辅助冷、热源防止焊缝凝固裂纹的研究

控制焊缝凝固时所受的拉伸应变是防止焊缝凝固裂纹产生的有效方法之一。利用数值模拟和试验研究了施加辅助冷、热源改变焊接温度场，减少焊缝所受的拉伸应变的规律以及施加冷、热源后对焊接接头组织和硬度的影响。研究表明：辅助热源的能量密度及施加位置合适时，可以有效地降低拉伸应变，防止凝固裂纹产生；施加辅助冷源也可以降低焊缝所受的拉伸应变，但效果不如辅助热源显著；在本试验条件下施加辅助冷、热源对焊接接头的组织影响不大，对硬度也无明显的影响。

PREVENTION OF SOLIDIFICATION CRACKING IN WELDS WITH AUXILIARY HEAT OR COOL SOURCE

Controlling the strain of weld metal during solidification is one of the effective methods to prevent solidification cracks in weld. In this project,the effects of auxiliary heat or cool sources on the temperature distribution,the tensile strain of weld metal during solidification as well as on the microstructure,hardness of joint are studied with numerical analysis and experimental methods.The results indicate that the auxiliary heat sources can effectively decrease the tensile strain of weld metal during solidification and prevent solidification cracking.Auxiliary cool source can also decrease the tensile strain,but its effect is less than that of auxiliary heat source.Auxiliary heat and cool sources have no distinct effects on the microstructures,hardness and crystal sizes of joints.