KR20150025950A - Steel plate and manufacturing method of the same - Google Patents
Steel plate and manufacturing method of the same Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 86
- 239000010959 steel Substances 0.000 title claims abstract description 86
- 238000004519 manufacturing process Methods 0.000 title abstract description 20
- 239000000463 material Substances 0.000 claims abstract description 38
- 239000011572 manganese Substances 0.000 claims abstract description 29
- 238000003303 reheating Methods 0.000 claims abstract description 25
- 239000010955 niobium Substances 0.000 claims abstract description 23
- 239000011575 calcium Substances 0.000 claims abstract description 21
- 238000000034 method Methods 0.000 claims abstract description 21
- 238000010791 quenching Methods 0.000 claims abstract description 21
- 230000000171 quenching effect Effects 0.000 claims abstract description 21
- 238000005496 tempering Methods 0.000 claims abstract description 21
- 239000010949 copper Substances 0.000 claims abstract description 19
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 18
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 18
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims abstract description 14
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 14
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 13
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims abstract description 13
- 239000010703 silicon Substances 0.000 claims abstract description 13
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 13
- 238000005096 rolling process Methods 0.000 claims abstract description 12
- 229910052791 calcium Inorganic materials 0.000 claims abstract description 11
- 229910052802 copper Inorganic materials 0.000 claims abstract description 11
- 238000005098 hot rolling Methods 0.000 claims abstract description 11
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims abstract description 10
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 10
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 10
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 9
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims abstract description 9
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 8
- 239000011593 sulfur Substances 0.000 claims abstract description 8
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 6
- 239000012535 impurity Substances 0.000 claims abstract description 6
- 239000011651 chromium Substances 0.000 claims description 23
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 12
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 12
- 229910052750 molybdenum Inorganic materials 0.000 claims description 12
- 239000011733 molybdenum Substances 0.000 claims description 12
- 229910052804 chromium Inorganic materials 0.000 claims description 11
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims description 11
- 229910052796 boron Inorganic materials 0.000 claims description 10
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 9
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 7
- 229910052698 phosphorus Inorganic materials 0.000 claims description 7
- 239000011574 phosphorus Substances 0.000 claims description 7
- 229910052720 vanadium Inorganic materials 0.000 claims description 4
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 claims description 2
- 230000008569 process Effects 0.000 abstract description 14
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 abstract description 12
- 229910045601 alloy Inorganic materials 0.000 abstract description 5
- 239000000956 alloy Substances 0.000 abstract description 5
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 23
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 12
- 230000000694 effects Effects 0.000 description 10
- 229910052759 nickel Inorganic materials 0.000 description 8
- 238000005204 segregation Methods 0.000 description 8
- 238000005336 cracking Methods 0.000 description 7
- 239000000203 mixture Substances 0.000 description 6
- 229910052757 nitrogen Inorganic materials 0.000 description 6
- 229910000859 α-Fe Inorganic materials 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 230000007797 corrosion Effects 0.000 description 5
- 238000005260 corrosion Methods 0.000 description 5
- 230000000087 stabilizing effect Effects 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- 229910001566 austenite Inorganic materials 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000005266 casting Methods 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 150000001247 metal acetylides Chemical class 0.000 description 3
- 239000006104 solid solution Substances 0.000 description 3
- 238000005728 strengthening Methods 0.000 description 3
- 229910052810 boron oxide Inorganic materials 0.000 description 2
- 238000009749 continuous casting Methods 0.000 description 2
- JKWMSGQKBLHBQQ-UHFFFAOYSA-N diboron trioxide Chemical compound O=BOB=O JKWMSGQKBLHBQQ-UHFFFAOYSA-N 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 150000004767 nitrides Chemical class 0.000 description 2
- 229910001562 pearlite Inorganic materials 0.000 description 2
- 230000002829 reductive effect Effects 0.000 description 2
- 230000035882 stress Effects 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000011265 semifinished product Substances 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 230000008646 thermal stress Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
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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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- 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
-
- 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
- C22C38/02—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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- 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
- C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
-
- 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
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
합금 성분 조절 및 제조 공정을 DQT(Direct Quenching&Tempering)으로 실시하여 재가열 공정을 1회로 간소화 함으로써, 생산성을 증대할 수 있고 평탄도가 우수한 강재 및 그 제조 방법에 대하여 개시한다.
본 발명에 따른 강재의 제조 방법은 (a) 탄소(C) : 0.08 ~ 0.16 중량%, 실리콘(Si) : 0.1 ~ 0.5 중량% 이하, 망간(Mn) : 1.0 ~ 1.7 중량%, 인(P) : 120 ppm 이하, 황(S) : 30 ppm 이하, 가용성 알루미늄(S-Al) : 0.01 ~ 0.05 중량%, 구리(Cu) : 0.01 ~ 0.20 중량%, 니오븀(Nb) : 0.01 중량% 이하, 보론(B) : 0.0005 중량% 이하, 칼슘(Ca) : 5 ~ 40 ppm 및 나머지 철(Fe)과 불가피한 불순물로 이루어지는 강 슬라브를 SRT(Slab Reheating Temperature) : 1150 ~ 1250℃로 재가열하는 단계; (b) 상기 재가열된 강재를 FRT(Finish Rolling Temperature) : 850 ~ 950℃ 조건으로 열간압연하는 단계; (c) 상기 열간압연된 강재를 켄칭하는 단계; 및 (d) 상기 냉각된 강재를 620 ~ 700℃에서 템퍼링하는 단계;를 포함하는 것을 특징으로 한다.A steel material excellent in flatness can be produced by simplifying the reheating process one step by performing DQT (Direct Quenching & Tempering) on the alloy component control and manufacturing process, and a manufacturing method thereof.
The method of manufacturing a steel material according to the present invention comprises the steps of: (a) providing 0.08 to 0.16 wt% of carbon (C), 0.1 to 0.5 wt% of silicon (Si), 1.0 to 1.7 wt% of manganese (Mn) : Not more than 120 ppm, sulfur (S): not more than 30 ppm, soluble aluminum (S-Al): 0.01 to 0.05 wt.%, Copper (Cu): 0.01 to 0.20 wt.%, Niobium (Nb) (Slab reheating temperature) of 1150 to 1250 캜, the steel slab comprising 0.0005 wt% or less of calcium (B), 5 to 40 ppm of calcium (Ca), and the balance of iron (Fe) and unavoidable impurities; (b) hot rolling the reheated steel material to a finishing rolling temperature (FRT) of 850 to 950 占 폚; (c) quenching the hot-rolled steel material; And (d) tempering the cooled steel at 620 to 700 占 폚.
