KR100336852B1 - Method for manufacturing high strength hyper-eutectoid steel for elongation - Google Patents

Method for manufacturing high strength hyper-eutectoid steel for elongation Download PDF

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KR100336852B1
KR100336852B1 KR1019960018188A KR19960018188A KR100336852B1 KR 100336852 B1 KR100336852 B1 KR 100336852B1 KR 1019960018188 A KR1019960018188 A KR 1019960018188A KR 19960018188 A KR19960018188 A KR 19960018188A KR 100336852 B1 KR100336852 B1 KR 100336852B1
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strength
temperature
steel
cooling
wire
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KR1019960018188A
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KR970073771A (en
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박경태
박수동
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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
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C21D8/08—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires for concrete reinforcement
    • 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
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/525—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length for wire, for rods
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Heat Treatment Of Steel (AREA)
  • Metal Extraction Processes (AREA)

Abstract

PURPOSE: A method for manufacturing high strength hyper-eutectoid steel having a tensile strength of greater than 180 kgm/mm¬2 after bluing suitable for use in bead wire or cable is provided. CONSTITUTION: The method includes the steps of hot rolling a steel slab comprising C 0.8 to 1.0 wt.%, Si 0.5 to 0.7 wt.%, Mn 0.6 to 0.9 wt.%, V 0.05 to 0.15 wt.%, S<0.01 wt.%, P<0.01 wt.%, a balance of Fe and incidental impurities into a wire rod having a diameter of 7 to 11 mm; continuous cooling the wire rod from the cooling initiation temperature range of 1050 to 1150°C to pearlite transformation initiation temperature at a cooling rate of 3 to 10°C/sec; cold elongation of the cooled wire rod at a cross sectional reduction ratio of 80 to 85 %; and bluing the cold elongated wire rod at 450 to 500°C.

Description

신선용 고강도 과공석 선재의 제조 방법Manufacturing method of high-strength over-drawing wire for drawing

본 발명은 신선용 고강도 과공석강 선재의 제조방법에 관한 것으로, 보다 상세하게는 중간 열처리를 생략하고 단면강소율 80-85%의 냉간신선시 인장강도 200kg/㎟ 이상, 신선후처리인 blueing 열처리 후 인장강도가 180kgm/㎟ 이상을 나타내는 신선용 고강도 과공석강 선재의 제조방법에 관한 것이다.More particularly, the present invention relates to a method of manufacturing a high strength super high strength superconducting wire having a tensile strength of 200 kg / mm &lt; 2 &gt; or more at cold drawing with a reduction ratio of 80-85% And more particularly to a method for producing a high strength super high strength superabsorbent wire rod having a tensile strength of 180 kg / mm 2 or more.

사장교, 현수교 등 특수교량에 있어서 하중의 대부분을 지지하는 케이블, 콘크리트 인장강도를 증가시키기 위해 사용되어지는 PC 강선 등 구조재료로 사용되어지는 강선에는 높은 강도가 요구되어지기 때문에 일반적으로 실용 재료 중 가장 고강도를 나타내는 냉간 신선을 거친 공석 강선 또는 과공석강선을 사용하고 있다.Cable for supporting most of the load in special bridges such as cable-stayed bridges and suspension bridges, and PC wires used for increasing the tensile strength of concrete are required to have high strength in the steel wire used as the structural material, Cold-drawn steel wire or high-strength steel wire with high strength is used.

위와 같은 공석강선 또는 과공석 강선들을 일반적으로 제철소에서 직경 5-15㎜의 선재로 제조된 후 수요가에서 신선에 적합한 조직인 미세한 펄라이트를 얻기위해 패턴팅(patenting) 열처리 공정을 거친 후 신선 공정을 거쳐 최종제품인 강선으로 제조된다.The above-mentioned vacant steel wire or over-laying steel wire is generally manufactured from a wire rod having a diameter of 5-15 mm in a steel mill, and then subjected to a patenting heat treatment process and then a drawing process to obtain fine pearlite, The final product is made of steel wire.

이하, 신선 전 원소재인 열간압연재를 선재라 칭하며, 수요가에서 신선 공정을 거친 신선재를 강선이라 칭한다.Hereinafter, the hot rolled material, which is a hot rolled raw material, is referred to as a wire rod, and the drawn material having undergone a drawing process at a demand price is referred to as a steel wire.

구조재료로 사용되어지는 강선들은 용도 특성상 수분, 염분 등 부식을 야기시키는 분위기하에서 장시간 노출되므로 내후성을 부여하기위해 통상 신선후 아연도금처리를 거친다.The steel wires used as structural materials are usually exposed to zinc for long time in an atmosphere causing corrosion such as moisture and salt, so they are usually galvanized after freshness to give weatherability.

