KR100276312B1 - The manufacturing method of 80kg grade direct quenching type high strength steel sheet with excellent toughness - Google Patents
The manufacturing method of 80kg grade direct quenching type high strength steel sheet with excellent toughness Download PDFInfo
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- KR100276312B1 KR100276312B1 KR1019960065185A KR19960065185A KR100276312B1 KR 100276312 B1 KR100276312 B1 KR 100276312B1 KR 1019960065185 A KR1019960065185 A KR 1019960065185A KR 19960065185 A KR19960065185 A KR 19960065185A KR 100276312 B1 KR100276312 B1 KR 100276312B1
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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
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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
- 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
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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
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
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- 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
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- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
Abstract
Description
본 발명은 압력용기 등의 소재로 사용되는 고장력강판의 제조방법에 관한 것으로써, 보다 상세하게는 충격파면 천이온도가 -80℃ 이하로 인성이 우수한 80kgf/㎟급 직접소입형 고장력강판의 제조방법에 관한 것이다.The present invention relates to a method for manufacturing high tensile steel sheet used as a material such as a pressure vessel, and more particularly, to a method of manufacturing 80kgf / mm2 direct quenched high tensile steel sheet having excellent toughness with a shock wave transition temperature of -80 ° C or less. It is about.
통상, 고장력강판은 용접공정을 통하여 압력용기, 기계장치, 각종 구조물 등에 이용되어 왔는데, 최근들어 상기 용접구조물의 대형화, 고기능화 되어가면서 용접성 및 경제성과 더불어 강인성을 동시에 가지는 고장력강판의 필요성이 대두되고 있다. 이와같은 특성을 만족시키기 위한 제조방법으로 제어압연 및 제어냉각법이 널리 이용 되었으나, 상기 제어압연법의 경우에는 강도향상의 한계와 생산성 저하를 초래하는 등의 문제가 있었다. 또한 상기 소입소려법은 재가열 소입처리가 필요하므로 경제성이 저하되는 부적합한 문제를 지니고 있었다. 이러한 문제를 해결하기 위하여 최근에는 강판을 열간압연한 후 냉각과정없이 직접소입한 다음 소려를 행하는 직접소입소려법을 이용하여 경제성 저하없이 강도를 증대시키는 방법이 개발되었고, 그 적용성 확대에도 큰 주목을 받고 있다. 특히, 상기 직접소입소려법은 통상의 소입소려법에 비해 가열온도가 높아서 오스테나이트의 결정립이 조대화되어 소입성이 증대될 뿐만 아니라 탄질화물의 고용도가 증대되어 고용강화에 의한 강도향상 효과가 크고 소려처리시 석출강화 효과가 높아지는 등의 특성이 있다.Conventionally, high tensile steel has been used in pressure vessels, mechanical devices, and various structures through welding processes. Recently, the need for high tensile steel sheet having both toughness and economical strength together with weldability and economic efficiency is increasing as the welding structure becomes larger and more functional. . Control rolling and control cooling have been widely used as a manufacturing method for satisfying such characteristics, but in the case of the control rolling method, there are problems such as a limitation in strength improvement and a decrease in productivity. In addition, the quenching method has an inadequate problem that the economic efficiency is lowered because the reheat quenching treatment is required. In order to solve this problem, recently, a method of increasing strength without deteriorating economic efficiency has been developed by using a direct quenching method, which hot-rolls steel sheet and then directly anneals it without cooling, and also pays attention to expanding its applicability. Is getting. In particular, the direct quenching method has a higher heating temperature than the conventional quenching method, so that the grains of austenite are coarsened to increase the quenchability, and the solid solubility of carbonitride is increased, thereby improving the strength by strengthening the solid solution. There is a characteristic that the precipitation strengthening effect is increased during large and light treatment.
