07 to 0.12%, Mn: 0.8 to 1.2%, P: 0.001 to 0.02%, S: 0.001 to 0.005%, N: 0.001 to 0.003%, Si: 0.001 to 0.1%, acid soluble Al: 0.03 ~ 0.07%, Ti : 0.03 ~ 0.06%, Nb: 0.03 ~ 0.06%, V: 0.02 ~ 0.04%, Mo: 0.001 ~ 0.1% and the balance unit a steel consisting of Fe and other unavoidable impurities Ar 3 Finishing hot rolling above the transformation point, winding in a temperature range of 550 to 650 ° C., performing cold rolling with pickling under normal conditions and a rolling reduction rate of 55% or more, and 800 in a continuous annealing furnace or an alloyed hot dip continuous furnace. Provided is a method for producing a high strength steel sheet, which is configured to perform recrystallization annealing at a temperature range of ˜820 ° C.

이러한 강판은 향상된 내충격성을 필요로 하는 자동차의 멤버(Member), 빔(Beam) , 필라(Pillar)등의 구조 부재에 사용하기에 적합하다. Such steel sheets are suitable for use in structural members such as members, beams, pillars, and the like, which require improved impact resistance.

저온 소둔형 석출강화형 고강도강판,고항복강도, 고항복비,우수한 도금 특성Low Temperature Annealed Precipitation-Reinforced High Strength Steel Sheet, High Yield Strength, High Yield Ratio, Excellent Plating Characteristics

Description

저온 소둔형 석출강화형 고강도강판의 제조방법{Manufacturing Method Of Low Temperature Annealed And Precipitation Hardened High Strength Steel Sheet }Manufacturing Method Of Low Temperature Annealed And Precipitation Hardened High Strength Steel Sheet}

본 발명은 저온 소둔형 석출강화형 고강도강판의 제조방법에 관한 것으로, 보다 상세하게는 자동차용 멤버류 등의 구조부재로 사용될 수 있도록 항복강도 380MPa 이상 확보 가능하며 항복비가 80% 이상인 냉연 또는 도금강판및 이의 제조 방법에 관한 것이다.
The present invention relates to a method for manufacturing a low-temperature annealing precipitation-reinforced high-strength steel sheet, more specifically, to yield a yield strength of 380MPa or more to be used as a structural member, such as automotive members, cold rolled or plated steel sheet having a yield ratio of 80% or more. And to a method for producing the same.

최근 자동차의 충격 안전성 규제가 확산되면서 차체의 내충격성 향상을 위하여 멤버(Member), 빔(Beam) , 필라(Pillar)등의 구조 부재에는 석출경화형 고강도 강판이 널리 이용되고 있다. 석출경화형 고강도강판은 자동차의 충돌에너지를 흡수하기 위하여 설계되었기 때문에 인장강도 대비 항복강도, 즉 항복비(YS/TS)가 높은 것을 특징으로 하고 있다.
Recently, as the impact safety regulations of automobiles are spreading, precipitation hardening type high strength steel sheets are widely used in structural members such as members, beams, pillars, etc. to improve impact resistance of the vehicle body. Precipitation hardening high strength steel sheet is designed to absorb the collision energy of the vehicle, characterized by high yield strength, that is, yield ratio (YS / TS) compared to tensile strength.

통상 강을 강화하는 방법에는 고용강화, 석출강화, 결정립 미세화에 의한 강화 및 변태강화 방법으로 요약할 수 있다.
In general, the method of strengthening the steel can be summarized as a method of strengthening solid solution, strengthening precipitation, strengthening by transformation of grains, and transformation.

고용강화 및 결정립 미세화 강화 방법은 인장강도 기준 490MPa급 이상의 고강도강을 제조하기가 매우 어렵고, 변태 강화 방법은 강도 확보 및 변태 조직 형성을 위해 다량의 합금 성분이 필요할 뿐만 아니라 그 하부 조직이 베이나이트 혹은 마르텐사이트로 이루어져 있기 때문에 인장강도 대비 항복강도, 즉 항복비가 낮아 자동차 충돌시 내충격성을 요구하는 부품에의 사용은 적절하지 못하다는 결점을 안고 있다.
Solid solution strengthening and grain refining strengthening method is very difficult to manufacture high strength steel of 490MPa or more based on tensile strength, and the transformation strengthening method requires a large amount of alloy components to secure strength and form metamorphic structure, and its underlying structure is bainite or Since martensite is composed of martensite, its yield strength, that is, its yield ratio is low, making it improper for use in parts requiring impact resistance in automobile collisions.

