KR101543874B1 - Hot rolled steel for complex corrosion resistance to hydrochloric acid and sulfuric acid, having excellent corrosion resistance, and method of manufacturing the same - Google Patents
Hot rolled steel for complex corrosion resistance to hydrochloric acid and sulfuric acid, having excellent corrosion resistance, and method of manufacturing the same Download PDFInfo
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- KR101543874B1 KR101543874B1 KR1020130145717A KR20130145717A KR101543874B1 KR 101543874 B1 KR101543874 B1 KR 101543874B1 KR 1020130145717 A KR1020130145717 A KR 1020130145717A KR 20130145717 A KR20130145717 A KR 20130145717A KR 101543874 B1 KR101543874 B1 KR 101543874B1
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- steel sheet
- sulfuric acid
- hydrochloric acid
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 60
- 239000010959 steel Substances 0.000 title claims abstract description 60
- 230000007797 corrosion Effects 0.000 title claims abstract description 58
- 238000005260 corrosion Methods 0.000 title claims abstract description 58
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 title claims abstract description 48
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 title claims abstract description 42
- 238000004519 manufacturing process Methods 0.000 title abstract description 16
- 238000000034 method Methods 0.000 claims abstract description 10
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 238000001816 cooling Methods 0.000 claims description 23
- 238000004804 winding Methods 0.000 claims description 9
- 238000005098 hot rolling Methods 0.000 claims description 7
- 238000003303 reheating Methods 0.000 claims description 5
- 238000010791 quenching Methods 0.000 claims description 3
- 230000000171 quenching effect Effects 0.000 claims description 3
- 239000011259 mixed solution Substances 0.000 claims description 2
- 238000007654 immersion Methods 0.000 claims 1
- 239000002131 composite material Substances 0.000 abstract description 8
- 239000010935 stainless steel Substances 0.000 abstract description 7
- FZUJWWOKDIGOKH-UHFFFAOYSA-N sulfuric acid hydrochloride Chemical compound Cl.OS(O)(=O)=O FZUJWWOKDIGOKH-UHFFFAOYSA-N 0.000 abstract description 7
- 238000006477 desulfuration reaction Methods 0.000 abstract description 6
- 230000023556 desulfurization Effects 0.000 abstract description 6
- 239000000463 material Substances 0.000 abstract description 6
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 abstract description 3
- 239000003546 flue gas Substances 0.000 abstract description 3
- 239000010949 copper Substances 0.000 description 29
- 230000000052 comparative effect Effects 0.000 description 10
- 239000000203 mixture Substances 0.000 description 10
- 229910045601 alloy Inorganic materials 0.000 description 9
- 239000000956 alloy Substances 0.000 description 9
- 230000000694 effects Effects 0.000 description 6
- 239000011572 manganese Substances 0.000 description 6
- 230000007547 defect Effects 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 238000005096 rolling process Methods 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 229910000655 Killed steel Inorganic materials 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 239000011593 sulfur Substances 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- KZBUYRJDOAKODT-UHFFFAOYSA-N Chlorine Chemical compound ClCl KZBUYRJDOAKODT-UHFFFAOYSA-N 0.000 description 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical compound OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000010828 elution Methods 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000001141 propulsive effect Effects 0.000 description 1
- 230000000979 retarding effect Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- CADICXFYUNYKGD-UHFFFAOYSA-N sulfanylidenemanganese Chemical compound [Mn]=S CADICXFYUNYKGD-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- 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
-
- 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
- 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
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
-
- 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
- C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
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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)
- Heat Treatment Of Sheet Steel (AREA)
Abstract
본 발명은 우수한 내식성을 갖는 황산 및 염산 복합내식용 열연강판 및 그 제조방법에 관한 것으로서, 보다 상세하게는 화력 발전소 탈황, 탈질설비, 예열기 및 이들의 부품 등의 소재로 바람직하게 적용될 수 있는 황산 및 염산 복합내식용 열연강판 및 그 제조방법에 관한 것이다. 본 발명의 일 실시형태는 중량%로, C: 0.05~0.1%, Mn: 0.5초과~1.5%, P: 0.02%이하, S: 0.02%이하, Al: 0.01%~0.1%, Cu: 0.2~0.7%, 잔부 Fe 및 기타 불가피한 불순물을 포함하고, 표면 직하에 200nm이상의 두께를 갖는 Cu 농축층이 형성된 우수한 내식성을 갖는 황산 및 염산 복합내식용 열연강판 및 그 제조방법을 제공한다.
본 발명에 따르면, 강판 표면에 내식층을 형성시킴으로써 종래 황산-염산 복합 내식강에 비하여 저합금계이면서도 우수한 내식성을 가지는 열연강판을 제공할 수 있다. 또한, 본 발명의 열연강판은 황산 및 염산에 대한 복합 부식이 발생하는 발전소 탈질, 탈황설비, 보일러의 배연가스 배관 및 예열기의 비교적 두꺼운 두께를 요구하는 소재에 적합하게 적용할 수 있을 뿐만 아니라, 이들의 수명을 크게 연장하는 효과가 있다.The present invention relates to a sulfuric acid and hydrochloric acid resistant hot rolled steel sheet having excellent corrosion resistance and a method of manufacturing the same, and more particularly, to a hot rolled steel sheet for sulfuric acid and hydrochloric acid resistant to sulfuric acid and hydrochloric acid which can be suitably applied as a material for desulfurization, And a method of manufacturing the same. An embodiment of the present invention is a steel sheet comprising, by weight, 0.05 to 0.1% of C, 0.5 to 1.5% of Mn, 0.02% or less of P, 0.02% or less of S, 0.01 to 0.1% 0.7% by weight of Fe, and the balance of Fe and other unavoidable impurities, and having a Cu concentration layer having a thickness of 200 nm or more directly under the surface, and a process for producing the same.
