KR101505303B1 - Steel sheet and method of manufacturing the same - Google Patents
Steel sheet and method of manufacturing the same Download PDFInfo
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- KR101505303B1 KR101505303B1 KR1020130074747A KR20130074747A KR101505303B1 KR 101505303 B1 KR101505303 B1 KR 101505303B1 KR 1020130074747 A KR1020130074747 A KR 1020130074747A KR 20130074747 A KR20130074747 A KR 20130074747A KR 101505303 B1 KR101505303 B1 KR 101505303B1
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 54
- 239000010959 steel Substances 0.000 title claims abstract description 54
- 238000004519 manufacturing process Methods 0.000 title abstract description 12
- 230000007797 corrosion Effects 0.000 claims abstract description 33
- 238000005260 corrosion Methods 0.000 claims abstract description 33
- 238000000034 method Methods 0.000 claims abstract description 15
- 238000003303 reheating Methods 0.000 claims abstract description 10
- 239000012535 impurity Substances 0.000 claims abstract description 8
- 238000003466 welding Methods 0.000 claims description 15
- 238000005266 casting Methods 0.000 claims description 8
- 238000005098 hot rolling Methods 0.000 claims description 8
- 239000000463 material Substances 0.000 claims description 7
- 230000008569 process Effects 0.000 abstract description 9
- 229910045601 alloy Inorganic materials 0.000 abstract description 6
- 239000000956 alloy Substances 0.000 abstract description 6
- 239000011651 chromium Substances 0.000 description 24
- 239000011575 calcium Substances 0.000 description 23
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 22
- 239000010949 copper Substances 0.000 description 20
- 239000011572 manganese Substances 0.000 description 18
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 11
- 229910052804 chromium Inorganic materials 0.000 description 11
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 10
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 10
- 229910052791 calcium Inorganic materials 0.000 description 10
- 229910052802 copper Inorganic materials 0.000 description 10
- 229910052759 nickel Inorganic materials 0.000 description 8
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 7
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 7
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 7
- 229910052799 carbon Inorganic materials 0.000 description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 7
- 229910052748 manganese Inorganic materials 0.000 description 7
- 229910052710 silicon Inorganic materials 0.000 description 7
- 239000010703 silicon Substances 0.000 description 7
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 6
- 229910052717 sulfur Inorganic materials 0.000 description 6
- 239000011593 sulfur Substances 0.000 description 6
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 3
- 229910052698 phosphorus Inorganic materials 0.000 description 3
- 239000011574 phosphorus Substances 0.000 description 3
- 229910000859 α-Fe Inorganic materials 0.000 description 3
- 229910004283 SiO 4 Inorganic materials 0.000 description 2
- 230000002159 abnormal effect Effects 0.000 description 2
- 238000004453 electron probe microanalysis Methods 0.000 description 2
- 230000003628 erosive effect Effects 0.000 description 2
- 229910052840 fayalite Inorganic materials 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000007747 plating Methods 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 238000005204 segregation Methods 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- 238000007711 solidification Methods 0.000 description 2
- 238000005211 surface analysis Methods 0.000 description 2
- 238000004804 winding Methods 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 239000010953 base metal Substances 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
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- 230000002441 reversible effect Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 239000002893 slag Substances 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
-
- 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
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
-
- 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
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
-
- 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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
Abstract
합금성분 조절 및 공정 조건의 제어를 통하여, 전기저항용접부의 구상부식성을 향상시킬 수 있는 강판 및 그 제조 방법에 대하여 개시한다.
본 발명에 따른 강판 제조 방법은 중량%로, C : 0.05 ~ 0.18%, Si : 0.025% 이하, Mn : 0.3 ~ 0.6%, P : 0.02% 이하, S : 0.003% 이하, Cu : 0.08 ~ 0.25%, Ni : 0.08% 이하, Cr : 0.08 ~ 0.3%, Ca : 0.001 ~ 0.003% 및 나머지 철(Fe)과 기타 불가피한 불순물로 조성되는 강 슬라브를 SRT(Slab Reheating Temperature) : 1220℃ 이상으로 재가열한 후, 열간압연하는 것을 특징으로 한다.A steel sheet capable of improving spherical corrosion resistance of an electric resistance welded portion through control of alloy components and process conditions and a method of manufacturing the same.
The method of manufacturing a steel sheet according to the present invention is characterized in that it comprises 0.05 to 0.18% of C, 0.025% or less of Si, 0.3 to 0.6% of Mn, 0.02% or less of P, 0.003% or less of S, , A steel slab composed of 0.08% or less of Ni, 0.08 to 0.3% of Cr, 0.001 to 0.003% of Ca and the balance of Fe and other unavoidable impurities is reheated to a slab reheating temperature (SRT) , And hot-rolled.
Description
본 발명은 강판 제조 기술에 관한 것으로, 보다 상세하게는 합금성분 조절 및 공정 조건의 제어를 통하여 전기저항용접부의 구상부식성을 향상시킬 수 있는 강판 및 그 제조 방법에 관한 것이다.
More particularly, the present invention relates to a steel sheet capable of improving spherical erosion resistance of an electric resistance welded portion by controlling an alloy component and controlling process conditions, and a method of manufacturing the same.