Description
본 발명은 강재 제조 기술에 관한 것으로, 보다 상세하게는 DQT(Direct Quenching&Tempering)후, 합금 성분 조정을 통해 평탄도를 관리할 수 있는 압력용기용 강재 및 그 제조 방법에 관한 것이다.
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel material manufacturing technique, and more particularly, to a steel material for a pressure vessel capable of managing flatness through DQT (Direct Quenching & Tempering) and alloy composition adjustment, and a manufacturing method thereof.
압력용기용으로 사용되는 A537-C2 강재는 주로 RQT(Reheat Quenching&Tempering)을 통해 생산된다. 이는 Ar3 온도 이상으로 재가열 및 켄칭(Quenching)한 후 다시 템퍼링(Tempering) 열처리를 하는 공정을 거친다. 이 공정은 재가열 공정이 2회이므로 제조원가가 많이 드는 문제점이 있었다.A537-C2 steels used for pressure vessels are mainly produced through RQT (Reheat Quenching & Tempering). It is subjected to a process of reheating and quenching at a temperature higher than the Ar3 temperature and then tempering again. This process has a problem that the reheating process is performed twice, and thus the manufacturing cost is large.
또한, RQT 공정은 켄칭시 불균일하게 실시되기 때문에 국부적으로 열응력, 변태응력이 다르므로 켄칭 후, 휘거나 균열이 발생할 수 있다.In addition, since the RQT process is performed nonuniformly at the time of quenching, the thermal stress and the transformation stress are different locally, so that warping or cracking may occur after quenching.
관련 선행문헌으로는 대한민국 공개특허공보 제10-2012-0074638호(2012.07.06. 공개)가 있으며, 상기 문헌에는 중심부 물성 및 수소유기균열 저항성이 우수한 압력용기용 극후물 강판 및 그 제조방법이 개시되어 있다.
As a related prior art, Korean Patent Laid-Open Publication No. 10-2012-0074638 (published on Jul. 6, 2012) discloses a pole steel sheet for pressure vessel excellent in core property and hydrogen organic cracking resistance and a method for producing the same. .
본 발명의 목적은 합금 성분 조절 및 제조 공정을 DQT(Direct Quenching&Tempering)으로 실시하여 재가열 공정을 1회로 간소화 함으로써, 생산성을 증대할 수 있고 평탄도가 우수한 강재 및 그 제조 방법을 제공하는 것이다.
It is an object of the present invention to provide a steel material which can increase productivity and simplify the reheating step by performing DQT (Direct Quenching & Tempering) of the alloy component adjustment and manufacturing process, and a method of manufacturing the same.
상기 목적을 달성하기 위한 본 발명의 실시예에 따른 강재의 제조 방법은 (a) 탄소(C) : 0.08 ~ 0.16 중량%, 실리콘(Si) : 0.1 ~ 0.5 중량% 이하, 망간(Mn) : 1.0 ~ 1.7 중량%, 인(P) : 120 ppm 이하, 황(S) : 30 ppm 이하, 가용성 알루미늄(S-Al) : 0.01 ~ 0.05 중량%, 구리(Cu) : 0.01 ~ 0.20 중량%, 니오븀(Nb) : 0.01 중량% 이하, 보론(B) : 0.0005 중량% 이하, 칼슘(Ca) : 5 ~ 40 ppm 및 나머지 철(Fe)과 불가피한 불순물로 이루어지는 강 슬라브를 SRT(Slab Reheating Temperature) : 1150 ~ 1250℃로 재가열하는 단계; (b) 상기 재가열된 강재를 FRT(Finish Rolling Temperature) : 850 ~ 950℃ 조건으로 열간압연하는 단계; (c) 상기 열간압연된 강재를 켄칭하는 단계; 및 (d) 상기 냉각된 강재를 620 ~ 700℃에서 템퍼링하는 단계;를 포함하는 것을 특징으로 한다.
In order to accomplish the above object, the present invention provides a method of manufacturing a steel material, comprising the steps of: (a) providing 0.08 to 0.16 wt% carbon, 0.1 to 0.5 wt% silicon, manganese (S): not more than 30 ppm, soluble aluminum (S-Al): 0.01 to 0.05 wt%, copper (Cu): 0.01 to 0.20 wt%, niobium A steel slab composed of Nb: 0.01 wt% or less, B: 0.0005 wt% or less, Ca: 5 to 40 ppm, and the balance iron (Fe) and unavoidable impurities is slab reheating temperature (SRT) Reheating to 1250 占 폚; (b) hot rolling the reheated steel material to a finishing rolling temperature (FRT) of 850 to 950 占 폚; (c) quenching the hot-rolled steel material; And (d) tempering the cooled steel at 620 to 700 占 폚.
상기 다른 목적을 달성하기 위한 본 발명의 실시예에 따른 강재는 탄소(C) : 0.08 ~ 0.16 중량%, 실리콘(Si) : 0.1 ~ 0.5 중량% 이하, 망간(Mn) : 1.0 ~ 1.7 중량%, 인(P) : 120 ppm 이하, 황(S) : 30 ppm 이하, 가용성 알루미늄(S-Al) : 0.01 ~ 0.05 중량%, 구리(Cu) : 0.01 ~ 0.20 중량%, 니오븀(Nb) : 0.01 중량% 이하, 보론(B) : 0.0005 중량% 이하, 칼슘(Ca) : 5 ~ 40 ppm 및 나머지 철(Fe)과 불가피한 불순물로 이루어지며, 인장강도(TS) : 500 ~ 600MPa 및 항복강도(YP) : 400 ~ 480MPa을 갖는 것을 특징으로 한다.
According to another aspect of the present invention, there is provided a steel material comprising 0.08 to 0.16% by weight of carbon (C), 0.1 to 0.5% by weight of silicon (Si), 1.0 to 1.7% by weight of manganese (Mn) (P): 120 ppm or less, S: 30 ppm or less, S-Al: 0.01 to 0.05 wt%, Cu: 0.01 to 0.20 wt%, Niobium (Nb) (Y) and a tensile strength (TS) of 500 to 600 MPa and a yield strength (YP) of at least 0.5% by weight, boron (B) at 0.0005% : 400 to 480 MPa.
본 발명에 따른 강재는 생산성을 향상시키기 위해, DQT 공정을 실시하면 평탄도가 저하되는 문제점을 합금 성분 및 제조 공정을 관리하여 평탄도가 우수한 유정관용 강재를 제공할 수 있다.
In order to improve the productivity of the steel material according to the present invention, it is possible to provide a well steel pipe having excellent flatness by controlling the alloy component and the manufacturing process, which is problematic in that the flatness is lowered by the DQT process.
도 1은 본 발명의 실시예에 따른 강재의 제조 방법을 나타낸 순서도이다.1 is a flowchart showing a method of manufacturing a steel material according to an embodiment of the present invention.