석출강화형 고강도강은 주로 Cu, Nb, Ti, V등과 같은 탄,질화물 형성원소 첨가에 의한 석출 강화 효과 및 결정립 미세화 효과에 의해 강도를 향상 시킨 강으로, 낮은 제조 원가로도 고강도화를 쉽게 이룰 수 있다는 장점을 가지고 있다.석출 강화 방법은 우선 강을 고온에서 용체화처리를 행한 다음, 냉각 중에 미세한 석출물들을 다수 형성 시켜 석출물 주변의 응력장에 의해 강화되는 현상이다. 통상 이러한 미세 석출물들은 열간압연 후 권취 중에 다량 형성되므로 냉간압연 후 소둔시 미세 석출물들에 의한 재결정온도가 매우 급격히 상승하여 고온 소둔을 실시하여야 하는 단점을 갖고 있다. 고온 소둔시 형상 불량 뿐만 아니라 특히, 도금강판의 경우 표면에 MnO 및 SiO2등의 각종 산화물이 형성되어 도금 특성을 저해하는 요소로 작용된다.
Precipitation-reinforced high-strength steel is a steel whose strength is enhanced by the precipitation strengthening effect by the addition of carbon and nitride forming elements such as Cu, Nb, Ti, V, etc., and the grain refinement effect. The precipitation strengthening method is a phenomenon in which steel is first solution-treated at a high temperature, and then a large number of fine precipitates are formed during cooling to be strengthened by the stress field around the precipitate. Usually, since these fine precipitates are formed in a large amount during winding after hot rolling, the recrystallization temperature caused by the fine precipitates during annealing after cold rolling has a very high temperature annealing. In addition to poor shape during high temperature annealing, in particular, in the case of a plated steel sheet, various oxides such as MnO and SiO 2 are formed on the surface to act as a factor that inhibits plating characteristics.

석출강화형 고강도강판 제조 방법으로 공지된 기술로는 일본 공개 특허 공보 56-84422호가 있으며, 여기에서는 0.15%C이하의 저탄소강을 기본 성분계로하여 Ti, Nb, V등을 1종 혹은 2종 이상 함유하고 최종 열간압연 마무리 온도를 750~950℃의 범위로, 권취온도를 450℃ 이하로 관리하여 석출강화형 고강도강을 제조하고 있다. 이 경우 권취온도가 매우 낮다. 이는 극미세 석출물을 형성하여 강도 기여 효과는 높으나, 열연판 형상 불량 뿐만 아니라 석출물 주변의 잔류응력의 증가로 냉간압연시 과부하 현상이 종종 발생하는 결점을 가지고 있다. 일본 공개 특개평 4-221015에서는 Nb혹은 V의 석출물 형성 원소를 이용하고 열간압연 후 가속 냉각에 의해 강도 상승 효과가 우수한 석출강화강의 제조 방법을 제시하고 있으나 ,이 경우도 권취온도가 400℃ 이하로 설정되어 있어서 앞서 언급한 문제가 있으며,그외에 균일한 페라이트 조직 형성 대신 베이나이트 혹은 마르텐사이트 조직이 형성되어 항복비(항복강도/인장강도)가 저하되는 즉 항복강도가 저하되는 결점을 갖고 있다. Cu석출물을 이용한 석출강화형 고강도 강판 제조방법으로는 일본 공개 특허 공보 3-140412 및 11-241119호가 있으며,여기에서는 Cu를 0.8wt%이상 첨가하여 제조하고 있으나 역시 Cu계 석출물에 의한 도금 강판의 합금화 불량 및 용접성에 문제가 있어 현장 적용에 문제점을 안고 있다.

