KR20080057844A - Hot-rolled steel sheet and pipe having superior characteristics of normalizing and method of manufacturing the same - Google Patents

Hot-rolled steel sheet and pipe having superior characteristics of normalizing and method of manufacturing the same Download PDF

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KR20080057844A
KR20080057844A KR1020060131636A KR20060131636A KR20080057844A KR 20080057844 A KR20080057844 A KR 20080057844A KR 1020060131636 A KR1020060131636 A KR 1020060131636A KR 20060131636 A KR20060131636 A KR 20060131636A KR 20080057844 A KR20080057844 A KR 20080057844A
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steel sheet
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박광균
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주식회사 포스코
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    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G79/00Macromolecular compounds obtained by reactions forming a linkage containing atoms other than silicon, sulfur, nitrogen, oxygen, and carbon with or without the latter elements in the main chain of the macromolecule
    • C08G79/02Macromolecular compounds obtained by reactions forming a linkage containing atoms other than silicon, sulfur, nitrogen, oxygen, and carbon with or without the latter elements in the main chain of the macromolecule a linkage containing phosphorus
    • C08G79/04Phosphorus linked to oxygen or to oxygen and carbon
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    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/38Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
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    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226Hot rolling
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    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/002Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/02Ferrous alloys, e.g. steel alloys containing silicon
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    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/24Ferrous alloys, e.g. steel alloys containing chromium with vanadium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/26Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • DTEXTILES; PAPER
    • D01NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01FCHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F6/00Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
    • D01F6/78Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolycondensation products
    • D01F6/84Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolycondensation products from copolyesters
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    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08KUse of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00Use of organic ingredients
    • C08K5/49Phosphorus-containing compounds
    • C08K5/51Phosphorus bound to oxygen
    • C08K5/53Phosphorus bound to oxygen bound to oxygen and to carbon only
    • C08K5/5313Phosphinic compounds, e.g. R2=P(:O)OR'
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D2211/00Microstructure comprising significant phases
    • C21D2211/005Ferrite
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D2211/00Microstructure comprising significant phases
    • C21D2211/009Pearlite
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T442/00Fabric [woven, knitted, or nonwoven textile or cloth, etc.]
    • Y10T442/20Coated or impregnated woven, knit, or nonwoven fabric which is not [a] associated with another preformed layer or fiber layer or, [b] with respect to woven and knit, characterized, respectively, by a particular or differential weave or knit, wherein the coating or impregnation is neither a foamed material nor a free metal or alloy layer
    • Y10T442/2631Coating or impregnation provides heat or fire protection
    • Y10T442/2672Phosphorus containing

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Abstract

A hot rolled steel sheet and a high strength pipe having high frequency normalizing characteristics, and a method of manufacturing the same are provided to contribute to generation of bainite and to increase hardenability of the steel plate after heat treatment by adding V, N, Cr, And Nb to a medium carbon steel. A method of manufacturing a hot rolled steel sheet having high frequency normalizing characteristics comprises the steps of: re-heating a slab consisting of, by weight%, C:0.25~0.45%, Si:0.20~0.60%, Mn:1.4~2.2%, P: less than 0.02%, S: less than 0.01%, Ti:0.005~0.03%, Nb:0.030~0.050%, Ca:0.001~0.006%, Al:0.01~0.06%, N: less than 0.008%, O: less than 0.006%, V:0.08~0.20%, Cr:0.10~0.50%, and the remainder Fe, and other unavoidable impurities; finishing-mill the slab at 800~900°C; and cooling the rolled steel sheet up to 550~700°C at 10~20°C/sec and then coiling the steel sheet. The structure of the steel sheet contains 10~30% of bainite, the remainder ferrite, and pearlite.

Description

고주파 열처리 특성이 우수한 열연강판 및 고강도 강관과 그 제조방법{Hot-rolled steel sheet and pipe having superior characteristics of normalizing and method of manufacturing the same}Hot-rolled steel sheet and pipe having superior characteristics of normalizing and method of manufacturing the same}

도 1은 본 발명의 강관의 열처리 패턴을 나타내는 곡선이다. 1 is a curve showing the heat treatment pattern of the steel pipe of the present invention.

도 2는 본 발명에 따라 압연된 상태의 열연강판의 미세조직을 나타내는 사진이다.Figure 2 is a photograph showing the microstructure of the hot rolled steel sheet in a rolled state according to the present invention.

도 3은 1000℃에서 소둔한 강관의 미세조직을 나타내는 사진이다.3 is a photograph showing the microstructure of the steel pipe annealed at 1000 ° C.

도 4는 1100℃에서 소둔한 강관의 미세조직을 나타내는 사진이다.Figure 4 is a photograph showing the microstructure of the steel pipe annealed at 1100 ℃.

본 발명은 고주파 열처리 특성이 우수한 강판 및 이를 사용하여 제조된 고강도 강관에 관한 것으로, 보다 상세하게는 고용원소를 증가시켜 열처리시 경화능을 증가시키고, 이러한 강판을 사용한 고강도 강관 및 이를 제조하는 방법에 관한 것이다.The present invention relates to a steel sheet having excellent high-frequency heat treatment characteristics and a high strength steel pipe manufactured using the same, and more particularly, to a high strength steel pipe using such a steel sheet and to a method of manufacturing the same. It is about.

