KR19980038066A - Manufacturing method of cold-rolled steel with excellent de-elasticity and softening heat treatment - Google Patents

Manufacturing method of cold-rolled steel with excellent de-elasticity and softening heat treatment Download PDF

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Publication number
KR19980038066A
KR19980038066A KR1019960056916A KR19960056916A KR19980038066A KR 19980038066 A KR19980038066 A KR 19980038066A KR 1019960056916 A KR1019960056916 A KR 1019960056916A KR 19960056916 A KR19960056916 A KR 19960056916A KR 19980038066 A KR19980038066 A KR 19980038066A
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South Korea
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steel
cold
heat treatment
rolled steel
softening heat
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KR1019960056916A
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Korean (ko)
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KR100415919B1 (en
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박성운
이덕락
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김종진
포항종합제철 주식회사
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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
    • C21D7/00—Modifying the physical properties of iron or steel by deformation
    • C21D7/02—Modifying the physical properties of iron or steel by deformation by cold working
    • 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
    • C21D1/26—Methods of annealing
    • C21D1/32—Soft annealing, e.g. spheroidising
    • 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
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium

Abstract

본 발명은 볼트, 너트용 소재로 사용되는 냉간압조용 강재의 제조방법에 관한 것으로, 내탈탄성이 우수하며 신속 연화 열처리가 가능한 냉간압조강의 제조 방법을 제공하는 것을 목적으로 한다.The present invention relates to a method for manufacturing cold-rolled steel used as a material for bolts and nuts, and to provide a method for manufacturing cold-rolled steel having excellent decarburization resistance and rapid softening heat treatment.

Description

내탈탄성 및 연화 열처리성이 우수한 냉간 압조용강의 제조방법Method for manufacturing cold-rolled steel with excellent de-elasticity and softening heat treatment

본 발명은 강재를 연화 열처리한후, 냉간압조가공하여 기계 부품의 체결용볼트, 너트를 만드는데 사용하는 강재의 제조방법에 관한 것으로, 보다 상세하게는, 종래재는 AC1변태 온도 이상에서 장시간 동안 유지함으로써 강을 연화시켰으나, 본 발명강은 AC1변태 온도 이하의 낮은 온도에서 단시간 동안 유지함으로써 종래재에 대비하여 동등 이상의 수준으로 강을 연화시키고 이어지는 냉간압조 공정에서도 종래재에 대비하여 우수한 가공 특성을 나타내는 볼트, 너트용 소재로 사용는 내탈탄성 및 연화 열처리성이 우수한 냉간 압조용강의 제조방법에 관한 것이다.The present invention relates to a method for manufacturing a steel material used for making bolts and nuts for fastening mechanical parts by cold working after softening heat treatment of the steel, and more specifically, the conventional material is maintained for a long time above the A C1 transformation temperature By softening the steel, however, the inventive steel softens the steel to the same level or higher than that of the conventional material by maintaining it for a short time at a temperature lower than the A C1 transformation temperature, and in the subsequent cold rolling process, has excellent processing characteristics compared to the conventional material. Use as a material for bolts and nuts shown relates to a method for producing cold-rolled steel with excellent de-elasticity and softening heat treatment.

일반적으로 자동차, 산업기계 등의 부품 체결용으로 사용되는 볼트, 너트는 표1에 나타낸 바와 같은 성분의 중탄소강 선재를 소재로 사용하며 제조공정은 도1 도시와 같다.In general, bolts and nuts used for fastening parts of automobiles, industrial machines, etc. are used as materials of medium carbon steel wires as shown in Table 1, and the manufacturing process is as shown in FIG.

표 1 (wt.%)Table 1 (wt.%)

종래강은 선재로 열간압연한 상태에서의 강도가 약 85 ㎏/㎟ 정도인데, 이러한 고강도강을 냉간에서 직접 압조하기가 곤란하기 때문에 통상 연화 열처리를 실시한다. 연화 열처리는 통상 AC1변태 온도 이상(약 750℃) 에서 일정 시간 유지한 후, AC1이하의 일정 온도(약 650℃) 까지 서냉한후 이 온도에서 일정 시간 유지 후 냉각한다.이와같은 냉간압조 가공을 통하여 제품화되는 종래 소재의 경우, 크게 두가지의 문제점을 가지고 있다. 한가지는 연화 소둔에 걸리는 시간이 너무 길고 또 소둔 온도가 높아서 생산성이 낮고, 제조비용이 높다는 것이다. 또 다른 문제점은 연화 소둔된 강재의 강도가 충분히 낮지 않기 때문에 냉간압조시 다이스의 수명이 단축되고 또 냉간압조된 제품 표면에 균열이 종종 발생되어 제품의 불량율을 높이는 것이다.Conventional steels have a strength of about 85 kg / mm 2 in a hot rolled state with a wire rod, and softening heat treatment is usually performed because it is difficult to directly press the high strength steel in cold form. Softening heat treatment is usually maintained for a certain time above the A C1 transformation temperature (about 750 ℃), then slowly cooled to a certain temperature (about 650 ℃) below A C1 , and then cooled after maintaining for a certain time at this temperature. In the case of conventional materials that are commercialized through processing, there are two major problems. One is that the time required for soft annealing is too long and the annealing temperature is high, resulting in low productivity and high manufacturing costs. Another problem is that since the strength of the soft annealed steel is not low enough, the die life during cold press is shortened, and cracks often occur on the surface of the cold annealed product to increase the defective rate of the product.