A technique known as a method of manufacturing a precipitation-reinforced high strength steel sheet is Japanese Laid-Open Patent Publication No. 56-84422, wherein one or two or more kinds of Ti, Nb, V, etc. are used based on low carbon steel of 0.15% C or less as a basic component system. Containing the final hot rolling finish temperature in the range of 750 ~ 950 ℃, winding temperature is controlled to 450 ℃ or less to produce precipitation strengthening high strength steel. In this case, the coiling temperature is very low. It has a high strength contribution effect by forming a very fine precipitate, but has the drawback that the overload phenomenon often occurs during cold rolling due to the increase in the residual stress around the precipitate as well as the shape of the hot-rolled sheet. Japanese Laid-Open Patent Publication No. 4-221015 discloses a method for producing precipitated tempered steel using Nb or V precipitate forming elements and having excellent strength synergistic effect by accelerated cooling after hot rolling. Since there is a problem described above, in addition to the formation of a uniform ferrite structure, bainite or martensite structure is formed, and thus the yield ratio (yield strength / tensile strength) is lowered, that is, the yield strength is lowered. JP-A-3140412 and 11-241119 are methods for manufacturing a precipitation-reinforced high strength steel sheet using Cu precipitates. Here, Cu is added by 0.8 wt% or more, but alloying of the plated steel sheet by Cu-based precipitates is also performed. There is a problem in the field application due to the problem of poor and weldability.

본 발명의 목적은 자동차용 구조부재등 내충격성 소재로 사용이 용이하도록 항복비가 80% 이상이면서 항복강도 기준 380Mpa 이상의 저온 소둔형 석출강화형 고강도 강판의 제조 방법에 관한 것이다.
An object of the present invention relates to a method for producing a low-temperature annealing precipitation-reinforced high strength steel sheet having a yield ratio of at least 80% and a yield strength of at least 80% so as to be easily used as an impact resistant material such as a structural member for automobiles.

본 발명에 의하면 중량 %로 C:0.07~0.12%, Mn:0.8~1.2%, P:0.001~0.02%, S:0.001~0.005%, N:0.001~0.003%, Si:0.001~0.1%, 산가용 Al:0.03~0.07%, Ti:0.03~0.06%, Nb:0.03~0.06%, V:0.02~0.04%, Mo:0.001~0.1% 및 잔부는 Fe 와 기타 불가피한 불순물로 구성되는 강을 Ar3변태점 이상에서 열간압연을 종료하고, 550~650 ℃의 온도 범위에서 권취를 행하는 단계, 통상 조건의 산세 및 55% 이상의 압하율로 냉간압연을 행하는 단계 및 연속 소둔로 또는 합금화 용융 도금 연속로에서 800~820 ℃의 온도 범위로 재결정 소둔을 행하는 단계로 구성되어서, 항복비 및 도금 특성이 우수한 저온 소둔형 석출강화형 고강도 강판의 제조 방법이 제공된다.According to the present invention, in weight% C: 0.07 to 0.12%, Mn: 0.8 to 1.2%, P: 0.001 to 0.02%, S: 0.001 to 0.005%, N: 0.001 to 0.003%, Si: 0.001 to 0.1%, acid soluble Al: 0.03 ~ 0.07%, Ti : 0.03 ~ 0.06%, Nb: 0.03 ~ 0.06%, V: 0.02 ~ 0.04%, Mo: 0.001 ~ 0.1% and the balance unit a steel consisting of Fe and other unavoidable impurities Ar 3 Finishing hot rolling above the transformation point, winding in a temperature range of 550 to 650 ° C., performing cold rolling with pickling under normal conditions and a rolling reduction rate of 55% or more, and 800 in a continuous annealing furnace or an alloyed hot dip continuous furnace. Consisting of recrystallization annealing in a temperature range of ˜820 ° C., a method for producing a low temperature annealing precipitation hardening type high strength steel sheet excellent in yield ratio and plating characteristics is provided.

이하에서는 본 발명을 보다 상세히 설명한다.
Hereinafter, the present invention will be described in more detail.