본 발명의 이점 및 특징, 그리고 그것들을 달성하는 방법은 첨부되는 도면과 함께 상세하게 후술되어 있는 실시예들을 참조하면 명확해질 것이다. 그러나, 본 발명은 이하에서 개시되는 실시예들에 한정되는 것이 아니라 서로 다른 다양한 형태로 구현될 것이며, 단지 본 실시예들은 본 발명의 개시가 완전하도록 하며, 본 발명이 속하는 기술분야에서 통상의 지식을 가진 자에게 발명의 범주를 완전하게 알려주기 위해 제공되는 것이며, 본 발명은 청구항의 범주에 의해 정의될 뿐이다. 명세서 전체에 걸쳐 동일 참조 부호는 동일 구성요소를 지칭한다.BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.
이하 첨부된 도면을 참조하여 본 발명의 바람직한 실시예에 따른 강재 및 그 제조 방법에 관하여 상세히 설명하면 다음과 같다.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a steel material according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.
강재Steel
본 발명에 따른 강재는 인장강도(TS) : 500 ~ 600MPa 및 항복강도(YP) : 400 ~ 480MPa을 만족하는 것을 목표로 한다.The steel material according to the present invention aims to satisfy a tensile strength (TS) of 500 to 600 MPa and a yield strength (YP) of 400 to 480 MPa.
이를 위해, 본 발명에 따른 강재는 탄소(C) : 0.08 ~ 0.16 중량%, 실리콘(Si) : 0.1 ~ 0.5 중량% 이하, 망간(Mn) : 1.0 ~ 1.7 중량%, 인(P) : 120 ppm 이하, 황(S) : 30 ppm 이하, 가용성 알루미늄(S-Al) : 0.01 ~ 0.05 중량%, 구리(Cu) : 0.01 ~ 0.20 중량%, 니오븀(Nb) : 0.01 중량% 이하, 보론(B) : 0.0005 중량% 이하, 칼슘(Ca) : 5 ~ 40 ppm 및 나머지 철(Fe)과 불가피한 불순물로 이루어질 수 있다.For this, the steel material according to the present invention contains 0.08 to 0.16% by weight of carbon (C), 0.1 to 0.5% by weight of silicon (Si), 1.0 to 1.7% by weight of manganese (Mn) (B) 0.01 to 0.20% by weight of niobium (Nb), 0.01 to 0.5% by weight of aluminum (S-Al) : 0.0005 wt% or less, calcium (Ca): 5 to 40 ppm, and the balance of iron (Fe) and unavoidable impurities.
또한, 본 발명에 따른 강재는 니켈(Ni) : 0.1 ~ 0.4 중량%, 크롬(Cr) : 0.1 ~ 0.3 중량%, 몰리브덴(Mo) : 0.02 ~ 0.12 중량%, 바나듐(V) : 0.005 ~ 0.030 중량% 및 질소(N) : 60 ppm 이하 중 선택된 1종 이상을 더 포함할 수 있다.
The steel material according to the present invention may further contain 0.1 to 0.4 wt% of nickel (Ni), 0.1 to 0.3 wt% of chromium (Cr), 0.02 to 0.12 wt% of molybdenum (Mo), 0.005 to 0.030 wt% of vanadium % And nitrogen (N): 60 ppm or less.
이하, 본 발명에 따른 강재에 포함되는 각 성분의 역할 및 그 함량에 대하여 설명하면 다음과 같다.
Hereinafter, the role and content of each component contained in the steel according to the present invention will be described.
탄소(C)Carbon (C)
탄소(C)는 강도 확보 및 미세조직 제어를 위해 첨가된다.Carbon (C) is added for securing strength and controlling microstructure.
탄소(C)는 본 발명에 따른 강재 전체 중량의 0.08 ~ 0.16 중량%의 함량비로 첨가하는 것이 바람직하다. 탄소(C)의 함량이 0.08 중량% 미만일 경우에는 제2상 조직의 분율이 저하되어 강도가 낮아지는 문제가 있다. 반대로, 탄소(C)의 함량이 0.16 중량%를 초과할 경우에는 인성 및 용접성이 저하되는 문제점이 있다.
The carbon (C) is preferably added in a content ratio of 0.08 to 0.16% by weight of the total weight of the steel material according to the present invention. When the content of carbon (C) is less than 0.08% by weight, the fraction of the second phase structure is lowered and the strength is lowered. On the contrary, when the content of carbon (C) exceeds 0.16% by weight, toughness and weldability are deteriorated.
실리콘(silicon( SiSi ))
실리콘(Si)은 페라이트 안정화 원소로써 페라이트 변태시 과냉도를 증가시켜 결정립을 미세화시키고 탄화물 형성을 억제하는 효과를 갖는다.Silicon (Si) is an element stabilizing ferrite, which has the effect of increasing subcooling during ferrite transformation to refine the grain and inhibit carbide formation.
실리콘(Si)은 본 발명에 따른 강재 전체 중량의 0.1 ~ 0.5 중량%의 함량비로 첨가하는 것이 바람직하다. 실리콘(Si)의 함량이 0.1 중량% 미만일 경우에는 그 첨가효과가 불충분한다. 반대로, 실리콘(Si)의 함량이 0.5 중량%를 초과할 경우에는 용접성을 떨어뜨리고 열연공정시 재가열 공정 및 열간 압연 시에 적스케일을 발생시켜 표면품질에 문제를 줄 뿐 아니라, 용접 후 도금성을 저해하는 문제점이 있다.
Silicon (Si) is preferably added in an amount of 0.1 to 0.5% by weight based on the total weight of the steel according to the present invention. When the content of silicon (Si) is less than 0.1% by weight, the effect of the addition is insufficient. On the other hand, when the content of silicon (Si) exceeds 0.5% by weight, the weldability is lowered, and the scale is generated at the reheating step and the hot rolling at the hot rolling step to cause problems in surface quality. There is a problem that it inhibits.
망간(manganese( MnMn ))
망간(Mn)은 오스테나이트 안정화 원소로서, 고용강화에 매우 효과적이고 강의 경화능 증가에 큰 영향을 미친다.Manganese (Mn) is an austenite stabilizing element, which is very effective for solid solution strengthening and has a great influence on the hardening ability of steel.
망간(Mn)은 본 발명에 따른 강재 전체 중량의 1.0 ~ 1.7 중량%의 함량비로 첨가하는 것이 바람직하다. 망간(Mn)의 함량이 1.0 중량% 미만일 경우에는 제2상 조직의 분율이 저하되어 강도 확보에 어려움이 따를 수 있다. 반대로, 망간(Mn)의 함량이 1.7 중량%를 초과할 경우에는 강에 고용된 황을 MnS로 석출하여 주조시 중심편석을 유발하여 강의 내부식성을 크게 떨어뜨린다.