According to the present invention, by forming a corrosion resistant layer on the surface of a steel sheet, a hot-rolled steel sheet having a corrosion resistance comparable to that of conventional sulfuric acid-hydrochloric acid composite corrosion resistant steel can be provided. In addition, the hot-rolled steel sheet of the present invention can be suitably applied to materials requiring relatively thick thicknesses of denitrification plants, desulfurization facilities, flue gas piping of boilers, and preheaters where complex corrosion of sulfuric acid and hydrochloric acid occurs, It is possible to greatly extend the life of the battery.
Description
본 발명은 우수한 내식성을 갖는 황산 및 염산 복합내식용 열연강판 및 그 제조방법에 관한 것으로서, 보다 상세하게는 화력 발전소 탈황, 탈질설비, 예열기 및 이들의 부품 등의 소재로 바람직하게 적용될 수 있는 황산 및 염산 복합내식용 열연강판 및 그 제조방법에 관한 것이다.
The present invention relates to a sulfuric acid and hydrochloric acid resistant hot rolled steel sheet having excellent corrosion resistance and a method of manufacturing the same, and more particularly, to a hot rolled steel sheet for sulfuric acid and hydrochloric acid resistant to sulfuric acid and hydrochloric acid which can be suitably applied as a material for desulfurization, And a method of manufacturing the same.
황산 또는 황산-염산 복합 내식강은 석탄 또는 석유 등 화석 연료를 연소하면서 생성되는 아황산가스 및 염소가스가 함유된 배기가스가 수분과 반응을 하여 황산 및 염산을 생성하여 황산 또는 황산-염산 복합 부식이 심각한 화력발전소 탈황 및 탈질설비 또는 복합 발전소의 배관 및 GGH(Gas Gas Heater)의 비교적 두꺼운 두께의 강판을 사용해야 하는 열소자(heat element)소재 등으로 이용된다.
Sulfuric acid or sulfuric acid-hydrochloric acid composite corrosion resistant steel reacts with moisture in exhaust gas containing sulfurous acid gas and chlorine gas generated by burning fossil fuel such as coal or petroleum to generate sulfuric acid and hydrochloric acid, and sulfuric acid or sulfuric acid- It is used as a heat element material which requires the use of a relatively thick steel sheet of a pipe and GGH (Gas Gas Heater) of a severe thermal power plant desulfurization and denitrification facility or a combined power plant.
일반적으로 황산-염산 복합 내식강은 황산 및 염산 복합 분위기에서 일반강 보다 부식속도를 지연시키기 위하여 강중에 구리(Cu)를 다량 첨가하는 것으로 알려져 왔다. Cu는 다른 첨가 원소에 비해 황산 부식속도를 크게 지연시키는 효과가 월등하지만 많이 첨가할 경우 열간압연시 강판의 크랙발생을 유발하는 등의 이유로 적당량의 Cu를 첨가하면서 다른 원소를 복합 첨가하는 강(특허문헌 1 내지 3)이 개발되었다.
In general, sulfuric acid - hydrochloric acid composite corrosion resistant steel has been known to add a large amount of copper (Cu) to the steel in order to delay the corrosion rate in a mixed atmosphere of sulfuric acid and hydrochloric acid. Cu has a superior effect of significantly retarding the sulfuric acid corrosion rate compared to other additive elements. However, when added in large amounts, Cu causes a crack in the steel sheet during hot rolling, Documents 1 to 3) have been developed.
이와 같이, 황산-염산 복합 내식강에서 Cu의 함량이 높을수록 내식성의 향상이 가능한 반면, Cu는 고가의 원소로서 함량이 증가할수록 제조원가가 높아질 뿐만 아니라 융점이 낮은 Cu가 편석되거나 농도가 높은 부위에서는 약간의 변형에 의해서도 크랙이 발생하기 쉬워, 연속 주조 과정에서 가공을 많이 받는 슬라브의 코너 등에 크랙이 발생하고 열간압연 후에는 표면결함으로 잔존하여 다른 부위보다 먼저 부식하는 문제점이 있다.
As described above, the higher the content of Cu in the sulfuric acid-hydrochloric acid composite corrosion resistant steel, the better the corrosion resistance. On the other hand, the higher the content of Cu is, the higher the production cost becomes. Cracks are easily generated even by slight deformation, cracks are generated in the corners of the slabs which are subjected to a lot of processing in the continuous casting process, and after the hot rolling, they remain as surface defects and corrode earlier than other parts.
이에, 황산-염산 복합 내식강에서 구리(Cu)의 함량은 최소화하면서, 높은 복합내식성을 확보할 수 있는 방안이 요구되고 있는 실정이다.
