采用宏观观察、化学成分分析、金相检验、扫描电镜及能谱分析等方法对Q235B钢中厚板弯曲开裂的原因进行分析,结果表明:开裂的Q235B钢中厚板近表面存在气泡,裂纹扩展和延伸处存在严重的偏析和硫化物偏聚;在冷弯过程中的应力作用下,Q235B钢中厚板近表面气泡位置首先形成裂纹源,裂纹沿着偏析带及硫化物延展方向扩展,最终导致钢板发生弯曲开裂。

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.