KR20010060763A - Method of manufacturing hot rolling steel sheet having high strength for linepipe - Google Patents
Method of manufacturing hot rolling steel sheet having high strength for linepipe Download PDFInfo
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- KR20010060763A KR20010060763A KR1019990063190A KR19990063190A KR20010060763A KR 20010060763 A KR20010060763 A KR 20010060763A KR 1019990063190 A KR1019990063190 A KR 1019990063190A KR 19990063190 A KR19990063190 A KR 19990063190A KR 20010060763 A KR20010060763 A KR 20010060763A
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- C—CHEMISTRY; METALLURGY
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
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- C—CHEMISTRY; METALLURGY
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- 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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- 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
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- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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Abstract
Description
본 발명은 석유수송용 재료로 사용되는 항복강도 100ksi(API-x100)급 라인파이프강의 제조방법에 관한 것으로, 보다 상세하게는 몰리브덴(Mo)과 바나듐(V)을 복합 첨가하고 직접 소입(Direct Quenching)과 템프링(Tempering) 공정을 적용하여 고강도 라인파이프용 열연강판을 제조하는 방법에 관한 것이다.The present invention relates to a method for producing a yield strength 100ksi (API-x100) class line pipe steel used as a material for petroleum transportation, and more specifically, molybdenum (Mo) and vanadium (V) are added and directly quenched (Direct Quenching) And a tempering process, the present invention relates to a method for manufacturing a hot rolled steel sheet for high strength line pipe.
종래의 항복강도 100ksi 급 라인파이프강은 중량%로, C:0.05∼0.07%, Mn:1.8∼2.0%, Si:0.3%이하, Cu:0.2-0.3%, Ni:0.3-0.5%, Mo:0.1-0.3%, Nb:0.03-0.05%, Ti:0.01-0.02%, P:0.015% 이하, S:0.010% 이하, N:0.0050% 이하, 나머지 Fe 및 기타 불가피한 불순물로 조성되는 강슬라브를 1150-1250℃ 의 범위에서 가열한 후 압연종료온도 750℃ 까지 제어압연하고 냉각속도 20-30℃/초 및 냉각종료온도 300-350℃ 범위로 가속냉각처리하여 제조되고 있다.Conventional yield strength 100ksi line pipe steel is in weight%, C: 0.05 ~ 0.07%, Mn: 1.8 ~ 2.0%, Si: 0.3% or less, Cu: 0.2-0.3%, Ni: 0.3-0.5%, Mo: 1150 steel slab composed of 0.1-0.3%, Nb: 0.03-0.05%, Ti: 0.01-0.02%, P: 0.015% or less, S: 0.010% or less, N: 0.0050% or less, remaining Fe and other unavoidable impurities After heating in the range of -1250 ℃ to control rolling rolling to the end temperature of the rolling 750 ℃, it is manufactured by accelerated cooling treatment in the cooling rate 20-30 ℃ / sec and cooling end temperature 300-350 ℃ range.
이와 같은 가속냉각조건을 적용으로 생성되는 미세조직은 베이나이트와 마르텐사이트의 혼합조직으로, 이러한 혼합조직을 갖는 강판은 인장시험시 연속항복현상이 나타나 항복강도가 규격에서 요구되고 있는 100ksi 보다 미달되는 경우가 대부분이다.The microstructure produced by applying this accelerated cooling condition is a mixed structure of bainite and martensite, and the steel plate with such mixed structure shows continuous yielding during tensile test, so that the yield strength is less than 100ksi required by the standard. This is most often the case.
따라서, 파이프제조시 확관공정에서 가공경화로 강도미달을 보상하여야 한다.Therefore, in case of pipe manufacturing, it is necessary to compensate the strength under process hardening in expansion process.
본 발명은 열간압연판상태에서 항복강도규격을 만족할 수 있는 열연판의 제조방법을 제공하는데 그 목적이 있는 것으로, 파이프제조시 강도보상을 위한 확관공정의 생략을 도모한다.The present invention has a purpose to provide a method for manufacturing a hot rolled sheet that can satisfy the yield strength standard in the hot rolled sheet state, it is to omit the expansion process for the strength compensation in the manufacture of pipes.