Therefore, there is a demand for a method for securing high complex corrosion resistance while minimizing the content of copper (Cu) in sulfuric acid-hydrochloric acid combined corrosion resistant steel.
본 발명은 전술한 문제점을 해결하기 위해 성분계와 공정조건을 적절하게 제어함으로써 동일 함량의 Cu를 첨가한 강에 비해 황산 및 염산이 복합적으로 존재하는 부식환경에서 우수한 내식성을 갖는 열연강판 및 그 제조방법을 제공하고자 하는 것이다.
The present invention provides a hot-rolled steel sheet having excellent corrosion resistance in a corrosive environment in which sulfuric acid and hydrochloric acid are present in a complex manner compared to a steel to which the same amount of Cu is added by appropriately controlling the component system and the process conditions to solve the above- .
본 발명의 일 실시형태는 중량%로, C: 0.05~0.1%, Mn: 0.5초과~1.5%, P: 0.02%이하, S: 0.02%이하, Al: 0.01%~0.1%, Cu: 0.2~0.7%, 잔부 Fe 및 기타 불가피한 불순물을 포함하고, 표면 직하에 200nm이상의 두께를 갖는 Cu 농축층이 형성된 우수한 내식성을 갖는 황산 및 염산 복합내식용 열연강판을 제공한다.
An embodiment of the present invention is a steel sheet comprising, by weight, 0.05 to 0.1% of C, 0.5 to 1.5% of Mn, 0.02% or less of P, 0.02% or less of S, 0.01 to 0.1% 0.7% by weight, the balance Fe and other unavoidable impurities, and having a Cu concentration layer having a thickness of at least 200 nm right under the surface, and having excellent corrosion resistance.
본 발명의 다른 실시형태는 중량%로, C: 0.05~0.1%, Mn: 0.5초과~1.5%, P: 0.02%이하, S: 0.02%이하, Al: 0.01%~0.1%, Cu: 0.2~0.7%, 잔부 Fe 및 기타 불가피한 불순물을 포함하는 강 슬라브를 1100~1300℃에서 재가열하는 단계; 상기 재가열된 강 슬라브를 850~950℃에서 마무리 열간압연하여 열연강판을 얻는 단계; 상기 열연강판을 80~100℃/sec로 급냉하는 단계; 상기 냉각된 강판을 670~750℃에서 권취하는 단계; 및 상기 권취된 강판을 30~50℃/hr로 300~400℃까지 서냉하는 단계를 포함하는 우수한 내식성을 갖는 황산 및 염산 복합내식용 열연강판의 제조방법을 제공한다.
In another embodiment of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: 0.05 to 0.1% of C, 0.5 to 1.5% of P, 0.02% or less of P, 0.02% or less of S, 0.7%, the balance Fe and other unavoidable impurities at 1100-1300 캜; Hot-rolling the reheated steel slab at 850 to 950 ° C to obtain a hot-rolled steel sheet; Quenching the hot-rolled steel sheet at 80 to 100 ° C / sec; Winding the cooled steel sheet at 670 to 750 ° C; And slowly cooling the rolled steel sheet at 30 to 50 ° C / hr to 300 to 400 ° C. The present invention also provides a method of manufacturing a hot rolled steel sheet for sulfuric acid and hydrochloric acid composite with excellent corrosion resistance.
본 발명에 따르면, 강판 표면에 내식층을 형성시킴으로써 종래 황산-염산 복합 내식강에 비하여 저합금계이면서도 우수한 내식성을 가지는 열연강판을 제공할 수 있다. 또한, 본 발명의 열연강판은 황산 및 염산에 대한 복합 부식이 발생하는 발전소 탈질, 탈황설비, 보일러의 배연가스 배관 및 예열기의 비교적 두꺼운 두께를 요구하는 소재에 적합하게 적용할 수 있을 뿐만 아니라, 이들의 수명을 크게 연장하는 효과가 있다.
According to the present invention, by forming a corrosion resistant layer on the surface of a steel sheet, a hot-rolled steel sheet having a corrosion resistance comparable to that of conventional sulfuric acid-hydrochloric acid composite corrosion resistant steel can be provided. In addition, the hot-rolled steel sheet of the present invention can be suitably applied to materials requiring relatively thick thicknesses of denitrification plants, desulfurization facilities, flue gas piping of boilers, and preheaters where complex corrosion of sulfuric acid and hydrochloric acid occurs, It is possible to greatly extend the life of the battery.
본 발명자들은 존 다량의 Cu를 포함하는 황산-염산 복합 내식강에 비해 합금조성을 최적화시키면서도 황산 및 염산에 대한 복합내식성이 우수한 열연강판을 얻기 위하여 깊이 연구한 결과, 합금조성을 보다 적극적으로 제어함과 동시에, 열간압연공정에서 냉각조건을 제어함으로써 Cu 농축층을 형성시킬 수 있고, 상기 Cu 농축층이 황산 및 염산이 복합적으로 존재하는 부식환경에서 내식층으로 변화함에 따라 매우 뛰어난 내식성을 확보할 수 있다는 식견하에 본 발명을 완성하게 되었다.
