KR20230022213A - Manufacturing method of ultra-low carbon steel products - Google Patents
Manufacturing method of ultra-low carbon steel products Download PDFInfo
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- 229910001209 Low-carbon steel Inorganic materials 0.000 title claims abstract description 35
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 22
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 66
- 239000010959 steel Substances 0.000 claims abstract description 66
- 230000009467 reduction Effects 0.000 claims abstract description 57
- 238000005098 hot rolling Methods 0.000 claims abstract description 28
- 238000000034 method Methods 0.000 claims abstract description 20
- 238000005096 rolling process Methods 0.000 claims abstract description 19
- 238000005266 casting Methods 0.000 claims abstract description 17
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 15
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 15
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 14
- 230000008569 process Effects 0.000 claims abstract description 11
- 229910052742 iron Inorganic materials 0.000 claims abstract description 7
- 238000005097 cold rolling Methods 0.000 claims description 34
- 238000007670 refining Methods 0.000 claims description 9
- 230000007547 defect Effects 0.000 abstract description 57
- 238000007711 solidification Methods 0.000 abstract description 7
- 230000008023 solidification Effects 0.000 abstract description 7
- 239000010960 cold rolled steel Substances 0.000 description 12
- 238000011282 treatment Methods 0.000 description 10
- 238000000137 annealing Methods 0.000 description 7
- 230000006835 compression Effects 0.000 description 6
- 238000007906 compression Methods 0.000 description 6
- 238000005246 galvanizing Methods 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 6
- 238000004513 sizing Methods 0.000 description 6
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- 239000011261 inert gas Substances 0.000 description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 3
- 238000009749 continuous casting Methods 0.000 description 3
- 238000007872 degassing Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 230000007246 mechanism Effects 0.000 description 3
- 238000005554 pickling Methods 0.000 description 3
- 229910001335 Galvanized steel Inorganic materials 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 238000005261 decarburization Methods 0.000 description 2
- 239000006260 foam Substances 0.000 description 2
- 239000008397 galvanized steel Substances 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 238000009616 inductively coupled plasma Methods 0.000 description 2
- 230000000149 penetrating effect Effects 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 238000004626 scanning electron microscopy Methods 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 238000011179 visual inspection Methods 0.000 description 2
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- 241001492658 Cyanea koolauensis Species 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 238000005422 blasting Methods 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000012790 confirmation Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000007704 transition Effects 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
- 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
- C21D8/0236—Cold rolling
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/02—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling heavy work, e.g. ingots, slabs, blooms, or billets, in which the cross-sectional form is unimportant ; Rolling combined with forging or pressing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
- B22D1/002—Treatment with gases
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/10—Supplying or treating molten metal
- B22D11/11—Treating the molten metal
- B22D11/116—Refining the metal
- B22D11/117—Refining the metal by treating with gases
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/12—Accessories for subsequent treating or working cast stock in situ
- B22D11/1206—Accessories for subsequent treating or working cast stock in situ for plastic shaping of strands
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/12—Accessories for subsequent treating or working cast stock in situ
- B22D11/128—Accessories for subsequent treating or working cast stock in situ for removing
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/068—Decarburising
-
- 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
- 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
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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
- 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
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- 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
- C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
-
- 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
Abstract
가령 응고 쉘에 기포가 포착된 경우라도, 열간 압연 공정 이후의 공정에서 블리스터 결함의 발생을 억제할 수 있는 극저탄소강 제품의 제조 방법을 제공한다. 적어도 용철의 탄소 농도를 조정하여 용강으로 하는 공정과, 상기 용강을 주조하여 슬래브로 하는 공정과, 상기 슬래브를 열간 압연하여 열연 강판으로 하는 공정을 갖는, 탄소 농도가 0.005질량％ 이하인 극저탄소강 제품의 제조 방법으로서, 슬래브의 압연 방향에 직교하는 방향의 슬래브폭에 따라서 미리 정해지는 압하량으로 상기 슬래브를 폭압하하는 폭압하 공정을 추가로 갖는다.Provided is a method for manufacturing an ultra-low carbon steel product capable of suppressing occurrence of blister defects in a process after a hot rolling process even when air bubbles are trapped in a solidification shell. An ultra-low carbon steel product having a carbon concentration of 0.005% by mass or less, comprising at least a step of adjusting the carbon concentration of molten iron to obtain molten steel, a step of casting the molten steel into a slab, and a step of hot-rolling the slab to obtain a hot-rolled steel sheet. The manufacturing method further includes a rolling reduction step of rolling down the slab at a rolling reduction amount predetermined according to the slab width in a direction orthogonal to the rolling direction of the slab.
Description
본 발명은, 블리스터 결함(blister defects)이 적은 극저탄소강 제품의 제조 방법에 관한 것이다.The present invention relates to a method for manufacturing an ultra-low carbon steel product with few blister defects.