본 발명에서 강 중 C는 석출물 형성 원소로 중요한 역할을 하나, 그 함량이 0.07wt% 미만의 경우 충분한 석출 효과를 얻을 수 없을 뿐만 아니라 TiC 혹은 NbC탄화물이 조대화되어 항복비가 낮아지는 경향이 있고, 강 중 C함량이 0.12wt%를 초과하게 되면 제강 연주 공정에서 주편 크랙 발생 가능성이 높아질 뿐만 아니라 열간압연 후 코일 권취시에 베이나이트 조직이 형성되어 열연판의 강도를 현저히 상승시킴으로서 냉간압연 부하를 가져오므로 그 함유량을 0.07~0.12wt%로 제한한다.
In the present invention, the C in the steel plays an important role as a precipitate forming element, but if the content is less than 0.07wt%, not only does not obtain sufficient precipitation effect, but also tends to lower yield ratio due to coarsening of TiC or NbC carbides, When the C content in the steel exceeds 0.12 wt%, the possibility of cast cracking in the steelmaking process increases, as well as the formation of bainite structure during coil winding after hot rolling, which significantly increases the strength of the hot rolled plate, resulting in cold rolling load. Therefore, the content is limited to 0.07 ~ 0.12wt%.

강 중 Mn은 고용강화 원소로 강도 상승에 기여할 뿐만 아니라 강중 S를 MnS로 석출시켜 열간압연시 S에 의한 판파단 발생 및 고온취화를 억제시키는 중요한 역할을 한다. 그 함량이 0.8wt% 미만의 경우 목적하는 강도 확보가 곤란하며 S성분이 원인이 되는 취화 현상을 완전히 억제하지 못하고, 1.2wt%를 초과하게 되면 목적하는 강도는 확보되나 연신율의 급격한 감소를 가져오며 소둔시 Mn산화물의 강판표면으로의 용출이 심하여 표면 청정도 및 내산화성에 미치는 영향이 크므로 그 성분함량범위를 0.8~1.2 wt%로 제한한다.
Mn in steel not only contributes to strength increase as a solid solution element, but also precipitates S in MnS and plays an important role in suppressing plate breakage and high temperature embrittlement caused by S during hot rolling. If the content is less than 0.8wt%, it is difficult to secure the desired strength, and the embrittlement phenomenon caused by the S component is not completely suppressed. If the content exceeds 1.2wt%, the desired strength is secured but the elongation is drastically decreased. The annealing of Mn oxide to the steel plate surface during annealing is severe and has a great effect on surface cleanliness and oxidation resistance. Therefore, the content range of the content is limited to 0.8 ~ 1.2 wt%.

강 중 P는 성형성을 크게 해치지 않으면서 강도 확보에 가장 유리한 원소이지만 과잉의 P첨가는 취성파괴 발생 가능성을 현저히 높여 열간압연 도중 슬라브의 판파단의 발생가능성이 증가될 뿐 아니라, 도금 표면 특성을 저해하는 원소로 작용하므로 그 함량을 0.001~0.02wt%로 제한한다.Although P is the most favorable element for securing strength without significantly deteriorating formability, excessive P addition significantly increases the possibility of brittle fracture, which increases the probability of slab breakage during hot rolling, and improves the plating surface characteristics. It acts as an inhibitory element, so its content is limited to 0.001 ~ 0.02wt%.

S 및 N은 강중 불순물 원소로써 가능한 한 낮게 관리하는 것이 중요하다. 우수한 용접 특성을 확보하기 위하여 그 함량들을 가능한 한 낮게 관리함이 바람직하나 이는 강의 정련 비용을 증대시킨다. 따라서, 조업조건이 가능한 범위인 S함량을 0.001~0.005 wt%, N함량을 0.001~0.003wt%로 제한한다.It is important to manage S and N as low as possible as impurity elements in the steel. It is desirable to keep the contents as low as possible to ensure good welding properties but this increases the cost of refining the steel. Therefore, the S content is 0.001 to 0.005 wt% and the N content is 0.001 to 0.003 wt%.

강 중 Si함량은 0.001~0.1wt%로 제한한다. 그 이상의 경우에는 도금 표면 특성이 매우 불량해지기 때문이다.Si content in steel is limited to 0.001 ~ 0.1wt%. If it is more than that, the plating surface properties become very poor.