The inventors of the present invention have conducted intensive studies to obtain a hot-rolled steel sheet excellent in complex corrosion resistance against sulfuric acid and hydrochloric acid while optimizing the composition of the alloy compared with the sulfuric acid-hydrochloric acid composite corrosion resistant steel containing a large amount of Cu, , The Cu concentration layer can be formed by controlling the cooling conditions in the hot rolling process, and the Cu concentration layer can be provided with excellent corrosion resistance as the corrosion resistant layer changes from the corrosive environment in which sulfuric acid and hydrochloric acid are mixed to the corrosion resistant layer To complete the present invention.
이하, 본 발명에 대하여 상세히 설명한다. 하기 설명되는 합금조성의 %는 중량%이다.
Hereinafter, the present invention will be described in detail. The percent of the alloy composition described below is% by weight.
C: 0.05~0.1%C: 0.05 to 0.1%
C는 강도를 향상시키기 위해 첨가하는 원소로서, 그 함량이 0.05% 미만일 경우에는 목표로 하는 강도 확보가 어려우며, 반면, 0.1%를 초과할 경우에는 용접성이 매우 저하되어 용접 적용시 결함이 발생할 가능성이 높고 내식성 또한 크게 저하한다. 따라서, 상기 C는 0.05~0.1%의 범위를 갖는 것이 바람직하다.
C is an element added to improve the strength. When the content is less than 0.05%, it is difficult to secure the desired strength. On the other hand, when the content exceeds 0.1%, the weldability is very low, And the corrosion resistance is greatly deteriorated. Therefore, it is preferable that C is in the range of 0.05 to 0.1%.
Mn: 0.5초과~1.5%Mn: more than 0.5 to 1.5%
Mn은 강중에 고용되어 있는 황을 망간황화물로 석출함으로써 상기 고용 황에 의한 적열취성(Hot shortness)을 방지하는 역할을 하며, 고용강화 효과를 발현하는 원소이다. 상기 Mn이 0.5%이하일 경우에는 MnS석출량이 적어 FeS생성에 의한 적열취성 발생 가능성이 있고 목표강도를 확보하기 곤란하다는 단점이 있으며, Mn함량이 1.5%를 초과하는 경우에는 적열취성이 발생할 확률이 적을 뿐만 아니라, 첨가량대비 강도 상승효과가 적으므로, 상기 Mn의 함량은 0.5초과~1.5%의 범위를 갖는 것이 바람직하다.
Mn plays a role of preventing hot shortness caused by the above-mentioned solid solution sulfur by precipitating sulfur dissolved in steel into manganese sulfide, and is an element which exhibits solid solution strengthening effect. When the content of Mn is 0.5% or less, there is a possibility that the amount of MnS precipitates is small, and there is a possibility of generation of fogging due to FeS generation and it is difficult to secure the target strength. When the Mn content exceeds 1.5% In addition, since the effect of increasing the strength with respect to the addition amount is small, the content of Mn is preferably in the range of more than 0.5 to 1.5%.
P: 0.02%이하P: not more than 0.02%
P는 강 중 불가피하게 첨가되는 원소이며, 그 함량이 0.02%를 초과하게 되면 목표로 하는 복합내식성이 크게 저하되는 문제가 있다. 따라서, P의 함량은 0.02%이하로 제어하는 것이 바람직하다.
P is an element which is inevitably added in the steel, and when the content exceeds 0.02%, there is a problem that the intended composite corrosion resistance is largely lowered. Therefore, it is preferable to control the P content to 0.02% or less.
S: 0.02%이하S: not more than 0.02%
S는 제조공정상 불가피하게 함유되는 불순물이나, 0.02%를 초과하는 경우에는 열간취성에 의한 결함이 발생할 가능성이 높고 내식성을 저하시키기 때문에, 상기 S의 함량은 0.02%이하로 제어하는 것이 바람직하다.
S is an impurity inevitably contained in the product inevitably in the manufacturing process. If it exceeds 0.02%, the possibility of occurrence of defects due to hot brittleness is high and the corrosion resistance is lowered. Therefore, the content of S is preferably controlled to 0.02% or less.
Al: 0.01%~0.1%Al: 0.01% to 0.1%
Al은 알루미늄 킬드강(Al-Killed)강 제조시 불가피하게 첨가되는 원소로서, 탈산효과를 위해 0.01%이상 첨가된다. 다만, 상기 Al이 0.1%를 초과하는 경우에는 강판의 표면결함을 유발할 확률이 높아질 뿐만 아니라 용접성이 저하하게 되는 문제가 있다. 따라서, 상기 Al의 함량은 0.0~0.1%의 범위를 갖는 것이 바람직하다.
Al is an element which is inevitably added in the production of aluminum killed steel (Al-Killed steel), and is added by 0.01% or more for deoxidizing effect. However, when the content of Al exceeds 0.1%, there is a problem that not only the probability of causing surface defects of the steel sheet increases but also the weldability is deteriorated. Therefore, it is preferable that the content of Al is in the range of 0.0 to 0.1%.
Cu: 0.2~0.7%Cu: 0.2 to 0.7%
Cu는 내황산 및 내염산의 복합부식특성을 고려하여 첨가하는 원소로서, 그 함량이 0.2% 미만이면 목표로 하는 복합내식성을 확보하기 어려우므로, 0.2% 이상으로 첨가하는 것이 바람직하다. 상기 Cu는 그 함량이 증가할수록 복합내식성을 향상시키지만, 그 함량이 0.7%를 초과하게 되면 내식성 증가폭이 크게 저하하고, 제조원가가 급격히 상승하는 문제가 있다. 따라서, 상기 Cu의 함량은 0.2~0.7%의 범위를 갖는 것이 바람직하다.