최근, 자동차나 캔용의 냉연 강판 또는 냉연 강판에 도금 처리를 실시한 표면 처리 강판에 대해서, 표면 품질에 대한 요구가 보다 한층 엄격해지고 있다. 그 중에서도, 강판 표면에 생기는 블리스터라고 칭해지는 표면 결함은, 가공에 의해 개구하여, 균열이나 내식성의 열화의 원인이 되기 때문에, 이 결함이 발생하면, 제품 출하 정지가 되는 경우도 있어, 수율 저하의 원인이 된다.In recent years, the demand for surface quality of cold-rolled steel sheets for automobiles and cans or cold-rolled steel sheets subjected to plating treatment has become more stringent. Among them, surface defects called blisters that occur on the surface of the steel sheet are opened by processing and cause cracks or deterioration in corrosion resistance. cause of
냉연 강판에 있어서의 블리스터 결함은, 비특허문헌 1에 개시되어 있는 바와 같이, 열간 압연 후의 산 세정 시에 강판에 침입한 수소가 강판 내의 기포에 체류하여, 냉간 압연 후의 어닐링 시의 가열과 함께 체적 팽창하고, 이에 따라 높아진 압력에 의해 가열에 의해 연화한 강판의 표면을 변형시키는 팽창 형상의 표면 결함이다.As disclosed in
이러한 블리스터의 발생을 억제시키는 기술로서, 특허문헌 1에는, 상부 자극(upper magnetic poles)과 하부 자극(lower magnetic poles)을 갖는 주형과, 상부 자극과 하부 자극에 의한 자장의 피크(peak) 위치의 사이에 용강의 토출공을 위치시킨 노즐을 갖는 연속 주조기를 이용하여, 용강류를 제어하면서 슬래브(slab)를 주조함으로써 기포가 응고 쉘(shell)에 포착되는 것을 억제하고, 이에 따라, 블리스터의 발생을 억제할 수 있는 것이 개시되어 있다.As a technique for suppressing the occurrence of such blisters,
그러나, 특허문헌 1에 개시된 기술은, 주로, 주조 단계에 있어서 블리스터 결함의 원인이 되는 기포가 응고 쉘에 포착되는 것을 억제하는 기술이다. 주조 공정에서는, 알루미나 등의 비금속 개재물이 침지 노즐의 내벽면에 부착되는 것을 방지하기 위해 침지 노즐에 불활성 가스가 도입되어 있기 때문에, 응고 쉘에 기포가 포착되는 것을 완전하게 방지하는 것은 어렵다. 이 때문에, 가령 응고 쉘에 기포가 포착되었다고 해도, 후의 열간 압연 공정 이후의 공정에서 블리스터 결함의 발생을 억제할 수 있는 방법이 요구되고 있다, 라는 과제가 있었다. 본 발명은, 이러한 종래 기술의 상황을 감안하여 이루어진 발명으로서, 그 목적은, 가령 응고 쉘에 기포가 포착된 경우라도, 열간 압연 공정 이후의 공정에서 블리스터 결함의 발생을 억제할 수 있는 극저탄소강 제품의 제조 방법을 제공하는 것이다.However, the technology disclosed in
상기 과제를 해결하는 본 발명의 요지는 이하와 같다.The gist of the present invention to solve the above problems is as follows.
(1) 적어도 용철의 탄소 농도를 조정하여 용강으로 하는 정련 공정과, 상기 용강을 주조하여 슬래브로 하는 주조 공정과, 상기 슬래브를 열간 압연하여 열연 강판으로 하는 열간 압연 공정을 갖는, 탄소 농도가 0.005질량％ 이하인 극저탄소강 제품의 제조 방법으로서, 상기 열간 압연 공정에 제공되는 상기 슬래브를, 상기 슬래브의 압연 방향에 직교하는 방향의 슬래브폭에 따라서 미리 정해지는 압하량으로 폭압하(width reduction)하는 폭압하 공정을 추가로 갖는, 극저탄소강 제품의 제조 방법.(1) at least a refining step of adjusting the carbon concentration of molten iron to obtain molten steel, a casting step of casting the molten steel into a slab, and a hot rolling step of hot-rolling the slab to obtain a hot-rolled steel sheet, wherein the carbon concentration is 0.005 A method for producing an ultra-low carbon steel product having a mass% or less, wherein the slab supplied in the hot rolling step is subjected to width reduction by a reduction amount determined in advance according to the slab width in a direction perpendicular to the rolling direction of the slab. A method for producing an ultra-low carbon steel product, further comprising a step under pressure.
(2) 적어도 용철의 탄소 농도를 조정하여 용강으로 하는 정련 공정과, 상기 용강을 주조하여 슬래브로 하는 주조 공정과, 상기 슬래브를 열간 압연하여 열연 강판으로 하는 열간 압연 공정과, 상기 열연 강판을 냉간 압연하여 냉연 강판으로 하는 냉간 압연 공정을 갖는, 탄소 농도가 0.005질량％ 이하인 극저탄소강 제품의 제조 방법으로서, 상기 냉간 압연 공정에서는, 상기 열연 강판의 판두께에 따라서 미리 정해지는 압하율로 냉간 압연하는, 극저탄소강 제품의 제조 방법.(2) at least a refining step of adjusting the carbon concentration of molten iron to obtain molten steel; a casting step of casting the molten steel into a slab; a hot rolling step of hot-rolling the slab to obtain a hot-rolled steel sheet; A method for producing an ultra-low carbon steel product having a carbon concentration of 0.005% by mass or less, including a cold-rolling step of rolling to obtain a cold-rolled steel sheet, wherein in the cold-rolling step, cold rolling is performed at a rolling reduction ratio determined in advance according to the sheet thickness of the hot-rolled steel sheet. A method for manufacturing ultra-low carbon steel products.