본 발명의 열연강판 및 강관은 주로 유정관용으로 사용되는 것으로 이러한 강관은 고강도, 내외압 압괴강도, 인성, 내지연 파괴성, 내황화수소 균열성 등이 요구된다. 이 때문에 열연강판을 조관한 후 열처리를 행하고 고강도화하는 방법이 일반적이다. 일반적으로 사용되는 유정관은 이음매 없는 강관 (Seamless 강관)이 주로 사용되며 그 제조방법은 고온에 가열되는 빌릿(billet)을 천공 압연기로 천공한 뒤, 플러그밀 (Plug mill), 맨드릴밀 (mandrel mill) 등의 압연기를 이용하여 압연한 뒤, 레듀사 (Reducer) 또는 사이저 (Sizer)를 이용하여 축경 또는 두께를 가공한 뒤, 담금질하고 템퍼링 열처리를 행한다. 담금질 및 템퍼링 열처리를 행하기 위하여 가열로, 균열로의 설치가 필요해지고, 고비용이 되지 않을 수 없다. Hot-rolled steel sheet and steel pipe of the present invention is mainly used for oil well pipes, such steel pipe is required high strength, internal and external pressure crushing strength, toughness, delayed fracture resistance, hydrogen sulfide cracking resistance and the like. For this reason, after hot-rolled steel sheet is made, the method of heat-treating and high strength is common. Generally used oil pipes are seamless steel pipes, and the method of manufacturing them is to drill a billet that is heated at a high temperature with a punching mill, and then plug mill and mandrel mill. After rolling using a rolling mill such as), the shaft diameter or thickness is processed using a reducer or sizer, and then quenched and tempered and heat treated. In order to perform quenching and tempering heat treatment, the installation of a heating furnace and a cracking furnace is required, and it is inevitably expensive.

이 때문에 최근에는 심리스 강관을 최종 압연후 열처리를 행하지 않고도 우수한 특성을 가지고, 대량 생산에 적당한 비조질 유정강관이 개발되어, 값싸게 제공되고 있다. 또한 종래의 노말라이징 처리 유정관의 경우 Mo를 첨가하여 강도를 확보하는 성분계를 사용하기도 하지만, 고가원가인 Mo첨가로 인해 생산원가가 높게 되어 제조비용이 증가되는 단점이 있었다.For this reason, in recent years, an amorphous crude steel pipe having excellent characteristics without being subjected to heat treatment after final rolling and suitable for mass production has been developed and is being provided at low cost. In addition, in the case of the conventional normalized oil well tube, a component system is used to secure the strength by adding Mo, but there is a disadvantage in that the production cost is increased due to the high cost of Mo added.

또한, 한국 공개특허공보 1993-0011409에서는 Mo를 함유하지 않은 유정용 강관의 제조방법에 관한 것이나, 이는 석출에 의한 경화만을 이용한 것으로 강도 증가에 한계가 있었으며, 과다한 석출물의 형성으로 인성이 열화되는 문제점이 있었다. In addition, Korean Laid-Open Patent Publication No. 1993-0011409 relates to a method for manufacturing a steel pipe for oil wells that does not contain Mo, but using only hardening by precipitation, there is a limit in increasing the strength, and the problem of deterioration of toughness due to formation of excessive precipitates. there was.

따라서, 이러한 강판 및 강관의 제조의 필요성은 부각되고 있으나, 아직 그 대안은 없는 실정이며, 특히 열처리 특성을 개선하여 강도를 확보하는 방안은 전무한 실정이다.Therefore, the necessity of manufacturing such a steel sheet and steel pipe is emerging, but there is no alternative yet, and in particular, there is no way to secure the strength by improving heat treatment characteristics.

본 발명은 강판의 고주파 열처리 특성을 개선하고, 이를 이용하여 고강도 강관을 제공하는 것을 목적으로 한다.An object of the present invention is to improve the high frequency heat treatment characteristics of the steel sheet, and to provide a high strength steel pipe using the same.

상기 목적을 달성하기 위한 본 발명의 열연강판은 중량%로, C: 0.25~0.45%, Si: 0.20~0.60%, Mn: 1.4~2.2%, P: 0.02%이하, S: 0.01%이하, Ti: 0.005~0.03%, Nb: 0.030~0.050%, Ca: 0.001~0.006%, Al:0.01~0.06%, N: 0.008%이하, O: 0.006%이하, V: 0.08~0.20%, Cr: 0.10~0.50%를 포함하고, 나머지는 Fe 및 기타 불가피한 불순물로 조성되며, 강판의 조직이 면적비로 40~50%는 페라이트이고, 나머지는 퍼얼라이트로 이루어진다.Hot-rolled steel sheet of the present invention for achieving the above object by weight, C: 0.25 ~ 0.45%, Si: 0.20 ~ 0.60%, Mn: 1.4 ~ 2.2%, P: 0.02% or less, S: 0.01% or less, Ti : 0.005 ~ 0.03%, Nb: 0.030 ~ 0.050%, Ca: 0.001 ~ 0.006%, Al: 0.01 ~ 0.06%, N: 0.008% or less, O: 0.006% or less, V: 0.08 ~ 0.20%, Cr: 0.10 ~ 0.50%, the remainder is composed of Fe and other unavoidable impurities, the structure of the steel sheet is 40-50% by area ratio of ferrite, the remainder is made of pearlite.

또한 상기 강판의 제조방법은 상기 조성의 슬라브를 재가열하는 단계; 상기 슬라브를 압연한 후 800~900℃의 마무리압연온도범위에서 마무리압연하는 단계; 상기 압연한 강재를 10~20℃/sec의 속도로 550~700℃까지 냉각한 다음 권취하는 단계를 포함하여 이루어진다.In addition, the manufacturing method of the steel sheet comprises the steps of reheating the slab of the composition; Rolling the slab and finishing rolling in a finishing rolling temperature range of 800 to 900 ° C .; The rolled steel is cooled to 550-700 ° C. at a rate of 10-20 ° C./sec and then wound.

상기 강판을 사용하여 제조된 고강도 강관은 상기 슬라브로 제조된 강관으로, 상기 강관의 조직은 면적비로 10~30%의 베이나이트이고, 나머지는 페라이트 및 펄라이트로 이루어진다.The high-strength steel pipe manufactured using the steel sheet is a steel pipe made of the slab, and the structure of the steel pipe is 10-30% bainite in area ratio, and the rest is made of ferrite and pearlite.

상기 고강도 강관의 제조방법은 상기 조성의 슬라브로 제조된 강판을 용접관으로 조관하는 단계; 상기 용접관을 950~1150℃로 고주파 유도가열형의 열처리로를 통해 소둔 (Normalizing) 열처리하고 공냉하는 단계를 포함하여 이루어진다.The method of manufacturing a high strength steel pipe comprises the steps of: manufacturing a steel pipe made of the slab of the composition by a weld pipe; The welding tube is made of an annealing (Normalizing) heat treatment and air-cooling through a high-frequency induction heating type heat treatment furnace at 950 ~ 1150 ℃.