Manganese (Mn) is preferably added in an amount of 1.0 to 1.7% by weight based on the total weight of the steel according to the present invention. When the content of manganese (Mn) is less than 1.0% by weight, the fraction of the second phase structure is lowered and it may be difficult to secure the strength. On the other hand, when the content of manganese (Mn) exceeds 1.7% by weight, sulfur precipitated in the steel is precipitated as MnS, which causes center segregation during casting, thereby greatly reducing the corrosion resistance of the steel.
인(P)In (P)
인(P)은 함량이 120 ppm을 초과할 경우에는 용접성을 악화시키고 슬라브 중심 편석에 의해 내부식성을 저하시키는 문제가 있다. 따라서, 인(P)은 본 발명에 따른 강재 전체 중량의 120 ppm 이하의 범위로 제한하는 것이 바람직하다.
When the content of phosphorus (P) exceeds 120 ppm, there is a problem that the weldability is deteriorated and the corrosion resistance is lowered due to slab center segregation. Therefore, phosphorus (P) is preferably limited to a range of 120 ppm or less based on the total weight of the steel material according to the present invention.
황(S)Sulfur (S)
황(S)은 함량이 30 ppm을 초과할 경우에는 강의 인성 및 용접성을 저해하고 MnS 비금속 개재물을 증가시켜 강의 내부식성을 저하시킬 수 있다. 따라서, 황(S)은 본 발명에 따른 강재 전체 중량의 30 ppm 이하의 범위로 제한하는 것이 바람직하다.
When the content of sulfur (S) exceeds 30 ppm, the toughness and weldability of the steel are impaired and the corrosion resistance of the steel may be lowered by increasing the MnS nonmetallic inclusions. Therefore, it is preferable to limit the sulfur (S) to a range of 30 ppm or less of the total weight of the steel material according to the present invention.
가용성 알루미늄(S-The soluble aluminum (S- AlAl ))
가용성 알루미늄(S-Al)은 강 중의 산소를 제거하기 위한 탈산제 역할을 한다.Soluble aluminum (S-Al) acts as a deoxidizer to remove oxygen in the steel.
가용성 알루미늄(S-Al)은 본 발명에 따른 강재 전체 중량의 0.01 ~ 0.05중량%의 함량비로 첨가하는 것이 바람직하다. 가용성 알루미늄(S-Al)의 함량이 0.01 중량% 미만일 경우에는 상기의 실리콘 첨가 효과를 제대로 발휘할 수 없다. 반대로, 가용성 알루미늄(S-Al)의 함량이 0.05 중량%를 초과할 경우에는 용접성을 저해하는 문제점이 있다.
The soluble aluminum (S-Al) is preferably added in an amount of 0.01 to 0.05% by weight based on the total weight of the steel according to the present invention. If the content of soluble aluminum (S-Al) is less than 0.01% by weight, the effect of adding silicon can not be exhibited properly. On the contrary, when the content of soluble aluminum (S-Al) exceeds 0.05% by weight, there is a problem that the weldability is deteriorated.
구리(Copper( CuCu ))
구리(Cu)는 고용강화에 기여하여 강도를 향상시키는 역할을 한다.Copper (Cu) contributes to solid solution strengthening and enhances strength.
구리(Cu)는 본 발명에 따른 강재 전체 중량의 0.01 ~ 0.20 중량%의 함량비로 첨가하는 것이 바람직하다. 구리(Cu)의 함량이 0.01 중량% 이하일 경우에는 그 첨가 효과가 미미하다. 반대로 구리(Cu)의 함량이 0.20 중량%를 초과할 경우에는 강재의 열간가공성을 저하시키고, 용접후 재열균열 감수성을 높이는 문제점이 있다.
Copper (Cu) is preferably added in an amount of 0.01 to 0.20% by weight based on the total weight of the steel according to the present invention. When the content of copper (Cu) is 0.01% by weight or less, the addition effect is insignificant. On the other hand, when the content of copper (Cu) exceeds 0.20% by weight, the hot workability of the steel is lowered and the susceptibility to reheat cracking after welding is increased.
니오븀(Niobium ( NbNb ))
니오븀(Nb)은 고온에서 탄소(C) 및 질소(N)와 결합하여 탄화물 또는 질화물을 형성한다. 니오븀계 탄화물 또는 질화물은 압연 시 결정립 성장을 억제하여 결정립을 미세화시킴으로써 강의 강도와 저온인성을 향상시킨다.Niobium (Nb) combines with carbon (C) and nitrogen (N) at high temperatures to form carbides or nitrides. Niobium-based carbides or nitrides improve grain strength and low-temperature toughness by suppressing grain growth during rolling and making crystal grains finer.
니오븀(Nb)은 본 발명에 따른 강판 전체 중량의 0.01 중량% 이하의 함량비로 첨가하는 것이 바람직하다. 니오븀(Nb)의 함량이 0.01 중량%를 초과할 경우에는 니오븀을 포함한 조대한 2차상들이 생성되어 균열이 발생하는 문제점이 있다.
Niobium (Nb) is preferably added at a content ratio of 0.01% by weight or less based on the total weight of the steel sheet according to the present invention. When the content of niobium (Nb) exceeds 0.01% by weight, coarse secondary phases including niobium are generated and cracks are generated.
보론(B)Boron (B)
보론(B)은 강력한 소입성 원소로서, 인(P)의 편석을 막아 강도를 향상시키는 역할을 한다. 만일, 인(P)의 편석이 발생할 경우에는 2차 가공취성이 발생할 수 있으므로, 보론(B)을 첨가하여 인(P)의 편석을 막아 가공취성에 대한 저항성을 증가시킨다.Boron (B) is a strong incipient element, which plays a role in blocking segregation of phosphorus (P) and improving strength. If segregation of phosphorus (P) occurs, secondary processing brittleness may occur, so boron (B) is added to block segregation of phosphorus (P) to increase resistance to process embrittlement.
보론(B)은 본 발명에 따른 강판 전체 중량의 0.0005 중량% 이하의 함량비로 첨가하는 것이 바람직하다. 보론(B)의 함량이 0.005 중량%를 초과하여 과다 첨가 될 경우에는 보론 산화물의 형성으로 강의 표면 품질을 저해하는 문제를 유발할 수 있다.
Boron (B) is preferably added in a content ratio of 0.0005% by weight or less based on the total weight of the steel sheet according to the present invention. If the boron (B) content exceeds 0.005% by weight, excess boron oxide may cause a problem of inhibiting the surface quality of the steel due to the formation of boron oxide.