(3) 상기 열간 압연 공정에 제공되는 상기 슬래브를, 상기 슬래브의 압연 방향에 직교하는 방향의 슬래브폭에 따라서 미리 정해지는 압하량으로 폭압하하는 폭압하 공정을 추가로 갖는 (2)에 기재된 극저탄소강 제품의 제조 방법.(3) The pole described in (2) further comprising a rolling reduction step of reducing the slab subjected to the hot rolling step at a rolling reduction amount determined in advance according to a slab width in a direction orthogonal to the rolling direction of the slab. Method for manufacturing low carbon steel products.
본 발명에 따른 극저탄소강 제품의 제조 방법을 실시함으로써, 기포를 포함하는 극저탄소강의 슬래브로부터 제조되는 극저탄소강 제품의 블리스터 결함의 발생을 억제할 수 있다. 이 블리스터 결함의 발생을 억제함으로써, 극저탄소강 제품의 제조 라인의 수율의 향상을 실현할 수 있다.By carrying out the manufacturing method of an ultra-low carbon steel product according to the present invention, it is possible to suppress the occurrence of blister defects in an ultra-low carbon steel product manufactured from a slab of ultra-low carbon steel containing air bubbles. By suppressing the occurrence of this blister defect, it is possible to realize an improvement in the yield of the production line of ultra-low carbon steel products.
도 1은, 폭압하량과 블리스터 결함의 발생률의 관계를 나타내는 그래프이다.
도 2는, 냉간 압연의 압하율과 블리스터 결함의 발생률의 관계를 나타내는 그래프이다.BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a graph showing the relationship between the amount of pressure reduction and the incidence rate of blister defects.
2 is a graph showing the relationship between the reduction ratio of cold rolling and the incidence of blister defects.
(발명을 실시하기 위한 형태)(Mode for implementing the invention)
블리스터 결함은, 전술한 바와 같이, 열간 압연 후의 산 세정 시에 강판에 침입한 수소가, 강판 내의 기포 등의 부위에 체류하여, 냉간 압연 후에 어닐링 시의 가열과 함께 체적 팽창하고, 이에 따라 높아진 압력에 의해, 가열에 의해 연화한 강판의 표면을 변형시킴으로써 발생한다. 본 발명자들은, 열간 압연에 제공되는 슬래브에, 당해 슬래브의 압연 방향에 직교하는 방향의 슬래브폭의 사이즈(치수)에 따라서 미리 정해지는 압하량으로 폭압하하여 슬래브에 포함되는 기포를 변형시킴으로써 블리스터 결함의 발생을 억제할 수 있는 것을 발견하여 본 발명을 완성시켰다. 이하, 본 발명을 발명의 실시 형태를 통하여 설명한다.As described above, the blister defect is caused by hydrogen penetrating into the steel sheet during pickling after hot rolling, staying in areas such as bubbles in the steel sheet, expanding in volume with heating during annealing after cold rolling, and thereby increasing It is generated by deforming the surface of a steel sheet softened by heating with pressure. The inventors of the present invention apply pressure to a slab subjected to hot rolling at an amount of reduction determined in advance according to the size (dimension) of the slab width in a direction orthogonal to the rolling direction of the slab, thereby deforming air bubbles contained in the slab, thereby forming blisters. The present invention was completed by discovering that generation of defects can be suppressed. Hereinafter, the present invention will be described through embodiments of the present invention.
본 실시 형태에 따른 극저탄소강 제품의 제조 방법은, 적어도, 용철의 탄소 농도를 조정하여 용강으로 하는 정련 공정과, 용강을 주조하여 슬래브로 하는 주조 공정과, 당해 슬래브를 폭압하하는 폭압하 공정과, 폭압하된 슬래브를 열간 압연하는 열간 압연 공정을 갖는다. 또한, 열간 압연 공정 후, 열연 강판을 냉간 압연하는 냉간 압연 공정을 갖는 경우도 있다. 극저탄소강의 용강은, 미리 전로(converter) 등의 정련 장치에 있어서 1차 정련 처리가 실시된 용강이, 추가로, RH 방식 등의 탈가스 장치를 이용하여 탈가스·탈탄 처리됨으로써 용제된다. 이들 처리를 포함하는 공정이 용철의 탄소 농도를 조정하여 용강으로 하는 정련 공정의 일 예이다. 본 실시 형태에 따른 정련 공정에서는, 탄소 농도가 0.005질량％ 이하가 되는 극저탄소강의 용강이 용제된다.The method for manufacturing an ultra-low carbon steel product according to the present embodiment includes, at least, a refining step of adjusting the carbon concentration of molten iron to obtain molten steel, a casting step of casting the molten steel into a slab, and a pressure reduction step of blasting and lowering the slab. and a hot rolling step of hot rolling the slab subjected to pressure reduction. Moreover, there may be a cold rolling step of cold rolling the hot rolled steel sheet after the hot rolling step. Molten steel of ultra-low carbon steel is molten by subjecting molten steel to which primary refining treatment has been performed in advance in a refining device such as a converter, and further subjected to degassing and decarburization treatment using a degassing device such as an RH system. A process including these treatments is an example of a refining process in which the carbon concentration of molten iron is adjusted to obtain molten steel. In the refining step according to the present embodiment, molten steel of ultra-low carbon steel having a carbon concentration of 0.005% by mass or less is melted.