또한 아연도금이 요구되지 않는 구조재료용 강선의 경우 신선에 의해 변화된 미세 조직을 안정화하기 위해 블루잉(Blueing) 열처리를 행한다.In the case of a steel wire for structural materials that does not require zinc plating, blueing heat treatment is performed to stabilize the microstructure changed by drawing.

통상 아연도금 온도와 시간은 블루잉(Blueing) 열처리 조건과 동일하므로 이하 blueing 열처리로 통칭한다.Since the zinc plating temperature and time are generally the same as the blueing heat treatment conditions, they are generally referred to as blueing heat treatment.

위에 언급한 강선을 제조하기 위한 여러 공정 중 강선의 강도에 영향을 미치는 공정은 패턴팅, 신선, 그리고 블루잉(Blueing) 열처리이다.Among the processes for manufacturing the steel wire mentioned above, the processes affecting the strength of the steel wire are patterning, drawing, and blueing heat treatment.

이들 공정중 패턴팅, 신선은 각각 조직 미세화와 가공경화에 의해 강도를 증가시키는 요인으로 작용하며 반면 블루잉(Blueing) 열처리는 강도 저하요인으로 작용한다.Among these processes, patterning and drawing each act as a factor to increase the strength by microstructure and work hardening, whereas the blueing heat treatment serves as a factor of strength deterioration.

그러나, 신선에 적합한 미세 펄라이트를 얻기위해 행하는 패턴팅 처리는 생산성 저하 및 환경오염 등의 문제점을 야기 시키므로 이를 해결하기 위해 패턴팅과 같은 항온변태가 아닌 강제송풍에 의한 연속제어냉각법을 적용하여 패턴팅 처리재와 유사한 미세조직과 강도를 갖는 패턴팅 처리 생략형 선재가 개발되고 있다.However, since the patterning process for obtaining micro pearlite suitable for drawing leads to problems such as lowering of productivity and environmental pollution, it is difficult to perform patterning by applying continuous control cooling method by forced air blowing instead of constant temperature transformation such as patterning There has been developed a patterning process abbreviation type wire having a microstructure similar to that of a processing material and having strength.

연속냉각에 의해 신선용 선재를 제조할 경우 문제점은 연속냉각시 적용되는 펄라이트 변태개시온도까지의 냉각속도가 부적절할 경우 신선시 단선을 유발하는 경(硬)조직인 초석 세멘타이트나 마르텐사이트를 발생시키는 것이다.The problem of producing wire rods by continuous cooling is that when the cooling rate up to the pearlite transformation starting temperature applied during continuous cooling is inadequate, a hard cementite or martensite, will be.

따라서 이를 억제하기 위해서는 합금성분을 고려하여 최적 냉각속도범위를결정해야한다.Therefore, in order to suppress this, the optimum cooling rate range should be determined by considering the alloy components.

통상 블루잉(Blueing) 열처리는 350-450C, 아연도금은 400-450C에서 행하여지며 블루잉(Blueing) 열처리의 경우 상대적으로 저온인 350C이하에서는 미세조직 안정화 효과가 작으며, 400C이하의 아연도금은 강도저하는 심하지 않으나 과도한 아연 부착에 의한 아연도금층의 불균일을 초래한다.In general, the blueing heat treatment is performed at 350-450C and the zinc plating is performed at 400-450C. In the case of blueing heat treatment, the microstructure stabilization effect is low at a temperature of 350C or less, which is relatively low temperature. The strength deterioration is not severe, but causes unevenness of the zinc plated layer due to excessive zinc adhesion.

그리고 450℃이상 고온에서의 블루잉(Blueing) 열처리나 아연도금은 각 공정의 목적을 충분히 만족시키나 그에 수반하여 강도 저하가 심한 단점이 있다.The blueing heat treatment at a high temperature of 450 ° C or more and the zinc plating sufficiently satisfy the purpose of each step, but the strength is deteriorated severely.

이와 같이 불루잉 열처리를 거친 강선의 최종 강도는 블루잉(Blueing) 열처리 조건에 의해 결정되므로 이에 의한 강도저하를 억제하기 위해 합금 성분을 조절하거나 블루잉 (Blueing) 조건을 최적화시키는 기술들이 개발되고 있다.Since the ultimate strength of the steel wire subjected to the heat treatment is determined by the blueing heat treatment conditions, techniques for controlling the alloy components or optimizing the blueing conditions have been developed .

블루잉(Blueing) 열처리를 거치는 고강도 과공석강선을 제조하는 종래의 기술로는 일본특허공보(평)3-278074, (평)3-284124, (평)5-105965를 들 수 있다.Japanese Patent Publication Nos. 3-278074, 3-284124, and 5-105965 disclose conventional techniques for manufacturing a high strength superalloy steel wire subjected to a blueing heat treatment.

