关键词: 罐箱用 316L 宽厚冷轧板, 白斑, 乳化液, 脱脂, 退火

Abstract: Serious white spots defect occurs on the surface of (4.4～4.6) mm×2050 mm wide-thick cold rolled strip of 316L stainless steel (/%:0.02C,17. 12Cr,10. 15Ni,2.06Mo) for tank container in production process. The causes of the white spots are researched by means of feature analysis, steels grades comparison and on-site defect tracking, the results show that there is much emulsion on the surface of cold rolled strip, on which the formed oxide scale is unevenly distributed in case of incompletely degreasing and annealing at 980 ℃,the color of the oxide scale on the surface with much emulsion is white, these white oxide scales are changed into white spots after pickling. Besides, the influencing factors of the residu al emulsion on the surface of rolled strip and the removal effect of residual emulsion are systematically studied. By applying oil scraping system for nonwoven-fabric roller, adding air knife purging system, controlling emulsion concentration 1.5%~ 3% and temperature(55±3)℃,repairing two sets of magnetic filtration system in rolling process, through controlling de- greasing electrical conductivity7.5 μs/cm and loop filling speed 50 m/min,adjusting9～12 area Furnace temperature to 1030 ℃,the unqualified rate of white spots is reduced from 10% to 0.5% or less.

Key words: 316L Wide ?thick Cold Rolled Strip for Tank Container, White Spots；Emulsion；Degreasing；Annealing