이하, 본 발명을 상세하게 설명한다.EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

본 발명자는 고주파 열처리후 고강도를 갖는 열연강판을 제조하는 방법을 연구하던 중, 중탄소강에 V, N, Cr 및 Nb 등을 첨가하고 조관후 열처리 공정 특히 유지온도를 적절히 제어하여 기지조직을 제어하면 중탄소 열연강판에서 고강도 강관을 확보할 수 있었다.The inventors of the present invention while studying a method of manufacturing a hot rolled steel sheet having a high strength after high frequency heat treatment, if V, N, Cr and Nb is added to the medium carbon steel, and after the tube is controlled by controlling the heat treatment process, especially the holding temperature appropriately High-strength steel pipe could be secured from the medium-carbon hot-rolled steel sheet.

즉, V, Cr이 종래에는 석출의 목적으로만 사용된데 비해 본 발명에서는 질소의 농도를 낮추어 V, Cr이 석출의 형태가 아닌 고용의 형태로 존재하게 되어 강도향상에 기여하게 되고 또한, 석출물의 양도 줄어듦으로써 인성이 열화되는 문제도 극복할 수 있었다. 이러한 고용원소들은 열처리시 베이나이트 생성에 기여하게되어 열처리 후 강관의 경화능을 향상시킬수 있었다.That is, while V and Cr are conventionally used only for the purpose of precipitation, in the present invention, the concentration of nitrogen is lowered so that V and Cr exist in the form of solid solution rather than precipitation, thereby contributing to the improvement of strength. Reducing the amount of 있었다 could overcome the problem of deterioration of toughness. These solid elements contribute to the formation of bainite during the heat treatment, thereby improving the hardenability of the steel pipe after the heat treatment.

이하 본 발명의 강성분의 조성범위를 설명한다.Hereinafter, the composition range of the steel component of the present invention will be described.

C: 0.25~0.45% C: 0.25-0.45%

상기 C는 강도, 인성 및 파이프라인 시공시의 원주 용접부 인성에 영향을 미치는 원소이다. 상기 C는 탄화물 형성 원소인 Nb, V, Ti과 페라이트 상 중에 NbC, VC, TiC 등의 석출물 또는 복합 석출물을 형성함으로써 강도를 증가시킨다. 또한, 열간 마무리 압연후의 냉각제어에 의하여 페라이트 변태 핵의 발생 빈도를 높이고 미세한 페라이트 입자를 형성하여 인성을 향상시킨다.C is an element that affects the strength, toughness and toughness of the circumferential weld portion during pipeline construction. C increases strength by forming precipitates or complex precipitates such as NbC, VC, TiC, etc. in the carbide forming elements Nb, V, Ti and ferrite phases. Further, by the cooling control after hot finishing rolling, the frequency of occurrence of ferrite transformation nuclei is increased, and fine ferrite particles are formed to improve toughness.

그 함량이 0.25% 미만인 경우 탄화물 형성이 부족하여 본 발명에서 목표로 하는 강도를 확보할 수 없으며, 0.45%를 초과하는 경우 인성의 저하 및 전기저항 용접시 용접성의 저하를 초래하므로, 상기 C의 함량은 0.25~0.45%로 제한하는 것이 바람직하다. 보다 바람직하게는 0.30~0.40% 이다.If the content is less than 0.25%, the formation of carbides may not be sufficient to secure the target strength in the present invention. If the content is more than 0.45%, the toughness may be reduced and the weldability may be reduced during electrical resistance welding. Is preferably limited to 0.25-0.45%. More preferably, it is 0.30 to 0.40%.

Si: 0.2~0.6% Si: 0.2 ~ 0.6%

상기 Si은 페라이트 상중의 C 활동도를 증가시키고, 페라이트 안정화를 촉진하는 작용을 하며, 고용강화에 의한 강도확보에 기여한다. 또한, 상기 Si은 ERW 용접시 Mn2SiO4 등의 저융점 산화물을 형성시키고 용접시에 산화물이 쉽게 배출되도록 한다. 그 함량이 0.2% 미만인 경우 제강상의 비용 문제가 발생하는 반면, 0.6% 를 초과하는 경우 Mn2SiO4 이외에 고융점의 SiO2 산화물의 형성량이 많아지고 전기저항 용접시 용접부의 인성을 저하시킬 수 있다. 따라서, 상기 Si의 함량은 0.2~0.6%로 제한하는 것이 바람직하다. 보다 바람직하게는 0.3~0.5%이다.The Si increases the C activity in the ferrite phase, promotes ferrite stabilization, and contributes to securing strength by solid solution strengthening. In addition, the Si forms a low melting point oxide such as Mn 2 SiO 4 during ERW welding, and the oxide is easily discharged during welding. If the content is less than 0.2%, the cost problem of steelmaking occurs, whereas if it exceeds 0.6%, the amount of SiO 2 oxides having high melting point other than Mn 2 SiO 4 is increased and the toughness of the weld part may be reduced during electric resistance welding. . Therefore, the content of Si is preferably limited to 0.2 ~ 0.6%. More preferably, it is 0.3 to 0.5%.

Mn: 1.4~2.2% Mn: 1.4-2.2%

상기 Mn은 오스테나이트/페라이트 변태 개시 온도에 큰 영향을 주고 변태 개시 온도를 저하시키는 원소로서, 파이프 모재부 및 용접부의 인성에 영향을 미치며, 고용강화 원소로써 강도 증가에 기여한다. 그 함량이 1.4% 미만에서는 상기의 효과를 기대하기 어려운 반면 2.2%를 초과하는 경우 편석대가 발생할 가능성이 높다. 따라서 상기 Mn의 함량은 1.4~2.2%로 제한하는 것이 바람직하다. 보다 바람직하게는 1.5~2.0%이다.The Mn is an element which greatly affects the austenite / ferrite transformation start temperature and lowers the transformation start temperature, affects the toughness of the pipe base material portion and the weld portion, and contributes to the increase in strength as a solid solution strengthening element. If the content is less than 1.4%, it is difficult to expect the above effect, while if it exceeds 2.2%, segregation zone is likely to occur. Therefore, the content of Mn is preferably limited to 1.4 ~ 2.2%. More preferably, it is 1.5 to 2.0%.

