KR100256330B1 - The manufacturing method for tensile strength 120kgf/mm2 high strength steel - Google Patents

The manufacturing method for tensile strength 120kgf/mm2 high strength steel Download PDF

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KR100256330B1
KR100256330B1 KR1019950056692A KR19950056692A KR100256330B1 KR 100256330 B1 KR100256330 B1 KR 100256330B1 KR 1019950056692 A KR1019950056692 A KR 1019950056692A KR 19950056692 A KR19950056692 A KR 19950056692A KR 100256330 B1 KR100256330 B1 KR 100256330B1
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steel
quenching
tensile strength
steel slab
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KR1019950056692A
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KR970043145A (en
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이창선
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이구택
포항종합제철주식회사
신현준
재단법인포항산업과학연구원
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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
    • 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
    • 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
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten

Abstract

PURPOSE: A method for manufacturing a high tensile steel having a tensile strength of 120 kgf/mm2 level is provided, which has a high toughness of 80 Jules or more of impact energy at -40 deg.C by quenching-tempering the reheated steel again after directly quenching the high tensile steel and appropriately reheating the steel differently from an existing direct quenching-tempering heat treatment method. CONSTITUTION: The method comprises the processes of finish rolling a steel slab comprising 0.15 to 0.20 wt.% of C, 0.1 to 0.4 wt.% of Mn, 0.15 to 0.4 wt.% of Si, 2.5 to 3.5 wt.% of Ni, 1 to 2 wt.% of Cr, 0.3 to 0.5 wt.% of Mo, 0.04 wt.% or less of V, 0.015 wt.% or less of P, 0.008 wt.% or less of S and a balance of Fe and other inevitable impurities at a temperature of 960 to 820 deg.C; directly quenching the water cooled steel slab after water cooling the steel slab right after the finish rolling; quenching the reheated steel slab again after reheating the quenched steel slab in the temperature range of 860 to 900deg.C; and tempering the quenched steel slab at the temperature range of 300 to 500deg.C.

Description

인장강도 120kgf/㎟ 급 고장력강의 제조방법Manufacturing method of tensile strength 120kgf / ㎠ class high tensile strength steel

본 발명은 방탄용 또는 내마모용 소재에 적합한 고장력강의 제조방법에 관한 것으로서, 보다 상세하게는 인장강도 120kgf/㎟이상, -40℃에서의 샤피(Charpy) 충격에너지(vE(-40))가 80주율(joule) 이상인 고인성 고자력강의 제조방법에 관한 것이다.The present invention relates to a method of manufacturing high tensile steel suitable for anti-ballistic or wear-resistant materials, and more specifically, the Charpy impact energy (vE (-40)) at tensile strength of 120 kgf / mm 2 or more and -40 ° C. It relates to a method for producing high toughness high magnetic steel of 80 joules or more.

일반적으로 인장강도가 60kgf/㎟ 이상인 고강도강은 압연후 공냉된 판을 재가열 소입후 소려처리함에 의해 생산된다. 즉, 오스테나이트 온도까지 가열한 후 소입처리하여 강도가 높은 마르텐사이트 조직을 얻는다. 소입 상태의 마르텐사이트는 강도는 높지만 인성이 낮기 때문에 소려 열처리를 행하여 강도-인성 균형을 맞춘다.In general, high-strength steel with a tensile strength of 60kgf / mm2 or more is produced by annealing after reheating and hardening the air-cooled plate after rolling. That is, it is heated to an austenite temperature and then quenched to obtain a martensite structure having high strength. Since martensite in the quenched state is high in strength but low in toughness, heat treatment is performed to balance the strength and toughness.

