KR960004787B1 - Method for removing a scale of martensite stainless steel strips - Google Patents
Method for removing a scale of martensite stainless steel strips Download PDFInfo
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- KR960004787B1 KR960004787B1 KR1019930025027A KR930025027A KR960004787B1 KR 960004787 B1 KR960004787 B1 KR 960004787B1 KR 1019930025027 A KR1019930025027 A KR 1019930025027A KR 930025027 A KR930025027 A KR 930025027A KR 960004787 B1 KR960004787 B1 KR 960004787B1
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
- C25F1/00—Electrolytic cleaning, degreasing, pickling or descaling
- C25F1/02—Pickling; Descaling
- C25F1/04—Pickling; Descaling in solution
- C25F1/06—Iron or steel
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
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- Chemical Kinetics & Catalysis (AREA)
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- Materials Engineering (AREA)
- Metallurgy (AREA)
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- Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
Abstract
Description
본 발명은 마르텐사이트계 스테인레스강대(steel strip)의 스케일 제거방법에 관한 것으로, 보다 상세히는 마르텐사이트계 스테인레스 열연강대를 소둔한 후, 단시간에 연속적으로 전해 산세척에 의해서 표면스케일을 제거하는 방법에 관한 것이다.The present invention relates to a method for descaling a martensitic stainless steel strip, and more particularly to a method for removing surface scale by an electrolytic pickling in a short time after annealing the martensitic stainless steel strip. It is about.
종래의 스테인레스 열연강대의 탈스케일 방법에는 열간압연후 AP 라인(Anealing and Pickling Line)이라고 하는 설비에서 소둔과 산세를 연속적으로 하는 오스테나이트계 스테인레스강대의 탈스케일 방법과 배치(batch)라는 별개의 상소둔로에서 소둔한 다음 연속적으로 산세하는 마르텐사이트계 스테인레스강대의 탈스케일 방법이 있다.The descaling method of the conventional stainless hot rolled steel strip is a separate method of descaling and batching of an austenitic stainless steel strip which is continuously annealed and pickled in a facility called an annealing and pickling line after hot rolling. There is a descale method of martensitic stainless steels that are annealed in a furnace and subsequently pickled.
상기 방법들에 의하면 스테인레스강대를 소둔산세할 경우 열간압연시 스테인레스강대 표면에 치밀하고 견고한 산화 스케일이 생성되기 때문에 이 스케일을 제거하기 위해서는 그라인더, 벤딩롤, 쇼트블래스트 등과 같은 기계적인 스케일 제거장치와 복수의 산세척조에 의한 산세장치가 필요하다.According to the above methods, when annealing the stainless steel strip, a dense and rigid oxide scale is formed on the surface of the stainless steel sheet during hot rolling, in order to remove the scale, a mechanical scale remover such as grinder, bending roll, shot blast, etc. A pickling device by pickling tank is required.
종래의 가장 일반적으로 쓰이는 복수의 산세척조를 이용한 산세방법으로 20% 전후의 황산조와 혼산조(질산+불화수소산)를 조합한 산세방법이 있다. 이 방법은 소둔시 입계에 생긴 크롬결핍층으로 인해 입계가 크게 침식되어 표면사상이 나빠질 뿐만 아니라 혼산조에서 발생되는 NOx는 환경오염의 원인이 되는 문제에도 불구하고 오스트나이트계 스테인레스강의 치밀한 스케일을 벗기기 위해서는 매우 유효한 방법이 되어 왔다.As a conventional pickling method using a plurality of pickling tanks, there is a pickling method combining a sulfuric acid tank and a mixed acid tank (nitric acid + hydrofluoric acid) of about 20%. In this method, the grain boundary is greatly eroded due to the chromium-deficient layer at the grain boundary during annealing, and the surface erosion is not only worsened. It has been a very effective way.
그러나, 질산 불화 수소산을 400계, 특히 마르텐사이트계 스테인레스강의 산세척에 사용할 경우, 격렬한 표면반응으로 인해 온도 및 농도제어가 어려울 뿐만 아니라 단시간에 산세액속의 급속이온량이 급격하게 증가함으로써 표면에 재부착되는 문제가 발생한다. 따라서 스케일 제거에 더 많은 시간이 필요하며 일정한 라인속도를 유지하기 위해서는 새로운 산을 투입하여 산도와 금속이온 농도를 일정하게 유지시켜야 하는데, 종래의 황산, 질산 불화 수소산의 복수 산세척조에 의한 산세는 입계부식에 의한 표면 침식, NOx 발생, 산농도와 온도제어의 어려움, 라인속도 저하에 따른 생산성 저하등의 문제가 빈번히 발생되었다.However, when nitrate hydrofluoric acid is used for pickling of 400-based, especially martensitic stainless steels, it is difficult to control the temperature and concentration due to violent surface reactions and reattach to the surface due to the rapid increase of the rapid ions in the pickling solution in a short time. Problem occurs. Therefore, more time is required to remove the scale, and to maintain a constant line speed, a new acid should be added to maintain the acidity and the metal ion concentration. The pickling by the multiple pickling tanks of the conventional sulfuric acid and hydrofluoric acid hydrofluoric acid is intergranular. Problems such as surface erosion due to corrosion, NOx generation, difficulty in acid concentration and temperature control, and productivity loss due to line speed decrease frequently occurred.