내구상 부식강은 전기저항용접(electric resistance welding, ERW)에 의해 제조된 강관에 있어서, 용접부를 따라 홈 형태로 나타나는 구상 부식에 대응하고자 개발되었다. 구상부식을 제어하기 위해서는 ERW 용접된 강관을 대략 900℃ 이상에서 열처리를 하거나, 강판에 함유된 황(S)의 함량을 극소로 낮추는 것이 필요하다.Internal spherical corrosion steel was developed to respond to spherical erosion in the form of grooves along the weld in steel pipes manufactured by electric resistance welding (ERW). In order to control the spherical corrosion, it is necessary to heat-treat the ERW-welded steel pipe at about 900 ° C or more, or to reduce the content of sulfur (S) contained in the steel sheet to a very low level.
이는 구상부식을 일으키는 주된 메커니즘이 강관의 용접부족이나 용접시 MnS가 용해되었다가 재응고되는 과정에서 완전히 재결합되지 못하여 모재 보다 -60mV의 전위차를 나타내고, 이러한 전위차는 이종금속 접촉부식을 만들어 부식을 가속화시키는 요인으로 작용하기 때문이다.
This is because the main mechanism causing the spherical corrosion is the lack of welding of the steel pipe or the welding of MnS at the time of welding and it is not completely recombined in the process of re-solidification, so that the potential difference of -60 mV is higher than that of the base metal. It is because it acts as a factor to cause.
본 발명에 관련된 배경기술로는 대한민국 공개특허공보 제10-2008-57845호(2008.06.25. 공개)가 있으며, 상기 문헌에는 연속로 열처리 특성이 우수한 열연강판 및 고강도 강관과 그 제조 방법이 기재되어 있다.
As a background art related to the present invention, Korean Patent Laid-Open Publication No. 10-2008-57845 (published on Jun. 25, 2008) discloses a hot-rolled steel sheet and a high-strength steel pipe excellent in heat- have.
본 발명의 목적은 합금성분 조절 및 공정 조건의 제어를 통하여, 전기저항용접부의 구상부식성을 향상시킬 수 있는 강판 및 그 제조 방법을 제공하는 것이다.
An object of the present invention is to provide a steel sheet capable of improving spherical corrosion resistance of an electric resistance welded portion through control of alloy components and process conditions and a method of manufacturing the same.
상기 목적을 달성하기 위한 본 발명의 실시예에 따른 강판 제조 방법은 중량%로, C : 0.05 ~ 0.18%, Si : 0% 초과 내지 0.025% 이하, Mn : 0.3 ~ 0.6%, P : 0% 초과 내지 0.02% 이하, S : 0% 초과 내지 0.003% 이하, Cu : 0.08 ~ 0.25%, Ni : 0% 초과 내지 0.08% 이하, Cr : 0.08 ~ 0.3%, Ca : 0.001 ~ 0.003% 및 나머지 철(Fe)과 기타 불가피한 불순물로 조성되는 강 슬라브를 SRT(Slab Reheating Temperature) : 1220℃ 이상으로 재가열한 후, 열간압연하는 것을 특징으로 한다. In order to achieve the above object, a steel sheet manufacturing method according to an embodiment of the present invention is characterized in that it comprises 0.05 to 0.18% of C, 0 to 0.025% of Si, 0.3 to 0.6% of Mn, 0 to 0% of P Of Cr, 0.08 to 0.3% of Ca, 0.001 to 0.003% of Ca, and 0.001 to 0.003% of Ca and 0.08 to 0.25% of Cu, 0.08 to 0.25% of Cu, ) And other unavoidable impurities is reheated to a slab reheating temperature (SRT) of 1220 占 폚 or higher and then hot rolled.
이때, 상기 슬라브는 용강을 0.9 ~ 1.1 m/min의 연주 속도로 주조하여 제조된 것을 이용하는 것이 바람직하다.At this time, it is preferable that the slab is manufactured by casting molten steel at a casting speed of 0.9 to 1.1 m / min.
또한, 상기 열간압연은 FDT(Finish Delivery Temperature) : 860 ~ 900℃ 조건으로 수행될 수 있다.
The hot rolling may be performed at a finishing delivery temperature (FDT) of 860 to 900 ° C.
상기 목적을 달성하기 위한 본 발명의 실시예에 따른 강판은 중량%로, C : 0.05 ~ 0.18%, Si : 0% 초과 내지 0.025% 이하, Mn : 0.3 ~ 0.6%, P : 0% 초과 내지 0.02% 이하, S : 0% 초과 내지 0.003% 이하, Cu : 0.08 ~ 0.25%, Ni : 0% 초과 내지 0.08% 이하, Cr : 0.08 ~ 0.3%, Ca : 0.001 ~ 0.003% 및 나머지 철(Fe)과 기타 불가피한 불순물로 조성되고, 구상부식계수(전기저항용접시 용접부 부식 깊이 ÷ 모재부 부식 깊이)가 1.0 이하인 것을 특징으로 한다. In order to achieve the above object, the steel sheet according to the present invention comprises 0.05 to 0.18% of C, 0 to 0.025% of Si, 0.3 to 0.6% of Mn, 0 to 0.02% of P, % Of Fe, 0.08 to 0.3% of Cr, 0.001 to 0.003% of Ca, 0.001 to 0.003% of Ca, 0.08 to 0.25% of Cu, And other inevitable impurities, and has a spherical corrosion coefficient (corrosion depth of weld portion in electrical resistance welding ÷ corrosion depth of base material portion) of 1.0 or less.