극저탄소강의 용강은, 턴디쉬(tundish), 주형(mold), 풋 롤(foot rolls), 가이드 롤, 핀치 롤(pinch rolls) 및 2차 냉각 장치 등을 구비하는 연속 주조기를 이용하여 슬래브로 연속 주조된다. 이 연속 주조기를 이용하여 용강으로부터 슬래브로 연속 주조하는 공정이, 용강을 주조하여 슬래브로 하는 주조 공정의 일 예이다.Molten steel of ultra-low carbon steel is continuously cast into slabs using a continuous casting machine equipped with tundish, mold, foot rolls, guide rolls, pinch rolls and a secondary cooling device. is cast The process of continuously casting molten steel into a slab using this continuous casting machine is an example of a casting process in which molten steel is cast into a slab.
그 후, 슬래브는 열간 압연이 실시되어 열연 강판이 되고, 이 열연 강판을 산 세정하여 열연 강판이 제조된다. 또한, 당해 열연 강판을 추가로, 냉간 압연, 어닐링 등이 실시되어 냉연 강판으로 해도 좋고, 추가로, 당해 냉연 강판에 합금화 용융 아연 도금 처리를 실시하여 합금화 용융 아연 도금 강판으로 해도 좋다. 이 산 세정 처리를 포함하는 슬래브를 열간 압연하여 열연 강판으로 하는 공정이, 슬래브를 열간 압연하는 열간 압연 공정의 일 예이고, 열연 강판에 냉간 압연, 어닐링 등을 실시하여 냉연 강판으로 하는 공정이, 열간 압연된 슬래브를 냉간 압연하는 냉간 압연 공정의 일 예이다.Thereafter, the slab is hot-rolled to become a hot-rolled steel sheet, and the hot-rolled steel sheet is pickled to produce a hot-rolled steel sheet. In addition, the hot-rolled steel sheet may be further subjected to cold rolling, annealing, etc. to obtain a cold-rolled steel sheet, or the cold-rolled steel sheet may be subjected to an alloyed hot-dip galvanizing treatment to obtain an alloyed hot-dip galvanized steel sheet. The process of hot-rolling the slab including this pickling treatment to obtain a hot-rolled steel sheet is an example of a hot-rolling process of hot-rolling the slab, and the process of cold-rolling, annealing, etc. This is an example of a cold rolling process of cold rolling a hot rolled slab.
주조 공정에서는, 턴디쉬 내의 용강은 침지 노즐을 통하여 주형에 주입된다. 탄소 농도가 0.005질량％ 이하의 극저탄소강은, RH 탈가스 장치로 탈탄·탈산 처리되는 과정에서 발생한 알루미나를 포함한다. 이 알루미나 등의 비금속 개재물이 침지 노즐의 내벽면에 부착·퇴적하여 침지 노즐이 폐색되는 것을 방지하기 위해, 턴디쉬로부터 주형에 용강을 주입하는 침지 노즐의 내벽면으로부터 노즐 내에 Ar 가스 등의 불활성 가스가 취입된다. 이 불활성 가스의 기포는, 침지 노즐의 용강 토출공으로부터 용강과 함께 주형 내에 토출된다.In the casting process, molten steel in the tundish is injected into the mold through a submerged nozzle. Ultra-low carbon steel having a carbon concentration of 0.005% by mass or less contains alumina generated in the course of decarburization and deoxidation treatment with an RH degassing device. In order to prevent the submerged nozzle from clogging due to adhesion and deposition of non-metallic inclusions such as alumina on the inner wall surface of the submerged nozzle, an inert gas such as Ar gas is inhaled into the nozzle from the inner wall surface of the submerged nozzle for injecting molten steel from the tundish into the mold. is taken in Bubbles of this inert gas are discharged from the molten steel discharge hole of the submerged nozzle into the mold together with the molten steel.
주형 내에 토출된 불활성 가스의 기포가 응고 쉘에 포착되면, 기포를 포함하는 슬래브가 주조된다. 이 기포를 포함하는 슬래브가 열연 강판이 되고, 당해 열연 강판이 산 세정되면, 기포 내에 수소가 체류하여, 냉간 압연 후의 어닐링 시의 가열과 함께 체적 팽창하고, 이에 따라 높아진 압력에 의해 가열에 의해 연화한 강판의 표면을 변형시켜 블리스터 결함이 발생한다.When bubbles of the inert gas discharged into the mold are captured by the solidification shell, a slab containing the bubbles is cast. The slab containing these bubbles becomes a hot-rolled steel sheet, and when the hot-rolled steel sheet is pickled, hydrogen stays in the bubbles, expands in volume with heating during annealing after cold rolling, and is softened by heating due to the increased pressure. Blister defects occur by deforming the surface of one steel sheet.
이러한 블리스터 결함에 대하여, 본 실시 형태에 따른 극저탄소강 제품의 제조 방법은, 열간 압연에 제공되는 슬래브를, 당해 슬래브의 압연 방향에 직교하는 방향의 슬래브폭에 따라서 미리 정해지는 압하량으로 폭압하하는 폭압하 공정을 추가로 갖는다. 구체적으로는, 사이징 프레스(sizing press)를 이용하여, 열간 압연에 제공되는 슬래브의 폭압하를 행한다. 이에 따라, 냉간 압연 후의 어닐링 시에 발생하는 블리스터 결함의 발생을 억제할 수 있다.In response to such a blister defect, in the manufacturing method of an ultra-low carbon steel product according to the present embodiment, the slab subjected to hot rolling is compressed at a rolling reduction amount predetermined according to the slab width in a direction orthogonal to the rolling direction of the slab Haha further has a process under pressure. Specifically, using a sizing press, the slab subjected to hot rolling is pressed down. Thereby, generation|occurrence|production of the blister defect which arises at the time of annealing after cold rolling can be suppressed.