칼슘(calcium( CaCa ))
칼슘(Ca)은 CaS를 형성시켜 강중의 황의 함량을 낮추고, 아울러 MnS 편석을 감소시켜 강의 청정도 및 황의 입계편석을 감소시켜 재가열 균열에 대한 저항성을 증가시키는 역할을 한다.Calcium (Ca) forms CaS to lower the content of sulfur in steel, and also reduces MnS segregation, thereby reducing steel segregation and sulfur segregation, thereby increasing resistance to reheating cracking.
칼슘(Ca)은 본 발명에 따른 강재 전체 중량의 5 ~ 40 ppm의 함량비로 첨가하는 것이 바람직하다. 칼슘(Ca)의 함량이 5 ppm 미만으로 첨가될 경우에는 칼슘(Ca)의 첨가효과를 보기 힘들다. 반대로, 칼슘(Ca)의 함량이 40 ppm을 초과할 경우 CaS 개재물을 형성함으로써 내부식성 및 용접성에 효과적은 MnS의 생성을 방해한다.
Ca is preferably added at a content ratio of 5 to 40 ppm based on the total weight of the steel according to the present invention. When the content of calcium (Ca) is less than 5 ppm, the addition of calcium (Ca) is hard to see. On the contrary, when the content of calcium (Ca) exceeds 40 ppm, formation of CaS inclusions hinders the production of MnS which is effective on corrosion resistance and weldability.
니켈(nickel( NiNi ))
니켈(Ni)은 망간(Mn)과 함께 대표적인 오스테나이트 안정화 원소로써 고용강화에 매우 효과적이고 강의 경화능 증가에 큰 영향을 미친다. 또한, 망간(Mn)과 마찬가지로 Ae1온도를 감소시킴으로써, 펄라이트의 라멜라 간격을 증가시킨다.Nickel (Ni), together with manganese (Mn), is a typical austenite stabilizing element, which is very effective in strengthening the solid solution and has a great influence on the increase of the hardenability of the steel. Further, by decreasing the temperature of Ae1 as in manganese (Mn), the lamellar spacing of pearlite is increased.
니켈(Ni)은 본 발명에 따른 강재 전체 중량의 0.1 ~ 0.4 중량%의 함량비로 첨가하는 것이 바람직하다. 니켈(Ni)의 함량이 0.1 중량% 미만일 경우에는 니켈 첨가 효과를 제대로 발휘할 수 없다. 반대로, 니켈(Ni)의 함량이 0.4 중량%를 초과하여 다량 첨가될 경우에는 적열취성을 유발하는 문제가 있다.
Nickel (Ni) is preferably added at a content ratio of 0.1 to 0.4% by weight based on the total weight of the steel material according to the present invention. If the content of nickel (Ni) is less than 0.1% by weight, the effect of adding nickel can not be exhibited properly. On the other hand, when the content of nickel (Ni) exceeds 0.4% by weight and is added in a large amount, there arises a problem of causing redispersible brittleness.
크롬(chrome( CrCr ))
크롬(Cr)은 페라이트 안정화 원소로 강도 향상에 기여한다. 또한 크롬은 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. In addition, chromium expands the delta ferrite region and transitions the hypo-peritectic region to the high carbon side to improve the slab surface quality.
크롬(Cr)은 본 발명에 따른 강재 전체 중량의 0.1 ~ 0.3 중량%로 첨가되는 것이 바람직하다. 크롬(Cr)의 함량이 0.1 중량% 미만일 경우, 그 첨가 효과가 미미하다. 반대로, 크롬(Cr)의 첨가량이 0.3 중량%를 초과하는 경우, 용접열영향부(HAZ) 인성 열화를 초래하는 문제점이 있다.
Cr (Cr) is preferably added in an amount of 0.1 to 0.3% by weight based on the total weight of the steel according to the present invention. When the content of chromium (Cr) is less than 0.1% by weight, the addition effect is insignificant. On the other hand, when the addition amount of chromium (Cr) exceeds 0.3% by weight, the weld heat affected zone (HAZ) tends to deteriorate toughness.
몰리브덴(molybdenum( MoMo ))
몰리브덴(Mo)은 안정적으로 탄화물을 생성하여, 크롬과 함께 고온강도 향상에 기여한다.Molybdenum (Mo) stably produces carbides, which together with chromium contribute to the improvement of high temperature strength.
몰리브덴(Mo)은 본 발명에 따른 강재 전체 중량의 0.02 ~ 0.12 중량%로 첨가되는 것이 바람직하다. 몰리브덴의 첨가량이 0.02 중량% 미만일 경우, 몰리브덴(Mo) 첨가에 따른 강도 향상 효과가 불충분하다. 반대로, 몰리브덴(Mo)의 첨가량이 0.12 중량%를 초과하면 저온 균열, 재열균열과 같은 용접성을 저해시키는 문제점이 있다.
Molybdenum (Mo) is preferably added in an amount of 0.02 to 0.12% by weight based on the total weight of the steel material according to the present invention. If the addition amount of molybdenum is less than 0.02 wt%, the effect of increasing the strength by adding molybdenum (Mo) is insufficient. On the contrary, if the amount of molybdenum (Mo) added exceeds 0.12 wt%, there is a problem that weldability such as low temperature cracking and reheat cracking is deteriorated.
바나듐(V)Vanadium (V)
바나듐(V)은 탄화물 생성원소로, 특히 고온강도를 상승시키는데 유효하다.Vanadium (V) is a carbide-generating element, and is particularly effective in increasing the high-temperature strength.
바나듐(V)은 본 발명에 따른 강재 전체 중량의 0.005 ~ 0.030 중량%로 첨가되는 것이 바람직하다. 바나듐(V)의 첨가량이 0.005 중량% 미만일 경우 강도 향상 효과가 불충분하다. 반대로, 바나듐(V)의 첨가량이 0.030 중량%를 초과하면 재열균열 감수성을 높이는 문제점이 있다.
Vanadium (V) is preferably added in an amount of 0.005 to 0.030% by weight based on the total weight of the steel material according to the present invention. When the addition amount of vanadium (V) is less than 0.005% by weight, the effect of improving the strength is insufficient. On the contrary, when the amount of vanadium (V) added exceeds 0.030 wt%, there is a problem of increasing the susceptibility to reheat cracking.
질소(N)Nitrogen (N)
질소(N)의 함량이 60 ppm을 초과할 경우에는 강의 충격특성 및 연신율을 떨어뜨리고 용접부 인성을 크게 저해한다. 따라서, 질소(N)는 본 발명에 따른 강재 전체 중량의 60 ppm 이하의 범위로 제한하는 것이 바람직하다.