상기 일본특허 공보(평)3-278074는 C : 0.9-1.25%, Si : 0.15-1.50%, Mn : 0.3-1.0%, Cr : 0.1-1.0%를 포함하는 강에서 패턴팅 열처리시 미세조직을 베이나이트(bainite)화하여 단면감소율 80-85%까지 신선 후 350-450C에서 블루잉 (Blueing) 열처리를 하여 고강도 과공석 강선을 제조하는 것을 특징으로 한다.Japanese Patent Application Laid-Open No. Hei 3-278074 discloses a method for manufacturing a steel sheet, comprising the steps of: forming a microstructure by patterning heat treatment in a steel containing 0.9-1.25% of C, 0.15-1.50% of Si, 0.3-1.0% of Mn and 0.1-1.0% Bainite, and then subjected to a blueing heat treatment at a temperature of 350-450 C after drawing to a reduction rate of 80-85%, thereby producing a high strength superalloy steel wire.

상기 기술에서 언급되어진 베이나이트 강선은 비록 펄라이트 강선에 비해 높은 강도를 나타내더라도 신선용 강선에서 가장 요구되어지는 신선성이 매우 열악하여 일반 신선 공정에서는 직접 적용이 곤란하며 따라서 신선 도중 1회 이상의 패턴팅 처리가 요구된다.Although the bainite steel wire mentioned in the above-mentioned technique exhibits a higher strength than the pearlitic steel wire, it is very difficult to directly apply it in a general drawing process due to the poor drawability which is most required in a steel wire for drawing, Processing is required.

상기 일본특허공보(평)3-284124S는 상기 일본특허공보(평)3-278074와 같은 합금성분을 갖는 과공석강을 열간압연 후 [%C]<0.16 log(냉각속도)+0.82의 식을 만족하는 냉각속도로 냉각, 400-650C에서 패턴팅 처리를 한 후 단면 감소율 86-94%의 식을 만족하는 냉각속도로 냉각, 400-650C에서 패턴팅 처리를 한 후 단면감소율 86-94%의 신선을 하여 350-450C에서 블루잉(Blueing) 열처리를 행함으로 고강도 과공석 강선을 제조하는 것을 특징으로 하나 패턴팅 처리의 생략이 불가능 하며 또한 냉각속도를 탄소함량으로 표시한 상기 식에서는 냉각속도의 상한을 설정하지 않아 마르텐사이트와 같은 신선시 단선을 유발하는 유해 미세조직을 발생시킬 우려가 있으므로 적용이 곤란하다.Japanese Patent Application Laid-Open No. 3-284124 S satisfies the expression of [% C] <0.16 log (cooling rate) +0.82 after hot rolling a superalloy steel having an alloy component such as the Japanese Patent Publication No. 3-278074 Cooling at a cooling rate of 400-650 C, cooling at a cooling rate satisfying the equation of a section reduction rate of 86-94%, patterning at 400-650 C, And a blueing heat treatment is performed at 350-450C to produce a high strength superalloy steel wire. However, it is impossible to omit the patterning treatment and the cooling rate is expressed as carbon content, It is difficult to apply it because there is a risk of generating a harmful microstructure that causes disconnection at the time of drawing such as martensite.

상기 일본특허공보평5-105965는 C : 0.9-1.10%, Si : 0.15-0.50%, Mn : 0.3-1.0%, Cr : 0.1-1.0%를 포함하는 강에서 냉각매체를 이용 냉각한후 400-500C 온도 구간의 패턴팅에 의해 조직을 상부 베이나이트화하여 단면감소율 87-94%까지 신선, 350-450C에서 블루잉(Blueing) 열처리를 하여 자동차 타이어 보강 비이드 외이어(bead wire)용 강선 등 극세선을 제조하는 기술로서 상기 일본특허공보평3-278074와 유사한 문제점을 갖고있으며 극세선 제조에 관한 기술로서 구조용 강선의 제조 방법으로는 적합하지 않다.Japanese Patent Laid-Open No. 5-105965 discloses a method of cooling a steel containing 0.9 to 1.10% of C, 0.15 to 0.50% of Si, 0.3 to 1.0% of Mn and 0.1 to 1.0% of Cr using a cooling medium, 500C temperature range, the structure is heated up to 87-94% in cross section reduction rate and blueing heat at 350-450C, and the steel wire for bead wire reinforcement bead wire etc. As a technique for manufacturing a super fine wire, it has problems similar to those of the above-mentioned Japanese Patent Publication No. 3-278074, and is not suitable as a method for manufacturing a structural steel wire as a technique for manufacturing ultra fine wire.

또한 상기한 기술들은 블루잉(Blueing) 열처리 온도를 350-450C로 제한하고 있는 바 이는 450C이상의 온도에서는 강도 저하가 심하여 고강도화를 이룰수 없기 때문이다.In addition, the above-mentioned techniques limit the blueing heat treatment temperature to 350-450C because the strength is lowered at 450C or higher, and the strength can not be enhanced.