산가용 Al은 강의 입도 미세화와 탈산을 위해서 첨가되는 원소이다. 그 함유량이 산가용 Al함량으로 0.03Wt% 미만의 경우 통상의 안정된 상태로 killed강을 제조할 수 없고, 함량이 0.07wt%를 초과하게 되면 결정립 미세화 효과로 강도 상승에는 유리하지만 제강 연주 조업시 개재물 과다 형성으로 인한 도금 강판 표면 불량 발생 가능성이 높아질 뿐만 아니라 제조 원가 상승을 가져 오므로, 그 함량을 0.03~0.07wt%로 제한한다.
Acid value Al is an element added for refinement and deoxidation of the particle size of steel. If the content is less than 0.03Wt% due to the acid value of Al, the killed steel cannot be manufactured in a normal stable state. If the content exceeds 0.07wt%, the grain refinement effect is advantageous to increase the strength, but the inclusions during steelmaking operation The possibility of surface defects of the coated steel sheet due to excessive formation not only increases, but also leads to an increase in manufacturing cost, so the content is limited to 0.03 to 0.07 wt%.

Nb및 Ti는 열간압연중 고용 C과 작용하여 (Ti,Nb)C복합 석출물을 형성한다. 복합 석출물은 단독 석출물에 비하여 재결정 온도를 현저히 낮추어 저온 재결정 소둔이 가능하게 함으로써 우수한 도금 표면 특성을 확보 할 수 있는 원소로 작용한다. Ti, Nb함량이 0.03wt% 미만의 경우에는 강도 확보를 위한 미세 석출물들이 충분히 석출되지 못하여 목적 강도를 확보할 수 없고, 함량이 0.06wt%를 초과하게 되면 도금 표면 특성 확보에 불리하고 냉간압연시 다량의 미세 석출물들에 의한 압연 부하가 증가하므로 그 함량을 각각 0.03~0.06wt%로 제한한다.
Nb and Ti react with solid solution C during hot rolling to form a (Ti, Nb) C complex precipitate. Compared with the single precipitate, the composite precipitate significantly lowers the recrystallization temperature and enables low temperature recrystallization annealing, thus acting as an element that can secure excellent plating surface properties. If the content of Ti and Nb is less than 0.03 wt%, the fine precipitates for securing strength cannot be sufficiently precipitated, so that the target strength cannot be obtained. If the content exceeds 0.06 wt%, it is disadvantageous to secure the plating surface properties and cold rolling. Since the rolling load by a large amount of fine precipitates increases, the content is limited to 0.03 to 0.06 wt%, respectively.

강 중 V은 Ti 와 Nb와 함께 석출 효과를 나타내는 원소로서, 그 함량이 0.02wt% 미만의 경우 충분한 석출 효과가 없고, 0.04wt% 를 초과하게 되면 재결정 온도가 급격히 상승되는 효과가 있으므로 그 함량을 0.02~0.04wt%로 제한한다.
In steel, V is an element that exhibits a precipitation effect together with Ti and Nb. If the content is less than 0.02 wt%, there is no sufficient precipitation effect. If the content exceeds 0.04 wt%, the recrystallization temperature is rapidly increased. Limit to 0.02 ~ 0.04wt%.

강 중 Mo는 고용 강화 효과 및 재결정 온도를 낮추는 경향이 있어 그 함량을 0.001~0.1wt%로 제한한다. 그 이상에서는 제조원가 상승 부담이 있고 연신율의 감소를 수반하기 때문이다.Mo in steel tends to lower the solid solution strengthening effect and the recrystallization temperature, so the content is limited to 0.001 to 0.1 wt%. Above that, there is a burden of rising manufacturing costs and a decrease in elongation.