상기 강판은, 인강강도(TS) : 380~480MPa 및 연신율(El) : 32% 이상을 나타낼 수 있다.
The steel sheet may exhibit a tensile strength (TS) of 380 to 480 MPa and an elongation (El) of 32% or more.
본 발명에 따른 강판 제조 방법에 의하면, 고가의 니켈(Ni) 함량을 0.08중량% 이하로 최소화하면서도, 구리, 크롬 등의 함량 제어 및 연속주조, 슬라브 재가열 등의 공정 제어를 통하여 전기저항용접부의 구상부식성을 향상시킬 수 있는 장점이 있다. According to the method for manufacturing a steel sheet according to the present invention, it is possible to minimize the nickel (Ni) content to 0.08 wt% or less while controlling the content of copper, chromium, etc. and controlling the process of continuous casting and slab reheating, There is an advantage that the corrosion resistance can be improved.
또한, 본 발명에 따른 강판 제조 방법에 의하면, 실리콘(Si)의 함량을 0.025 중량% 이하로 제어함으로써, 고온에서 철감람석(fayalite, Fe2SiO4)으로 변하는 것을 억제하여 도금성 불량을 방지할 수 있다.
Further, according to the method for manufacturing a steel sheet according to the present invention, by controlling the content of silicon (Si) to 0.025 wt% or less, it is possible to suppress the change to fayalite (Fe 2 SiO 4 ) at a high temperature, .
도 1은 실시예 1에 따른 시편의 EPMA 표층 분석 결과를 나타낸 것이다.
Fig. 1 shows the result of EPMA surface analysis of the specimen according to Example 1. Fig.
본 발명의 특징과 이를 달성하기 위한 방법은 첨부되는 도면과, 후술되어 있는 실시예를 참조하면 명확해진다. 그러나 본 발명은 이하에 개시되는 실시예에 한정되는 것은 아니며, 서로 다른 다양한 형태로 구현될 수 있다. 본 실시예는 본 발명의 개시가 완전하도록 하기 위함이며, 본 발명이 속하는 기술분야에서 통상의 지식을 가진 자에게 발명의 범주를 완전하게 알려주기 위해 제공되는 것이다. 본 발명은 청구항의 기재에 의해 정의될 뿐이다.The features of the present invention and the method for achieving the same will be apparent from the accompanying drawings and the embodiments described below. However, the present invention is not limited to the embodiments described below, but may be embodied in various forms. The present embodiments are provided so that the disclosure of the present invention is complete and that those skilled in the art will fully understand the scope of the present invention. The invention is only defined by the description of the claims.
이하 첨부된 도면을 참조하여 본 발명의 바람직한 실시예에 따른 전기저항용접부의 구상부식성이 우수한 강판 및 그 제조 방법에 관하여 상세히 설명하면 다음과 같다.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a steel sheet excellent in spherical corrosion resistance of an electric resistance welded portion according to a preferred embodiment of the present invention and a method of manufacturing the same will be described in detail with reference to the accompanying drawings.
강판Steel plate
본 발명에 따른 강판은 중량%로, 탄소(C) : 0.05 ~ 0.18%, 실리콘(Si) : 0% 초과 내지 0.025% 이하, 망간(Mn) : 0.3 ~ 0.6%, 인(P) : 0% 초과 내지 0.02% 이하, 황(S) : 0% 초과 내지 0.003% 이하, 구리(Cu) : 0.08 ~ 0.25%, 니켈(Ni) : 0% 초과 내지 0.08% 이하, 크롬(Cr) : 0.08 ~ 0.3% 및 칼슘(Ca) : 0.001 ~ 0.003%를 포함한다.The steel sheet according to the present invention comprises 0.05 to 0.18% of carbon (C), more than 0% to 0.025% of silicon (Si), 0.3 to 0.6% of manganese (Mn) (Ni): more than 0% to less than 0.08%; chromium (Cr): 0.08 to 0.3%; % And calcium (Ca): 0.001 to 0.003%.
상기 합금성분 외 나머지는 철(Fe)과 제강 과정 등에서 불가피하게 포함되는 불순물로 조성된다.The remainder of the alloy component is composed of iron (Fe) and impurities inevitably included in the steelmaking process and the like.
이하, 본 발명에 따른 강관용 열연강판에 포함되는 각 성분의 역할 및 그 함량에 대하여 설명하면 다음과 같다.
Hereinafter, the role and content of each component included in the hot-rolled steel sheet for a steel pipe according to the present invention will be described as follows.
탄소(C)Carbon (C)
탄소(C)는 강도를 확보하기 위하여 첨가되며, 용접성에 가장 큰 영향을 미치는 원소이다.Carbon (C) is added to secure strength and is the most influential element in weldability.
탄소(C)는 강판 전체 중량의 0.05 ~ 0.18 중량%로 첨가하는 것이 바람직하다. 상기 탄소(C)의 함량이 0.05 중량% 미만일 경우에는 충분한 강도를 확보하는 데 어려움이 따를 수 있다. 반대로, 탄소(C)의 함량이 0.18 중량%를 초과할 경우에는 인성 저하를 야기할 수 있으며, 전기저항용접(ERW)시 용접성의 저하를 가져오는 문제점이 있다.