Cu is an element to be added in consideration of the complex corrosion property of sulfuric acid and hydrochloric acid. When the content is less than 0.2%, it is difficult to secure the intended complex corrosion resistance. Therefore, it is preferable that Cu is added in an amount of 0.2% or more. As the content of Cu increases, the complex corrosion resistance is improved. However, when the content of Cu exceeds 0.7%, the increase in corrosion resistance greatly decreases and the manufacturing cost increases sharply. Therefore, the content of Cu is preferably in the range of 0.2 to 0.7%.
본 발명이 제안하는 열연강판은 전술한 합금조성 이외에 잔부 Fe 및 불가피한 불순물로 이루어진다. 다만, 상기 합금조성 이외에 다른 조성이 포함될 수 없음을 배제하는 것은 아니다.
The hot-rolled steel sheet proposed by the present invention is composed of the remainder Fe and inevitable impurities in addition to the alloy composition described above. However, it is not excluded that compositions other than the alloy composition can not be included.
한편, 본 발명이 제안하는 열연강판은 그 표면 직하에 표면 직하에 200nm이상의 두께를 갖는 Cu 농축층이 형성되는 것이 바람직하다. 상기 Cu 농축층은 강재 제조시에는 농화된 상태로 존재하다가 황산 및 염산에 의한 부식환경하에서는 CuxO 등과 같은 Cu 산화물의 형태로 변하게 됨으로써 내식성을 매우 우수한 수준으로 향상시킨다. 상기 농축층이 200nm 미만일 경우에는 본 발명이 목표로 하는 8.0mg/㎠/Hr이하의 부식감량을 확보하기 곤란하여 우수한 내식성을 얻기 곤란하다. 상기 Cu 농축층은 두꺼워질수록 부식감량이 낮아지므로, 본 발명에서는 상기 Cu 농축층 두께의 상한에 대해서 특별히 한정하지 않는다. 다만, 400nm를 초과하는 경우에는 다량의 합금 첨가 대비 내식성 향상 효과가 낮아질 뿐만 아니라 제조원가가 과도하게 상승하는 문제가 있으므로, 상기 Cu 농축층은 200~400nm의 두께를 가지는 것이 바람직하다.
On the other hand, in the hot-rolled steel sheet proposed by the present invention, it is preferable that a Cu concentrated layer having a thickness of 200 nm or more is formed directly under the surface immediately below the surface. The Cu-enriched layer is present in a concentrated state during the manufacture of steel, and in the corrosive environment of sulfuric acid and hydrochloric acid, it changes into Cu oxide such as Cu x O, thereby improving the corrosion resistance to a very good level. When the concentration of the concentrated layer is less than 200 nm, it is difficult to secure a corrosion loss of 8.0 mg / cm 2 / Hr or less, which is the target of the present invention, and thus it is difficult to obtain excellent corrosion resistance. As the thickened Cu layer becomes thicker, the amount of corrosion loss decreases. In the present invention, the upper limit of the thickness of the Cu thick layer is not particularly limited. However, when it is more than 400 nm, there is a problem that the effect of improving the corrosion resistance as compared with the addition of a large amount of alloy is lowered and the manufacturing cost is increased excessively, so that the Cu concentration layer preferably has a thickness of 200 to 400 nm.
전술한 바와 같이 제공되는 본 발명의 강판은 황산 및 염산에 대한 복합 부식 환경하에서 부식감량이 8mg/㎠/Hr이하로서 매우 우수한 내식성을 확보할 수 있어, 황산/염산 복합 부식이 발생하는 발전소 탈질, 탈황설비, 보일러의 배연가스 배관이나 예열기 열소자 등에 바람직하게 적용될 수 있다.
The steel sheet of the present invention provided as described above has a corrosion loss of not more than 8 mg / cm 2 / Hr under a complex corrosion environment for sulfuric acid and hydrochloric acid, so that excellent corrosion resistance can be secured and denitrification of power plants, Desulfurization equipment, flue gas piping of boilers, preheater thermal elements, and the like.
이하, 본 발명의 강판 제조방법에 대하여 설명한다.
Hereinafter, the steel sheet manufacturing method of the present invention will be described.
우선, 전술한 바와 같이 제안되는 성분계를 갖는 강 슬라브를 준비한 뒤, 재가열하는 공정을 거친다. 통상, 재가열 공정은 후속되는 압연을 원활히 하기 위하여 행해지는 것으로서, 압연 온도를 확보할 수 있는 온도범위에서 행해지는 것이 바람직하다. 본 발명에서는 상기 재가열 공정이 1100~1300℃의 온도범위에서 행하여는 것이 바람직하며, 이때 재가열 온도가 1300℃를 초과하게 되면 융점이 낮은 Cu가 용출하여 슬라브 표면에 크랙(crack)이 발생할 가능성이 높으며, 반면 1100℃ 미만이면 후속되는 열간압연시의 온도를 확보하기 어려운 문제가 있다.