상기 목적을 달성하기 위한 본 발명의 열연강판 제조방법은, 중량%로, C:0.05∼0.07%, Mn:1.8∼2.0%, Si:0.3%이하, Cu:0.2∼0.3%, Ni:0.3∼0.5%, Mo:0.2∼0.3%, V:0.04∼0.05%, Ti:0.01∼0.02%, P:0.015%, S:0.010%이하, N:0.0050%이하, 나머지 Fe 및 기타 불가피한 불순물로 조성되는 강슬라브를 1150∼1250℃의 범위에서 가열한후 900℃의 압연종료온도 조건으로 열간압연하고, 20℃/sec이상의 냉각속도로 상온까지 직접소입한 다음, 600∼650℃의 온도범위에서 템퍼링하는 것을 포함하여 구성된다.Hot-rolled steel sheet manufacturing method of the present invention for achieving the above object, by weight%, C: 0.05-0.07%, Mn: 1.8-2.0%, Si: 0.3% or less, Cu: 0.2-0.3%, Ni: 0.3- 0.5%, Mo: 0.2-0.3%, V: 0.04-0.05%, Ti: 0.01-0.02%, P: 0.015%, S: 0.010% or less, N: 0.0050% or less, remaining Fe and other unavoidable impurities The steel slab is heated in the range of 1150 to 1250 ℃, hot rolled at the end temperature of 900 ℃ rolling, directly quenched to room temperature at a cooling rate of 20 ℃ / sec or more, and then tempered in the temperature range of 600 ~ 650 ℃ It is configured to include.
이하, 본 발명을 상세히 설명한다.Hereinafter, the present invention will be described in detail.
본 발명에서는 가속냉각법이 아니라, 직접 소입과 템퍼링의 방법으로 제조함으로써 Mo과 V 의 석출강화를 이용하여 파이프 제조조전의 강판상태에서 규격의 항복강도(100ksi=688MPa)를 충분히 확보한다는데, 그 특징이 있다. 이를 강성분계와 제조조건으로 구분하여 설명한다.In the present invention, by using the method of direct hardening and tempering rather than accelerated cooling method, by using the precipitation strengthening of Mo and V to secure a sufficient yield strength (100ksi = 688MPa) of the standard in the steel sheet state before the pipe manufacturing, its features There is this. This will be described by dividing it into a steel component system and manufacturing conditions.
[강 성분계][Strong component system]
C는 강도와 용접성을 지배하는 가장 중요한 원소로 강도 확보를 위하여 0.05% 이상 첨가되어야 하며, 0.07% 이상 첨가시는 용접부에서의 충격인성을 확보하기가 어려우므로 0.05-0.07% 범위로 제한하는 것이 바람직하다.C is the most important element that controls strength and weldability. It should be added more than 0.05% to secure the strength, and when it is added more than 0.07%, it is difficult to secure impact toughness at the weld, so it is desirable to limit it to 0.05-0.07%. Do.
Mn은 직접 소입시 경화능을 증대시키기 위하여 1.8% 이상 첨가시켜야 하고 2.0% 이상 첨가시는 중심편석에 의한 기계적 성질의 불균일을 조장하기 때문에 1.8-2.0%로 제한하는 것이 바람직하다.Mn should be added at least 1.8% in order to increase the hardenability when directly quenched, and when added at 2.0% or more, it should be limited to 1.8-2.0% because it promotes nonuniformity of mechanical properties due to central segregation.
Si은 탈산제로 첨가되는 원소로 다량 첨가시는 강판 표면의 스케일흠을 발생하기 쉬우므로 0.3% 이하로 제한하는 것이 바람직하다.Si is an element added as a deoxidizer, and when a large amount is added, scale defects on the surface of the steel sheet are likely to occur, so it is preferably limited to 0.3% or less.
Cu는 황화수소 분위기에서 발생하는 수소 유기균열을 방지하기 위하여 첨가되는 원소로 0.2% 이상 첨가하여야 효과가 있고 0.3% 이상 다량 첨가시에는 고온균열을 일으키므로 0.2-0.3% 로 제한하는 것이 바람직하다.Cu is an element added in order to prevent hydrogen organic cracking occurring in a hydrogen sulfide atmosphere, and it is effective to add 0.2% or more. It is preferable to limit it to 0.2-0.3% because it causes high temperature cracking when a large amount of 0.3% or more is added.
Ni은 Cu 의 고온균열을 방지하기 위하여 0.3% 이상 첨가시켜야 하고 고가의 원소이므로 0.5% 이하로 제한하는 것이 바람직하다.Ni should be added at least 0.3% in order to prevent high temperature cracking of Cu, and it is preferable to limit it to 0.5% or less since it is an expensive element.
Mo은 본 발명의 중요한 원소로 직접 소입후의 템퍼링시 탄화물을 형성하여 템프링에 의한 강도의 하락을 방지하는 역활을 하기 때문에 0.2% 이상 첨가를 하고 고가의 원소이므로 0.3% 이하로 첨가량을 제한하는 것이 바람직하다.Mo is an important element of the present invention, since it forms a carbide during tempering after direct quenching and prevents a drop in strength due to tempering. Therefore, Mo is added at least 0.2% and limited to 0.3% or less since it is an expensive element. desirable.