그러나, 상기 직접소입소려법은 강도향상과는 달리 실제 조업시 인성을 통상의 재가열 소입소려강 이상으로 확보하는 것이 어렵다는 문제가 있다. 즉, 직접소입소려강은 열간압연에 의해 연신된 가공조직이 그대로 소입되어 잔존하게 되므로 이방성이 커져서 기계적성질이 저하되고, 또한 충격흡수에너지의 급격한 저하를 초래한다. 이와같은 문제를 해결하여 인성을 향상시키는 것이 직접소입소려방법에 있어서 가장 핵심적인 야금기술이다. 이러한 문제를 해결하기 위한 종래기술로 일본특허공개공보 59-159932, 58-158320 호를 예로 들수 있는데, 그 제시된 내용의 요지는 마무리압연온도조건을 제어하면 그 해결을 도모할 수 있다는 것이다.However, the direct quenching method has a problem that, unlike the strength improvement, it is difficult to secure the toughness at the time of actual operation more than the normal reheating quenching steel. That is, in the direct quenched steel, the processed structure drawn by hot rolling is quenched and remains as it is, so that the anisotropy is increased, the mechanical properties are lowered, and the impact absorption energy is drastically lowered. Improving toughness by solving these problems is the most important metallurgical technology in the direct quenching method. For example, Japanese Patent Laid-Open Publication No. 59-159932, 58-158320 is a conventional technique for solving such a problem. The gist of the proposed contents can be solved by controlling the finishing rolling temperature conditions.
그리나, 강판의 인성을 지배하는 인자는 마무리압연온도외에도 강재의 화학조성, 냉각속도, 마무리 압하율, 압연후 소입까지의 유지시간 등의 제조인자들이 다양하고 복합적으로 작용하는데, 상기 제안은 이중 마무리압연온도만 고려하였기 때문에 통상의 소입소려강에 비해 강도는 우수하나 인성이 여전히 좋지 않은 문제가 있다.However, the factors governing the toughness of the steel sheet are not only the finish rolling temperature but also various manufacturing factors such as chemical composition of the steel, cooling rate, finish reduction rate, holding time until rolling and quenching, and the like. Since only the rolling temperature is considered, the strength is superior to that of ordinary hardened steel, but toughness is still not good.
따라서, 본 발명은 인성에 영향을 미치는 상기 조건들의 복합적인 관계를 야금학적인 연구와 실험을 행하고 그 결과에 근거하여 제안하는 것으로서, 본 발명은 강 성분계를 적절히 설정하고, 상기 강성분중 B 과 N의 함량에 따라 마무리 압연온도를 제어함으로써 충격파면 천이온도가 -80℃ 이하로 인성이 우수한 80kgf/㎟급 직접소입형 고장력강판의 제조방법을 제공하고자 하는데 그 목적이 있다.Accordingly, the present invention proposes a complex relationship between the above conditions affecting toughness based on the results of metallurgical studies and experiments, and the present invention sets up a steel component system appropriately, and B and N among the steel components. The purpose of the present invention is to provide a manufacturing method of 80kgf / mm2 direct annealed high tensile strength steel sheet having excellent toughness with the impact wave surface transition temperature of -80 ℃ or less by controlling the finish rolling temperature according to the content of.