다음으로 블리스터 결함의 발생이 억제되는 메커니즘을 설명한다. 슬래브에 포함되는 기포를 들보(beam)로서 생각하면, 기포의 팽창량(δ)은, 양단이 지지된 들보 계산식을 이용하여 하기 (1)식으로 나타난다.Next, the mechanism by which the occurrence of blister defects is suppressed will be described. Considering the foam contained in the slab as a beam, the amount of expansion (δ) of the foam is expressed by the following formula (1) using a beam calculation formula supported at both ends.
δ＝WL2/384EI···(1)δ = WL 2 /384EI ... (1)
상기 (1)식에 있어서, δ는 팽창량(m)이고, W는 응력(N)이고, L은 기포폭(m)이고, E는 영률(㎫)이고, I는 단면 2차 모멘트(m4)이다.In the above equation (1), δ is the amount of expansion (m), W is the stress (N), L is the cell width (m), E is the Young's modulus (MPa), and I is the moment of inertia of area (m) 4 ) is.
사이징 프레스에 의해 슬래브를 폭압하함으로써 기포폭이 좁아지기 때문에, 상기 (1)식의 L이 작아진다. L이 작아지면, 들보 중앙의 팽창량(δ)도 작아지기 때문에, 이 효과에 의해 기포의 팽창이 억제되고, 이에 따라, 블리스터 결함의 발생이 억제되는 것이라고 생각된다.Since the cell width is narrowed when the slab is pressed down by the sizing press, L in the above equation (1) is reduced. When L is small, the amount of expansion (δ) at the center of the crossbeam is also small, so it is thought that this effect suppresses the expansion of the air bubbles, thereby suppressing the occurrence of blister defects.
다음으로, 슬래브의 폭압하량과 블리스터 결함의 발생률의 관계에 대해서 설명한다. 폭치수가 1100∼2100㎜인 슬래브를, 사이징 프레스에 의해 압하량을 바꾸어, 각각 500t 이상 폭압하했다. 이들 폭압하한 슬래브를 각각 열간 압연하여 열연 강판(판두께 2.6∼4.0㎜)으로 한 후, 염산으로 산 세정하고, 이어서 일정한 압하율(0.72∼0.76)로 냉간 압연하여 냉연 강판으로 했다. 얻어진 냉연 강판에 합금화 용융 아연 도금 처리를 실시하고, 이 합금화 용융 아연 도금 강판에 대해서, 온라인 표면 결함계로 표면 결함을 연속적으로 측정했다. 이 표면 결함을 외관 검사, SEM 분석, ICP 분석 등을 이용하여 표면 결함이 블리스터 결함인지 아닌지를 육안으로 확인하여, 블리스터 결함이 발생한 코일 질량을 전체 코일 질량으로 나눈 값에 100을 곱하여 블리스터 결함의 발생률을 산출했다. 또한, 냉간 압연의 압하율은 하기 (2)식으로 산출했다.Next, the relationship between the amount of pressure reduction of the slab and the incidence rate of blister defects will be described. A slab having a width of 1100 to 2100 mm was reduced by 500 t or more each by varying the amount of reduction by using a sizing press. Each of these slabs of reduced pressure was hot-rolled to obtain a hot-rolled steel sheet (2.6 to 4.0 mm in thickness), pickled in hydrochloric acid, and then cold-rolled at a constant reduction ratio (0.72 to 0.76) to obtain a cold-rolled steel sheet. The resulting cold-rolled steel sheet was subjected to hot-dip galvanizing treatment, and surface defects were continuously measured on the alloyed hot-dip galvanized steel sheet by an online surface defect meter. This surface defect is visually checked using visual inspection, SEM analysis, ICP analysis, etc. to determine whether or not the surface defect is a blister defect, and the value obtained by dividing the coil mass with the blister defect by the total coil mass is multiplied by 100 to determine the blister The incidence of defects was calculated. In addition, the rolling reduction of cold rolling was computed by the following formula (2).