The carbon (C) is preferably added in an amount of 0.05 to 0.18% by weight based on the total weight of the steel sheet. If the content of carbon (C) is less than 0.05% by weight, it may be difficult to secure sufficient strength. On the contrary, when the content of carbon (C) exceeds 0.18% by weight, the toughness may be lowered and weldability may be deteriorated during electrical resistance welding (ERW).
실리콘(Si)Silicon (Si)
실리콘(Si)은 강 중 탈산제로 작용하며, 강도 확보에 기여한다.Silicon (Si) acts as a deoxidizer in the steel and contributes to securing strength.
다만, 본 발명에서 실리콘(Si)의 함량이 열연강판 전체 중량의 0.025 중량%를 초과하여 다량 첨가될 경우, 표면장력을 높여 젖음성을 감소시키거나, 고온에서 철감람석(fayalite, Fe2SiO4)으로 변하여 도금 중 이상석출을 야기하여 도금성을 급격히 저하시키는 문제가 있다. However, when a large amount of silicon (Si) is added in an amount exceeding 0.025% by weight of the total weight of the hot-rolled steel sheet in the present invention, the surface tension may be increased to reduce wettability or fayalite (Fe 2 SiO 4 ) Resulting in abnormal precipitation during plating, which causes a drastic decrease in the plating ability.
이에, 본 발명에서는 실리콘의 함량을 강판 전체 중량의 0중량% 초과 내지 0.025 중량% 이하로 제한하였다.
Therefore, in the present invention, the content of silicon is limited to more than 0 wt% and not more than 0.025 wt% of the total weight of the steel sheet.
망간(Mn)Manganese (Mn)
망간(Mn)은 인성을 열화시키지 않고 강도를 향상시키는데 유용한 원소이다. Manganese (Mn) is an element useful for improving strength without deteriorating toughness.
상기 망간(Mn)은 강판 전체 중량의 0.3 ~ 0.6 중량%의 함량비로 첨가하는 것이 바람직하다. 망간(Mn)의 함량이 0.3 중량% 미만일 경우에는 그 첨가 효과가 불충분하다. 반대로, 망간(Mn)의 함량이 0.6 중량%를 초과할 경우에는 템퍼 취화(Temper Embrittlement) 감수성을 증대시키는 문제점이 있다.
The manganese (Mn) is preferably added in an amount of 0.3 to 0.6% by weight based on the total weight of the steel sheet. When the content of manganese (Mn) is less than 0.3% by weight, the effect of addition thereof is insufficient. On the contrary, when the content of manganese (Mn) exceeds 0.6% by weight, the sensitivity to temper embrittlement increases.
인(P), 황(S)Phosphorus (P), sulfur (S)
인(P)은 강도 향상에 기여하나, 과다 함유될 경우, 중심 편석은 물론 미세 편석도 형성하여 재질에 좋지 않은 영향을 주며, 또한 용접성을 악화시킬 수 있다. 이에 본 발명에서는 인의 함량을 강판 전체 중량의 0중량% 초과 내지 0.02 중량% 이하로 제한하였다.Phosphorus (P) contributes to strength improvement, but if it is contained in excess, fine segregation is formed as well as center segregation, which adversely affects the material and may deteriorate the weldability. Therefore, in the present invention, the content of phosphorus is limited to more than 0% by weight and not more than 0.02% by weight of the total weight of the steel sheet.
또한, 황(S)은 강의 인성 및 용접성을 크게 저해하는 원소로서, 본 발명에서는 황(S)의 함량을 강판 전체 중량의 0중량% 초과 내지 0.003 중량% 이하로 제한하였다.
Sulfur (S) is an element which greatly inhibits the toughness and weldability of steel. In the present invention, the content of sulfur (S) is limited to more than 0% by weight and not more than 0.003% by weight of the total weight of the steel sheet.
구리(Cu)Copper (Cu)
구리(Cu)는 고용강화에 기여하여 강도를 향상시키는 역할을 한다.Copper (Cu) contributes to solid solution strengthening and enhances strength.
상기 구리는 강판 전체 중량의 0.08 ~ 0.25 중량%로 첨가되는 것이 바람직하다. 구리의 함량이 0.08 중량% 미만일 경우에는 상기의 효과를 제대로 발휘할 수 없다. 반대로, 구리의 함량이 0.25 중량%를 초과할 경우에는 강판 가공성을 저하시키고, 용접후 재열균열(Stress Relief Cracking) 감수성을 높이는 문제가 있다.
The copper is preferably added in an amount of 0.08 to 0.25% by weight based on the total weight of the steel sheet. When the content of copper is less than 0.08% by weight, the above effect can not be exhibited properly. On the other hand, if the content of copper exceeds 0.25% by weight, there is a problem that the workability of the steel sheet is lowered and the susceptibility to stress relief cracking after welding is increased.
니켈(Ni)Nickel (Ni)
니켈(Ni)은 소입성을 향상시키면서 인성 개선에 유효하며, 전기저항용접부 구상부식성을 향상시키는 원소이다. 그러나, 니켈은 고가의 원소로서, 강판 제조 비용을 크게 상승시키는 요인이 된다.Nickel (Ni) is effective in improving toughness while improving incombustibility and is an element that improves the spherical corrosion resistance of the electric resistance welded portion. However, nickel is an expensive element, which causes a considerable increase in steel plate production cost.