따라서, 본 발명은 종래의 질산 불화 수소산 사용에 따른 상기와 같은 문제점들을 해결하기 위하여 제안된 것으로서 산세액으로 황산만을 사용하고 전해 산세법에 의해서 마르텐사이트계 스테인레스강대의 스케일을 제거하는 방법을 제공하고자 하는데 그 목적이 있다.Accordingly, the present invention has been proposed to solve the above problems caused by the conventional use of hydrofluoric acid nitric acid, to provide a method of using only sulfuric acid as the pickling solution and removing the scale of martensitic stainless steel by electrolytic pickling. Its purpose is to.
이하, 본 발명을 설명한다.Hereinafter, the present invention will be described.
본 발명은 마르텐사이트계 스테인레스강대의 스케일 제거방법에 있어서, 200-300g/l 농도의 황산 수용액을 산세액으로 하여, 전류밀도 : 5-20A/dm2, 전해시간 2-3분으로 상온에서 전해 산세하는 것을 특징으로 하는 마르텐사이트계 스테인레스강대의 스케일 제거방법에 관한 것이다.In the present invention, in the descaling method of martensitic stainless steel strips, an aqueous sulfuric acid solution having a concentration of 200-300 g / l is used as a pickling solution, and is electrolyzed at room temperature with a current density of 5-20 A / dm 2 and an electrolysis time of 2-3 minutes. It relates to a descaling method of martensitic stainless steel strips characterized by pickling.
이하, 본 발명의 전해 상세조건에 대한 수치한정 이유에 대하여 설명한다.EMBODIMENT OF THE INVENTION Hereinafter, the reason for numerical limitation with respect to the electrolytic detailed conditions of this invention is demonstrated.
본 발명은 종래의 질산 불화 수소산을 산세액으로 사용하는 방법과는 달리 산세액으로 황산 수용액을 단독으로 사용함으로써, 종래의 질산 불화 수소산의 사용에 따른 입계부식에 의한 스테인레스강대의 표면침식을 방지할 수 있고, 종래의 혼산사용시 발생되는 NOx로 인한 환경오염도 방지할 수 있는 장점이 있다.The present invention, unlike the conventional method of using hydrochloric acid nitric acid as a pickling solution, by using a sulfuric acid aqueous solution as a pickling solution alone, it is possible to prevent the surface erosion of stainless steel by intergranular corrosion caused by the use of conventional hydrofluoric acid nitric acid And, there is an advantage to prevent the environmental pollution due to NOx generated in the conventional mixed acid use.
본 발명에 사용되는 황산의 농도는 200-300g/l가 바람직한데, 그 이유는 황산 수용액의 농도가 200g/l 이하로 되면 산세가 미흡하게 되며, 300g/l 이상으로 되면 격렬한 표면반응으로 스테인레스강대 표면조도가 거칠게 되기 때문이다.The concentration of sulfuric acid used in the present invention is preferably 200-300g / l, the reason is that when the concentration of sulfuric acid solution is less than 200g / l, the pickling is insufficient, when the concentration of 300g / l or more stainless steel strip This is because the surface roughness becomes rough.
본 발명에 있어서, 또 다른 특징은 상기 황산 산세액과 더불어 전해 산세를 하는 방법인데, 이때의 전류밀도를 5A/dm2이하로 하면 산세가 되지 않으며, 20A/dm2이상으로 올리면 과산세가 되어 바람직하지 않다.In the present invention, another feature is a method of electrolytic pickling together with the sulfuric acid pickling solution, if the current density at this time is 5A / dm 2 or less, it is not pickled, and when raised to 20A / dm 2 or more, it becomes peracid Not desirable
상기 전해 산세의 경우 전해시간은 2-3분으로 하는 것이 바람직한데, 그 이유는 2분 이하로 하게 되면 산세가 이루어지지 않고, 3분 이상으로 하게 되면 과산세가 되기 때문이다.In the case of the above-mentioned electrolytic pickling, the electrolysis time is preferably 2-3 minutes because the pickling is not carried out when it is set to 2 minutes or less, and when it is set to 3 minutes or more, the pickling is performed.