상기와 같은 조성을 갖도록 조정된 강을 먼저, 통상의 열간 압연 조건인 Ar3이상의 온도에서 열간압연을 종료하고 550~650℃ 구간에서 권취를 행한다. 본 발명에서 권취온도는 특히 중요하다. 550℃이하에서의 권취는 고용 C을 완전히 석출하지 못하여 석출강화 효과가 떨어질 뿐만 아니라 권취시 판 형상 불량의 문제가 나타나고, 권취온도가 650℃를 초과하게 되면 석출물들이 현저하게 조대화 되는 경향을 가지므로 석출강화 효과가 크지 않아 항복비가 낮아지는 경향을 갖기 때문에 권취온도를 상기 범위로 제한한다. 권취 후 냉간압연하되,냉간압연의 그 최소 압하율을 55% 이상으로 제한 한다. 본 발명에 의하면 냉간압하율이 증가함에 따라 재결정온도는 현저하게 감소하여 낮은 재결정 소둔이 가능하므로 우수한 도금 표면 특 성을 확보하는데 중요한 역할을 한다. 압하율이 55% 미만의 경우 재결정온도를 충분히 낮추는 효과가 없을 뿐만 아니라 석출물 형성을 위한 임계 핵생성 사이트의 감소로 충분한 석출물이 형성되지 않는 것으로 밝혀졌다.냉간압연 후 연속 소둔로 또는 합금화 용융 도금 연속로에서 800~820℃의 온도 범위로 재결정 소둔을 행한다. 연속소둔로 또는 합금화 용융도금 연속로에서 재결정 소둔시 800℃미만의 소둔 조건은 미재결정 영역으로서 강판 코일내 재질 편차가 너무 커서 불량제품으로 되고, 820℃이상의 조건에서는 고온 소둔에 따른 석출물 조대화 경향으로 충분한 석출강화효과가 나타나지 않을 뿐만 아니라 소둔시 표면에 농화되는 산화물 및 개재물 형성 가능성이 높아 도금 표면 특성에 불리하므로 소둔온도를 상기와 같이 제한한다.
The steel adjusted to have the composition as described above is first hot rolled at a temperature of Ar 3 or more which is a normal hot rolling condition, and then wound in a 550 to 650 ° C section. The coiling temperature is particularly important in the present invention. Winding at 550 ℃ or less does not completely precipitate solid solution C, which lowers the effect of strengthening precipitation and causes problems of plate shape during winding. When winding temperature exceeds 650 ℃, precipitates tend to be significantly coarsened. Therefore, the precipitation strengthening effect is not so large that the yield ratio tends to be lowered, so the winding temperature is limited to the above range. Cold rolling after winding, limits the minimum rolling rate of cold rolling to 55% or more. According to the present invention, as the cold reduction rate is increased, the recrystallization temperature is remarkably reduced, so that low recrystallization annealing is possible, thereby playing an important role in securing excellent plating surface properties. If the reduction ratio is less than 55%, not only does it not sufficiently reduce the recrystallization temperature, but it has been found that the reduction of the critical nucleation site for the formation of precipitates does not form sufficient precipitates. Recrystallization annealing is carried out in a furnace at a temperature in the range of 800 to 820 ° C. When recrystallization annealing in continuous annealing furnace or alloyed hot dip continuous furnace, the annealing condition of less than 800 ℃ is unrecrystallized area, so the material variation in steel coil is so large that it becomes a poor product. Not only does not exhibit sufficient precipitation strengthening effect, but also has a high possibility of forming oxides and inclusions that are concentrated on the surface during annealing, so that the annealing temperature is limited as described above.

이하에서는 본 발명의 실시예를 설명한다.
Hereinafter, embodiments of the present invention will be described.

아래의 표1과 같은 조성을 갖는 발명강(1-3)과 비교강(1-2)의 슬라브를 연속주조하여 제조하였다. 비교강1은 발명강의 조성에 비해 저탄소강이고 Mn함량은 높다. 비교강2는 발명강의 조성에 비해 고탄소강이고 Mn,Nb의 함량을 낮게 하였다. 연속주조된 상기 조성의 슬라브를 통상의 조건으로 열간압연-산세-냉간압연을 행한 다음 각각에 대해 열처리 시뮬레이터를 이용하여 소둔 열처리를 행하였다. 아래의 표 2는 표1 조성의 각 강을 권취온도, 냉간압하율, 소둔온도를 달리하였을 때의 강판 재질 특성을 나타낸 것이다. 이때 인장시험은 JIS 5호 시편을 이용하였다. 한편 도금표면 특성은 관능검사로 하였는 바, 도금표면이 육안으로 보아 거칠은 정도가 심하면 불량(x), 도금표면이 육안으로 보아 매끄럽게 보이고 잡티가 없으면 우수( ○), 그 중간은 보통(△)으로 판단하였다.
The slabs of the inventive steel (1-3) and the comparative steel (1-2) having the composition shown in Table 1 below were manufactured by continuous casting. Comparative steel 1 is a low carbon steel and a high Mn content compared with the composition of the invention steel. Comparative steel 2 is a high carbon steel and a low content of Mn, Nb compared to the composition of the invention steel. The slabs of the above-mentioned composition which were continuously cast were subjected to hot rolling, pickling, and cold rolling under normal conditions, and then subjected to annealing heat treatment using a heat treatment simulator for each. Table 2 below shows the properties of the steel sheet when the steels of Table 1 have different winding temperatures, cold rolling rates, and annealing temperatures. At this time, the tensile test was used JIS 5 specimens. On the other hand, the surface characteristics of the plating were measured by the sensory test. If the surface of the plating is visually severe, the surface is bad (x), and the surface of the plating is visually smooth. Judging by.