V은 본 발명의 핵심원소로 직접 소입후 템프링시 V 탄질화물을 석출하여 항복강도를 상승시키는 가장 중요한 원소로 석출강화 효과를 충분히 얻기 위하여 0.04% 이상 첨가하여야 하고 고가의 원소이므로 0.05% 이하로 제한하는 것이 바람직하다.V is the most important element that precipitates V carbonitride and increases yield strength during tempering after direct quenching as a key element of the present invention. In order to obtain sufficient precipitation strengthening effect, it must be added at least 0.04% and is less than 0.05% because it is an expensive element. It is desirable to limit.
Ti는 질소화합물을 형성하여 슬라브 재가열시 결정립의 성장을 억제하고 용접시 고용질소량을 감소시켜 저온인성을 향상시키므로 0.01% 이상 첨가하고 0.02% 이상 첨가시 고용 Ti 에 의한 역효과가 생기므로 0.02% 이하로 제한하는 것이 바람직하다.Ti forms nitrogen compounds to suppress grain growth during slab reheating and decreases the amount of solid solution in welding to improve low temperature toughness. Therefore, when added over 0.01% and when added over 0.02%, Ti causes adverse effects due to solid Ti. It is desirable to limit.
P는 저온충격인성을 해치므로 그 함량을 0.015% 이하로 제한한다.P impairs low temperature impact toughness and limits its content to 0.015% or less.
S는 충격흡수에너지를 저하시키는 원소이므로 그 함량을 0.005% 이하로 제한한다.S is an element that lowers the impact absorption energy, so the content is limited to 0.005% or less.
N는 용접시 고용질소량이 증가하면 저온 충격인성을 해치므로 0.0050% 이하로 제한한다.N is limited to 0.0050% or less because the amount of solid solution in welding damages low temperature impact toughness.
[제조조건][Production conditions]
상기와 같이 조성되는 슬라브를 가열하여 열간압연하는데, 가열온도는 첨가된 합금원소가 충분히 고용될 수 있는 1150℃이상에서 오스테나이트 결정립의 조대화가 방지되는 1250℃ 이하로 제한하는 것이 바람직하다.The slab formed as described above is heated and hot rolled, and the heating temperature is preferably limited to 1250 ° C. or lower at which coarsening of austenite grains is prevented at 1150 ° C. or higher where the added alloy element can be sufficiently dissolved.
열간압연은 직접 소입시 오스테나이트상태에서 급냉이 될 수 있도록 900℃ 이상에서 압연을 종료하는 조건으로 열간압연한다.Hot rolling is hot-rolled under the condition of finishing rolling at 900 ° C. or more so that it can be quenched in the austenite state when directly quenched.
상기와 같이 열간압연한 직후에 직접 소입하는데, 이때의 냉각속도는 본 명강의 조직이 베이나이트와 마르텐사이트의 혼합조직을 템퍼링한 것이되도록 하여야 하므 베이나이트 조직이 생성될 수 있는 20℃/초 이상의 속도로 상온까지 냉각하는 것이 바람직하다.Directly quenched immediately after hot rolling as above, and the cooling rate at this time should be such that the structure of the present Myeonggang tempered the mixed structure of bainite and martensite, so that the bainite structure can be formed at 20 ° C / sec or more. It is preferable to cool to room temperature.
템퍼링은 600∼650℃에서 행하는데, 이는 템퍼링효과를 위해서는 600℃이상은 되어야 하며, 650℃를 넘으면 강도가 오히려 떨어지기 때문이다.Tempering is carried out at 600 to 650 ° C., because the tempering effect should be at least 600 ° C., if it exceeds 650 ° C., the strength is rather deteriorated.
이하, 본 발명을 실시예를 통하여 보다 구체적으로 설명한다.Hereinafter, the present invention will be described in more detail with reference to Examples.
[실시예]EXAMPLE
아래 표 1의 발명강과 비교강을 표 2의 조건으로 제조한 다음, 그 기계적성질을 측정한 다음 그 결과를 표 2에 나타내었다.The inventive steel and comparative steel of Table 1 below were prepared under the conditions of Table 2, and then the mechanical properties thereof were measured, and the results are shown in Table 2.
표 1의 발명강은 직접 소입후 템퍼링에 의한 석출강화가 일어날 수 있는 Mo 과 V 의 복합첨가강인데 반하여, 비교강은 강가속 냉각시 변태강화를 목적으로 하고 있기 때문에 경화능 증대에 효과적인 Nb 등이 첨가되어 있음을 보여준다.Inventive steel of Table 1 is a composite additive steel of Mo and V which can cause precipitation hardening by tempering directly after quenching, whereas comparative steel is Nb, etc. Shows that it is added.
