Analysis and control measures of the corner crack defects in Q235 slab
The crack defects at the corners of the hot-rolled structural steel Q235 produced by Meishan Iron&Steel Co.,Ltd.were investigated.The research result shows that the main reasons for the formation of this defect are the unreasonable carbon content of Q235 steel and the influence of aluminum nitride precipitation on the high-temperature plasticity of the matrix.In the original composition design,aluminum nitride tends to precipitate at the austenite grain boundary,causing stress concentration and damage to the continuity of the steel matrix when the slab passes through the straightening zone,thereby forming cracks.Through measures such as optimizing the composition design of Q235 steel,reducing the secondary cooling strength of continuous casting,optimizing the performance of protective slag,and improving the precision of casting equipment,the corner crack defects of Q235 steel slabs have been effectively controlled,with the defect occurrence index dropping from 4.3 to 0.9.
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