따라서 블루잉(Blueing) 열처리 온도를 상승시키고 동시에 강도 저하를 억제할 경우 블루잉(Blueing) 처리 시간을 단축시켜 생산성을 향상시킬 수 있는 잇점이 있다.Therefore, when the temperature of the blueing heat treatment is increased and the decrease in the strength is suppressed, the productivity can be improved by shortening the blueing treatment time.

본 발명은 상기한 문제점을 해결하기 위해 제안된 것으로서, 강도를 증가시키면서 생산성 증가 및 환경오염을 방지할 수 있는 신선용 고강도 과공석 선재의 제조방법을 제공하는데 그 목적이 있다.It is an object of the present invention to provide a method for manufacturing a high-strength over-drawing wire which can increase productivity and prevent environmental pollution while increasing strength.

상기 한 목적을 달성하기 위해 본 발명은 중량 %로 C : 0.8-1.0%, Si : 0.5-0.7%, Mn : 0.6-0.9%, V : 0.05-0.15%, S : < 0.01%, P : < 0.01%, 잔부 Fe및 불가피한 불순물로 구성되는 강들을 직경 7-11㎜의 선재로 열간압연 후 1050-1150℃의 냉각개시 온도에서 펄 라이트 변태 개시온도까지 3-10℃/sec의 냉각 속도로 연속 냉각한 다음 패턴팅 처리없이 80-85%의 단면감소율로 냉간신선하고, 450-500℃에서 블루잉(Blueing) 열처리를 하는 것을 특징으로 하는 신선용 고강도 과공석 선재의 제조방법을 제공한다.In order to achieve the above object, the present invention provides a ferritic stainless steel comprising, by weight percent, 0.8-1.0% of C, 0.5-0.7% of Si, 0.6-0.9% of Mn, 0.05-0.15% of V, 0.01%, the remainder Fe, and unavoidable impurities were hot-rolled into a wire having a diameter of 7 to 11 mm, and then continuously heated at a cooling rate of 3 to 10 캜 / sec from the cooling start temperature of 1050 to 1150 캜 to the pearlite transformation starting temperature And then cold-drawn at a reduction ratio of 80-85% without a patterning treatment, and subjected to a blueing heat treatment at 450-500 ° C.

이하 본 발명의 상세한 내용을 설명한다.Hereinafter, the details of the present invention will be described.

본 발명의 화학성분을 중량%로 C : 0.8-1.0%, Si : 0.5-0.7%, Mn : 0.6-0.9%, V : 0.05-0.15%, S : < 0.01%, P : < 0.01%, 잔부 Fe 및 불가피한 불순물로 한정하는 것이 바람직하며 그 이유는 다음에 기술하는 바와 같다.The chemical composition of the present invention is characterized by containing, as a weight%, 0.8-1.0% of C, 0.5-0.7% of Si, 0.6-0.9% of Mn, 0.05-0.15% of V, 0.01% Fe and unavoidable impurities, and the reason thereof is as follows.

상기 탄소는 강도증가에 가장 효과적인 원소로 주지되고 있으나 본 발명재에서 탄소량은 0.8-1.0%로 한정하는 것이 바람직하며 이는 0.8% 이하에서는 초석 페라이트가 생성되어 강도 저하요인으로 작용하며 또한 초석 페라이트가 존재할 경우 펄라이트와 초석 페라이트 계면에서 균열이 발생하여 신선시 단선을 유발시키는 원인을 제공할 확율이 높아지기 때문이다.Although carbon is known to be the most effective element for increasing the strength, it is preferable that the amount of carbon in the present invention be limited to 0.8-1.0%. If the carbon content is less than 0.8%, pro-eutectoid ferrite is generated, The presence of cracks at the interface between the perlite and the pro-eutectoid ferrite increases the probability of providing a cause of disconnection at the time of freshness.

0.1%이상의 탄소 함유시에는 상기 냉각속도의 범위에서 초석 세멘타이트가 석출되기 용이하며 이로 인하 신선시 단선을 방지하기 위해 1.0% 이하로 제한하는 것이 바람직하다.When 0.1% or more of carbon is contained, quartzite cementite is easily precipitated in the range of the cooling rate, and therefore, it is preferable to be limited to 1.0% or less in order to prevent disconnection in cutting.

상기 실리콘은 강의 탈산에 필수적인 원소이며, 펄라이트를 미세화시킴과 동시에 펄라이트내 페라이트에 고용되어 펄라이트의 강도를 증가시키는 원소의 하나이다.The silicon is an element essential for the deoxidation of steel, and is one of the elements that refines pearlite and is dissolved in ferrite in pearlite to increase the strength of pearlite.