표 1, 2에 나타난 바와 같이, 본 발명에 부합한 발명강은 파이프 조관전의강판상태에서 규격의 요구강도를 만족시킬수 있음을 알 수 있었다.As shown in Tables 1 and 2, it can be seen that the inventive steel according to the present invention can satisfy the required strength of the standard in the state of the steel sheet before pipe piping.
그 이유는 다음과 같이 집약된다.The reason is concentrated as follows.
첫째, 직접소입후 템프링시 V 탄질화물이 석출에 의한 항복강도 증가효과가 크고 Mo 탄화물의 생성에 의하여 V 탄질화물의 급격한 성장이 억제되므로 적정한 탬퍼링온도 구간에서 강화효과가 최상되기 때문이다.First, the V carbonitride increases the yield strength due to precipitation during direct quenching and the rapid growth of V carbonitride is suppressed by the generation of Mo carbide, so the reinforcing effect is best at the proper tampering temperature range.
둘째, 가속냉각을 적용하는 종래의 제조법에서는 유동선위(mobile dislocation)가 많이 생성되어 인장시험시 연속항복인상을 나타나지만, 직접소입과 템퍼링공정을 적용하는 본 발명에서는 유동전위가 탬퍼링에 의하여 소멸되기 때문에 연속항복현상이 나타나지 않기 때문에 항복강도가 높게 측정되는 것이다.Second, in the conventional manufacturing method applying accelerated cooling, a lot of mobile dislocations are generated, resulting in continuous yield increase in the tensile test, but in the present invention applying the direct quenching and tempering process, the flow potential is extinguished by tampering. Therefore, the yield strength is high because the continuous yield does not appear.
상술한 바와 같이, 본 발명에서는 Mo 과 V 을 복합첨가하고, 직접소입과 템퍼링공정을 적용함으로써 파이프조관전의 강판상태에서 규격에서 요구되고 있는 항복강도 100ksi를 만족하는 강재를 제공할 수 있는 효과가 있는 것이다.As described above, in the present invention, by adding a combination of Mo and V, and by applying a direct hardening and tempering process, it is possible to provide a steel material that satisfies the yield strength of 100 ksi required by the specification in the state of the steel sheet before pipe piping It is.
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Cited By (4)
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KR100723169B1 (en) * | 2005-12-26 | 2007-05-30 | 주식회사 포스코 | A method for manufacturing precipitaion hardened steel for linepipe having excellent property of hot rolling |
WO2012043984A2 (en) | 2010-09-29 | 2012-04-05 | 현대제철 주식회사 | Steel plate for line pipe, having excellent hydrogen induced crack resistance, and preparation method thereof |
CN103131965A (en) * | 2011-11-25 | 2013-06-05 | 中国石油天然气集团公司 | X100 large deformation pipeline steel for based on strain design, and preparation method thereof |
CN105803327A (en) * | 2016-05-13 | 2016-07-27 | 江阴兴澄特种钢铁有限公司 | Economic HIC-resistant X90 pipeline steel plate and manufacturing method thereof |
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KR900004845B1 (en) * | 1986-12-29 | 1990-07-08 | 포항종합제철 주식회사 | Making process for high-tensile steel |
EP0360037B1 (en) * | 1988-09-19 | 1994-11-17 | Siemens Aktiengesellschaft | Damping mass for SW elements |
JPH04154913A (en) * | 1990-10-15 | 1992-05-27 | Sumitomo Metal Ind Ltd | Production of high tensile strength bent pipe excellent in corrosion resistance |
JPH09111344A (en) * | 1995-10-18 | 1997-04-28 | Nippon Steel Corp | Production of high strength and low yield ratio seamless steel pipe |
KR20010060389A (en) * | 1999-12-20 | 2001-07-07 | 이구택 | Method for manufacturing pressure vessel plates with excellent weldability |
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Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR100723169B1 (en) * | 2005-12-26 | 2007-05-30 | 주식회사 포스코 | A method for manufacturing precipitaion hardened steel for linepipe having excellent property of hot rolling |
WO2012043984A2 (en) | 2010-09-29 | 2012-04-05 | 현대제철 주식회사 | Steel plate for line pipe, having excellent hydrogen induced crack resistance, and preparation method thereof |
CN103131965A (en) * | 2011-11-25 | 2013-06-05 | 中国石油天然气集团公司 | X100 large deformation pipeline steel for based on strain design, and preparation method thereof |
CN105803327A (en) * | 2016-05-13 | 2016-07-27 | 江阴兴澄特种钢铁有限公司 | Economic HIC-resistant X90 pipeline steel plate and manufacturing method thereof |
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