최근에는 압연후 곧바로 수냉처리를 행한 후 소려처리(직접 소입-소려처리: DQT)를 하여 기존의 재가열 소입-소려 처리강보다 우수한 물성을 얻는 법이 개발되었다(일본특개소 58-96817, 61-60891, 61-133312 , 60-174810, 평 2-166227, 평 2-205627, 평 6-2054019). 상기 직접 소입-소려 처리법은 기존의 재가열소입-소려 처리법에 비해 강도-인성 조합을 향상시키는 장점이 있다. 그러나, 인장강도 120kgf/㎟ 이상을 유지하면서 -40℃ 에서의 충격시험시 80 주울 이상의 인정을 보유한 고장력강을 얻기 위해서 종래의 직접 소입-소려에 의한 방법을 적용하는 경우 인장강도는 확보가 가능하나 인성이 다소 저하되는 문제가 있었다.Recently, a method of obtaining physical properties superior to conventional reheated quenched-soil treated steels has been developed by performing water-cooling treatment immediately after rolling, followed by soaking treatment (direct quenching-dipped treatment: DQT) (Japanese Patent Application Laid-Open No. 58-96817, 61-). 60891, 61-133312, 60-174810, Pyeong 2-166227, Pyeong 2-205627, Pyeong 6-2054019). The direct quenching-treatment method has an advantage of improving the strength-toughness combination compared to the conventional reheat quenching-treatment method. However, when the conventional direct quenching-applied method is applied to obtain a high tensile strength steel having the approval of 80 joules or more in the impact test at -40 ℃ while maintaining the tensile strength of 120kgf / mm2, the tensile strength can be secured but the toughness is maintained. There was a problem of this somewhat deterioration.

따라서, 본 발명은 종래의 직접 소입-소려 열처리 방법과는 달리, 고장력강을 직접 소입후 적절한 재가열후 다시 소입-소려하므로서 -40℃의 충격에너지가 80 주울이상의 고인성을 갖는 인장강도 120kgf/㎟ 급 고장력강의 제조방법을 제공하고자 하는데, 그 목적이 있다.Therefore, the present invention, unlike the conventional direct quenching-treatment heat treatment method, by direct quenching high tensile strength steel and then quenching-re-sealing after appropriate reheating, the tensile strength of -40 ℃ has a toughness of more than 80 joules tensile strength 120kgf / ㎜ grade An object of the present invention is to provide a method of manufacturing high tensile steel.

이하, 본 발명을 설명한다.Hereinafter, the present invention will be described.

본 발명은, 중량%로, C: 0.15-0.20%, Mn : 0.1-0.4%, Si: 0.15-0.4%, Ni: 2.5-3.5%, Cr:1-2%, Mo: 0.3-0.5%, V: 0.04%이하, P: 0.015% 이하, S: 0.008%이하, 나머지는 Fe 및 기타 불가피한 불순물을 포함하여 조성되는 강슬라브를 960-820℃의 온도에서 마무리 압연하고 바로 직접 소입한 후, 860-900℃의 온도범위에서 재가열한 다음 소입하고, 300-500℃의 온도범위에서 소려하는 인장강도 120kgf/㎟ 급 고장력강의 제조방법에 관한 것이다.The present invention, in weight percent, C: 0.15-0.20%, Mn: 0.1-0.4%, Si: 0.15-0.4%, Ni: 2.5-3.5%, Cr: 1-2%, Mo: 0.3-0.5%, V: 0.04% or less, P: 0.015% or less, S: 0.008% or less, the remainder is steel slab composed of Fe and other unavoidable impurities after finishing rolling at a temperature of 960-820 ° C. and directly quenched, followed by 860 The present invention relates to a method for producing a tensile strength 120kgf / mm2 high tensile strength steel which is reheated and then quenched in a temperature range of -900 ° C and considered in a temperature range of 300-500 ° C.

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

본 발명에 의한 강슬라브중에 함유되는 탄소는 그 함량이 높을 경우 강도는 증가하나 용접성이 저하하며, 그리고 그 함량이 낮은 경우 용접성은 향상되나 강도가 감소하므로 C 함량을 0.15-0.20%로 제한함이 바람직하다.The carbon contained in the steel slab according to the present invention increases the strength when the content is high, but the weldability is lowered, and when the content is low, the weldability is improved but the strength is reduced, thereby limiting the C content to 0.15-0.20%. desirable.

상기 Mn은 소입성 증가에 의해 강도를 증가시키나 용접성을 해치며 또한 소려 취성을 유발시키므로 0.1-0.4%로 제한한다.The Mn increases the strength by increasing the hardenability but impairs the weldability and also causes brittleness, so it is limited to 0.1-0.4%.