압하율＝(냉압 입구에서의 강판 두께－냉압 출구에서의 강판 두께)/냉압 입구에서의 강판 두께···(2)Reduction ratio = (Steel plate thickness at the cold-pressure inlet - Steel plate thickness at the cold-pressure outlet)/Steel plate thickness at the cold-pressure inlet... (2)
블리스터 결함의 발생률의 확인은, 성분 농도의 규격값이, C 농도: 0.0000∼0.0020, Si 농도: 0.00∼0.03질량％, Mn 농도: 0.10∼0.25질량％, P 농도: 0.010∼0.020질량％, S 농도: 0.003∼0.010질량％, N 농도: 0.0000∼0.0035질량％인 극저탄소강(1)과, 성분 농도의 규격값이, C 농도: 0.0000∼0.0015, Si 농도: 0.00∼0.03질량％, Mn 농도: 0.05∼0.18질량％, P 농도: 0.000∼0.010질량％, S 농도: 0.003∼0.009질량％, N 농도: 0.0000∼0.0030질량％인 극저탄소강(2)을 이용하여 실시했다.Confirmation of the occurrence rate of blister defects is as follows: C concentration: 0.0000 to 0.0020, Si concentration: 0.00 to 0.03 mass%, Mn concentration: 0.10 to 0.25 mass%, P concentration: 0.010 to 0.020 mass%, S concentration: 0.003 to 0.010% by mass, N concentration: 0.0000 to 0.0035% by mass of
도 1은, 사이징 프레스에 의한 폭압하량과 블리스터 결함의 발생률의 관계를 나타내는 그래프이다. 도 1에 있어서, 가로축은, 슬래브의 폭압하량(㎜)이고, 세로축은 블리스터 결함의 발생률(％)이다. 도 1에 나타내는 바와 같이, 폭압하량을 100∼150㎜로부터 150∼200㎜로 늘리면 약간 블리스터 결함의 발생률이 상승하기는 했지만, 전체적으로 슬래브의 폭압하량을 크게 함으로써 블리스터 결함의 발생률이 낮아지는 경향이 있는 것을 알 수 있다. 이 결과로부터, 열간 압연에 제공되는 슬래브에 슬래브의 압연 방향에 직교하는 방향의 슬래브폭에 따른 소정의 압하량으로 폭압하함으로써, 블리스터 결함의 발생을 억제할 수 있는 것을 알 수 있다.BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a graph showing the relationship between the amount of compression reduction by a sizing press and the incidence rate of blister defects. In Fig. 1, the abscissa is the amount of compression reduction of the slab (mm), and the ordinate is the incidence rate of blister defects (%). As shown in FIG. 1, although the incidence rate of blister defects slightly increased when the amount of compression reduction was increased from 100 to 150 mm to 150 to 200 mm, the incidence rate of blister defects tended to decrease by increasing the amount of compression reduction of the slab as a whole. It can be seen that there is From this result, it can be seen that the occurrence of blister defects can be suppressed by reducing the slab subjected to hot rolling at a predetermined reduction according to the slab width in a direction orthogonal to the rolling direction of the slab.
또한, 슬래브폭에 따른 폭압하량은, 도 1에 나타낸 폭압하량과 블리스터 결함의 발생률의 관계를 실험 등으로 파악해 둠으로써 미리 정해진다. 즉, 도 1에 나타낸 예에 있어서는, 폭치수가 1100∼2100㎜인 슬래브에 대해서는, 사이징 프레스에 의해 200∼250㎜ 이상의 압하량으로 폭압하를 행하면 좋고, 이에 따라, 블리스터 결함의 발생률을 크게 저감할 수 있는 것을 알 수 있다.In addition, the amount of compression reduction according to the slab width is determined in advance by grasping the relationship between the amount of compression reduction and the incidence rate of blister defects shown in FIG. 1 through experiments or the like. That is, in the example shown in Fig. 1, for a slab having a width of 1100 to 2100 mm, the sizing press may be applied with a rolling reduction of 200 to 250 mm or more, thereby increasing the incidence of blister defects. know what can be reduced.
이상 설명한 바와 같이 본 실시 형태에 따른 극저탄소강 제품의 제조 방법을 실시함으로써, 기포를 포함하는 극저탄소강의 슬래브로부터 제조되는 극저탄소강 제품의 블리스터 결함의 발생을 억제할 수 있다. 이 블리스터 결함의 발생을 억제함으로써, 극저탄소강 제품의 제조 라인의 수율의 향상을 실현할 수 있다.As described above, by carrying out the manufacturing method of the ultra-low carbon steel product according to the present embodiment, it is possible to suppress the occurrence of blister defects in the ultra-low carbon steel product manufactured from the slab of the ultra-low carbon steel containing air bubbles. By suppressing the occurrence of this blister defect, it is possible to realize an improvement in the yield of the production line of ultra-low carbon steel products.
또한, 슬래브의 폭압하를 대신하여, 또는, 슬래브의 폭압하와 함께, 열연 강판의 판두께에 따라서 미리 정해지는 압하율로 냉간 압연해도 좋다. 소정의 압하율로 냉간 압연을 행함으로써, 강 조직 중의 전이 밀도가 상승하고, 어닐링 시에 있어서 재결정립이 작아져 강판의 강도가 높아진다. 이 강도의 상승에 의해, 블리스터 결함의 발생이 억제된다.Alternatively, cold rolling may be performed at a reduction ratio determined in advance according to the sheet thickness of the hot-rolled steel sheet in place of the reduction of the slab or together with the reduction of the reduction of the slab. By performing cold rolling at a predetermined reduction ratio, the transition density in the steel structure is increased, recrystallized grains are reduced during annealing, and the strength of the steel sheet is increased. This increase in strength suppresses the occurrence of blister defects.