따라서 펄라이트내 페라이트에서의 실리콘의 고용강화에 의해 신선 전 열간압연 선재의 초기강도를 효과적으로 증가시키기 위해 본 발명에서는 실리콘의 함량을 통상의 공석가에 비해 많은 0.5%이상으로 하는것이 바람직하다.Therefore, in order to effectively increase the initial strength of the pre-drawn hot-rolled wire by strengthening the solubility of silicon in the ferrite in the pearlite, it is preferable in the present invention that the content of silicon is more than 0.5% in comparison with the normal vacancy.

여기서 실리콘은 강의 경화능을 향상시키며, 과다 첨가시 탄소의 활동도를 증가시켜 표면 탈탄을 조장하므로 0.7%이하로 제한하는 것이 바람직하다.Here, silicon improves the hardenability of the steel and increases the activity of carbon when it is added in excess, which promotes surface decarburization, so that it is preferable to limit it to 0.7% or less.

상기 망간은 강의 제조시 탈산 효과가 크며, 강의 제조시 필수적으로 함유되는 황과 반응, 황화망간(MnS)를 형성하여 황의 결정립계 편석에 의한 적열취성을 방지하는 효과를 나타낸다.The manganese exhibits a large deoxidizing effect in the production of steel and reacts with sulfur contained in the steel in the preparation thereof to form manganese sulphide (MnS), thereby preventing the brittleness due to grain boundary segregation of sulfur.

일반적으로 0.5%이상의 망간 첨가시에는 경화능 향상 효과, 편석에 의해 저온조직 을 발생시킬 수 있으나 강도 증가에 효과적이므로 본 발명 재에는 0.6% 이상 첨가하여 1% 이상의 망간 첨가시에는 저온조직 발생을 억제하기 위해 서냉을 하게되므로 과공석강의 경우 초석 세멘타이트 석출을 야기시키며, 또한 서냉에 의해 조대한 펄라이트가 생성되어 원하는 강도를 얻을 수 없으므로 본 발명의 목적에 부합하도록 0.9%이하로 제한하는것이 바람직하다.In general, when 0.5% or more manganese is added, hardening effect is improved and segregation can generate low-temperature structure, but it is effective to increase the strength. Therefore, 0.6% or more is added to the present invention, It is preferable to limit the amount of the pearlite to 0.9% or less in order to meet the object of the present invention since the pearlite precipitates in the case of the overcrystallized steel, .

상기 바나듐은 선재 열간압연 후 연속냉각에 의한 펄라이트 변태시 펄라이트를 미세화시킴과 동시에 펄라이트내 페라이트에 바나듐 카보나이트라이드 [vanadium carbonitride, V(C,N)]로 석출되어 펄라이트의 강도를 향상시키는 원소로서 0.05%이하 첨가시 페라이트내 바나듐 고용한도 이하로 석출물보다는 고용 상태로 존재하여 강도증가 효과가 작으므로 0.05%이상을 첨가하는 것이 바람직하다.The vanadium is an element which fines pearlite during pearlite transformation by continuous cooling after hot rolling and simultaneously precipitates vanadium carbonitride (V (C, N)) on the ferrite in pearlite to improve the strength of pearlite. %, It is preferable to add not less than 0.05% of vanadium because it exists in a solid state rather than a precipitate and has a small effect of increasing the strength.

또한 바나듐은 망간과 더불어 경화능 향상 효과가 뛰어나 부적절한 냉각시 신선성을 저하시키는 마르텐사이트와 같은 저온조직을 발생시킬 우려가 있으며 과다 첨가할 경우 블루잉(Blueing) 처리시 석출물이 조대화하여 강도 저하를 조장하므로 본 발명의 목적과 같이 블루잉(Blueing)처리시 강도 저하를 억제하기위해서는 0.15% 이하로 한정하는 것이 바람직하다.In addition, vanadium is excellent in improving the hardenability with manganese, and there is a possibility of generating low-temperature structure such as martensite which deteriorates the drawability upon inadequate cooling. In the case of excessive addition, precipitates are coarsened during blueing, It is preferable to limit it to not more than 0.15% in order to suppress the strength decrease in the blueing treatment as in the present invention.

상기 인은 제강시 중심부에 가장 편석되기 쉬우며, 경화능을 향상시키는 원소로서 선재 압연 후에도 중심부에 편석대를 형성하여 통상의 서냉 조건에서도 저온조직을 발생시키키 쉬우므로 0.01% 이하로 관리하는 것이 바람직하다.Since phosphorus tends to be segregated most at the center of steelmaking during steelmaking, it is an element which improves the hardenability, and it is easy to form a segregation zone at the central portion even after rolling the wire, Do.

상기 황은 결정립계에 편석되기 쉬운 원소로서 결정립계에 편석될 경우 결정립계를 취약하게하여 특히 고온 압연시 적열취성을 일으키므로 0.01% 이하로 관리하는 것이 바람직하다.When sulfur is segregated in the grain boundaries as an element which is liable to segregate in the grain boundaries, the grain boundary is weakened, and especially in hot rolling, it causes brittleness.