If the content of nitrogen (N) exceeds 60 ppm, the impact characteristics and elongation of the steel are lowered and the toughness of the welded portion is significantly deteriorated. Therefore, nitrogen (N) is preferably limited to a range of 60 ppm or less of the total weight of the steel material according to the present invention.
또한, 본 발명에 따른 압력용기용 강재는 하기 식 1에 의해 정해지는 탄소 당량(Ceq)이 하기 식 2를 만족하는 것이 바람직하다.In the steel material for a pressure vessel according to the present invention, the carbon equivalent (Ceq) determined by the following formula 1 preferably satisfies the following formula (2).
식 1 : 0.43 ≥ Ceq Equation 1: 0.43? Ceq
식 2 : Ceq = [C] + [Si]/24 + [Mn]/6 + [Cr]/5 + [Mo]/4 + [V]/14 ([ ]는 각 성분의 중량%)[Formula 1] Ceq = [C] + [Si] / 24 + [Mn] / 6 + [Cr] / 5 + [Mo] / 4 + [V] / 14 [
탄소당량(Ceq)이 강재의 두께와 관계없이 0.43 미만인 경우, 고온강도가 부족하였다. 따라서, 탄소 당량은 0.43 이하가 바람직하고, 이를 만족하도록 탄소, 실리콘, 망간, 크롬, 몰리브덴 및 바나듐의 첨가량이 조절될 수 있다.
When the carbon equivalent (Ceq) was less than 0.43 regardless of the thickness of the steel, the high temperature strength was insufficient. Therefore, the carbon equivalent is preferably 0.43 or less, and the addition amount of carbon, silicon, manganese, chromium, molybdenum, and vanadium can be adjusted to satisfy the requirement.
강재의 제조 방법Manufacturing method of steel
도 1은 본 발명의 실시예에 따른 강재의 제조 방법을 나타낸 순서도이다.1 is a flowchart showing a method of manufacturing a steel material according to an embodiment of the present invention.
도 1을 참조하면, 본 발명에 따른 강재의 제조 방법은 슬라브 재가열 단계(S110), 열간 압연 단계(S120), 켄칭 단계(S130) 및 템퍼링 단계(S140)를 포함한다. 이때, 슬라브 재가열 단계(S110)는 반드시 수행되어야 하는 것은 아니나, 석출물의 재고용 등의 효과를 도출하기 위하여 실시하는 것이 더 바람직하다.
Referring to FIG. 1, a method of manufacturing a steel material according to the present invention includes a slab reheating step S110, a hot rolling step S120, a quenching step S130, and a tempering step S140. At this time, the slab reheating step (S110) is not necessarily performed, but it is more preferable to carry out the reheating step to obtain effects such as reuse of precipitates.
본 발명에 따른 강재의 대상이 되는 반제품 상태의 강 슬라브는 탄소(C) : 0.08 ~ 0.16 중량%, 실리콘(Si) : 0.1 ~ 0.5 중량% 이하, 망간(Mn) : 1.0 ~ 1.7 중량%, 인(P) : 120 ppm 이하, 황(S) : 30 ppm 이하, 가용성 알루미늄(S-Al) : 0.01 ~ 0.05 중량%, 구리(Cu) : 0.01 ~ 0.20 중량%, 니오븀(Nb) : 0.01 중량% 이하, 보론(B) : 0.0005 중량% 이하, 칼슘(Ca) : 5 ~ 40 ppm 및 나머지 철(Fe)과 불가피한 불순물로 이루어질 수 있다.The steel slab in the semi-finished product state to be the subject of the steel according to the present invention is composed of 0.08 to 0.16 wt% of carbon (C), 0.1 to 0.5 wt% or less of silicon (Si), 1.0 to 1.7 wt% of manganese (Mn) (P): 120 ppm or less, S: 30 ppm or less, S-Al: 0.01 to 0.05 wt%, Cu: 0.01 to 0.20 wt%, Niobium: , Boron (B): 0.0005 wt% or less, calcium (Ca): 5 to 40 ppm, and the balance of iron (Fe) and unavoidable impurities.
또한, 본 발명에 따른 강재는 니켈(Ni) : 0.1 ~ 0.4 중량%, 크롬(Cr) : 0.1 ~ 0.3 중량%, 몰리브덴(Mo) : 0.02 ~ 0.12 중량%, 바나듐(V) : 0.005 ~ 0.030 중량% 및 질소(N) : 60 ppm 이하 중 선택된 1종 이상을 더 포함할 수 있다.
The steel material according to the present invention may further contain 0.1 to 0.4 wt% of nickel (Ni), 0.1 to 0.3 wt% of chromium (Cr), 0.02 to 0.12 wt% of molybdenum (Mo), 0.005 to 0.030 wt% of vanadium % And nitrogen (N): 60 ppm or less.
슬라브 재가열Reheating slabs
슬라브 재가열 단계(S110)에서는 상기 조성을 갖는 강 슬라브를 SRT(Slab Reheating Temperature) : 1150 ~ 1250℃로 300 ~ 400분 동안 재가열한다. 여기서, 상기 강 슬라브는 제강공정을 통해 원하는 조성의 용강을 얻은 다음에 연속주조공정을 통해 얻어질 수 있다. 이때, 슬라브 재가열 단계(S110)에서는 연속주조공정을 통해 확보한 강 슬라브를 재가열하는 것을 통하여, 주조 시 편석된 성분을 재고용한다.In the slab reheating step S110, the steel slab having the above composition is reheated at a slab reheating temperature (SRT) of 1150 to 1250 占 폚 for 300 to 400 minutes. Here, the steel slab can be obtained through a continuous casting process after obtaining a molten steel having a desired composition through a steelmaking process. At this time, in the slab reheating step (S110), the steel slabs obtained through the continuous casting process are reheated to reuse the segregated components during casting.
이때, 슬라브 재가열 온도(SRT)가 1150℃ 미만일 경우에는 주조시 편석된 성분들이 충분히 분포되지 않는 문제점이 있다. 반대로, 슬라브 재가열 온도가 1250℃를 초과할 경우에는 조대한 오스테나이트가 형성되어 강도 확보가 어렵다.
If the slab reheating temperature (SRT) is less than 1150 ° C, the segregated components are not sufficiently distributed during casting. On the other hand, when the slab reheating temperature exceeds 1250 DEG C, coarse austenite is formed and it is difficult to secure strength.
열간 압연Hot rolling
열간 압연 단계(S120)에서는 재가열된 강재를 고르기 압연 및 길이내기 압연으로 마무리 압연 온도 FRT(Finish Rolling Temperature) : 850 ~ 950℃ 조건으로 열간 압연을 실시한다.In the hot rolling step (S120), the reheated steel is subjected to hot rolling at a finishing rolling temperature FRT (Finish Rolling Temperature) of 850 to 950 DEG C by means of rough rolling and longitudinal cold rolling.