상기 목적을 달성하기 위하여 본 발명은 고장력강판의 제조방법에 있어서, 중량%로, C:0.06-0.16% Mn:0.60-1.60%, B:0.0003-0.0020%, N:0.001-0.004%, Si:0.10-0.50%, Cu:0.05-0.50%, Ni:0.05-1.0%, Cr:0.05-1.0%, Mo:0.05-0.80%, Al:0.01-0.10%, Ti:0.005-0.030%, 잔부 Fe 및 기타불가피하게 함유되는 불순물로 조성되는 강을 1100-1300℃의 온도범위로 가열한 후 상기 B/N비가 0.4 이하인 경우는 850℃-950℃의 마무리압연온도조건으로 열간압연하고, 상기 B/N비가 0.4초과인 경우는 750-850℃의 마무리압연온도조건으로 열간압연 한 직후 소입하고, 이어 500℃-Acl의 온도범위에서 소려함을 특징으로 하는 인성이 우수한 80kgf/㎟급 직접소입형 고장력강판의 제조방법에 관한 것이다.In order to achieve the above object, the present invention provides a high-strength steel sheet in weight%, C: 0.06-0.16% Mn: 0.60-1.60%, B: 0.0003-0.0020%, N: 0.001-0.004%, Si: 0.10-0.50%, Cu: 0.05-0.50%, Ni: 0.05-1.0%, Cr: 0.05-1.0%, Mo: 0.05-0.80%, Al: 0.01-0.10%, Ti: 0.005-0.030%, balance Fe and If the B / N ratio is 0.4 or less after heating the steel composed of other inevitable impurities contained in the temperature range of 1100-1300 ℃ hot-rolled under the conditions of the finish rolling temperature of 850 ℃ -950 ℃, the B / N If the ratio is more than 0.4, it is hardened immediately after hot rolling under the finishing rolling temperature condition of 750-850 ℃, and then it is attractive in the temperature range of 500 ℃ -A cl . It relates to a method for producing a plate.
이하, 본 발명을 상세히 설명한다.Hereinafter, the present invention will be described in detail.
우선, 강중에 첨가되는 C는 강의 강도확보를 위한 필수성분으로 그 첨가량이 0.06%미만에서는 경제적인 강도확보 측면에서 불리하며, 0.16%를 초과시에는 모재의 인성 저하는 물론 용접성이 현저히 나빠지므로 첨가량은 0.06%-0.16% 범위가 바람직하다.First of all, C added to steel is an essential component for securing the strength of steel, and its content is disadvantageous in terms of economic strength when the added amount is less than 0.06%. When the content exceeds 0.16%, the toughness of the base material and the weldability are significantly worsened. A range of 0.06% -0.16% is preferred.
상기 Mn은 C와 함께 강판의 강도 향상을 위해 필수적인 성분으로서, 소입성을 향상시키고 고강도, 고인성을 얻기 위해서 0.60% 이상을 필요로 하지만 1.60%를 초과하면 모제 및 용접부 인성을 저하시키므로 그 성분함량은 0.60%-1.60% 범위가 바람직하다.The Mn is an essential component for improving the strength of the steel sheet together with C, and requires 0.60% or more to improve the hardenability and obtain high strength and high toughness, but when it exceeds 1.60%, the base material and the welded part decrease the toughness. Silver is preferably in the range of 0.60% -1.60%.
상기 B은 직접소입소려강의 소입성을 가장 효율적이고 경제적으로 향상시킬 수 있는 필수 성분으로 0.0003% 미만에서는 현저한 소입성효과가 나타나지 않으므로 그 하한을 0.0003%로 하고 0.0020% 이상에서는 저질소계강(질소가 60ppm 이하인 강을말함)의 경우 과잉의 B화합물 형성에 기인한 열간취성이 발생하므로 그 성분함량은 0.0003-0.0020% 범위가 바람직하다.The B is an essential component that can improve the hardenability of the direct quenched steel most efficiently and economically. Since it is less than 0.0003%, there is no significant hardenability effect. Therefore, the lower limit is 0.0003% and the low nitrogen-based steel (nitrogen) is more than 0.0020%. In the case of less than 60 ppm), the hot brittleness caused by the formation of excess B compound occurs, the content of the component is preferably 0.0003-0.0020% range.
상기 N 은 A1N, TiN등 질화물 형성원소로서, 오스테나이트 결정립 미세화를 통한 강의 인성 개선을 위해 0.001% 이상을 필요로 하지만, 0.004% 이상 첨가시 N과 친화력이 강한 B와 결합하여 B 의 소입성이 소실되고 게다가 고용 N양이 증대되어 강의 강도 및 인성을 저하시키므로 그 상한을 0.004% 로 제한하는 것이 바람직하다.The N is a nitride forming element such as A1N, TiN, and requires 0.001% or more to improve the toughness of the steel through the refinement of austenite grains, but when 0.004% or more is added, the hardenability of B is combined with B having affinity for N. It is preferable to limit the upper limit to 0.004% because the amount of solid solution N is lost and the amount of solid solution N is increased to lower the strength and toughness of the steel.
