Causes of bending crack of Q460C medium thick steel plate

Cracks appeared in the bending process of Q460C steel plate with thickness of 20 mm produced by a factory. The causes of cracks were analyzed by means of macroscopic observation, chemical composition analysis, metallographic examination, scanning electron microscopy and energy spectrum analysis. The results show that the main reasons for the bending crack of the sample were that the content of P and S elements in the molten steel during the steelmaking process was too high, and there was slag in the ladle during the continuous casting process, which led to the segregation of P and S elements in the slab, and there were a large number of non－metallic inclusions in the slab. As the temperature of the rolling process continued to decrease, a serious banded structure was formed inside the steel plate, which eventually led to cracking of the steel plate during the bending process.