본 발명자들은 최근에 개발된 기술들이 가지고 있는 이러한 문제점들, 즉 연화 소둔시간이 5 시간 이상으로 여전히 길다는 것과 표면 탈탄에 의한 제품 기능 저하가 발생하는 문제점들을 해결하기 위해 연구와 실험을 행하여 이루어진 것으로, 내탈탄성이 우수하며 신속 연화 열처리가 가능한 냉간압조용 강재의 제조 방법을 제공하는 것을 목적으로 한다.The inventors have conducted research and experiments to solve these problems of recently developed technologies, that is, the softening annealing time is still longer than 5 hours, and the problem that product deterioration occurs due to surface decarburization. It is an object of the present invention to provide a method for manufacturing cold-rolled steel having excellent decarburization resistance and rapid softening heat treatment.

도1은 냉간압조부품의 제조공정을 블록으로 도시한 도면,1 is a block diagram illustrating a manufacturing process of a cold press component;

도2는 연화 열처리 시간에 따른 강재의 경도 변화를 나타낸 그래프도,Figure 2 is a graph showing the hardness change of the steel according to the softening heat treatment time,

도3은 연화 열처리후의 종래강과 본 발명강의 경도를 비교하여 나타낸 그래프도, 도4(가)는 연화 열처리후의 본발명강의 표면 탈탄을 보여주는 조직 사진, (나)는 비교강의 표면 탈탄을 보여주는 조직 사진,Figure 3 is a graph showing the hardness of the conventional steel and the inventive steel after softening heat treatment, Figure 4 (a) is a structure photograph showing the surface decarburization of the present invention steel after softening heat treatment, (b) is a structure photo showing the surface decarburization of comparative steel ,

도5는 냉간압조시 본발명강과 비교강의 변형저항의 변화를 나타내는 그래프도,5 is a graph showing changes in deformation resistance of the present invention steel and the comparative steel during cold pressing;

도6은 본 발명강과 비교강의 한계 압조율을 비교하여 나타낸 그래프도이다.6 is a graph showing the comparison between the critical pressure ratio of the inventive steel and the comparative steel.

이하에서는 양호한 실시예와 관련하여 본 발명을 상세하게 설명한다.연을 실시하고, 이후 10 % 이상의 가공량으로 냉간가공후, 650∼740℃의 온도 범위에 0.5∼4 시간 동안 유지하여 강재를 연화시켜 제조하는 구성이다. 이와 같이 제조된 강재를 냉간압조 가공하여 체결용 볼트, 너트를 제조하게 된다.바나듐(V)은 강중에서 질소와 결합하여 VN 을 형성한다. 이 VN은 열처리시 흑연 입자의 핵생성 자리 역할을 하므로 흑연화를 매우 효과적으로 촉진시킨다.Hereinafter, the present invention will be described in detail with reference to the preferred embodiments. After performing the lead and cold working at a processing amount of 10% or more, the steel is softened by maintaining it at a temperature range of 650 to 740 ° C for 0.5 to 4 hours. It is a structure manufactured by making it. The steel thus produced is cold pressed to manufacture bolts and nuts for fastening. Vanadium (V) combines with nitrogen in steel to form VN. This VN acts as a nucleation site of the graphite particles during the heat treatment, thus promoting the graphitization very effectively.

상기와 같은 방법으로 재질을 연화시킨 강재는 용도에 맞게 다양한 형태로 냉간압조하여 제품을 만든 후 소입, 소려 열처리하여 강재를 강인화시켜 사용한다.Steels softened by the method described above are cold pressed in various forms to suit the purpose, and then used to harden the steel by hardening and roughening heat treatment.

이하 실시예를 통하여 본 발명을 보다 구체적으로 설명한다.The present invention will be described in more detail with reference to the following Examples.

(실시예) (Example)

이후, 냉간 압연기를 이용하여 열간 압연판을 냉간에서 50 % 압연을 실시하지 않는다.정에서 흑연의 핵생성 자리가 될 수 있는 미세한 질화물들이 충분히 생성될 수 없다. 가열 온도가 1250℃ 이상이 되면 탈탄이 심하게 발생하게 되어 최종 제품의 재질 특성을 심하게 떨어뜨리게 된다.C1소가 다량 첨가된 비교강의 탈탄층 깊이는 약 0.23 ㎜ 로 매우 깊다.Thereafter, the hot rolled sheet is not subjected to 50% rolling in cold using a cold rolling mill. Fine nitrides which may become nucleation sites of graphite in the well cannot be produced sufficiently. When the heating temperature is higher than 1250 ℃, decarburization occurs badly, which seriously degrades the material properties of the final product. The depth of the decarburized layer of the comparative steel to which a large amount of C1 is added is about 0.23 mm, which is very deep.