P: 0.02% 이하P: 0.02% or less

상기 P은 고용강화 원소로서, 오스테나이트/페라이트 변태 개시 온도를 대폭적으로 상승시키는 작용을 하고, 조대한 페라이트 입자를 형성하는데 유용하게 작용한다. 그 함량이 0.02%를 초과하는 경우 상기의 효과를 확보하기 어려우므로, 상기 P의 함량은 0.02%로 제한하는 것이 바람직하다. 보다 바람직하게는 0.015% 이하이다.P is a solid solution strengthening element, which greatly increases the austenite / ferrite transformation start temperature and is useful for forming coarse ferrite particles. If the content is more than 0.02% it is difficult to ensure the above effects, it is preferable to limit the content of P to 0.02%. More preferably, it is 0.015% or less.

S: 0.01% 이하 S: 0.01% or less

상기 S은 조대한 개재물을 형성하기 쉬운 원소이고, 인성 저하나 크랙 진전을 조장하므로 가능한 한 낮게 제한하는 것이 바람직하므로, 상기 S의 함량은 0.01% 이하로 제한하는 것이 바람직하다. 보다 바람직하게는 0.005% 이하이다.S is an element that is easy to form coarse inclusions, and is preferably limited as low as possible because it promotes toughness reduction or crack growth, and therefore, the content of S is preferably limited to 0.01% or less. More preferably, it is 0.005% or less.

Nb : 0.030~0.050%Nb: 0.030 ~ 0.050%

상기 Nb은 미세한 페라이트 입자(저온변태 페라이트, 베이나이틱페라이트)를 제어 압연에 의해 발생시키는데 유효한 원소로서, 열간 압연 과정으로의 오스테나이트 재결정을 지연시키는 작용을 한다. 또한, 상기 Nb은 탄화물을 형성하여 강도 증가에 기여한다. 그 함량이 0.03% 미만에서는 이러한 효과를 확보할 수 없는 반면, 0.050%를 초과하면 담금질성이 현저하게 상승하고 용접부 인성이 저하될 수 있다. 따라서 상기 Nb의 함량은 0.030~0.050%인 것이 바람직하다.The Nb is an effective element for generating fine ferrite particles (low temperature transformation ferrite, bainitic ferrite) by controlled rolling, and serves to delay austenite recrystallization in the hot rolling process. In addition, the Nb forms carbide to contribute to the increase in strength. If the content is less than 0.03%, such an effect cannot be secured, while if the content is more than 0.050%, hardenability is remarkably increased and the weld toughness may be reduced. Therefore, the content of Nb is preferably 0.030 ~ 0.050%.

Ti: 0.005~0.03% Ti: 0.005-0.03%

상기 Ti은 질화물 형성 원소로서, 슬라브 응고 과정에서 N 고정에 유효하게 작용한다. 또한 상기 Ti은 탄화물 형성을 수반하고 강도 증가에 기여한다. 그 함량이 0.005% 미만인 경우 이러한 효과를 기대할 수 없는 반면, 0.03%를 초과하면 오스테나이트/페라이트 변태 개시 온도를 현저히 상승시키고 조대한 페라이트 입자를 형성할 가능성이 높다. 따라서 상기 Ti의 함량은 0.005~0.03%인 것이 바람직하다. 보다 바람직하게는 0.005~0.02%이다.Ti is a nitride forming element and effectively acts to fix N in slab solidification. The Ti also involves carbide formation and contributes to increased strength. If the content is less than 0.005%, such an effect cannot be expected, while if it exceeds 0.03%, the austenite / ferrite transformation start temperature is significantly increased and coarse ferrite particles are likely to be formed. Therefore, the content of Ti is preferably 0.005 to 0.03%. More preferably, it is 0.005 to 0.02%.

Ca: 0.001~0.006% Ca: 0.001-0.006%

상기 Ca은 유화물의 형태 제어를 위해 첨가한다. 그 함량이 0.006%를 초과하는 경우 소강중의 S량에 대하여 과잉하게 첨가되어 CaO 클러스터(cluster)의 CaS가 발생하는 반면, 0.001% 미만인 경우에는 MnS가 발생하고 인성의 저하를 초래할 수 있다. 또한 S량이 많다면 CaS 클러스터가 발생을 방지하기 위해 동시에 S량도 제어하는 것이 바람직하다. 즉 철중의 S량 및 O량에 따라 Ca량을 제어하는 것이 바람직하다. 따라서 상기 Ca의 함량은 0.0001~0.006%인 것이 바람직하다.The Ca is added for morphology control of the emulsion. If the content is more than 0.006% is excessively added to the amount of S in the steel is generated CaS of CaO cluster (cluster), while less than 0.001% MnS may occur and may cause toughness. If the amount of S is large, it is preferable to control the amount of S at the same time in order to prevent the CaS cluster from occurring. That is, it is preferable to control Ca amount according to S amount and O amount in iron. Therefore, the content of Ca is preferably 0.0001 to 0.006%.

Al: 0.01~0.06% Al: 0.01 ~ 0.06%

상기 Al은 제강시의 탈산을 위해 첨가한다. 그 함량이 0.01% 미만인 경우 이러한 작용이 부족한 반면, 0.06%를 초과하는 경우 전기저항 용접시 용접부에 알루미나 또는 알루미나 산화물을 포함하는 복합 산화물의 형성이 조장되고 용접부 인성을 손상시킬 수 있다. 따라서 상기 Al의 함량은 0.01~0.06%인 것이 바람직하다. 보다 바람직하게는 0.015~0.05%이다.Al is added for deoxidation during steelmaking. If the content is less than 0.01%, such action is insufficient, while if the content exceeds 0.06%, the formation of a composite oxide including alumina or alumina oxide in the weld during electrical resistance welding may be encouraged and damage to the weld toughness may occur. Therefore, the content of Al is preferably 0.01 ~ 0.06%. More preferably, it is 0.015 to 0.05%.