이에 본 발명에서는 니켈의 함량을 강판 전체 중량의 0중량% 초과 내지 0.08 중량% 이하로 제한하였으며, 니켈의 함량 저하로 인한 구상부식성 저하 등의 문제점은 크롬, 구리 등의 첨가 및 연속주조 및 슬라브 재가열 등의 공정 조건 제어를 통하여 해결하였다.
Therefore, in the present invention, the content of nickel is limited to more than 0 wt% to 0.08 wt% or less of the total weight of the steel sheet, and problems such as decrease in spherical corrosion due to reduction in nickel content are caused by addition of chromium, copper, And so on.
크롬(Cr)Chromium (Cr)
크롬(Cr)은 페라이트 안정화 원소로 강도 향상에 기여한다. 또한 크롬(Cr)은 δ페라이트영역을 확대하고, 아포정(hypo-peritectic)역을 고탄소 측으로 이행시켜 슬라브 표면품질을 개선하는 역할을 한다.Chromium (Cr) is a ferrite stabilizing element and contributes to strength improvement. Chromium (Cr) also plays a role in enlarging the delta ferrite region and shifting the hypo-peritectic region to the high carbon side to improve the slab surface quality.
상기 크롬(Cr)은 강판 전체 중량의 0.08 ~ 0.3 중량%의 함량비로 첨가하는 것이 바람직하다. 크롬(Cr)의 함량이 0.08 중량% 미만일 경우에는 그 첨가 효과를 제대로 발휘할 수 없다. 반대로, 크롬(Cr)의 함량이 0.3 중량%를 초과할 경우에는 용접 열영향부(HAZ) 인성 열화를 초래하는 문제점이 있다.
The chromium (Cr) is preferably added in a content ratio of 0.08 to 0.3% by weight based on the total weight of the steel sheet. When the content of chromium (Cr) is less than 0.08% by weight, the effect of the addition can not be exhibited properly. On the contrary, when the content of chromium (Cr) exceeds 0.3% by weight, there is a problem that toughness of the weld heat affected zone (HAZ) deteriorates.
칼슘(Ca)Calcium (Ca)
칼슘(Ca)은 CaS 개재물을 형성시킴으로써 MnS 개재물의 생성을 방해함으로써, 전기저항 용접성을 향상시키기 위한 목적으로 첨가된다. 즉, 칼슘(Ca)은 망간(Mn)에 비하여 황과의 친화도가 높으므로 칼슘의 첨가시 CaS 개재물이 생성되고 MnS 개재물의 생성은 감소한다. 이러한 MnS는 열간압연 중에 연신되어 전기저항 용접(ERW)시 후크 결함 등을 유발하는 요인이므로, 칼슘 첨가에 의해 구상의 CaS를 형성함으로써 전기저항 용접성이 향상될 수 있다.Calcium (Ca) is added for the purpose of improving electrical resistance weldability by inhibiting the formation of MnS inclusions by forming CaS inclusions. That is, calcium (Ca) has a higher affinity with sulfur than manganese (Mn), so CaS inclusions are formed and CaS inclusions are reduced when calcium is added. Since such MnS is a factor which causes a hook defect or the like in the case of electric resistance welding (ERW) by being stretched during hot rolling, the electric resistance weldability can be improved by forming spherical CaS by adding calcium.
상기 칼슘(Ca)은 강판 전체 중량의 0.001 ~ 0.003 중량%로 첨가되는 것이 바람직하다. 칼슘(Ca)의 함량이 0.001 중량% 미만으로 첨가될 경우에는 상기의 효과를 제대로 발휘할 수 없다. 반대로, 칼슘(Ca)의 함량이 0.003 중량%를 초과할 경우에는 CaO 개재물의 생성이 과도해져 전기저항 용접성을 떨어뜨리는 문제점이 있다.
The calcium (Ca) is preferably added in an amount of 0.001 to 0.003% by weight based on the total weight of the steel sheet. When the content of calcium (Ca) is less than 0.001 wt%, the above effect can not be exhibited properly. On the contrary, when the content of calcium (Ca) exceeds 0.003% by weight, generation of CaO inclusions is excessively generated, and electrical resistance weldability is deteriorated.
상기 합금조성을 갖는 본 발명에 따른 강판은 후술하는 공정 제어를 통하여 구상부식계수(전기저항용접시 용접부 부식 깊이 ÷ 모재부 부식 깊이)가 1.0 이하를 나타낼 수 있다. 구상부식계수가 작을수록 전기저항용접부 구상부식성이 우수하다고 볼 수 있다. 본 발명에 따른 강판의 경우, 구상부식계수가 1.0 이하로서, 이는 전기저항용접시 용접부의 부식 깊이가 모재부 부식 깊이보다 같거나 오히려 작아, 전기저항용접부 구상부식성이 매우 우수한 것을 의미한다. The steel sheet according to the present invention having the above alloy composition can exhibit a spherical corrosion coefficient (corrosion depth of weld portion in the case of electrical resistance welding ÷ corrosion depth of the base material portion) of 1.0 or less through the process control described later. The smaller the spherical corrosion factor, the better the spherical corrosion resistance of the electric resistance welded part. In the case of the steel sheet according to the present invention, the spherical corrosion coefficient is 1.0 or less, which means that the corrosion depth of the weld portion is less than or equal to the corrosion depth of the base portion in the electrical resistance welding, and the spherical corrosion resistance of the electric resistance weld portion is excellent.