마무리 압연 온도가 850℃ 미만일 경우에는 압연 중 변형 유기 페라이트 변태가 발생하여 펄라이트 양이 감소하므로 강도 저하를 야기시킨다. 반대로, 마무리 압연 온도가 950℃를 초과할 경우에는 연성 및 인성은 우수하나, 강도가 급격히 저하되는 문제가 있다.
If the finish rolling temperature is less than 850 ° C, the modified organic ferrite transformation occurs during rolling, and the amount of pearlite is reduced, which causes a decrease in strength. On the other hand, when the finish rolling temperature exceeds 950 DEG C, ductility and toughness are excellent, but the strength is rapidly lowered.
켄칭Quenched
켄칭(Quenching) 단계(S130)는 열간압연을 실시한 강재에 강도와 경도를 부여하기 위한 공정으로써, 켄칭 개시 온도는 910 ~ 950℃ 조건으로 스프레이 켄칭을 실시하여 상온까지 급랭을 실시한다.The quenching step (S130) is a step for imparting strength and hardness to the hot-rolled steel material. The quenching is started at a temperature of 910 to 950 占 폚, followed by quenching to room temperature.
켄칭 단계(S130)는, 열간 압연된 강재가 압연라인에 설치된 냉각존을 통과하면서 직접소입(Direct Quenching; DT)될 수 있다. 따라서, 종래의 재가열 켄칭 방법 중 재가열에 의한 오스테나이트화 열처리 공정을 생략함으로써, 제조원가를 절감할 수 있다. In the quenching step S130, the hot-rolled steel material may be directly quenched (DT) while passing through a cooling zone provided in the rolling line. Therefore, the manufacturing cost can be reduced by omitting the austenitizing heat treatment step by reheating in the conventional reheating quenching method.
또한, 켄칭 개시 온도가 910℃ 미만일 경우에는 표층부에 조대한 페라이트가 형성되어 인성이 크게 떨어진다. 반대로, 켄칭 개시 온도가 950℃를 초과할 경우에는 저온변태 조직들이 다량 형성되는 문제점이 있다.
When the quenching start temperature is less than 910 占 폚, coarse ferrite is formed in the surface layer portion and the toughness is greatly deteriorated. On the other hand, when the quenching start temperature exceeds 950 占 폚, there is a problem that a large amount of low-temperature transformation structures are formed.
템퍼링Tempering
템퍼링(Tempering) 단계(S140)는 켄칭을 실시한 강재의 내부응력을 제거하기 위한 공정으로써, 620 ~ 700℃의 조건으로 실시하는 것이 바람직하다. 템퍼링 온도가 620℃ 미만일 경우에는 템퍼링의 효과가 저조하여 인성의 확보가 어렵다. 반대로, 템퍼링 온도가 700℃를 초과할 경우에는 강도를 확보하는 것이 어렵다.The tempering step S140 is a step for removing the internal stress of the quenched steel, and is preferably carried out at a temperature of 620 to 700 占 폚. When the tempering temperature is less than 620 占 폚, the effect of tempering is low and it is difficult to secure toughness. On the other hand, when the tempering temperature exceeds 700 캜, it is difficult to secure the strength.
이때, 템퍼링 유지시간은 2.7*t + 10분 ~ 2.7*t + 30분 (t : 강재의 두께) 동안 실시하는 것이 바람직하다. 템퍼링 유지시간을 상술한 조건으로 실시할 때 충분한 인성을 확보할 수 있으며, 평탄도가 우수한 강재를 제조할 수 있다. 템퍼링 공정이 종료된 강재는 공랭을 통해 상온까지 냉각할 수 있다.
At this time, it is preferable to perform the tempering holding time for 2.7 * t + 10 min to 2.7 * t + 30 min (t: thickness of the steel). When the tempering holding time is carried out under the above-mentioned conditions, sufficient toughness can be ensured and a steel material having excellent flatness can be produced. The steel material after the tempering process can be cooled to room temperature through air cooling.
상기의 과정(S110 ~ S140)으로 제조되는 강재는 DQT(Direct Quenching&Tempering)를 실시함으로써, 재가열 공정을 2회에서 1회로 간소화하여 생산성이 우수하다.The steel produced in the above steps S110 to S140 is subjected to DQT (Direct Quenching & Tempering), so that the reheating process is simplified from one to two times, and productivity is excellent.
또한, 상기 방법으로 제조되는 강재는 인장강도(TS) : 500 ~ 600MPa 및 항복강도(YP) : 400 ~ 480MPa을 만족할 수 있다.
Also, the steel material produced by the above method can satisfy a tensile strength (TS) of 500 to 600 MPa and a yield strength (YP) of 400 to 480 MPa.
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 1 및 표 2에 기재된 조성 및 표 3에 기재된 공정 조건으로 실시예 1 ~ 3 및 비교예 1 ~ 2에 따른 시편들을 제조하였다. 이때, 실시예 1 ~ 3 및 비교예 1 ~ 2에 따른 시편들의 경우, 각각의 조성을 갖는 잉곳을 제조하고, 이를 압연모사 시험기를 이용하여 가열한 후, 열간 압연하고 공냉하였다.
The specimens according to Examples 1 to 3 and Comparative Examples 1 and 2 were prepared with the compositions shown in Tables 1 and 2 and the process conditions shown in Table 3. At this time, in the case of the specimens according to Examples 1 to 3 and Comparative Examples 1 and 2, ingots having respective compositions were prepared and heated using a rolling simulation tester, followed by hot rolling and air cooling.
[표 1] (단위 : 중량%)[Table 1] (unit:% by weight)
[표 2] (단위 : 중량%)[Table 2] (unit:% by weight)
[표 3][Table 3]
2. 기계적 물성 평가2. Evaluation of mechanical properties
표 4은 실시예 1 ~ 3 및 비교예 1 ~ 2에 따라 제조된 시편들의 기계적 물성에 대한 평가 결과를 나타낸 것이다.
Table 4 shows the evaluation results of the mechanical properties of the specimens prepared according to Examples 1 to 3 and Comparative Examples 1 and 2.
[표 4][Table 4]
표 1 내지 표 4를 참조하면, 실시예 1 ~ 3에 따라 제조된 시편들은 목표값에 해당하는 인장강도(TS) : 400 ~ 480MPa 이상 및 항복강도(YP) : 500 ~ 600MPa을 모두 만족하는 것을 알 수 있다.
Referring to Tables 1 to 4, the specimens prepared according to Examples 1 to 3 satisfy a tensile strength (TS) of 400 to 480 MPa or more and a yield strength (YP) of 500 to 600 MPa Able to know.