N: 0.008% 이하 N: 0.008% or less

상기 N는 고용 상태에서는 시효 열화를 일으키는 원인이므로, Ti, Al등의 질화물로서 고정된다. 그 함량이 0.008%를 초과하는 경우 Ti, Al등의 첨가량 증가가 불가피하고 Cr, V를 고용의 형태가 아닌 석출물로 다량 생성시키는 문제가 있으므로, 상기 N의 함량은 0.008%이하인 것이 바람직하다. 보다 바람직하게는 0.005%이 하이다.Since N is the cause of aging deterioration in the solid solution state, it is fixed as nitrides such as Ti and Al. If the content exceeds 0.008%, the addition amount of Ti, Al, etc. is inevitably increased, and there is a problem in that a large amount of Cr and V are formed as precipitates, not in the form of a solid solution, so that the content of N is preferably 0.008% or less. More preferably, it is 0.005% or less.

O: 0.006% 이하 O: 0.006% or less

상기 O는 산화물계 개재물로서, 그 함량이 0.006%를 초과하면 저온인성이나 CTOD 특성의 저하를 초래할 수 있다. 따라서 상기 O의 함량은 0.006%이하인 것이 바람직하다. 보다 바람직하게는 0.005%이하이다.O is an oxide-based inclusion, when the content exceeds 0.006% may cause low temperature toughness or degradation of CTOD properties. Therefore, the content of O is preferably 0.006% or less. More preferably, it is 0.005% or less.

V: 0.08~0.20% V: 0.08-0.20%

V는 고용원소로 작용하여 강도향상에 기여한다. 이러한 V의 고용에 의한 강도향상을 얻기 위해서는 0.08%이상 첨가하여야 하나, 0.20%를 초과하면 인성을 저해할 수 있으며, 또한 고가의 원소이므로 열처리후 강도의 증대를 위해 0.08~0.20% 범위에서 첨가하는 것이 바람직하다.V acts as an element of employment, contributing to increased strength. In order to obtain the strength improvement by solid solution of V, it should be added more than 0.08%, but if it exceeds 0.20%, toughness may be inhibited, and since it is an expensive element, it is added in the range of 0.08 ~ 0.20% to increase the strength after heat treatment. It is preferable.

Cr: 0.10~0.50% Cr: 0.10 to 0.50%

상기 Cr은 Mn과 마찬가지로 오스테나이트/페라이트 변태 개시 온도를 내리는 효과를 가진다. 또한 V와 마찬가지로 고용원소로 작용하여 강도향상에 기여하게 된다. 이러한 효과를 위해서는 0.10% 이상 첨가하여야 한다. 또한 상기 Cr은 Mn보다 편석되기 어려운 반면, Mn보다 산소와의 친화력이 강하므로 0.50%를 초과하게 되면 용접부에 산화물을 남길 수 있다. 따라서 상기 Cr의 함량은 0.10~0.50%로 제한하는 것이 바람직하다.Cr has the effect of lowering the austenite / ferrite transformation start temperature as Mn. Like V, it also serves as an element of employment, contributing to the increase in strength. For this effect, 0.10% or more should be added. In addition, Cr is more difficult to segregate than Mn, but since the affinity with oxygen is stronger than that of Mn, an amount of more than 0.50% may leave an oxide in the weld. Therefore, the content of Cr is preferably limited to 0.10 to 0.50%.

본 발명은 상기한 성분 이외에 나머지는 Fe 및 기타 불가피한 불순물로 조성된다.The present invention is composed of Fe and other unavoidable impurities in addition to the above components.

이하, 상기 열연강판의 제조방법에 대하여 상세히 설명한다.Hereinafter, a method of manufacturing the hot rolled steel sheet will be described in detail.

먼저, 상기와 같이 조성되는 강 슬라브를 재가열한 후, 조압연한 다음 800~900℃의 마무리 압연온도범위에서 마무리압연을 종료한다. 마무리 압연온도가 800℃미만이면 설비자체의 부하에 의해 생산성이 저하되며, 900℃초과하면 입자 조대화에 의해 인성저하의 문제가 발생하므로 마무리 압연온도는 800~900℃임이 바람직하다. First, after reheating the steel slab formed as described above, rough rolling, and finish rolling in the finish rolling temperature range of 800 ~ 900 ℃. If the finish rolling temperature is less than 800 ℃, the productivity is lowered by the load of the equipment itself, and if it exceeds 900 ℃, the problem of toughness decreases due to the coarsening of particles, the finish rolling temperature is preferably 800 ~ 900 ℃.

열간압연한 후 10~20℃/s의 속도로 냉각하고, 550~700℃까지 냉각한다. 저온까지 냉각할 경우 취약상 형성으로 인성이 저하되어 조관특성을 저해하며, 고온까지의 냉각의 경우 조대립의 형성으로 인성이 저하되므로 적절한 냉각속도 및 온도를 유지하여야 한다. 냉각속도가 10℃/s 미만이면 생산성이 저하되는 문제가 발생하며, 20℃/s 를 초과하는 경우에는 마르텐사이트등의 경화상이 발생하는 문제가 있다. 냉각 온도가 550℃미만이면 취약상 형성으로 인성이 저하되어 조관특성을 저해하며, 700℃를 초과하는고온까지의 냉각의 경우 조대립의 형성으로 인성이 저하되므로 550~700℃까지 냉각하는 것이 바람직하다.After hot rolling, it is cooled at a rate of 10 to 20 ° C./s and cooled to 550 to 700 ° C. When cooling to low temperature, toughness is degraded due to fragile phase formation, which hinders tubing characteristics. In case of cooling to high temperature, toughness is reduced due to formation of coarse grains, and therefore, proper cooling speed and temperature must be maintained. If the cooling rate is less than 10 ° C / s, there is a problem that the productivity is lowered, and if the cooling rate exceeds 20 ° C / s there is a problem that a hardened phase such as martensite occurs. If the cooling temperature is less than 550 ℃, the toughness is reduced due to the formation of a weak phase to inhibit the tubing characteristics, in the case of cooling to a high temperature exceeding 700 ℃ it is preferable to cool to 550 ~ 700 ℃ because toughness is reduced by the formation of coarse grains Do.