상기 Si은 강판 제조시 탈산작용 및 강의 강도 확보에 유용한 원소로, 0.10% 이하에서는 강도 증가에 따라 인성이 저하하고 0.50% 이상에서는 용접경화성이 높아지므로 그 함량범위를 0.10%-0.50%로 하는 것이 바람직하다.The Si is an element useful for deoxidation and securing the strength of steel when manufacturing a steel sheet, the toughness of which decreases with increasing strength at 0.10% or less, and the welding hardenability of 0.50% or more, so that the content range is 0.10% -0.50%. desirable.
상기 Cu는 Ni과 함께 강판의 인성향상에 유용한 원소로서 그 하한은 현저한 인성개선 효과가 나타나지 않는 0.05%로 하고 상한은 과잉 첨가에 의해 다발하는 표면결함을 방지하기 위한 양으로서 0.50%로 하는 것이 바람직하다.Cu is an element useful for improving the toughness of the steel sheet together with Ni. The lower limit thereof is 0.05%, which does not show a significant toughness improvement effect, and the upper limit is 0.50% as an amount for preventing surface defects caused by excessive addition. Do.
상기 Ni은 강판의 인성향상과 고용강화에 의한 강도증가에 유효하지만 0.05% 이하로 첨가하면 그 효과가 거의 나타나지 않으며 1.0%를 초과할 경우 유화수소에 의한 균열감수성이 높아지고 강 제조원가가 비싸지므로 그 성분범위를 0.05-1.0%로 하는 것이 바람직하다.The Ni is effective for increasing the toughness of steel sheet and increasing the strength by solid solution strengthening. However, when Ni is added at 0.05% or less, the effect of Ni is higher than 1.0%. It is preferable to make the range 0.05-1.0%.
상기 Cr은 강의 강도확보에 유효한 원소이지만 첨가량이 0.05% 미만에서는 그 효과가 거의 없으며 1.0%를 넘으면 Cr 탄화물이 다량 생성되어 강의 인성을 저하시키고 동시에 용접성을 해치므로 그 상한을 1.0%로 하는 것이 바람직하다.The Cr is an effective element to secure the strength of the steel, but if the addition amount is less than 0.05%, the effect is almost no, and if it is more than 1.0%, a large amount of Cr carbide is formed, which lowers the toughness of the steel and at the same time damages the weldability. Therefore, the upper limit is preferably 1.0%. Do.
상기 Mo은 모재의 강도확보 및 소려취화 저항능을 향상시키는 원소이지만 0.05% 미만에서는 그 효과가 없고 0.80%를 넘으면 모재 인성 및 용접성이 열화되므로 그 함량 범위를 0.05-0.80%로 하는 것이 바람직하다.The Mo is an element that improves the strength of the base material and improves the resistance to brittle embrittlement, but when the content is less than 0.05%, the effect of the base material deteriorates when the base material toughness and weldability deteriorate, so that the content range is 0.05-0.80%.
상기 Al은 탈산을 위해 필수적으로 첨가되어야 하며 질소와 결합하여 AlN을 형성하므로서 강의 조직을 미세화시키고 고용 질소를 저감시키므로서 인성을 향상시키는데 그 하한은 상기의 효과들이 거의 나타나지 않는 O.01%로 하고 0.10%를 넘으면 과잉의 미세 개재물 형성으로 강의 인성이 현저히 저하되므로 그 상한을 0.10%로 하는 것이 바람직하다.Al must be added for deoxidation and combine with nitrogen to form AlN to refine the structure of steel and reduce toughness of nitrogen to improve toughness. The lower limit is O.01% which hardly exhibits the above effects. If it exceeds 0.10%, the toughness of the steel is considerably lowered due to the formation of excess fine inclusions, so the upper limit is preferably 0.10%.