First, a steel slab having a component system as described above is prepared and then subjected to a reheating step. In general, the reheating step is performed in order to smooth subsequent rolling, and is preferably performed in a temperature range in which the rolling temperature can be ensured. In the present invention, it is preferable that the reheating process is performed in a temperature range of 1100 to 1300 ° C. At this time, when the reheating temperature exceeds 1300 ° C., there is a high possibility that cracks are generated on the slab surface due to elution of Cu having a low melting point On the other hand, if it is less than 1100 ° C, there is a problem that it is difficult to secure the temperature at the time of the subsequent hot rolling.
상기 재가열된 강 슬라브를 850~950℃에서 마무리 열간압연하여 열연강판을 얻는다. 상기 마무리 압연온도가 850℃미만일 경우에는 연신된 결정립의 생성으로 인해 연신율이 크게 저하하고 방향별 재질 편차가 심해질 우려가 있으며, 950℃를 초과하는 경우에는 결정립이 과도하게 성장하여 강도가 저하될 수 있으므로, 상기 마무리 열간압연온도는 850~950℃의 범위를 갖는 것이 바람직하다.
The reheated steel slab is hot-rolled at 850 to 950 ° C to obtain a hot-rolled steel sheet. If the finish rolling temperature is lower than 850 ° C, the elongation rate may be significantly lowered due to the formation of the elongated crystal grains and the material deviation may be increased by the direction. When the finish rolling temperature exceeds 950 ° C, Therefore, the finish hot rolling temperature is preferably in the range of 850 to 950 ° C.
상기 얻어진 열연강판을 강판 표면온도기준으로 80~150℃/sec로 급냉한다. 상기와 같은 높은 속도의 냉각을 통해 권취 후 내식성에 유리한 합금원소가 이동하는데 필요한 추진력을 증가시킬 수 있다. 다만, 상기 냉각속도가 80℃/sec미만일 경우에는 추진력이 낮아 원자이동이 어려워지며, 이에 따라 복합적인 부식환경에서 내식층의 형성량이 적어지는 단점이 있다. 상기 냉각속도가 증가할수록 원자이동의 추진력이 증가하나, 150℃/sec를 초과할 경우에는 내부 온도가 너무 낮아져 복열이 활발히 진행되지 않아 내식층 형성에 유리한 합금원소의 이동이 원활하게 이루어지지 않을 수 있다. 따라서, 상기 냉각속도는 80~150℃/sec의 범위인 것이 바람직하다. 상기 냉각속도는 90~150℃/sec인 것이 보다 바람직하며, 100~150℃/sec인 것이 보다 더 바람직하다.
The obtained hot-rolled steel sheet is quenched at 80 to 150 ° C / sec based on the steel sheet surface temperature. Through such high speed cooling, it is possible to increase the propulsive force necessary for the alloying element to favor the corrosion resistance after winding. However, when the cooling rate is less than 80 ° C / sec, the driving force is low and the movement of the atoms becomes difficult, which results in a disadvantage that the formation amount of the corrosion resistant layer is reduced in a complex corrosive environment. When the cooling rate is increased, the driving force of the atomic movement is increased. However, when the cooling rate is higher than 150 ° C / sec, the internal temperature becomes too low and the double heat does not progress actively. have. Therefore, the cooling rate is preferably in the range of 80 to 150 DEG C / sec. The cooling rate is more preferably 90 to 150 DEG C / sec, and still more preferably 100 to 150 DEG C / sec.
이후, 상기 강판을 670~750℃에서 권취한다. 상기 권취온도가 670℃미만일 경우에는 권취공정에서 원자의 이동이 용이하지 않아 농축층의 형성이 곤란하여 부식환경에서 내식층이 형성되지 않아 충분한 내식성을 확보하기 어려울 수 있다. 상기 권취온도가 750℃를 초과하는 경우에는 복열되는 온도가 너무 높아 권취된 강판이 찌그러지는 등 결함이 발생할 수 있으므로, 상기 권취온도는 670~750℃의 범위를 갖는 것이 바람직하다.
Thereafter, the steel sheet is wound at 670 to 750 ° C. If the coiling temperature is less than 670 캜, it is difficult to move the atoms in the winding step, so that it is difficult to form a thickened layer, so that a corrosion resistant layer is not formed in a corrosive environment and it may be difficult to secure sufficient corrosion resistance. When the coiling temperature exceeds 750 캜, the coiling temperature may be too high to cause defects such as warpage of the wound steel sheet. Therefore, the coiling temperature preferably ranges from 670 to 750 캜.
한편, 상기 권취시에는 상기 강판의 표면이 복열현상에 의해 700℃이상이 되도록 하는 것이 바람직하다. 상기 냉각 공정을 통해 강판 내부의 온도가 670~750℃의 범위를 갖도록 하더라도 상기 강판의 표면은 급냉에 의해 상기 온도범위보다 낮은 온도를 가지게 된다. 따라서, 상기 복열 과정을 거침으로써 내식층 형성에 유리한 합금원소의 이동이 활발해지도록 하고, 이를 통해 농축층이 충분한 두께로 형성되도록 할 수 있다. 상기 효과를 충분히 얻기 위해서는 상기 복열을 거친 강판의 표면 온도가 700℃이상인 것이 바람직하다. 다만, 충분한 복열 과정을 거치라도 강판의 표면온도가 750℃를 초과하기는 어렵다.