표1 Table 1

Figure 112003047871172-pat00001

Figure 112003047871172-pat00001

표2 Table 2

Figure 112003047871172-pat00002

Figure 112003047871172-pat00002

표2 에서 알 수 있는 바와같이, 항복강도≥380MPa, 항복비≥80%의 조건이 만족되려면 강의 조성과 강판 제조조건(권취온도550~650℃,냉간압연의 압하율 55%이상, 재결정 소둔온도 800~820℃)이 충족되어야만 한다는 것을 알 수 있다. 즉 비교강 1의 경우 상기 제조조건이 충족되지 않는 때는 항복강도, 항복비가 상기 조건에 도달하지 않으며 도금 특성도 우수하지 않은 것으로 나타났으며, 설사 상기 제조조건이 충족되더라도 강 조성에 문제가 있기때문에 표면도금 특성은 우수한 것으로 나타났으나 항복강도,항복비면에서 불량한 것으로 나타났다. 표2에서 비교강 및 본 발명강이 상기 제조조건 및 재질특성 조건(항복강도≥380MPa, 항복비≥80%, 우수한 표면도금특성)에 부적합한 경우를 ※로 표시 했으며, 발명강 중 상기 제조조건에 부적합한 경우는 어느 경우나 상기의 항복강도, 항복비, 도금표면 특성 중 어느 하나이상이 불량한 것을 보여주고 있다. 예를들면, 발명강 1에서 냉간압하율이 부족한 경우, 상기 조건의 재결정 소둔온도범위에서 재결정을 하더라도, 미재결정 영역이 발생하여 연신율의 급격한 감소를 가져왔으며 항복강도도 상기 재질특성 조건을 충족시키지 못하는 것으로 나타났다.
As can be seen from Table 2, if the conditions of yield strength ≥ 380 MPa and yield ratio ≥ 80% are satisfied, the steel composition and steel plate manufacturing conditions (coiling temperature 550-650 ℃, cold rolling rate over 55%, recrystallization annealing temperature) 800 ~ 820 ° C.) should be satisfied. That is, in case of Comparative Steel 1, the yield strength and yield ratio did not reach the above conditions and the plating characteristics were not excellent when the manufacturing conditions were not satisfied, and even if the manufacturing conditions were met, there was a problem in the steel composition. The surface plating characteristics were excellent but poor in yield strength and yield ratio. In Table 2, the case where the comparative steel and the inventive steel are inadequate to the above manufacturing conditions and material characteristic conditions (yield strength ≥ 380 MPa, yield ratio ≥ 80%, excellent surface plating characteristics) is indicated by *, In any case, it is shown that at least one of the above-described yield strength, yield ratio, and plating surface properties is poor. For example, in the case of the cold rolling reduction in the invention steel 1, even if recrystallization in the recrystallization annealing temperature range of the above conditions, unrecrystallized region occurs, the elongation is drastically reduced and the yield strength also does not meet the material characteristics conditions It did not appear.

이상으로부터, 강 성분계의 적절한 조절 및 냉간압하율의 제어등 강판의 제조조건의 제어에 의해 820℃ 이하의 낮은 소둔온도 하에서도 안정된 재질이 확보되고 도금 표면 특성이 우수한 석출강화형 고강도강판을 얻을 수 있는 것으로 나타났다.
From the above, stable material is secured even under low annealing temperature of 820 ℃ or less by appropriate control of steel system and control of cold rolling rate, and precipitation hardening type high strength steel sheet with excellent plating surface characteristics can be obtained. Appeared to be.