본 발명에 있어서 냉각개시온도 범위를 1050-1150℃로 한정하는 이유는 다음과 같다.In the present invention, the reason why the cooling start temperature range is limited to 1050 to 1150 占 폚 is as follows.

냉각개시온도는 통상 선재압연 전 빌렛의 가열온도와 같으며, 1050℃이하에서는 바나듐이 완전 고용되지 않고 조대한 석출물로 존재하여 미세 석출물에 의한 석출강화 효과를 충분히 얻을 수 없으며, 또한 1050℃ 이하의 상대적인 저온에서 압연시 압연과부하에 의한 소재형상 불균일 등 압연불량를 초래한다.The cooling start temperature is usually the same as the heating temperature of the billet before rolling. When the temperature is lower than 1050 ° C, the vanadium is not completely dissolved and is present as a coarse precipitate. As a result, precipitation strengthening effect by micro precipitates can not be sufficiently obtained. Rolling at relative low temperatures causes rolled failure such as irregularity of work shape due to rolling overload.

1150℃ 이상에서는 선재 열간압연시 표면흠에 의한 불량, 권취 불량등 선재품질의 저하를 야기시키므로 가열온도 즉, 선재 냉각개시 온도는 1050-1150℃로 한정하는 것이 바람직하다.When the temperature is higher than 1150 占 폚, it is preferable to limit the heating temperature, that is, the wire rod cooling start temperature, to 1050 to 1150 占 폚, since it causes poor quality due to surface scratches and wire roughening during wire rod hot rolling.

본 발명에 있어서 냉각속도를 3-10 C/sec으로 한정하는 이유는 다음과 같다.The reason why the cooling rate is limited to 3-10 C / sec in the present invention is as follows.

본 발명에서 열간압연 후 선재를 연속냉각시 3C/sec 이상으로 한정하는 이유는 상기 강종의 탄소함량에서 3℃/sec 이하로 냉각시 오스테나이트 입계로 탄소가 확산하는데 충분한 시간을 부여하여 초석 세멘타이트가 석출 신선시 단선을 유발할 가능성이 높으며,또한 과냉도가 충분하지 못하여 조대 펄라이트를 형성하여 과공석강의 가장 큰 잇점인 고강도를 얻지 못하기 때문이다.In the present invention, the wire material after hot rolling is limited to 3 C / sec or more in the case of continuous cooling. This is because when the carbon content of the steel material is cooled to 3 DEG C / sec or less, sufficient time for carbon diffusion into the austenite- Is likely to induce disconnection during precipitation and freshness, and because supercooling is insufficient, coarse pearlite is formed and high strength, which is the greatest advantage of overglaze, can not be obtained.

이 경우 과냉도는 평형상태 변태온도와 실제 변태와의 차이를 의미하고, 이 값은 펄라이트의 강도를 결정하는 주인자인 라멜라(lamella)간격과 반비례 한다.In this case, the supercooling means the difference between the equilibrium state transformation temperature and the actual transformation, and this value is inversely proportional to the lamella spacing, which is the main factor determining the strength of the pearlite.

펄라이트의 강도는 라멜라 간격이 작을수록 증가하며, 따라서 과냉도가 작아질 경우 라멜라 간격이 크게되어 고강도를 얻을 수 없다.The strength of pearlite increases with decreasing lamellar spacing, and therefore, when the supercooling degree is reduced, the lamellar spacing becomes large and high strength can not be obtained.

또한 상기 강종의 실리콘, 망간 및 바나듐 함량에 대해 13℃/sec 이상의 냉각속도를 부여할 경우 경화능이 향상, 펄라이트 변태가 완료되기 전에 일부 오스테나이트가 저온조직인 베이나이트나 마르텐사이트로 무확산 변태되어 신선시 균열 발생 위치로 작용하여 신선성을 저하시킨다.When a cooling rate of 13 DEG C / sec or more is given to the silicon, manganese, and vanadium contents of the above steel species, the hardenability is improved, and before the pearlite transformation is completed, some austenite is spread and transformed into bainite or martensite, And acts as a crack generation position to lower the freshness.

본 발명에 있어서 블루잉(Blueing) 온도를 한정하는 이유는 다음과 같다.The reasons for limiting the blueing temperature in the present invention are as follows.

통상 블루잉(Blueing) 처리는 350-450℃, 아연도금은 400-450℃에서 행하고 있다.Usually, the blueing treatment is performed at 350-450 ° C, and the zinc plating is performed at 400-450 ° C.

그러나 블루잉(Blueing) 처리시 350℃ 이하에서는 온도에 의존하는 열적 활성화에 의한 미세조직 안정화 효과가 감소되며 , 400℃이하의 온도에서 아연도금을 실시할 경우 아연 부착량이 많아질 뿐만아니라 아연도금층의 두께가 불균일하게되는 도금 불량을 야기시킨다.However, in the case of the blueing treatment, the effect of stabilizing the microstructure due to the temperature-dependent thermal activation is reduced at a temperature of less than 350 ° C. When zinc plating is performed at a temperature of 400 ° C or less, Which causes plating defects that cause uneven thicknesses.