상기 Ti은 Al과 함게 질소와 결합하여 TiN을 형성하므로서 강의 조직을 미세화시키고 고용 질소를 저감시키므로서 인성을 향상시키는데 그 하한은 상기의 효과들이 거의 나타나지 않는 0.005%로 하고 0.030%를 넘으면 과잉의 미세 개재물 형성으로 강의 인성이 현저히 저하되므로 그 상한을 0.030%로 하는 것이 바람직하다.The Ti combines with nitrogen to form TiN with Al to refine the structure of the steel and improve the toughness by reducing the dissolved nitrogen. The lower limit is 0.005% where the above effects are hardly exhibited. Since the toughness of steel remarkably falls by inclusion formation, it is preferable to make the upper limit into 0.030%.
상기와 같은 성분을 필수성분으로 함유하는 슬라브를 1100℃-1300℃로서 고온가열을 행하는데 이는 앞서 언급한 직접소입강의 충격흡수에너지 감소가 가열온도와 밀접한 관련이 있으며 또한, 직접소입강의 고용강화에 의한 강도향상과도 관계가 있으므로 그 효과가 거의 나타나지 않는 110O℃를 하한으로 설정하고 그 상한은 가열 에너지의 절약 및 오스테나이트 결정립의 조대화에 따른 인성의 저하가 현저해지는 1300℃로 하는 것이 바람직하다.The slab containing the above components as essential components is heated at 1100 ℃ -1300 ℃ at high temperature. This is because the above-mentioned reduction of impact absorption energy of direct quenched steel is closely related to heating temperature. It is also preferable to set the lower limit of 110 ° C, which has little effect, because it is related to the increase in strength, and the upper limit is 1300 ° C, in which the reduction of toughness due to saving of heating energy and coarsening of austenite grains becomes remarkable. .
상기 고온 가열후 실시되는 압연의 마무리온도는 본 발명에 있어서 가장 중요한 제조인자로서 직접소입소려강의 최종 조직, 결정립 크기, B의 소입성 효과 등에 영향을 미치고, 결국 강판의 기계적성질을 좌우하는 요인이 된다.The finishing temperature of the rolling carried out after the high temperature heating is the most important manufacturing factor in the present invention affects the final structure, grain size, B quenching effect of the direct quenched steel, and ultimately the factors that influence the mechanical properties of the steel sheet. Becomes
따라서, 결정립에 편석되어 결정립크기에 영향을 미치는 B의 함유량과 마무리압연 온도의 관계를 통하여 결정립의 크기를 제어함으로서 강도와 인성을 확보하는데 본 발명의 특징이 있다.Therefore, there is a feature of the present invention to secure the strength and toughness by controlling the size of the grains through the relationship between the content of B segregated in the grains and affecting the grain size and the finish rolling temperature.
즉, B 의 입계편석에 영향을 미치는 N와 B 의 비인 B/N값이 0.4이하인 경우는 석출물이 생기지 않고 결정립계에 B이 편석하여 결정립 미세화에 유리하게 작용하므로 850-950℃의 온도범위에서 마무리 압연하는 것이 바람직한데, 850℃ 이하에서 압연이 마무리되면 결정립크기 및 B 의 입계 비평형편석 거동이 본 발명의 효과를 나타내지 못하고, 950℃ 이상인 경우에는 압연시간이 부족하고, 결정립이 너무 조대해진다.In other words, if the B / N value, which is the ratio of N and B, affecting the grain boundary segregation of B is 0.4 or less, no precipitates are formed and B segregates in the grain boundary, which is advantageous for grain refinement, thus finishing in the temperature range of 850-950 ° C. Although rolling is preferable, when rolling is completed at 850 degrees C or less, the grain size and grain boundary equilibrium segregation behavior of B do not show the effect of this invention, and when it is 950 degrees C or more, rolling time runs short and a grain becomes too coarse.