또한, 본 발명에 따른 강판은 기계적 물성 측면에서, 인강강도(TS) : 380~480MPa 및 연신율(El) : 32% 이상을 나타낼 수 있다.
The steel sheet according to the present invention may exhibit a tensile strength (TS) of 380 to 480 MPa and an elongation (El) of 32% or more in terms of mechanical properties.
강판 제조 방법Steel plate manufacturing method
본 발명에 따른 강판 제조 방법은 중량%로, C : 0.05 ~ 0.18%, Si : 0% 초과 내지 0.025% 이하, Mn : 0.3 ~ 0.6%, P : 0% 초과 내지 0.02% 이하, S : 0% 초과 내지 0.003% 이하, Cu : 0.08 ~ 0.25%, Ni : 0% 초과 내지 0.08% 이하, Cr : 0.08 ~ 0.3%, Ca : 0.001 ~ 0.003% 및 나머지 철(Fe)과 기타 불가피한 불순물로 조성되는 강 슬라브를 SRT(Slab Reheating Temperature) : 1220℃ 이상으로 재가열한 후, 열간압연하는 것을 특징으로 한다. 물론, 열간압연 후에는 대략 550~650℃ 정도에서의 권취 과정이 포함될 수 있고, 권취 이후, 대략 800℃ 이상에서 20분 정도 노멀라이징 처리하는 과정이 포함될 수도 있다. The steel sheet manufacturing method according to the present invention is characterized in that it comprises 0.05 to 0.18% of C, 0 to 0.025% of Si, 0.3 to 0.6% of Mn, 0 to 0.02% of P, (Fe) and other unavoidable impurities, in which the content of Fe is 0.03-0.03%, the content of Cu is 0.08-0.25%, the content of Ni is more than 0% to 0.08%, the content of Cr is 0.08-0.3%, the content of Ca is 0.001-0.003% The slab is reheated to a slab reheating temperature (SRT) of 1220 占 폚 or more, and then hot-rolled. Of course, after the hot rolling, a winding process at about 550 to 650 DEG C may be included, and after winding, a process of normalizing at about 800 DEG C or more for about 20 minutes may be included.
상기 슬라브 재가열은 SRT(Slab Reheating Temperature) : 1220℃ 이상, 보다 바람직하게는 SRT : 1220~1300℃ 조건으로 수행될 수 있다. 이와 같이, 슬라브 재가열 온도(SRT)를 1220℃ 이상의 고온 영역에서 실시하는 것은 강 슬라브에 포함되어 있는 구리(Cu), 크롬(Cr) 등의 합금 성분을 충분히 용해시키기 위함이다. 슬라브 재가열 온도(SRT)가 1220℃ 미만일 경우에는 구리(Cu), 크롬(Cr) 등의 합금 성분이 충분히 용해되지 못하여 내식성을 확보하는 데 어려움이 따를 뿐만 아니라, 재가열 온도가 낮아 압연 부하가 커지는 문제가 있다.The slab reheating may be performed under the conditions of a slab reheating temperature (SRT) of 1220 DEG C or higher, more preferably a SRT of 1220 to 1300 DEG C. The reason for performing the slab reheating temperature (SRT) at a high temperature region of 1220 DEG C or more is to sufficiently dissolve alloy components such as copper (Cu) and chromium (Cr) contained in the steel slab. When the SRT is less than 1220 deg. C, alloying elements such as copper (Cu) and chromium (Cr) are not sufficiently dissolved so that it is difficult to secure corrosion resistance and the rolling load is increased due to low reheating temperature .
또한, 상기 강 슬라브는 용강을 0.9 ~ 1.1 m/min의 연주 속도로 주조하여 제조된 것을 이용하는 것이 바람직하다. 이때, 주조 속도를 0.9 ~ 1.1m/min로 실시하는 것은 연주 과정에서 연주 속도를 낮추어 응고속도를 엄격히 제어함으로써 슬라브 크랙을 방지할 수 있음과 더불어, 실리콘 : 0.0025 중량% 이하, 황 : 0.003 중량% 이하, 칼슘 : 0.001 ~ 0.003 중량%의 함량비로 제어하는 것을 동시에 달성하기 위함이다. 연주 속도가 0.9m/min 미만일 경우에는 그 속도가 너무 느린 관계로 생산성이 저하되는 문제가 있다. 반대로, 주조 속도가 1.1m/min을 초과할 경우에는 슬래그의 혼입을 야기할 수 있음과 더불어, 슬라브 크랙 발생을 유발하는 문제가 있다.The steel slab is preferably manufactured by casting molten steel at a casting speed of 0.9 to 1.1 m / min. In this case, when the casting speed is set to 0.9 to 1.1 m / min, the slab crack can be prevented by strictly controlling the solidification speed by lowering the performance speed in the performance process, and the silicon content is 0.0025 wt% or less, the sulfur content is 0.003 wt% By weight, and calcium in an amount of 0.001 to 0.003% by weight. When the performance speed is less than 0.9 m / min, the productivity is deteriorated because the speed is too slow. On the contrary, when the casting speed is more than 1.1 m / min, mixing of slag may be caused and slab cracks may occur.