다음으로, 냉간 압연의 압하율과 블리스터 결함의 발생률의 관계에 대해서 설명한다. 사이징 프레스를 일정한 폭압하량(0∼100㎜)으로 행한 슬래브를 열간 압연하여 열연 강판(판두께 2.6∼4.0㎜)으로 한 후, 염산으로 산 세정하고, 이어서, 압하율을 바꾸어 냉간 압연하여 압하율이 상이한 냉연 강판을 각각 200t 이상 제작했다. 얻어진 냉연 강판의 각각에 합금화 용융 아연 도금 처리를 실시하고, 이 합금화 용융 아연 도금 강판에 대해서, 온라인 표면 결함계로 표면 결함을 연속적으로 측정했다. 이 표면 결함을 외관 검사, SEM 분석, ICP 분석 등을 이용하여 표면 결함이 블리스터 결함인지 아닌지 확인하여, 블리스터 결함의 발생률을 산출했다.Next, the relationship between the reduction ratio of cold rolling and the occurrence rate of blister defects will be described. A slab subjected to a sizing press at a constant pressure reduction (0 to 100 mm) is hot-rolled to make a hot-rolled steel sheet (plate thickness 2.6 to 4.0 mm), pickled with hydrochloric acid, and then cold-rolled at a different reduction ratio to obtain a reduction ratio. 200 tons or more of these different cold-rolled steel sheets were produced, respectively. Alloying hot-dip galvanizing treatment was performed on each of the obtained cold-rolled steel sheets, and the surface defects of the alloyed hot-dip galvanizing steel sheets were continuously measured by an online surface defect meter. This surface defect was confirmed by using a visual inspection, SEM analysis, ICP analysis or the like to determine whether or not the surface defect was a blister defect, and the incidence rate of the blister defect was calculated.
도 2는, 냉간 압연의 압하율과 블리스터 결함의 발생률의 관계를 나타내는 그래프이다. 도 2에 있어서, 가로축은, 냉간 압하율(-)이고, 세로축은 블리스터 결함의 발생률(％)이다. 도 2에 나타내는 바와 같이, 냉간 압연의 압하율도 블리스터 결함의 발생률에 상관이 있어, 냉간 압연의 압하율을 크게 함으로써 블리스터 결함의 발생률이 낮아지는 경향이 있는 것을 알 수 있다. 이 결과로부터, 슬래브의 폭압하를 대신하여, 또는, 슬래브의 폭압하와 함께 열연 강판의 판두께에 따라서 미리 정해지는 압하율로 냉간 압연해도 좋고, 이에 따라, 블리스터 결함의 발생을 억제할 수 있는 것을 알 수 있다.2 is a graph showing the relationship between the reduction ratio of cold rolling and the incidence of blister defects. In FIG. 2 , the horizontal axis is the cold reduction rate (-), and the vertical axis is the incidence rate (%) of blister defects. As shown in FIG. 2, it is understood that the reduction rate of cold rolling also correlates with the incidence rate of blistering defects, and the incidence rate of blistering defects tends to decrease by increasing the reduction rate of cold rolling. From this result, it is possible to perform cold rolling at a reduction ratio determined in advance according to the sheet thickness of the hot-rolled steel sheet instead of, or together with the slab reduction, thereby suppressing the occurrence of blister defects. can know that
또한, 열연 강판의 두께에 따른 압하율은, 도 2에 나타낸 냉간 압연의 압하율과 블리스터 결함의 발생률의 관계를 실험 등에 의해 파악해 둠으로써 미리 정해진다. 즉, 도 2에 나타낸 예에 있어서는, 두께 2.6∼4.0㎜의 열연 강판에 대해서는, 0.76 이상의 압하율로 냉간 압연을 행하면 좋고, 이에 따라, 블리스터 발생률을 크게 저감할 수 있는 것을 알 수 있다.In addition, the reduction ratio according to the thickness of the hot-rolled steel sheet is determined in advance by grasping the relationship between the reduction ratio in cold rolling shown in FIG. 2 and the incidence rate of blister defects through experiments or the like. In other words, in the example shown in FIG. 2 , cold rolling may be performed at a reduction ratio of 0.76 or more for a hot-rolled steel sheet having a thickness of 2.6 to 4.0 mm, and as a result, it can be seen that the blistering rate can be greatly reduced.
또한, 전술한 바와 같이, 슬래브의 폭압하에 의한 블리스터 결함의 발생 억제 메커니즘은, 냉간 압연에 의한 블리스터 결함의 발생 억제 메커니즘과 상이하기 때문에, 이들을 병용함으로써 블리스터 결함의 발생을 더욱 억제할 수 있는 것을 알 수 있다. 이와 같이, 슬래브의 폭압하와 냉간 압연을 병용하는 경우에는, 상이한 복수의 압하량으로 폭압하를 행한 슬래브를 준비하고, 당해 슬래브로부터 제조된 열연 강판의 냉간 압하율과 블리스터 결함의 발생률의 관계를 미리 실험 등에 의해 파악해 둠으로써, 슬래브폭의 사이즈에 따른 폭압하의 압하량과, 열연 강판의 판두께에 따른 냉간 압연의 압하율을 미리 정할 수 있다.In addition, as described above, since the mechanism for suppressing the occurrence of blister defects due to the pressure of the slab is different from the mechanism for suppressing the occurrence of blister defects due to cold rolling, the occurrence of blister defects can be further suppressed by using these together. it can be seen that there is In this way, when the slab pressure reduction and cold rolling are used together, slabs subjected to pressure reduction at a plurality of different rolling reduction amounts are prepared, and the relationship between the cold rolling reduction rate and the occurrence rate of blister defects of the hot-rolled steel sheet produced from the slab is analyzed. By grasping in advance by experiments or the like, it is possible to determine in advance the amount of reduction under pressure reduction according to the size of the slab width and the reduction rate in cold rolling according to the sheet thickness of the hot-rolled steel sheet.
