Cold-rolled packaging steel strip pit of reason and solution

( 1) Defect features: the packaging steel strip surface asperity or black dot patches. Article, points, block, with local or continuous piece distribution size different pits, individual in black hemp spot. ( 2) Reasons (1) strip steel raw material a slight pressure oxidation of iron, while rolling or pickling fall off into a rough surface or not do. (2) of cold rolling emulsion is too dirty. Impurities assure people, black pockmark after annealing. ( 3) For LiaoChang take measures to prevent and eliminate method (1). The surface of strip steel materials pressure tin oxide. (2) often clean rolling mill and the change of emulsion. Ensure rolling emulsion is clean. ( 4) ①用肉眼检査检査判断。 (2) high quality board I livor board opposite allow 嵙 within a quarter plate thickness tolerance is not greater than the minimum thickness within the scope of the slight pitting. U set both sides plate is allowed within the scope of one half the thickness tolerance is not greater than the minimum thickness within the scope of the slight pitting. Three groups of plate is allowed within one half the thickness tolerance is not greater than the minimum thickness within the scope of the minor pitting and localized pitting. Reverse side is allowed within the scope of the tolerance range is not greater than the minimum thickness of slight pitting. Ordinary plate gb regulation, allows for depth is not more than half the thickness tolerance of localized pitting. Common plate or regulations, the depth is allowed no greater than 厗 degree of tolerance of 0. 7 times of localized pitting. (3) local pitting can use grinding method is clear.