또한, B/N계가 0.4를 초과하는 경우에는 B 이 과잉이 상태가 되어 입계에 편석하기보다는 석출물이 되므로 마무리압연온도를 750-850℃로 하는 것이 바람직한데, 750℃ 이하이면 오스테나이트에서 원하지 않는 페라이트 조직이 생기고, 850℃ 이상되면 결정립크기 및 B 의 입계 평형 편석거동이 본 발명의 효과를 나타내지 못하게 작용한다.In addition, when the B / N system exceeds 0.4, the excess B becomes a precipitate rather than segregation at the grain boundary. Therefore, it is preferable to set the finish rolling temperature to 750-850 ° C. If a ferrite structure is formed, and the grain size and the grain boundary equilibrium segregation behavior of B are higher than 850 DEG C, the effect of the present invention is suppressed.
상기의 조건으로 압연이 마무리된 후 소입된 강판은 500℃-Acl의 온도범위에서 소려함으로써 소입에 의해 강판 내부에 형성된 응력을 제거하고 또한 적절한 인성을 부여 한다.After the rolling is finished under the above conditions, the hardened steel sheet is removed at a temperature in the range of 500 ° C-A cl to remove stresses formed inside the steel sheet by hardening, and to impart appropriate toughness.
이하, 실시예를 통하여 본 발명을 구체적으로 설명한다.Hereinafter, the present invention will be described in detail through examples.
[실시예 1]Example 1
중량%로, C:0.1%, Mn:0.8%, Si:0.25%, Cu:0.3%, N i:0.8%, Cr:0.25%, Mo:0.45%, Ti:0.015%, Al:0.06%을 기본성분계로 하고 B 및 N의 함량이 하기 표1과 같이 조성된 강의 슬라브를 이용하여 하기 표2의 제조조건을 적용하여 고장력강판을 제조하고, 이에 대한 기계적성질 즉, 항복강도, 인장강도, 흡수에너지, 파면천이온도를 측정하고 그 결과를 하기 표2에 나타내었다.By weight%, C: 0.1%, Mn: 0.8%, Si: 0.25%, Cu: 0.3%, Ni: 0.8%, Cr: 0.25%, Mo: 0.45%, Ti: 0.015%, Al: 0.06% By using the slab of steel composed of B and N as the basic component system and the composition of Table 1 below, the high tensile strength steel sheet was manufactured by applying the manufacturing conditions of Table 2 below, and the mechanical properties thereof, that is, yield strength, tensile strength, and absorption Energy, wavefront transition temperature was measured and the results are shown in Table 2 below.
[표 1]TABLE 1
[표 2]TABLE 2
상기 표2에 나타난 바와같이 본 발명재(1-4)가 본 발명의 범위를 벗어난 비교재(1-6) 및 종래의 재가열소입법에 의해 제조된 종래재(1) 보다 항복강도 및 인장강도가 높을 뿐만아니라 층격파면천이온도는 낮게 나타남을 알 수 있었다.As shown in Table 2 above, the present invention material (1-4) is higher than the comparative material (1-6) outside the scope of the present invention and the yield material and the tensile strength of the conventional material (1) manufactured by the conventional reheat quenching method. Was not only high, but the stratification wave transition temperature was low.
상술한 바와같이, 본 발명의 제조방법에 의하면 강도와 인성을 동시에 향상시키고 게다가 강판의 경제적 생산을 가능하게 할 뿐만아니라 직접소입강의 제조시 가장 큰 문제점인 이방성 저감 및 인성확보가 용이하게 이루어지는 효과가 있다. 또한, 직접소입소려 처리함으로써 저원가 및 고능률로 고장력강판을 제조할 수 있는 효과가 있다.As described above, according to the manufacturing method of the present invention, the strength and toughness are simultaneously improved, and the economical production of the steel sheet is not only possible, but also the effect of easily reducing the anisotropy and toughness, which are the biggest problems in the manufacture of direct quenched steel, is easily achieved. have. In addition, the direct quenching treatment has the effect of producing a high tensile strength steel sheet at low cost and high efficiency.
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