상기 Si은 탈산제로 첨가되며, 항복강도는 증가시키지만 충격천이온도를 낮추고 용접성을 해치므로 0.15-0.4%로 제한한다.The Si is added as a deoxidizer, and the yield strength is increased but is limited to 0.15-0.4% because it lowers the impact transition temperature and damages the weldability.

상기 Ni은 저온 인성 확보를 위해 2.5-3.5%로 제한함이 바람직하다.The Ni is preferably limited to 2.5-3.5% to ensure low temperature toughness.

또한, Cr 및 Mo은 소입성을 향상시키며 강도 증가에 기여하지만 용접성을 해치며 고가이므로 각각 Cr: 1-2%, Mo: 0.3-0.5%로 함이 바람직하다.In addition, Cr and Mo improve the hardenability and contribute to the increase in strength, but it is desirable to set Cr: 1-2% and Mo: 0.3-0.5%, respectively, because it damages weldability and is expensive.

상기 V은 Cr, Mo과 같이 소입성을 향상시켜 강도를 증가시키나 다량 함유되면 오히려 강의 인성을 저하하므로 그 함량은 0.04% 이하로 제한함이 바람직하다.The V increases the hardenability, such as Cr, Mo to increase the strength, but when contained in a large amount, the toughness of the steel is lowered, so the content is preferably limited to 0.04% or less.

상기 P와 S는 함량이 낮을수록 좋으나 제강과정에서 피할 수 없는 불순물이므로 물성에 해로운 영향을 끼치지 않도록 각각 P: 0.015% 이하 S: 0.010% 이하로 함이 바람직하다.The lower the content of P and S but the inevitable impurities in the steelmaking process, P: 0.015% or less S: 0.010% or less so as not to adversely affect the physical properties, respectively.

상기와 같이 조성된 강을 본 발명에서는 통상의 방법으로 재가열한 후, 열간압연한 다음, 직접 소입-재가열소입-소결처리를 행한다. 이때, 마무리 압연온도는 960-820℃ 사이로 행하는 것이 바람직한데 그 이유는 마무리 압연온도가 960℃ 보다 큰 경우 오스테나이트 결정립이 조대하여 기계적물성이 나빠지며, 820℃ 보다 낮은 경우 페라이트가 형성되어 물성이 저하되기 때문이다. 이와 같이 마무리 압연후 곧바로 수냉한다. 수냉된 강판은 다시 860-900℃ 사이로 재가열한 후 수냉하는 데, 이때 재가열온도가 900℃보다 높은 경우 오스테나이트 결정립이 조대하여 기계적물성이 나빠지며, 860℃보다 낮은 경우 합금원소의 재고용이 이루어지지 않아 물성이 저하된다. 상기와 같이 재가열소입한 다음, 우수한 강도-인성 조합을 얻기 위해 300-500℃ 사이에서 소려 처리한다. 소려처리온도가 500℃보다 높은 경우 강도가 저하되며, 300℃ 보다 낮은 경우 인성이 저하된다.In the present invention, the steel formed as described above is reheated by a conventional method, followed by hot rolling, followed by direct quenching, reheating and sintering. At this time, the finish rolling temperature is preferably carried out between 960-820 ℃, the reason is that if the finish rolling temperature is greater than 960 ℃ austenite grains coarse, the mechanical properties worsen, if lower than 820 ℃ ferrite is formed and the physical properties This is because it is degraded. In this way, it is cooled by water immediately after finishing rolling. The water-cooled steel sheet is then reheated to between 860-900 ° C and then water-cooled. At this time, when the reheating temperature is higher than 900 ° C, the austenite grains are coarse and the mechanical properties deteriorate. The physical properties are lowered. After reheat firing as above, it is then treated between 300-500 ° C. to obtain a good strength-toughness combination. If the soaking temperature is higher than 500 ° C., the strength is lowered. If it is lower than 300 ° C., the toughness is lowered.