또한, 상기 열간압연은 FDT(Finish Delivery Temperature) : 860 ~ 900℃ 조건으로 수행되는 것이 바람직하다. 마무리 열간압연온도가 860℃ 미만일 경우에는 이상역 압연에 의한 혼립 조직이 발생하는 등의 문제가 발생할 수 있다. 반대로, 마무리 열간압연온도가 900℃를 초과할 경우에는 오스테나이트 결정립이 조대화되어 변태후 페라이트 결정립 미세화가 충분히 이루어지지 않으며, 이에 따라 강도 확보가 어려워질 수 있다.
It is preferable that the hot rolling is performed under the FDT (Finish Delivery Temperature): 860 to 900 ° C. If the final hot rolling temperature is less than 860 캜, there may arise problems such as the occurrence of blistering due to abnormal reverse rolling. On the other hand, when the final hot rolling temperature exceeds 900 ° C, the austenite grains are coarsened, and after the transformation, the ferrite grains are not finely refined sufficiently, which may make it difficult to ensure strength.
실시예Example
이하, 본 발명의 바람직한 실시예를 통해 본 발명의 구성 및 작용을 더욱 상세히 설명하기로 한다. 다만, 이는 본 발명의 바람직한 예시로 제시된 것이며 어떠한 의미로도 이에 의해 본 발명이 제한되는 것으로 해석될 수는 없다.Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.
여기에 기재되지 않은 내용은 이 기술 분야에서 숙련된 자이면 충분히 기술적으로 유추할 수 있는 것이므로 그 설명을 생략하기로 한다.
The contents not described here are sufficiently technically inferior to those skilled in the art, and a description thereof will be omitted.
1. 시편의 제조1. Preparation of specimens
표 1의 조성 및 표 2의 공정 조건으로 실시예 1 ~ 3 및 비교예 1 ~ 3에 따른 시편을 제조하였다. The specimens according to Examples 1 to 3 and Comparative Examples 1 to 3 were prepared with the compositions of Table 1 and the process conditions of Table 2.
[표 1] (단위 : 중량%)[Table 1] (unit:% by weight)
[표 2] [Table 2]
2. 물성 평가2. Property evaluation
실시예 1 ~ 3 및 비교예 1 ~ 3에 따른 시편들에 대한 인장강도(TS), 연신율(El) 및 구상부식계수(전기저항용접시 용접부 부식 깊이 ÷ 모재부 부식 깊이)를 평가하였으며, 그 결과를 표 2에 나타내었다. The tensile strength (TS), elongation (El) and spherical corrosion factor (corrosion depth of weld portion in electrical resistance welding ÷ corrosion depth of the base material portion) of the specimens according to Examples 1 to 3 and Comparative Examples 1 to 3 were evaluated, The results are shown in Table 2.
구상 부식 계수 평가를 위하여, 실시예 1 ~ 3 및 비교예 1 ~ 3에 따른 시편들을 플라즈마 커팅으로 25mm(가로)*60mm(세로)*5mm(두께)의 크기로 각각 절단하여 실시예 1 ~ 3 및 비교예 1 ~ 3에 따른 시편들을 2개씩 각각 수득하였다. 다음, 실시예 1 ~ 3 및 비교예 1 ~ 3에 따라 제조된 각각의 2개의 시편들을 30℃로 유지되는 침지용액(10wt% NaCl + HCl, pH 0.85)내에서 168시간 동안 침지시킨 다음, 증류수로 세척하고 나서 용접 재료를 이용한 맞대기 용접을 전기저항용접 방식으로 실시한 다음, 30℃로 유지되는 3% NaCl 수용액 내에서 144시간 동안 -550mV의 조건으로 정전위 분극을 시켜 용접부와 모재부 간의 부식 깊이를 측정하여 구상부식계수를 도출하였다. 맞대기 용접을 위해 사용된 용접 재료는 중량%로, C : 0.06%, Si : 0.40%, Mn : 1.00%, P 0.015% S : 0.011%, Ni : 0.30%, Cr : 0.03%, Mo ; 0.025%, Ti : 0.025%, Al : 0.015%, V : 0.02%, B : 0.0003%, Cu : 0.2%, Nb : 0.012% 및 나머지 철(Fe)과 기타 불순물을 포함하는 금속을 이용하였다.
The specimens according to Examples 1 to 3 and Comparative Examples 1 to 3 were cut into pieces each having a size of 25 mm (width) * 60 mm (length) * 5 mm (thickness) by plasma cutting for evaluating spherical corrosion coefficient, And two specimens according to Comparative Examples 1 to 3, respectively. Next, each of the two specimens prepared according to Examples 1 to 3 and Comparative Examples 1 to 3 was immersed in an immersion solution (10 wt% NaCl + HCl, pH 0.85) maintained at 30 ° C for 168 hours, , And then subjected to electric-resistance welding at a temperature of -550 mV in a 3% aqueous solution of NaCl maintained at 30 ° C. for 144 hours to measure the corrosion depth between the weld and the base material And the spherical corrosion coefficient was calculated. The welding material used for the butt welding is composed of 0.06% of C, 0.40% of Si, 1.00% of Mn, 0.011% of P, 0.011% of P, 0.30% of Ni, 0.03% of Cr, 0.03% of Mo, 0.025% of Ti, 0.025% of Al, 0.015% of Al, 0.02% of V, 0.0003% of B, 0.2% of Cu, 0.012% of Nb and the balance of Fe and other impurities.
