According to the characteristics of decarburization in the metallographic structure of SS400 steel plate surface cracks and the results of inclusion energy spectrum analysis, it can be concluded that the cracks on the steel plate surface originated from the cracks on the continuous casting billet. In the subsequent rolling process of the billet, the cracks further spread along the rolling direction to form SS400 steel plate surface cracks.
In order to improve the quality of continuous casting billet and avoid surface cracks of SS400 steel plate, continuous casting and rolling process were improved and optimized, and the following improvement measures were taken:
1) Adjust the drawing speed of continuous casting billet to reduce it.
2) The cold billet is loaded in the rolling furnace, and the hot billet is finished off the line. After the production line, the edge and corner of SS400 steel plate were cleaned and chamfered with the flame of air cutting gun.
3) During rolling, increase descaling water pressure in rough rolling and finishing rolling passes according to the thickness specifications of finished products to ensure descaling effect. Taking the above measures to improve the process, and strengthening the supervision and spot check of the implementation of process discipline, the situation of surface cracks on the side of SS400 steel plate after rolling is obviously reduced.
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