工程机械用Q690D钢板焊后中心开裂原因及改善

Analysis of the Cause of Cracking in the Center of Q690D Steel after Welding

为找出Q690D钢板焊后中心开裂原因,对取样板进行了成分、组织、气体、低倍和夹杂物分析,结果显示,钢中氢和氮异常,气体含量偏高。除按标准要求对取样板进行常规拉伸、冲击试验外,同时进行了Z向拉伸检验。整体结果表明,钢板强韧性能良好,但Z向性能较差。通过Z向断口观察,出现大量孔洞及浮云状组织,为钢中气体含量高所致,同时也是造成Q690D焊后产生中心裂纹的根本原因。经采取工艺改进措施后,钢中气体含量降低,铸坯质量提升,钢板各项性能优异。

In order to find out the cause of the center cracking of the Q690D steel plate after welding,the sample plate was analyzed on composition,structure,gas,low magnification and inclusions.The results showed that the hydrogen and nitrogen in the steel were abnormal and the gas content was high.In addition to the conventional tensile and impact tests on the sample plates according to the requirements of the standard,the Z-direction tensile test was carried out at the same time.The overall results show that the strength and toughness of the steel plate are good,but the Z-direction performance is poor.Observed through the Z-direction fracture,a large number of pores and cloud-like structures appear,which are caused by the high gas content in the steel and are also the root cause of the central crack after Q690D welding.After the process improvement measures are taken,the gas content in the steel is reduced,the quality of the cast slab is improved,and the performance of the steel plate is excellent.