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

[실시예]EXAMPLE

하기표 1과 같은 조성을 갖는 두께 140mm의 4가지 종류의 강슬라브를 1200℃에서 가열하고, 하기표 2와 같은 서로 다른 제조공정으로 최종 두께가 17.0mm인 강판을 제조하였다.Four kinds of steel slabs having a thickness of 140 mm having a composition as shown in Table 1 were heated at 1200 ° C., and steel sheets having a final thickness of 17.0 mm were prepared by different manufacturing processes as shown in Table 2 below.

상기 표 2에서의 제강공정중 QT는 압연후 공랭한 판을 900℃로 재가열하고 수냉하여 소입하는 종래의 공정이며, DQT는 압연후 바로 수냉하여 직접 소입한 다음, 소려하는 종래의 공정이고, DQQT는 압연후 바로 수냉하여 직접 소입한 다음 860-900℃로 재가열후 다시 소입, 소려하는 본 발명에 의한 공정을 의미한다.In the steelmaking process in Table 2, QT is a conventional process of reheating an air-cooled plate after rolling to 900 ° C., water-cooling and quenching, and DQT is a conventional process of water-cooling and directly quenching immediately after rolling, and DQQT. Refers to the process according to the present invention which is directly quenched by water after rolling and directly quenched and then reheated to 860-900 ° C.

또한, 상기 표 2의 압연 조건중In addition, in the rolling conditions of Table 2

A는 12 패스를 연속압연하여 960℃의 재결정 영역에서 마무리 압연하는 것이며,A finish rolling 12 passes and finish-rolling in the recrystallization area | region of 960 degreeC,

B는 900℃까지 9패스를 행하여 29.4mm로 한 후 미재결정 영역인 860-840℃에서 3패스를 마무리 압연하는 것이며,B is 9pass to 900 ℃ to make 29.4mm, and then finish rolling 3 passes at 860-840 ℃ which is the uncrystallized region.

C는 미세한 재결정 오스테나이트를 얻기 위해 1150℃까지 5패스 압연하여 60.9mm로 한 후 재결정 영역인 1010-910℃에서 5패스 압연하는 것이며, 마지막으로C is 5 pass rolling to 1150 ° C to 60.9mm to obtain fine recrystallized austenite, and then 5 pass rolling at 1010-910 ° C, the recrystallization area.

D는 미세한 미재결정 오스테나이트를 얻기 위해 1100℃까지 5패스 압연하여 60.9mm로 한 후, 1000에서 950℃까지 4패스 압연하여 29.4mm로 한 다음, 미재결정 영역인 850-820℃에서 3패스 압연을 행하는 것이다.In order to obtain fine uncrystallized austenite, 5 passes were rolled up to 1100 ° C. to 60.9 mm, followed by 4 passes rolling from 1000 to 950 ° C. to 29.4 mm, followed by 3 passes rolling at 850-820 ° C. in the unrecrystallized area. To do.

상기한 조건에 의해 제조된 강판을 소입후 300-500℃로 소려처리한 다음, 얻어진 시편에 대하여 인장강도 및 -40℃에서의 충격시험치를 측정하고, 그 결과를 하기 표 3에 나타내었다.After quenching the steel sheet prepared by the above conditions at 300-500 ° C., the tensile strength and the impact test value at −40 ° C. were measured on the obtained specimen, and the results are shown in Table 3 below.

상기 표 2,3에 나타난 바와 같이, 압연 후 공랭한 강판을 재가열하여 소입-소려처리한 종래재(1-2)의 경우 인장강도 110-130kgf/㎟, -40℃에서의 충격값이 40-90 주울로 본 발명에서 목표로 하는 기계적 특성에 미치지 못함을 알 수 있다. 또한, 압연후 바로 직접 소입-소려처리한 비교재(1-4)의 경우에는 종래재(1-2)의 경우에 비해 인장강도가 약 10kgf/㎟ 정도 높았지만, 종래재에 비해 거의 동등 또는 약 10 주울 정도 높아 역시 본 발명에서 목표로 하는 기계적 특성을 갖지 못함을 알 수 있다.As shown in Tables 2 and 3, in the case of the conventional material (1-2) which reheated and quenched and cooled the steel sheet after rolling, the impact value at the tensile strength of 110-130kgf / mm2 and -40 ° C was 40-. It can be seen that the 90 joules fall short of the mechanical properties targeted in the present invention. In addition, in the case of the comparative material (1-4), which was directly quenched and annealed immediately after rolling, the tensile strength was about 10 kgf / mm 2 higher than that of the conventional material (1-2). As high as about 10 joules, it can also be seen that it does not have the mechanical properties targeted in the present invention.

