Q1400超高强钢激光-MAG复合焊抗裂性研究

Study on Crack Resistance of Q1400 Ultra-high Strength Steel by Hybrid Laser-MAG Welding

针对超高强钢在焊接过程中容易产生裂纹等问题,采用激光-电弧复合焊对20 mm厚Q1400E超高强钢进行了抗裂性研究。通过斜Y坡口裂纹敏感性试验发现,在焊缝中心偏上位置易产生焊接裂纹。经过金相组织检查、表面形貌检查、EDS能谱分析等检测手段,确定此裂纹为凝固裂纹。裂纹产生原因:(1)液态金属补缩不足导致缩松;(2)C、S、P等有害元素发生微观偏析;(3)母材淬硬性大,坡口尖角处的拘束应力大。利用激光复合焊接方法深熔焊接特点及焊前预热措施进一步降低了焊接拘束应力,结果表明,采用激光功率8 500 W,焊接电流250 A,焊接电压24 V,焊接速度1.2 m/min,预热200℃的工艺参数可以有效解决20 mm厚Q1400超高强钢的焊接裂纹问题。

The crack resistance of 20 mm thick Q1400E ultra-high strength steel is studied using a laser arc hybrid welding method.Through the crack sensitivity examination of the inclined Y-groove,it is found that welding cracks are easy to occur at the upper position of the weld center.Through metallographic examination,surface morphology examination,and EDS analysis,it is determined that the crack is a solidification crack.Causes of cracks:(1)insufficient shrinkage of liquid metal leading to shrinkage porosity;(2)micro segregation of harmful elements such as C,S and P occurs;(3)the base metal possesses a high hardenability and high binding strain at the pointed corners of the groove.The characteristics of deep penetration welding using laser hybrid welding and pre welding preheating measures are used to further reduce the welding restriction stress.The results reveal that when using welding parameters such as laser power 8500 W,welding current 250 A,welding voltage 24 V,welding speed 1.2 m/min,and preheating 200℃,the welding crack problem of 20 mm thick Q1400 ultra high strength steel can be efficiently solved.