한편, 종래의 상세조건의 경우, 산세액의 급격한 온도상승 및 용존 금속농도의 급격한 증가등으로 산세조건을 제어하는데 어려움이 있었으나, 본 발명에서는 상온에서 작업함으로써 온도와 농도의 관리가 용이하다.On the other hand, in the case of the conventional detailed conditions, it was difficult to control the pickling conditions due to the rapid temperature rise of the pickling solution and the sudden increase of the dissolved metal concentration, but in the present invention, it is easy to manage the temperature and concentration by working at room temperature.
이하, 실시예를 통하여 본 발명을 상세히 설명한다.Hereinafter, the present invention will be described in detail through examples.
[실시예]EXAMPLE
열간압연후 상소둔로(Batch Annealing Furnace)에서 소둔한 다음 쇼트 블라스트로 전처리된 마르텐사이트계 420JZ 스테인레스강대를 소지금속으로 하여 하기 표 1과 같은 산세액 및 산세조건에서 상기 소지금속을 전해 상세하여 탈스케일 정도를 판독하고, 그 결과를 하기 표 1에 나타내었다.After hot rolling, the martensitic 420JZ stainless steel band annealed in a batch annealing furnace and then shot blasted was used as the base metal, and then the base metal was electrolyzed and desorbed under the pickling solution and pickling conditions as shown in Table 1 below. The degree of scale was read and the results are shown in Table 1 below.
기호 ○ : 탈스케일 양호Symbol ○: Good descaling
기호 △ : 미소스케일 잔류 또는 과산세Symbol △: microscale residue or tax
기호 × : 스케일 잔류Symbol ×: Scale Residue
기호 * : 1차 황산조 조건Symbol *: Primary sulfuric acid bath conditions
기호 # : 2차 질산, 불화 수소산조 조건Symbol #: secondary nitric acid, hydrofluoric acid bath conditions
상기 표 1에서 나타난 바와 같이, 본 발명예(1-9)의 경우, 종래의 방법으로 1차 및 2차 산세를 한 종래예(18-23)의 경우보다 짧은 산세시간, 낮은 용액온도, 공정의 간략화에도 불구하고 양호한 상세성과 우수한 표면사상을 나타내었다.As shown in Table 1, in the case of the present invention (1-9), a short pickling time, a lower solution temperature, a process Despite the simplification of, it showed good detail and excellent surface finish.
또한, 본 발명의 조건을 벗어난 비교예(10-17)의 경우 산세후 표면사상이 나쁘므로, 본 발명에 의한 완전한 탈스케일 조건은 황산 수용액의 농도가 200-300g/l, 전류밀도를 5-20A/dm2, 전해시간을 2-3분으로 하는 것이 바람직하다는 것을 알 수 있다.In addition, in the case of Comparative Example (10-17) outside the conditions of the present invention, since the surface image after pickling is bad, the complete descale condition according to the present invention is 200-300g / l concentration of sulfuric acid solution, 5- It turns out that it is desirable to set the electrolysis time to 20 A / dm <2> and 2-3 minutes.
상술한 바와 같이 본 발명은 마르텐사이트계 스테인레스강의 열연, 소둔강대를 황산 수용액에 전해 산세함으로써, 산세시간 단축, 공정의 간략화, 낮은 온도에서의 산세등으로 에너지 비용의 절감 및 NOx 발생으로 인한 환경오염등을 방지할 수 있는 효과가 있는 것이다.As described above, according to the present invention, electrolytic pickling of hot-rolled and annealed steel strips of martensitic stainless steel in an aqueous sulfuric acid solution reduces the pickling time, simplifies the process, and pickles at low temperatures, thereby reducing energy costs and environmental pollution due to NOx generation. There is an effect that can be prevented.
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR101064407B1 (en) * | 2004-03-12 | 2011-09-14 | 주식회사 포스코 | Stainless hot coil strip improving the pickling rate |
KR20200046845A (en) | 2018-10-25 | 2020-05-07 | 주식회사 포스코 | Scale removing apparatus and method for low chromium ferritic stainless steel hot-rolled steel sheet |
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CN110747481A (en) * | 2018-07-23 | 2020-02-04 | 太原天择金属表面技术有限责任公司 | Method for removing oxide skin on surface of hot-rolled nickel stainless steel |
CN112430714A (en) * | 2020-09-27 | 2021-03-02 | 甘肃酒钢集团宏兴钢铁股份有限公司 | Annealing process of 04Cr13Ni5Mo hydroelectric super martensitic stainless steel medium plate |
KR102546880B1 (en) * | 2020-12-02 | 2023-06-26 | 주식회사 포스코 | Stainless steel electrolytic pickling method using highly conductive sulfuric acid solution |
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
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KR101064407B1 (en) * | 2004-03-12 | 2011-09-14 | 주식회사 포스코 | Stainless hot coil strip improving the pickling rate |
KR20200046845A (en) | 2018-10-25 | 2020-05-07 | 주식회사 포스코 | Scale removing apparatus and method for low chromium ferritic stainless steel hot-rolled steel sheet |
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