또한 450℃이상의 고온에서의 블루잉(Blueing), 아연도금시 강도의 저하가 극심하여 최종목표 인장강도를 나타내지 못한다.In addition, blueing at a high temperature of 450 DEG C or more and reduction in strength at the time of galvanizing are extremely severe, and the final target tensile strength is not exhibited.

본 발명에서 제안한 450℃ 이상의 블루잉(Blueing) 혹은 아연도금온도에서는 바나듐 석출물이 펄라이트의 페라이트에 재고용되지 않는 온도이므로 강도저하를 최대로 억제하여 고강도를 유지할 수 있다.Since the temperature at which the vanadium precipitate is not reusable to the ferrite of the pearlite at the bluing or zinc plating temperature of 450 DEG C or more proposed in the present invention, the strength drop can be suppressed to a maximum and high strength can be maintained.

그러나 500℃ 이상의 고온에서는 석출물이 조대화되어 석출물에 의한 강화 효과가 감소하여 강도저하를 효과적으로 억제할 수 없게 된다.However, at a high temperature of 500 占 폚 or more, the precipitate becomes coarse, so that the strengthening effect by the precipitate is reduced, and the strength drop can not be effectively suppressed.

이하 본 발명을 실시예를 통하여 보다 구체적으로 설명한다.Hereinafter, the present invention will be described more specifically with reference to Examples.

(실시예)(Example)

표1의 화학성분을 갖는 과공석가의 인고트(ingot)를 진공유도용해로에서 제조, 압연비 10:1로 열간압연을 한 후, 신선을 위한 지름 8㎜의 붕상시편을 가공한 후 1100℃에서 5분간 가열한 후 본 발명에서 제안된 냉각속도 범위내에 속하는 7C/sec으로 상온까지 냉각하였다.The ingot of the superstructure having the chemical composition shown in Table 1 was prepared in a vacuum induction melting furnace, hot rolled at a rolling ratio of 10: 1, and then subjected to a heat treatment at a temperature of 1100 ° C For 5 minutes and then cooled to room temperature at a rate of 7 C / sec falling within the cooling rate range proposed in the present invention.

본 발명에 있어서 비교재로는 바나듐이 첨가되지 않은 아공석강(1번 비교재)및 과공석강(2번 ~ 6번 비교재)이 사용되었다.In the present invention, as the comparative material, austenitic steel (comparative material No. 1) and superalloyed steel (comparative materials No. 2 to No. 6) without vanadium were used.

냉각된 붕상의 시편으로부터 조직 검사용 시편을 채취하여 초석 세멘타이트와 저온조직인 마르텐사이트 발생 여부를 조사하였다.The specimens were taken from the cooled specimens and examined for the formation of martensite, which is a cementite and a cold tissue.

이때 초석 세멘타이트와 저온조직인 마르텐사이트 발생 여부를 조사하였다.At this time, the occurrence of martensite, which is a cornerstone cementite and a low temperature structure, was investigated.

이때 초석 세멘타이트와 마르텐사이트의 석출 여부는 500배 배율 하의 광학현미경 관찰로서 판단하였다.At this time, the precipitation of cementite cementite and martensite was judged by optical microscope observation at a magnification of 500 times.

[표 1] 비교재 및 발명재의 화학성분(중량%) 및 미세조직[Table 1] Chemical composition (% by weight) and microstructure

표1에 나타낸 바와 같이 비교재1은 아공석 조성으로서 7℃/sec의 냉각속도하에서 초석 페라이트가 관찰되었으며, 실리콘 함량이 높은 비교재 4와 6에서는 마르텐사이트가 발생하였다.As shown in Table 1, in comparison material 1, pro-eutectoid ferrite was observed at a cooling rate of 7 ° C / sec as an acetylacetonous composition, and martensite was generated in comparative materials 4 and 6 having a high silicon content.

또한 표1에서 P는 완전 펄라이트, P+F는 펄라이트에 초석 페라이트가 석출한 조직, P+M은 펄라이트에 마르텐사이트가 석출한 조직을 의미한다.In Table 1, "P" is a perfect pearlite, "P + F" is a structure in which pro-eutectoid ferrite is precipitated in pearlite, and "P + M" is a structure in which martensite is precipitated in pearlite.

그리고 신선은 신선속도 3m/sec의 10패스를 행하였고, 각 패스당 평균단면감소율은 20%였으며, 신선에 의한 총단면감소율은 84%였다.Then, 10 passes were made with a freshness rate of 3 m / sec. The average cross section reduction rate per pass was 20% and the total cross section reduction rate by freshness was 84%.