On the other hand, at the time of winding, it is preferable that the surface of the steel sheet is heated to 700 ° C or more by double heat. The surface of the steel sheet has a temperature lower than the temperature range by quenching even if the temperature inside the steel sheet is in the range of 670 to 750 ° C through the cooling process. Therefore, by moving the alloying element advantageous for the formation of the corrosion resistant layer through the repetition process, the concentrated layer can be formed to have a sufficient thickness. In order to sufficiently obtain the above effect, it is preferable that the surface temperature of the steel sheet subjected to the double heat treatment is 700 ° C or higher. However, it is difficult for the surface temperature of the steel sheet to exceed 750 ° C even after sufficient repetition.
상기 권취된 강판을 30~50℃/hr의 속도로 300~400℃까지 서냉한다. 상기 냉각속도가 과도하게 빠른 경우에는 농축층을 형성하는 원소인 Cu의 이동이 충분하지 못하여 충분한 두께의 농축층 형성이 곤란할 수 있으므로, 상기 냉각속도는 50℃/hr 이하의 범위를 갖는 것이 바람직하다. 반면, 30℃/hr미만일 경우에는 결정립의 크기가 과도하게 커져 강도가 낮아질 수 있으므로, 상기 냉각속도는 30~50℃/hr의 범위를 갖는 것이 바람직하다. 따라서, 상기 냉각속도는 30~50℃/hr의 범위인 것이 바람직하다. 상기 냉각속도는 30~40℃/hr인 것이 보다 바람직하다. 한편, 상기 냉각정지온도가 300℃ 미만일 경우에는 냉각시간이 너무 길어 생산성에 문제가 있고, 반면 400℃를 초과하는 경우에는 농축층의 두께가 충분하지 못하여 내식성이 열위하는 문제가 있을 수 있다. 따라서, 상기 냉각정지온도는 300~400℃의 범위인 것이 바람직하다.
The rolled steel sheet is slowly cooled to 300 to 400 ° C at a rate of 30 to 50 ° C / hr. If the cooling rate is excessively high, the movement of Cu, which is an element forming the dense layer, may not be sufficient and it may be difficult to form a dense layer having a sufficient thickness. Therefore, the cooling rate is preferably 50 ° C / hr or less . On the other hand, when the cooling rate is less than 30 ° C / hr, the grain size becomes excessively large and the strength may be lowered. Therefore, the cooling rate is preferably in the range of 30 to 50 ° C / hr. Therefore, the cooling rate is preferably in the range of 30 to 50 DEG C / hr. The cooling rate is more preferably 30 to 40 ° C / hr. On the other hand, when the cooling stop temperature is less than 300 ° C, the cooling time is too long to cause a problem in productivity. On the other hand, when the cooling stop temperature is more than 400 ° C, the thickness of the concentrated layer is insufficient. Therefore, the cooling stop temperature is preferably in the range of 300 to 400 ° C.
이하, 실시예를 통해 본 발명을 보다 상세히 설명한다. 다만, 하기 실시예는 본 발명을 보다 상세히 설명하기 위한 예시일 뿐, 본 발명의 권리범위를 한정하지 않는다.
Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are only illustrative of the present invention in more detail and do not limit the scope of the present invention.
(실시예)(Example)
하기 표 1과 같은 성분계를 갖는 슬라브를 준비한 뒤, 1200℃에서 재가열한 뒤 1시간 유지하고, 900℃에서 열간압연을 실시하여 4.5mm 두께의 열연강판 시편을 제조하였다. 상기 열연강판 시편을 700℃까지 하기 표 2의 조건에 기재된 냉각속도로 냉각하였다. 상기 시편을 권취로에서 하기 표 2에 기재된 온도 조건으로 권취한 뒤, 권취로에서 40℃/hr의 속도로 서냉하였다. 상기 시편을 권취로에서 추출하였으며, 이 때 시편의 온도는 350℃였다. 이와 같이 제조된 시편들에 대하여 황산-염산 복합부식조건에서 부식특성을 조사하기 위하여, 황산 16.9vol% + 염산 0.35vol% 혼합용액에 60℃에서 6시간 동안 침지하여 각 시편의 부식감량을 측정하였다. 또한 각 시편들의 부식감량 측정 후 시편의 단면을 절단하여 내식층의 두께를 측정하였다. 이렇게 측정된 결과를 하기 표 3에 나타내었다.
Slabs having the same composition as shown in Table 1 were prepared, reheated at 1200 ° C, held for 1 hour, and hot rolled at 900 ° C to prepare hot-rolled steel sheet specimens having a thickness of 4.5 mm. The hot-rolled steel sheet specimen was cooled to 700 ° C at the cooling rate shown in Table 2 below. The specimens were wound in a winding furnace under the temperature conditions shown in Table 2 below and then slowly cooled at a speed of 40 占 폚 / hr in a winding furnace. The specimen was taken out of the winding furnace, and the temperature of the specimen was 350 ° C. In order to investigate the corrosion characteristics of the specimens prepared in this way, the corrosion loss of each specimen was measured by immersing it in a mixed solution of sulfuric acid 16.9vol% + 0.35vol% hydrochloric acid at 60 ℃ for 6 hours . In addition, after measuring the corrosion loss of each specimen, the cross section of the specimen was cut to measure the thickness of the corrosion resistant layer. The results thus obtained are shown in Table 3 below.