본 발명에 의하면,강 성분계의 적절한 조절 및 냉간압하율의 제어등 강판의 제조조건의 제어에 의해 항복강도≥380MPa, 항복비≥80%, 및 우수한 표면도금특성을 갖는 강판을 얻을 수 있으며, 이러한 강판은 향상된 내충격성을 필요로 하는, 자동차의 멤버(Member), 빔(Beam) , 필라(Pillar)등의 구조 부재에 사용하기에 적합하다.According to the present invention, a steel sheet having yield strength ≥ 380 MPa, yield ratio ≥ 80%, and excellent surface plating characteristics can be obtained by controlling steel sheet manufacturing conditions such as appropriate adjustment of steel component system and control of cold rolling rate. The steel sheet is suitable for use in structural members such as members, beams, pillars and the like of automobiles, which require improved impact resistance.

Claims (1)

중량 %로 C:0.07~0.12%, Mn:0.8~1.2%, P:0.001~0.02%, S:0.001~0.005%, N:0.001~0.003%, Si:0.001~0.1%, 산가용 Al:0.03~0.07%, Ti:0.03~0.06%, Nb:0.03~0.06%, V:0.02~0.04%, Mo:0.001~0.1% 및 잔부는 Fe 와 기타 불가피한 불순물로 구성되는 강을 Ar3변태점 이상에서 열간압연을 종료하고, 550~650℃의 온도 범위에서 권취를 행하는 단계;Weight% C: 0.07 ~ 0.12%, Mn: 0.8 ~ 1.2%, P: 0.001 ~ 0.02%, S: 0.001 ~ 0.005%, N: 0.001 ~ 0.003%, Si: 0.001 ~ 0.1%, Acid value Al: 0.03 ~ 0.07%, Ti: 0.03 ~ 0.06%, Nb: 0.03 ~ 0.06%, V: 0.02 ~ 0.04%, Mo: 0.001 ~ 0.1% and remainder are hot-rolled steels consisting of Fe and other unavoidable impurities above Ar 3 transformation point Finishing rolling and winding in a temperature range of 550 to 650 ° C; 통상 조건의 산세 및 55% 이상의 압하율로 냉간압연을 행하는 단계; 및Performing cold rolling with pickling under normal conditions and a rolling reduction of at least 55%; And 연속 소둔로 또는 합금화 용융 도금 연속로에서 800~820℃의 온도 범위로 재결정 소둔을 행하는 단계로 구성됨을 특징으로 하는 저온 소둔형 석출강화형 고강도강판의 제조방법.Process for producing a low-temperature annealing precipitation-reinforced high strength steel sheet characterized in that it comprises a step of performing a recrystallization annealing in a temperature range of 800 ~ 820 ℃ in a continuous annealing furnace or alloyed hot-dip continuous furnace.
KR1020030091534A 2003-12-15 2003-12-15 Manufacturing method of low temperature annealing precipitation hardening type high strength steel sheet KR101048061B1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS57155329A (en) 1981-07-20 1982-09-25 Nippon Steel Corp Production of high-strength cold-rolled steel sheet excellent in strain age-hardenability
KR910010055B1 (en) * 1989-07-15 1991-12-12 재단법인 산업과학기술연구소 Making process for cold rolled steel plate
KR100259404B1 (en) * 1995-03-16 2000-06-15 에모또 간지 Thin steel sheet excellent in press formability and production thereof
KR20020072624A (en) * 2001-03-12 2002-09-18 주식회사 포스코 A method for manufacturing bake hardenable coating steel sheet with good formability

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS57155329A (en) 1981-07-20 1982-09-25 Nippon Steel Corp Production of high-strength cold-rolled steel sheet excellent in strain age-hardenability
KR910010055B1 (en) * 1989-07-15 1991-12-12 재단법인 산업과학기술연구소 Making process for cold rolled steel plate
KR100259404B1 (en) * 1995-03-16 2000-06-15 에모또 간지 Thin steel sheet excellent in press formability and production thereof
KR20020072624A (en) * 2001-03-12 2002-09-18 주식회사 포스코 A method for manufacturing bake hardenable coating steel sheet with good formability

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