이하, 본 발명의 고강도 유정관에 대하여 상세하게 설명한다. Hereinafter, the high strength oil well tube of this invention is demonstrated in detail.

상기 강관의 조직은 면적비로 10~30%의 베이나이트이고, 나머지는 페라이트 및 펄라이트로 이루어진다. 이러한 베이나이트는 유정관의 강도를 크게 증가시키는 효과가 있다. The structure of the steel pipe is 10-30% bainite by area ratio, and the rest is made of ferrite and pearlite. Such bainite has the effect of greatly increasing the strength of the well tube.

이하, 본 발명의 고강도 유정관의 제조방법에 대하여 상세하게 설명한다.Hereinafter, the manufacturing method of the high strength oil pipe of this invention is demonstrated in detail.

상기 조성의 강판을 용접관으로 조관하고 950~1150℃로 고주파 유도가열형 열처리로를 통해 소둔 열처리를 하고 공냉하는 단계를 포함한다. 열처리온도가 950℃미만이면 강도의 확보가 불가능하며, 1150℃를 초과하면 인성저하의 문제가 발생하는 바, 950~1150℃가 바람직하다.Including the steel sheet of the composition to the welded tube and the annealing heat treatment through a high frequency induction heating type heat treatment furnace at 950 ~ 1150 ℃ and air-cooling. If the heat treatment temperature is less than 950 ° C., it is impossible to secure the strength. If the heat treatment temperature exceeds 1150 ° C., a problem of deterioration of toughness may occur, and 950 to 1150 ° C. is preferable.

본 발명을 한정하지는 않으나, 본 발명의 강관은 두께 12mm이하인 것이 보다 바람직하다. 일반적으로 두께가 높을수록 열처리후 공냉시 냉각속도가 느리므로 인해 페라이트의 양이 많아져 강도를 확보할수 있는 퍼얼라이트 및 베이나이트의 확보가 어려워지므로, 본 발명의 경우는 제조공정과 생산원가 측면에서는 12mm이하인 것이 보다 바람직하다. Although it does not limit this invention, It is more preferable that the steel pipe of this invention is 12 mm or less in thickness. In general, the higher the thickness, the slower the cooling rate during air cooling after heat treatment, so that the amount of ferrite becomes harder to secure the ferrite and bainite which can secure the strength. Therefore, in the case of the present invention, in terms of manufacturing process and production cost, It is more preferable that it is 12 mm or less.

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

(실시예)(Example)

하기 표 1과 같이 조성되는 강 슬라브를 마무리 압연온도는 800~900℃이며, 550~700℃까지 냉각하였다. 이후 2인치에서 6인치로 전기저항 용접관을 조관하며, 이후 고주파 유도가열형의 열처리로를 통해 950~1150℃의 온도에서 소둔 (Normalizing) 열처리되며, 이때의 유지시간은 10초 이내이며, 그후 파이프는 공냉된다.The steel slab, which is formed as shown in Table 1 below, has a finish rolling temperature of 800 to 900 ° C and was cooled to 550 to 700 ° C. Thereafter, the electric resistance welded pipe is piped from 2 inches to 6 inches, and then annealing is performed at a temperature of 950 to 1150 ° C. through a high frequency induction heating furnace, and the holding time is within 10 seconds. The pipe is air cooled.

얻어진 강판 및 강관은 인장시험기를 이용하여 항복강도(0.5언더로드), 인장강도 및 연신율을 측정하였으며, 일반적으로 통용되는 ASTM A370에 준하여 시험하였다.The obtained steel sheets and steel pipes were measured for yield strength (0.5 underload), tensile strength and elongation using a tensile tester, and were tested according to ASTM A370.

표 2는 본 발명강과 비교강의 조직 및 기계적 성질을 나타낸 것이다.Table 2 shows the structure and mechanical properties of the inventive steels and comparative steels.

강종Steel grade 성분함량(중량%)Ingredient Content (wt%) CC SiSi MnMn PP SS AlAl NbNb VV TiTi CrCr MoMo NN CaCa 발명강AInventive Steel A 0.300.30 0.300.30 1.51.5 <0.015<0.015 <0.005<0.005 0.030.03 0.0300.030 0.100.10 0.0100.010 0.300.30 00 0.00400.0040 0.00200.0020 비교강 BComparative Steel B 0.320.32 0.320.32 1.61.6 0.0100.010 0.0010.001 0.030.03 0.060.06 00 00 00 00 0.00400.0040 0.00200.0020 비교강CComparative Steel C 0.250.25 0.250.25 1.51.5 0.0100.010 0.0010.001 0.030.03 00 00 00 0.300.30 00 0.00400.0040 0.00200.0020 비교강DComparative Steel D 0.070.07 0.250.25 1.61.6 0.0100.010 0.0010.001 0.030.03 0.0600.060 0.050.05 0.0150.015 00 0.250.25 0.00400.0040 0.00200.0020 비교강EComparative Steel E 0.180.18 0.250.25 1.51.5 0.0100.010 0.0010.001 0.030.03 0.0400.040 00 00 00 00 0.00400.0040 0.00200.0020