반면에 본 발명에 따라 마무리 압연된 후 소입한 다음 다시 860-900℃에서 재가열 소입-소려 처리된 발명재(1-8)의 경우에는 비교재와 유사한 인장강도를 갖고, 종래재에 비해서는 약 10kgf/㎟ 정도 높았으며, -40℃에서의 충격치는 종래재 또는 비교재에 비하여 약 30주울 정도 높아, 본 발명에서 목표로 하는 기계적 특성을 얻고 있음을 알 수 있다.On the other hand, in the case of the invention material (1-8) which has been finish-rolled and then hardened according to the present invention and then reheated and annealed at 860-900 ° C., it has a tensile strength similar to that of the comparative material, and compared with the conventional material. It was about 10 kgf / mm 2, and the impact value at -40 ° C. was about 30 Joules higher than that of the conventional material or the comparative material, and it can be seen that the mechanical properties targeted by the present invention are obtained.

이와같이, 본 발명은 강성분을 적절히 제어하는 동시에 압연후 수냉시킨 다음, 다시 재가열하여 소입-소려 함으로써, 종래의 열처리재보다도 인장강도가 약 10kgf/㎟ 정도 향상되고 -40℃에서 충격값이 약 30주울 정도 높은 고강도-고인성강을 제공하는 효과가 있다.As described above, the present invention provides adequate control of the steel component, water-cooling after rolling, and then reheating and quenching-preheating to improve the tensile strength by about 10 kgf / mm 2 and improve the impact value at -40 ° C. by about 30 kg. It is effective in providing high strength-toughness steel that is as high as joules.

Claims (1)

중량%로, C: 0.15-0.20%, Mn : 0.1-0.4%, Si: 0.15-0.4%, Ni: 2.5-3.5%, Cr:1-2%, Mo: 0.3-0.5%, V: 0.04%이하, P: 0.015% 이하, S: 0.008%이하, 나머지는 Fe 및 기타 불가피한 불순물을 포함하여 조성되는 강슬라브를 960-820℃의 온도에서 마무리 압연하고 바로 수냉하여 직접 소입한 후, 860-900℃의 온도범위에서 재가열한 다음 소입하고, 300-500℃의 온도범위에 소려하는 인장강도 120kgf/㎟ 급 고장력강의 제조방법.By weight, C: 0.15-0.20%, Mn: 0.1-0.4%, Si: 0.15-0.4%, Ni: 2.5-3.5%, Cr: 1-2%, Mo: 0.3-0.5%, V: 0.04% Or less, P: 0.015% or less, S: 0.008% or less, and the remainder is a steel slab formed by Fe and other unavoidable impurities at the temperature of 960-820 ° C., followed by direct rolling and water quenching, followed by direct quenching, 860-900 A method of manufacturing a tensile strength 120kgf / mm2 high tensile strength steel which is reheated and then hardened in a temperature range of ℃ to a temperature range of 300-500 ℃.
KR1019950056692A 1995-12-26 1995-12-26 The manufacturing method for tensile strength 120kgf/mm2 high strength steel KR100256330B1 (en)

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KR910012297A (en) * 1989-12-30 1991-08-07 정명식 Manufacturing method of high strength steel for tensile strength 100kgf / mm2 welded structure
KR950003456A (en) * 1993-07-30 1995-02-16 조말수 Method of manufacturing 80kgf / mm2 unpainted weathering steel with tensile strength

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KR910012297A (en) * 1989-12-30 1991-08-07 정명식 Manufacturing method of high strength steel for tensile strength 100kgf / mm2 welded structure
KR950003456A (en) * 1993-07-30 1995-02-16 조말수 Method of manufacturing 80kgf / mm2 unpainted weathering steel with tensile strength

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