상기 표 1 및 2에서 알 수 있듯이, 본 발명이 제안하는 합금조성과 제조조건을 만족하는 발명예 1 내지 3의 경우에는 250nm이상의 내식층이 형성됨으로써 황산 및 염산에 의한 부식환경하에서 부식감량이 8mg/㎠/Hr이하로 매우 우수한 내식특성을 가지고 있음을 알 수 있다.
As can be seen from Tables 1 and 2, in the case of Inventive Examples 1 to 3, which satisfy the alloy composition and manufacturing conditions proposed by the present invention, a corrosion resistant layer of 250 nm or more is formed, / Cm2 / Hr or less.
비교예 1의 경우에는 본 발명의 합금조성을 만족하나, 권취온도가 500℃로 낮아 내식층이 충분히 형성되지 않았으며, 이로 인해 부식감량이 14.8mg/㎠/Hr로서 발명예들에 비하여 내식성이 매우 낮은 것을 알 수 있다.
In the case of Comparative Example 1, the alloy composition of the present invention was satisfied but the coiling temperature was lowered to 500 占 폚 and the corrosion resistant layer was not sufficiently formed. As a result, the corrosion loss was 14.8 mg / cm2 / Hr, Low.
비교예 2 내지 4의 경우에는 본 발명의 합금조성을 만족하나, 냉각속도가 10℃/s로서 낮은 수준이어서, 충분한 두께의 내식층이 형성되지 않아 부식감량이 낮은 수준임을 확인할 수 있다.
In the case of the comparative examples 2 to 4, the alloy composition of the present invention is satisfied, but the corrosion rate is low because the corrosion rate of the corrosion resistant layer is not sufficient because the cooling rate is as low as 10 캜 / s.
비교예 5의 경우에는 Cu가 첨가되지 않아 본 발명의 제조조건을 만족하더라도 내식층이 전혀 형성되지 않았으며, 이로 인해 부식감량이 25.9mg/㎠/Hr로서 내식성이 매우 낮은 수준임을 알 수 있다.In the case of Comparative Example 5, no Cu was added, and no corrosion resistant layer was formed at all even when the manufacturing conditions of the present invention were satisfied. As a result, the corrosion loss was 25.9 mg / cm 2 / Hr and the corrosion resistance was extremely low.
Claims (5)
표면 직하에 200nm이상의 두께를 갖는 Cu 농축층이 형성된 우수한 내식성을 갖는 황산 및 염산 복합내식용 열연강판.0.05 to 0.1% of Mn, 0.5 to 1.5% of P, 0.02% or less of P, 0.02% or less of S, 0.01 to 0.1% of Al, 0.2 to 0.7% of Cu, Including unavoidable impurities,
And a Cu concentration layer having a thickness of 200 nm or more formed directly under the surface, and having excellent corrosion resistance.
상기 Cu 농축층은 황산 및 염산 부식환경에서 Cu 산화물로 존재하는 것을 특징으로 하는 우수한 내식성을 갖는 황산 및 염산 복합내식용 열연강판.The method according to claim 1,
Wherein the Cu enriched layer is present as Cu oxide in a sulfuric acid and hydrochloric acid corrosion environment.
상기 열연강판은 16.9vol%의 황산과 0.35vol%의 염산의 혼합용액에 60℃에서 6시간 동안 침지하여 측정한 부식감량이 8mg/㎠/Hr이하인 우수한 내식성을 갖는 황산 및 염산 복합내식용 열연강판.The method according to claim 1,
The hot-rolled steel sheet had a corrosion resistance of 8 mg / cm 2 / Hr or less as measured by immersion in a mixed solution of 16.9 vol% sulfuric acid and 0.35 vol% hydrochloric acid at 60 ° C for 6 hours, .
상기 재가열된 강 슬라브를 850~950℃에서 마무리 열간압연하여 열연강판을 얻는 단계;
상기 열연강판을 80~100℃/sec로 급냉하는 단계;
상기 냉각된 강판을 670~750℃에서 권취하는 단계; 및
상기 권취된 강판을 30~50℃/hr로 300~400℃까지 서냉하는 단계를 포함하는 우수한 내식성을 갖는 황산 및 염산 복합내식용 열연강판의 제조방법.0.05 to 0.1% of Mn, 0.5 to 1.5% of P, 0.02% or less of P, 0.02% or less of S, 0.01 to 0.1% of Al, 0.2 to 0.7% of Cu, Reheating the steel slab containing unavoidable impurities at 1100 to 1300 占 폚;
Hot-rolling the reheated steel slab at 850 to 950 ° C to obtain a hot-rolled steel sheet;
Quenching the hot-rolled steel sheet at 80 to 100 ° C / sec;
Winding the cooled steel sheet at 670 to 750 ° C; And
And slowly cooling the rolled steel sheet at 30 to 50 占 폚 / hr to 300 to 400 占 폚.
상기 권취시 상기 강판의 표면이 복열현상에 의해 700℃이상이 되도록 하는 우수한 내식성을 갖는 황산 및 염산 복합내식용 열연강판의 제조방법.The method of claim 4,
Wherein the surface of the steel sheet at the time of winding is 700 占 폚 or higher due to a double heat phenomenon.
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