구분division 강종Steel grade 열처리온도 (℃)Heat treatment temperature (℃) 결정립분율(%)Grain fraction (%) 기계적성질Mechanical property 페라 이트Ferrite 퍼얼라 이트Performance 베이나 이트Bainite 항복강도 (MPa)Yield strength (MPa) 인장강도 (MPa)Tensile Strength (MPa) 항복비 (YS/TS)Yield Ratio (YS / TS) 연신율 (%)Elongation (%) 비교재1Comparative Material 1 발명강AInventive Steel A 900900 5050 4545 55 494.3494.3 668.8668.8 0.740.74 3030 발명재1Invention 1 10001000 4545 4040 1515 587.4587.4 804.2804.2 0.730.73 2323 발명재2Invention 2 11001100 3535 4040 2525 664.9664.9 898.3898.3 0.740.74 2222 비교재2Comparative Material 2 비교강BComparative Steel B 900900 5555 4545 00 442.3442.3 671.8671.8 0.660.66 2121 비교재3Comparative Material 3 10001000 5555 4545 00 494.3494.3 752.2752.2 0.660.66 2020 비교재4Comparative Material 4 11001100 5555 4040 55 483.5483.5 756.1756.1 0.640.64 2020 비교재5Comparative Material 5 비교강CComparative Steel C 900900 7575 2525 00 422.7422.7 679.6679.6 0.620.62 2020 비교재6Comparative Material 6 10001000 7575 2525 00 457.0457.0 734.5734.5 0.620.62 1919 비교재7Comparative Material7 11001100 7070 3030 00 442.3442.3 706.1706.1 0.630.63 2020 비교재8Comparative Material 8 비교강DComparative Steel D 900900 9292 88 00 401.1401.1 658.0658.0 0.610.61 2424 비교재9Comparative Material 9 10001000 9292 88 00 447.2447.2 668.8668.8 0.670.67 2323 비교재10Comparative Material 10 11001100 9393 77 00 424.6424.6 638.4638.4 0.670.67 2424 비교재11Comparative Material 11 비교강EComparative Steel E 900900 8080 2020 00 372.7372.7 618.8618.8 0.600.60 2323 비교재12Comparative Material 12 10001000 8080 2020 00 402.1402.1 609.0609.0 0.660.66 2424 비교재13Comparative Material 13 11001100 7575 2525 00 383.5383.5 597.2597.2 0.640.64 2323

상기 표 2에서 나타난 바와 같이 본 발명의 성분범위를 만족하는 발명강(A)을 이용하여 본 발명의 제조방법에 따라 제조된 발명재1,2의 경우, 고주파 열처리후 항복강도, 인장강도 확보를 위한 10%이상의 베이나이트를 확보하여 항복강도 550MPa 이상 및 인장강도 690MPa 이상의 고강도를 확보할 수 있었다. As shown in Table 2, in the case of Inventive Materials 1 and 2 manufactured according to the manufacturing method of the present invention using the inventive steel (A) satisfying the component range of the present invention, yield strength and tensile strength are secured after high frequency heat treatment. By securing more than 10% of bainite, yield strength of 550 MPa or more and tensile strength of 690 MPa or more were secured.

그러나, 본 발명의 성분범위를 만족하는 발명강A을 이용하여 본 발명의 제조방법에 따라 제조되지 않은 비교재1의 경우, 고주파 열처리후 충분한 베이나이트상을 확보하지 못한 관계로 고강도의 항복강도 및 인장강도를 확보할 수 없었다. However, in the case of Comparative Material 1, which is not manufactured according to the manufacturing method of the present invention using the invention steel A satisfying the component range of the present invention, the yield strength of high strength and Tensile strength could not be secured.

상술한 바와 같이, 본 발명은 열연 강판의 고주파 열처리 특성을 개선하여 고강도 유정강관을 제공할 수 있는 유용한 효과가 있다.As described above, the present invention has a useful effect that can provide a high-strength well steel pipe by improving the high frequency heat treatment characteristics of the hot rolled steel sheet.

Claims (4)