표 2를 참조하면, 실시예 1 ~ 3에 따라 제조된 시편들의 경우, 인장강도(TS) : 380 ~ 480MPa 및 연신율(EL) : 32% 이상을 모두 만족하였다. Referring to Table 2, the tensile strength (TS) of 380 to 480 MPa and the elongation (EL) of 32% or more satisfied all of the specimens prepared according to Examples 1 to 3.
반면, 비교예 1 ~ 3에 따른 시편들의 경우, 강도, 연신율의 경우 대체로 실시예 1 ~ 3에 따라 제조된 시편들과 유사한 경향을 나타내었으나, 구상부식계수가 1.0을 초과하였다.
On the other hand, in the case of the specimens according to Comparative Examples 1 to 3, the strength and elongation were similar to those of the specimens prepared in Examples 1 to 3, but the spherical corrosion coefficient exceeded 1.0.
도 1은 실시예 1에 따른 시편의 EPMA 표층 분석 결과를 나타낸 것이다. Fig. 1 shows the result of EPMA surface analysis of the specimen according to Example 1. Fig.
도 1을 참조하면, 실시예 1에 따른 시편의 경우, 표면에 구리(Cu)만 존재할 뿐, 니켈이 거의 존재하지 않는 것을 볼 수 있다. 이는 본 발명에 따른 강판의 경우, 니켈의 첨가량이 극소임에도 불구하고, 전기저항용접부의 구상부식성 확보가 가능한 것을 의미한다.
Referring to FIG. 1, in the case of the specimen according to Example 1, only copper (Cu) exists on the surface, but nickel is hardly present. This means that, in the case of the steel sheet according to the present invention, the spheroidal corrosion resistance of the electrical resistance welded portion can be ensured although the amount of nickel added is minimal.
이상에서는 본 발명의 실시예를 중심으로 설명하였지만, 당업자의 수준에서 다양한 변경이나 변형을 가할 수 있다. 이러한 변경과 변형이 본 발명의 범위를 벗어나지 않는 한 본 발명에 속한다고 할 수 있다. 따라서 본 발명의 권리범위는 이하에 기재되는 청구범위에 의해 판단되어야 할 것이다.While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. Such changes and modifications are intended to fall within the scope of the present invention unless they depart from the scope of the present invention. Accordingly, the scope of the present invention should be determined by the following claims.
Claims (5)
The steel sheet according to any one of claims 1 to 3, wherein the steel sheet contains 0.05 to 0.18% of C, 0 to 0.025% of Si, 0.3 to 0.6% of Mn, 0 to 0.02% of P, (Slab reheating temperature) of 0.08 to 0.25%, a steel slab composed of more than 0% to 0.08% of Ni, 0.08 to 0.3% of Cr, 0.001 to 0.003% of Ca and the balance of Fe and other unavoidable impurities, : After reheating to 1220 占 폚 or more, hot rolling is performed.
상기 슬라브는 용강을 0.9 ~ 1.1 m/min의 연주 속도로 주조하여 제조된 것을 특징으로 하는 강판 제조 방법.
The method according to claim 1,
Wherein the slab is manufactured by casting molten steel at a casting speed of 0.9 to 1.1 m / min.
상기 열간압연은 FDT(Finish Delivery Temperature) : 860 ~ 900℃ 조건으로 수행되는 것을 특징으로 하는 강판 제조 방법.
The method according to claim 1,
Wherein the hot rolling is performed at a finishing delivery temperature (FDT) of 860 to 900 占 폚.
구상부식계수(전기저항용접시 용접부 부식 깊이 ÷ 모재부 부식 깊이)가 1.0 이하인 것을 특징으로 하는 강판.
The steel sheet according to any one of claims 1 to 3, wherein the steel sheet contains 0.05 to 0.18% of C, 0 to 0.025% of Si, 0.3 to 0.6% of Mn, 0 to 0.02% of P, 0.08 to 0.25% of Ni, more than 0 to 0.08% of Ni, 0.08 to 0.3% of Cr, 0.001 to 0.003% of Ca, and the balance of Fe and other unavoidable impurities,
Wherein the spherical corrosion coefficient (the corrosion depth of the welded portion in the electrical resistance welding ÷ the corrosion depth of the base material portion) is 1.0 or less.
상기 강판은
인강강도(TS) : 380~480MPa 및 연신율(El) : 32% 이상을 나타내는 것을 특징으로 하는 강판.5. The method of claim 4,
The steel sheet
(TS) of 380 to 480 MPa and elongation (El) of 32% or more.
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| KR20000045514A (en) * | 1998-12-30 | 2000-07-15 | 이구택 | Method for producing high-strength thick steel strip having low yield ratio |
| JP3219510B2 (en) * | 1992-12-02 | 2001-10-15 | 株式会社神戸製鋼所 | High strength hot rolled steel sheet with excellent stretch flangeability |
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| JP3219510B2 (en) * | 1992-12-02 | 2001-10-15 | 株式会社神戸製鋼所 | High strength hot rolled steel sheet with excellent stretch flangeability |
| KR20000045514A (en) * | 1998-12-30 | 2000-07-15 | 이구택 | Method for producing high-strength thick steel strip having low yield ratio |
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