이때 신선 각 패스 마다 5개의 시편을 채취, 인장실험을 통해 인장강도를 측정하였다.At this time, five specimens were taken for each fresh pass and tensile strength was measured by tensile test.

여기서 인장강도는 인장속도 5㎜/min의 일축인장시 파단이 일어나는 강도를 의미한다.Here, the tensile strength means the strength at which a fracture occurs at uniaxial tensile strength of 5 mm / min.

[표 2] 비교재 및 발명재의 신선재 인장강도 및 블루잉(Blueing) 처리재 인장강도[Table 2] Fresh Tensile Strength and Blueing Treatment Tensile Strength of Comparative Material and Inventive Material

표2에 총단면감소율 84%에서 비교재 및 발명재의 동일한 5개의 시편에서 측정된 평균인장강도를 나타내었다.Table 2 shows the average tensile strengths measured in the same five specimens of comparative and inventive materials at a total cross-sectional reduction of 84%.

표2에 나타낸 바와같이 비교재는 공히 목표강도인 200kg/㎟이하를 나타냈으나 발명재는 모두 목표강도를 훨씬 초과하는 210kg/㎟ 이상을 나타내었다.As shown in Table 2, the comparative material showed a target strength of 200 kg / mm 2 or less, but all the inventive materials showed a target strength of 210 kg / mm 2 or more.

그리고 블루잉(Blueing) 열처리는 최종 신선재에 대해 염욕 내에서 450℃, 500℃에서 각 5분씩 행하였으며, 신선재의 경우와 동일한 조건에서 인장실험을 행하였다.The blueing heat treatment was performed for 5 minutes at 450 ° C and 500 ° C in a salt bath for the final drawing material. Tensile tests were carried out under the same conditions as for the drawing material.

또한 5개의 동일한 조건에서 블루잉(Blueing) 처리를한 시편에 대한 평균 인장강도르 표2에 나타내었으며, 비교재의 경우에는 신선재이 인장강도가 목표강도인 200㎏/㎟에 미달하므로 블루잉(Blueing) 처리를 행하지 않았다.Table 2 shows the average tensile strength of specimens subjected to bluing treatment under the same five conditions. In the case of the comparative material, the tensile strength of the pre-drawn specimens is less than the target strength of 200 kg / ) Processing was not performed.

이때 표2에서와 같이 발명재는 본 발명의 블루잉(Blueing) 열처리 온도 구간인 450-500 C에서 공히 목표 강도인 180㎏/㎟이상을 나타냄을 알 수 있다.In this case, as shown in Table 2, the inventive material shows a target strength of 180 kg / mm 2 or more at 450-500 C, which is the blueing heat treatment temperature range of the present invention.

Claims (1)

중량%로 C : 0.8-1.0%, Si : 0.5-0.7%, Mn : 0.6-0.9%, V : 0.05-0.15%, S : <0.01%, P : < 0.01%, 잔부 Fe 및 불가피한 불순물로 구성되는 강들을 직경 7-11㎜의 선재로 열간압연 후 1050-1150℃의 냉각개시온도에서 펄라이트 변태 개시온도까지 3-10℃/sec의 냉각속도로 연속 냉각한 다음 패턴팅 처리없이 80-85%의 단면감소율로 냉간신선하고, 450-500℃에서 블루잉(Blueing) 열처리하는 것을 특징으로 하는 신선용 고강도 과공석 선재의 제조방법.And the balance Fe and inevitable impurities in terms of% by weight, in terms of% by weight, 0.8-1.0% of C, 0.5-0.7% of Si, 0.6-0.9% of Mn, 0.05-0.15% of V, 0.01% Were continuously hot-rolled at a cooling rate of 3-10 DEG C / sec from the cooling start temperature of 1050-1150 DEG C to the pearlite transformation starting temperature, and then heat-treated at 80-85% And a blueing heat treatment is performed at 450-500 占 폚.
KR1019960018188A 1996-05-28 1996-05-28 Method for manufacturing high strength hyper-eutectoid steel for elongation KR100336852B1 (en)

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KR100347581B1 (en) * 1997-12-27 2002-10-25 주식회사 포스코 Method for preparing wire rod with high stiffness
KR100342673B1 (en) * 1997-12-29 2002-10-11 주식회사 포스코 A method of manufacturing meduium carbon steel wire rods for spheroidization heat treatment
KR100544644B1 (en) * 2001-12-24 2006-01-24 주식회사 포스코 Method for manufacturing high carbon wire rod having superior strength
KR100946068B1 (en) * 2002-12-26 2010-03-10 주식회사 포스코 High strength hypereutectoid steel and method for manufacturing hypereutectoid steel rod wire using the same

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101328298B1 (en) * 2011-12-20 2013-11-14 주식회사 포스코 High strength wire rod, stell wire having excellent drawability and method for manufacturing thereof

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