700 MPa 级高强度大梁钢冲压开裂原因与控制措施

采用 OM 和 SEM 对 700 MPa 级高强度大梁钢冲压开裂原因进行了分析。结果表明，在高强度大梁钢冲压过程中出现的纵梁穿线孔裂纹主要为连冲工艺不当导致；纵梁端部折弯角部裂纹主要是由于原板坯存在内裂纹和大尺寸 TiN 夹杂物，在冲压过程中外表面受到拉应力产生裂纹，裂纹沿横纵向扩展导致。通过将钛质量分数由 0.10% 降至 0.07%，将氮质量分数控制在不大于 0.004% 的范围内，降低大尺寸TiN析出量。化学成分调整后，力学性能满足供货技术条件要求，对钢板进行冲压验证，端部完好，未见折弯裂纹存在，彻底解决了该缺陷。

Causes and control measures of stamping cracking #br#of 700 MPa grade high strength beam steel

The causes of stamping cracking of 700 MPa high strength beam steel were analyzed by OM and SEM. The results showed that the cracks in the stringer hole of the longitudinal beam were mainly caused by the improper continuous stamping process. The corner cracks at the end of the longitudinal beam were mainly due to the internal cracks and large sized TiN inclusions in the original slab, which caused cracks when the outer surface of the beam was subjected to tensile stress during the stamping process, and the cracks expanded along the longitudinal and transverse directions resulted in the corner cracks. By reducing the titanium mass fraction from 0.10% to 0.07%, and controlling the nitrogen mass fraction below 0.004%, the amount of large sized TiN was lower. After the chemical composition adjustment, the mechanical properties could meet the requirements of the technical. The stamping verification of the steel plate showed that the end of the longitudinal beam was intact and there were no corner crack defects, which completely solved the defect.