반면, 실시예 1과 비교하여, 합금 성분 및 그 조성 범위가 다르게 첨가되었으며, RQT(Reheat Quenching&Tempering)을 실시한 비교예 1 및 비교예 2에 따라 제조된 시편은 항복강도(YP)는 목표값을 만족하였으나, 인장강도(TS) 및 탄소당량(Ceq)은 목표값을 만족하지 못하는 것을 알 수 있다.
On the other hand, in comparison with Example 1, the specimens prepared according to Comparative Example 1 and Comparative Example 2 in which RQT (Reheat Quenching & Tempering) was applied were different in alloy component and composition range, and yield strength (YP) However, it can be seen that the tensile strength (TS) and the carbon equivalent (Ceq) do not satisfy the target value.
따라서, 본 발명에 따른 강재는 합금 성분 및 DQT 공정 조건 제어를 통해 재가열 공정을 1회로 간소화함으로써, 생산비용을 감소시킬 수 있고, 항복강도 : 400 ~ 480MPa 및 인장강도 : 500 ~ 600MPa을 만족하면서도 평탄도가 우수한 강재를 제공할 수 있다.
Therefore, the steel according to the present invention can reduce the production cost by simplifying the reheating process one time by controlling the alloying components and the DQT process condition, and it is possible to reduce the production cost by satisfying the yield strength: 400 to 480 MPa and the tensile strength: 500 to 600 MPa, It is possible to provide a steel material having a high degree of corrosion resistance.
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.
S110 : 슬라브 재가열 단계
S120 : 열간 압연 단계
S130 : 켄칭 단계
S140 : 템퍼링 단계S110: Slab reheating step
S120: Hot rolling step
S130: Quenching step
S140: Tempering step
Claims (6)
(b) 상기 재가열된 강재를 FRT(Finish Rolling Temperature) : 850 ~ 950℃ 조건으로 열간압연하는 단계;
(c) 상기 열간압연된 강재를 켄칭하는 단계; 및
(d) 상기 냉각된 강재를 620 ~ 700℃에서 템퍼링하는 단계;를 포함하는 것을 특징으로 하는 강재의 제조 방법.
(S): not more than 0.1 to 0.5 wt%, manganese (Mn): 1.0 to 1.7 wt%, phosphorus (P): not more than 120 ppm, sulfur (S) : Not more than 30 ppm, soluble aluminum (S-Al): 0.01 to 0.05 wt%, copper: 0.01 to 0.20 wt%, niobium (Nb): not more than 0.01 wt%, boron (B) Reheating a steel slab composed of calcium (Ca): 5 to 40 ppm and the balance of iron (Fe) and unavoidable impurities to a slab reheating temperature (SRT) of 1150 to 1250 占 폚;
(b) hot rolling the reheated steel material to a finishing rolling temperature (FRT) of 850 to 950 占 폚;
(c) quenching the hot-rolled steel material; And
(d) tempering the cooled steel at 620 to 700 占 폚.
상기 (a) 단계에서,
상기 강 슬라브는
니켈(Ni) : 0.1 ~ 0.4 중량%, 크롬(Cr) : 0.1 ~ 0.3 중량%, 몰리브덴(Mo) : 0.02 ~ 0.12 중량%, 바나듐(V) : 0.005 ~ 0.030 중량% 및 질소(N) : 60 ppm 이하 중 선택된 1종 이상을 더 포함하는 것을 특징으로 하는 강재의 제조 방법.
The method according to claim 1,
In the step (a)
The steel slab
(Ni): 0.1 to 0.4 wt%, chromium (Cr): 0.1 to 0.3 wt%, molybdenum (Mo): 0.02 to 0.12 wt%, vanadium (V): 0.005 to 0.030 wt% ppm or less, based on the total weight of the steel material.
상기 (a) 단계에서
상기 강 슬라브는
하기 수학식 1을 만족하는 탄소당량(Ceq)을 가지며,
하기 수학식 2를 만족하는 함량비로 탄소, 실리콘, 망간, 크롬, 몰리브덴 및 바나듐을 포함하는 것을 특징으로 하는 강재의 제조 방법.
식 1 : 0.43 ≥ Ceq
식 2 : Ceq = [C] + [Si]/24 + [Mn]/6 + [Cr]/5 + [Mo]/4 + [V]/14 ([ ]는 각 성분의 중량%)
(여기서, [ ]는 각 원소의 중량%)
The method according to claim 1,
In the step (a)
The steel slab
Has a carbon equivalent (Ceq) satisfying the following formula (1)
Silicon, manganese, chromium, molybdenum and vanadium in a content ratio satisfying the following formula (2).
Equation 1: 0.43? Ceq
[Formula 1] Ceq = [C] + [Si] / 24 + [Mn] / 6 + [Cr] / 5 + [Mo] / 4 + [V] / 14 [
(Where [] is the weight percentage of each element)
상기 (d) 단계에서
상기 템퍼링 유지시간은 2.7*t + 10분 ~ 2.7*t + 30분 (t : 강재의 두께)동안 실시하는 것을 특징으로 하는 강재의 제조 방법.
The method according to claim 1,
In the step (d)
Wherein said tempering holding time is performed for 2.7 * t + 10 min to 2.7 * t + 30 min (t: thickness of steel material).
인장강도(TS) : 500 ~ 600MPa 및 항복강도(YP) : 400 ~ 480MPa을 갖는 것을 특징으로 하는 강재.
(Si): 0.1 to 0.5 wt% or less, manganese (Mn): 1.0 to 1.7 wt%, phosphorus (P): 120 ppm or less, sulfur (S): 30 ppm 0.01 to 0.20 wt% of soluble aluminum (S-Al), 0.01 to 0.20 wt% of copper (Cu), 0.01 wt% or less of niobium (Nb), 0.0005 wt% or less of boron (B) ): 5 to 40 ppm and the balance of iron (Fe) and unavoidable impurities,
A tensile strength (TS) of 500 to 600 MPa and a yield strength (YP) of 400 to 480 MPa.
상기 강재는
니켈(Ni) : 0.1 ~ 0.4 중량%, 크롬(Cr) : 0.1 ~ 0.3 중량%, 몰리브덴(Mo) : 0.02 ~ 0.12 중량%, 바나듐(V) : 0.005 ~ 0.030 중량% 및 질소(N) : 60 ppm 이하 중 선택된 1종 이상을 더 포함하는 것을 특징으로 하는 강재.
6. The method of claim 5,
The steel
(Ni): 0.1 to 0.4 wt%, chromium (Cr): 0.1 to 0.3 wt%, molybdenum (Mo): 0.02 to 0.12 wt%, vanadium (V): 0.005 to 0.030 wt% ppm. < RTI ID = 0.0 > 11. < / RTI >
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