중량%로, C: 0.25~0.45%, Si: 0.20~0.60%, Mn: 1.4~2.2%, P: 0.02%이하, S: 0.01%이하, Ti: 0.005~0.03%, Nb: 0.030~0.050%, Ca: 0.001~0.006%, Al:0.01~0.06%, N: 0.008%이하, O: 0.006%이하, V: 0.08~0.20%, Cr: 0.10~0.50%를 포함하고, 나머지는 Fe 및 기타 불가피한 불순물로 조성되며, 강판의 조직이 면적비로 40~50%는 페라이트이고, 나머지는 퍼얼라이트로 이루어지는 고주파 열처리 특성이 우수한 열연강판.By weight%, C: 0.25-0.45%, Si: 0.20-0.60%, Mn: 1.4-2.2%, P: 0.02% or less, S: 0.01% or less, Ti: 0.005-0.03%, Nb: 0.030-0.050% , Ca: 0.001 to 0.006%, Al: 0.01 to 0.06%, N: 0.008% or less, O: 0.006% or less, V: 0.08 to 0.20%, Cr: 0.10 to 0.50%, the rest is Fe and other unavoidable It is composed of impurities, hot-rolled steel sheet having excellent high-frequency heat treatment characteristics consisting of 40-50% of the structure of the steel sheet by the area ratio of ferrite, the remainder is a ferrite. 중량%로, C: 0.25~0.45%, Si: 0.20~0.60%, Mn: 1.4~2.2%, P: 0.02%이하, S: 0.01%이하, Ti: 0.005~0.03%, Nb: 0.030~0.050%, Ca: 0.001~0.006%, Al:0.01~0.06%, N: 0.008%이하, O: 0.006%이하, V: 0.08~0.20%, Cr: 0.10~0.50%를 포함하고, 나머지는 Fe 및 기타 불가피한 불순물로 조성되는 슬라브를 재가열하는 단계;By weight%, C: 0.25-0.45%, Si: 0.20-0.60%, Mn: 1.4-2.2%, P: 0.02% or less, S: 0.01% or less, Ti: 0.005-0.03%, Nb: 0.030-0.050% , Ca: 0.001 to 0.006%, Al: 0.01 to 0.06%, N: 0.008% or less, O: 0.006% or less, V: 0.08 to 0.20%, Cr: 0.10 to 0.50%, the rest is Fe and other unavoidable Reheating the slabs composed of impurities; 상기 슬라브를 압연한 후 800~900℃의 마무리압연온도범위에서 마무리압연하는 단계;Rolling the slab and finishing rolling in a finishing rolling temperature range of 800 to 900 ° C .; 상기 압연한 강재를 10~20℃/sec의 속도로 550~700℃까지 냉각한 다음 권취하는 단계를 포함하여 이루어지는 고주파 열처리 특성이 우수한 열연강판의 제조방법.Cooling the rolled steel to 550 ~ 700 ℃ at a rate of 10 ~ 20 ℃ / sec, and then winding the step of producing a hot rolled steel sheet excellent in high-frequency heat treatment properties. 중량%로, C: 0.25~0.45%, Si: 0.20~0.60%, Mn: 1.4~2.2%, P: 0.02%이하, S: 0.01%이하, Ti: 0.005~0.03%, Nb: 0.030~0.050%, Ca: 0.001~0.006%, Al:0.01~0.06%, N: 0.008%이하, O: 0.006%이하, V: 0.08~0.20%, Cr: 0.10~0.50%를 포함하고, 나머지는 Fe 및 기타 불가피한 불순물로 조성되는 슬라브로 제조된 강관으로,By weight%, C: 0.25-0.45%, Si: 0.20-0.60%, Mn: 1.4-2.2%, P: 0.02% or less, S: 0.01% or less, Ti: 0.005-0.03%, Nb: 0.030-0.050% , Ca: 0.001 to 0.006%, Al: 0.01 to 0.06%, N: 0.008% or less, O: 0.006% or less, V: 0.08 to 0.20%, Cr: 0.10 to 0.50%, the rest is Fe and other unavoidable Steel pipe made of slabs composed of impurities, 상기 강관의 조직은 면적비로 10~30%의 베이나이트이고, 나머지는 페라이트 및 펄라이트로 이루어진 고주파 열처리 특성이 우수한 고강도 강관. The structure of the steel pipe is 10-30% bainite by area ratio, the remainder is a high-strength steel pipe excellent in high-frequency heat treatment consisting of ferrite and pearlite. 중량%로, C: 0.25~0.45%, Si: 0.20~0.60%, Mn: 1.4~2.2%, P: 0.02%이하, S: 0.01%이하, Ti: 0.005~0.03%, Nb: 0.030~0.050%, Ca: 0.001~0.006%, Al:0.01~0.06%, N: 0.008%이하, O: 0.006%이하, V: 0.08~0.20%, Cr: 0.10~0.50%를 포함하고, 나머지는 Fe 및 기타 불가피한 불순물로 조성되는 슬라브로 제조된 강판을 용접관으로 조관하는 단계;By weight%, C: 0.25-0.45%, Si: 0.20-0.60%, Mn: 1.4-2.2%, P: 0.02% or less, S: 0.01% or less, Ti: 0.005-0.03%, Nb: 0.030-0.050% , Ca: 0.001 to 0.006%, Al: 0.01 to 0.06%, N: 0.008% or less, O: 0.006% or less, V: 0.08 to 0.20%, Cr: 0.10 to 0.50%, the rest is Fe and other unavoidable Manipulating a steel sheet made of slabs composed of impurities with a weld tube; 상기 용접관을 950~1150℃로 고주파 유도가열형의 열처리로를 통해 소둔 (Normalizing) 열처리하고 공냉하는 단계를 포함하여 이루어지는 고주파 열처리 특성이 우수한 고강도 강관의 제조방법. A method of manufacturing a high strength steel pipe having excellent high frequency heat treatment characteristics comprising the step of annealing (Normalizing) and air-cooling the welded tube through a high frequency induction heating type heat treatment furnace at 950 to 1150 ° C.
KR1020060131636A 2006-12-21 2006-12-21 Hot-rolled steel sheet and pipe having superior characteristics of normalizing and method of manufacturing the same KR20080057844A (en)

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Cited By (6)

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CN102400057A (en) * 2011-11-28 2012-04-04 宝山钢铁股份有限公司 Low-alloy steel used for oil well pipe with carbon dioxide corrosion resistance and manufacturing method thereof
KR101412438B1 (en) * 2012-06-28 2014-06-25 현대제철 주식회사 High strength steel sheet for line pipe and method of manufacturing the same
KR101461741B1 (en) * 2012-12-21 2014-11-14 주식회사 포스코 Thick hot rolled steel plate for steel pipe and steel pipe produced therefrom having excellent impact toughness and method for manufacturing thereof
KR20160001520A (en) * 2014-06-27 2016-01-06 현대제철 주식회사 Method of manufacturing hot-rolled steel sheet and method of manufacturing steel pipe
CN110273109A (en) * 2019-07-30 2019-09-24 马鞍山钢铁股份有限公司 A kind of 450MPa grades of submerged pipeline roll of steel plate and preparation method thereof
CN114619004A (en) * 2022-02-28 2022-06-14 包头钢铁(集团)有限责任公司 Rare earth microalloying cold-drawn high-strength seamless steel tube for hydraulic cylinder and preparation method thereof

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102400057A (en) * 2011-11-28 2012-04-04 宝山钢铁股份有限公司 Low-alloy steel used for oil well pipe with carbon dioxide corrosion resistance and manufacturing method thereof
CN102400057B (en) * 2011-11-28 2014-12-03 宝山钢铁股份有限公司 Low-alloy steel used for oil well pipe with carbon dioxide corrosion resistance and manufacturing method thereof
KR101412438B1 (en) * 2012-06-28 2014-06-25 현대제철 주식회사 High strength steel sheet for line pipe and method of manufacturing the same
KR101461741B1 (en) * 2012-12-21 2014-11-14 주식회사 포스코 Thick hot rolled steel plate for steel pipe and steel pipe produced therefrom having excellent impact toughness and method for manufacturing thereof
KR20160001520A (en) * 2014-06-27 2016-01-06 현대제철 주식회사 Method of manufacturing hot-rolled steel sheet and method of manufacturing steel pipe
CN110273109A (en) * 2019-07-30 2019-09-24 马鞍山钢铁股份有限公司 A kind of 450MPa grades of submerged pipeline roll of steel plate and preparation method thereof
CN114619004A (en) * 2022-02-28 2022-06-14 包头钢铁(集团)有限责任公司 Rare earth microalloying cold-drawn high-strength seamless steel tube for hydraulic cylinder and preparation method thereof
CN114619004B (en) * 2022-02-28 2024-06-11 包头钢铁(集团)有限责任公司 Rare earth microalloyed seamless steel tube for cold drawn high-strength hydraulic cylinder barrel and preparation method thereof

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