Bending cracking reason of Q235B steel plate of moderate thickness

The bending cracking reason of Q235B steel plate of moderate thickness was analyzed by means of macroscopic observation, chemical composition analysis, metallographic examination and scanning electron microscopy and energy spectrum analysis. The results showed that there were bubbles on the near surface of the cracked Q235B steel plate of moderate thickness, and there were serious segregation and sulfide segregation at the crack propagation and extension. Under the action of stress during cold bending, the crack source was first formed at the near surface bubble position of Q235B steel plate of moderate thickness, and the crack propagated along the segregation band and sulfide extension direction, which eventually led to bending cracking.