Method for preventing yellow discolouration of surface of acid-cleaned steel sheet
A technology for the surface layer of steel plate and steel plate, applied in the furnace type, furnace, heat treatment furnace and other directions, can solve problems such as damage to appearance quality, achieve chemical conversion treatment, excellent corrosion resistance after painting, and prevent yellowing effect.
Active Publication Date: 2014-09-17
JFE STEEL CORP
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Problems solved by technology
[0009] However, in cold-rolled steel sheets produced by pickling, re-pickling, water washing (rinsing), and drying steel sheets after continuous annealing, the surface of the steel sheet may be discolored to yellow, which significantly impairs the appearance quality.
Method used
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Embodiment
[0093] Steel materials A to F shown in Table 1 containing a large amount of Si and Mn were subjected to hot rolling, hot-rolled sheet pickling, cold rolling, continuous annealing, and then pickling under various conditions shown in Table 2. Washing, pickling, water washing, and drying to make high-strength cold-rolled steel sheets with various strengths. Next, samples were cut from each of the above-mentioned high-strength cold-rolled steel sheets, and the degree of yellowing on the surface of the steel sheets was evaluated by the following method, and after chemical conversion treatment and coating treatment were performed under the following conditions in the same way, they were subjected to salt-warm water Corrosion resistance after coating is evaluated by three types of corrosion tests: immersion test, salt spray test, and combined cycle corrosion test.
[0094] (1) Evaluation of yellowing
[0095] A test piece of 70 mm x 150 mm was cut out from the sample cut out from th...
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Abstract
A method for preventing the yellow discolouration of the surface of a steel sheet having been continuously annealed, subjected to acid cleaning, the Si-containing oxide layer in the surface layer of which has been removed, then having been re-subjected to acid cleaning, rinsed and dried. In the method, the surface of the steel sheet is kept in a wet state between the acid washing and the repetition of the acid washing, and between the repetition of the acid washing and the rinsing, and it is preferable that the rinsing is carried out using rinse water having an iron ion concentration which has been reduced to 20g / L or less, and thus the yellow discolouration of the surface of the acid-cleaned steel sheet is prevented, therefore enabling the stable manufacture of a cold-rolled steel sheet which has excellent aesthetic qualities, excellent chemical conversion properties and excellent corrosion resistance after coating.
Description
technical field [0001] The present invention relates to a technique for preventing yellowing of the surface of a steel sheet after pickling. Background technique [0002] In recent years, improvement in fuel efficiency of automobiles has been strongly demanded from the viewpoint of protecting the global environment. In addition, from the viewpoint of ensuring the safety of occupants at the time of collision, there is a strong demand for improvement in the safety of automobiles. In order to meet these demands, it is necessary to reduce the weight and increase the strength of the automobile body at the same time, and the cold-rolled steel sheet that is a raw material for automobile components is actively pursuing thinning based on the increase in strength. However, most automobile components are manufactured by forming steel sheets, and therefore, these steel sheets are required to have excellent formability in addition to high strength. [0003] There are various methods fo...
Claims
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IPC IPC(8): C23G1/08C22C38/00C22C38/06
CPCC23G1/081C21D8/02C23G1/08C22C38/00C22C38/06C22C38/04C23G1/086C23G1/085C23G1/00C22C38/02C21D8/0278C21D9/562
Inventor 增冈弘之安藤聪相泽重行中里和树平章一郎
Owner JFE STEEL CORP