따라서,상기 설명한 바와 같이, 본 발명의 내탈탄성 및 연화 열처리성이 우수한 냉간압조용 강재의 제조방법에 의하면, 강중 규소, 바나듐 함량을 적절히 첨가하여 강 조성을 제어하는 한편, 냉간가공을 직절히 수행함으로써, 낮은 온도 및 짧은 시간에 강재를 효과적으로 연화시킬 수 있을 뿐 아니라, 열처리 과정중 탈탄도 효과적으로 억제할 수 있다. 따라서, 연화 열처리 공정을 경제적, 효율적으로 수행하는데 효과가 크며, 이어지는 냉간압조 공정에서 다이스 수명 연장 및 생산성 향상 효과를 기할 수 있다. 뿐만아니라, 연화 소둔 공정에서 탈탄을 효과적으로 억제함으로써 최종 제품이 요구하는 기계적 성질 개선을 효과적으로 확보하는데 유용한 발명인 것이다.Therefore, as described above, according to the method for manufacturing a cold-rolled steel having excellent decarburization resistance and softening heat treatment property of the present invention, by appropriately adding silicon and vanadium content in the steel to control the steel composition, by performing cold working directly In addition, it can effectively soften steels at low temperatures and short time periods, and can also effectively suppress decarburization during heat treatment. Therefore, it is effective to perform the softening heat treatment process economically and efficiently, and it is possible to extend the die life and improve the productivity in the subsequent cold rolling process. In addition, by effectively suppressing the decarburization in the soft annealing process is useful invention to effectively secure the improvement of mechanical properties required by the final product.

Claims (1)

냉간압조용 강재의 제조방법에 있어서, 중량 % 로, C:0.3∼0.6 %, Si:0.8∼1.4 %, Mn:0.1∼0.8 %, P:0.03 % 이하, S:0.05 % 이하, V:0.01∼0.1 %, Al:0.01∼0.1 %, B:0.0005∼0.005 %, N:0.001∼0.005 % 를 함유하고, 잔부 Fe 및 기타 불가피하게 함유되는 불순물로 조성되는 강을, 950∼l250℃ 의 온도 범위로 가열한 후, 열간압연을 실시한 다음,10 % 이상의 가공량으로 냉간가공한 후, 다시 650∼740℃의 온도 영역으로 가열하여 이 온도에서 0.5∼4 시간 동안 유지하여 강재를 연화시키는 것을 특징으로 하는 내탈탄성 및 연화 열처리성이 우수한 냉간압조용 강재의 제조방법.In the method for producing cold-rolled steel, in weight%, C: 0.3 to 0.6%, Si: 0.8 to 1.4%, Mn: 0.1 to 0.8%, P: 0.03% or less, S: 0.05% or less, V: 0.01 The temperature range of 950-1250 degreeC for the steel which contains -0.1%, Al: 0.01-0.1%, B: 0.0005-0.005%, N: 0.001-0.005%, and consists of remainder Fe and other unavoidable impurities. After heating to hot rolling, and then cold working to 10% or more of the processing amount, and then heated to a temperature range of 650 ~ 740 ℃ again and maintained at this temperature for 0.5 to 4 hours to soften the steel Method for producing cold-rolled steel having excellent de-elasticity and softening heat treatment.
KR1019960056916A 1996-11-23 1996-11-23 Manufacturing method of steel for cold heading having superior decarburization resistance and softening heat treatment property KR100415919B1 (en)

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Cited By (1)

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Publication number Priority date Publication date Assignee Title
US8681017B2 (en) 2009-12-28 2014-03-25 Korea Electronics Technology Institute Visible light communication apparatus for vehicle, system and method for vehicular communication inside tunnel using visible light communication

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JPS5945748B2 (en) * 1980-03-19 1984-11-08 住友金属工業株式会社 Damping steel plate for processing and its manufacturing method
KR900007446B1 (en) * 1987-12-28 1990-10-10 포항종합제철 주식회사 Method for producing a high tensile steel having a good properties of strength resistant abraison resistant carrosion
US5476556A (en) * 1993-08-02 1995-12-19 Kawasaki Steel Corporation Method of manufacturing steel for machine structural use exhibiting excellent free cutting characteristic, cold forging characteristic and post-hardening/tempering fatigue resistance

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8681017B2 (en) 2009-12-28 2014-03-25 Korea Electronics Technology Institute Visible light communication apparatus for vehicle, system and method for vehicular communication inside tunnel using visible light communication

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