또한, 본 실시 형태에 따른 극저탄소강 제품의 제조 방법으로 제조되는 극저탄소강 제품이란, 폭압하에 의해 블리스터 결함의 발생을 억제하는 경우에는, 0.005질량％ 이하의 극저탄소강 슬래브가 소정의 폭압하량으로 폭압하되고, 열간 압연 및 산 세정된 열간 압연 강판이다. 또한, 냉간 압연의 압하량에 의해 블리스터 결함의 발생을 억제하는 경우에는, 본 실시 형태에 따른 극저탄소강 제품의 제조 방법으로 제조되는 극저탄소강 제품이란 0.005질량％ 이하의 극저탄소강 슬래브를 열간 압연하고, 산 세정하고, 냉간 압연한 냉연 강판이라도 좋고, 추가로, 당해 냉연 강판에 합금화 용융 아연 도금 처리를 실시한 합금화 용융 아연 도금이라도 좋다.In addition, the ultra-low carbon steel product produced by the manufacturing method of an ultra-low carbon steel product according to the present embodiment is, when the occurrence of blister defects is suppressed under pressure, an ultra-low carbon steel slab of 0.005% by mass or less is subjected to a predetermined pressure It is a hot-rolled steel sheet that has been blown down under a load, and has been hot-rolled and pickled. In addition, when the occurrence of blistering defects is suppressed by the amount of reduction in cold rolling, the ultra-low carbon steel product manufactured by the method for manufacturing an ultra-low carbon steel product according to the present embodiment is an ultra-low carbon steel slab of 0.005% by mass or less. The cold-rolled steel sheet may be hot-rolled, pickled, and cold-rolled, or may be hot-rolled hot-dip galvanizing obtained by subjecting the cold-rolled steel sheet to hot-dip galvanizing treatment.
또한, 본 실시 형태에 따른 극저탄소강의 제조 방법은, 전술한 극저탄소강 1, 2에 한정하지 않고, 성분 농도의 규격값이, C 농도: 0.0000∼0.0030, Si 농도: 0.00∼0.03질량％, Mn 농도: 0.10∼0.25질량％, P 농도: 0.015∼0.030질량％, S 농도: 0.005∼0.012질량％, N 농도: 0.0000∼0.0035질량％인 극저탄소강(3)이나, 성분 농도의 규격값이 C 농도: 0.0000∼0.0020, Si 농도: 0.00∼0.04질량％, Mn 농도: 0.10∼0.25질량％, P 농도: 0.000∼0.010질량％, S 농도: 0.004∼0.012질량％, N 농도: 0.0000∼0.0030질량％인 극저탄소강(4)에도 적용할 수 있다.In addition, the method for producing ultra-low carbon steel according to the present embodiment is not limited to the above-described ultra-low carbon steels 1 and 2, and the standard values of the component concentrations are C concentration: 0.0000 to 0.0030, Si concentration: 0.00 to 0.03 mass%, Mn concentration: 0.10 to 0.25% by mass, P concentration: 0.015 to 0.030% by mass, S concentration: 0.005 to 0.012% by mass, N concentration: 0.0000 to 0.0035% by mass of ultra-low carbon steel (3), and the standard value of component concentration C concentration: 0.0000 to 0.0020, Si concentration: 0.00 to 0.04 mass%, Mn concentration: 0.10 to 0.25 mass%, P concentration: 0.000 to 0.010 mass%, S concentration: 0.004 to 0.012 mass%, N concentration: 0.0000 to 0.0030 mass% It can also be applied to ultra-low carbon steel 4 with %.
Claims (3)
상기 열간 압연 공정에 제공되는 상기 슬래브를, 상기 슬래브의 압연 방향에 직교하는 방향의 슬래브폭에 따라서 미리 정해지는 압하량으로 폭압하하는 폭압하 공정을 추가로 갖는, 극저탄소강 제품의 제조 방법.At least a refining step of adjusting the carbon concentration of molten iron to obtain molten steel, a casting step of casting the molten steel into a slab, and a hot rolling step of hot-rolling the slab to obtain a hot-rolled steel sheet, wherein the carbon concentration is 0.005% by mass or less. As a method for manufacturing ultra-low carbon steel products,
Further comprising a reduction step of reducing the slab provided in the hot rolling step at a reduction amount determined in advance according to a slab width in a direction orthogonal to the rolling direction of the slab.
상기 냉간 압연 공정에서는, 상기 열연 강판의 판두께에 따라서 미리 정해지는 압하율로 냉간 압연하는, 극저탄소강 제품의 제조 방법.At least a refining process of adjusting the carbon concentration of molten iron to obtain molten steel, a casting process of casting the molten steel into a slab, a hot rolling process of hot-rolling the slab to obtain a hot-rolled steel sheet, and cold-rolling the hot-rolled steel sheet by cold rolling. A method for producing an ultra-low carbon steel product having a carbon concentration of 0.005% by mass or less, which has a cold rolling step to make a steel sheet,
In the cold rolling step, cold rolling is performed at a reduction ratio determined in advance according to the sheet thickness of the hot rolled steel sheet.
상기 열간 압연 공정에 제공되는 상기 슬래브를, 상기 슬래브의 압연 방향에 직교하는 방향의 슬래브폭에 따라서 미리 정해지는 압하량으로 폭압하하는 폭압하 공정을 추가로 갖는, 극저탄소강 제품의 제조 방법.According to claim 2,
Further comprising a reduction step of reducing the slab provided in the hot rolling step at a reduction amount determined in advance according to a slab width in a direction orthogonal to the rolling direction of the slab.
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