焊接熔池表面凝固速率测量的新方法

A NOVEL MEASUREMENT METHOD FOR SOLIDIFICATION RATE OF WELD POOL SURFACE

设计了低碳钢激光点焊工艺,显示了小尺寸液态熔池均匀回缩的凝固过程,以此作为平台,进行了焊接熔池表面温度与凝固速率测量方法的研究.采用红外测温仪从熔池表面直接获取熔池凝固过程温度曲线;利用金属固相与液相表面发射率的差异从熔池凝固温度曲线中提取能准确反映液固转变的特征信息,以此推算了熔池表面的凝固速率;并通过进一步的工艺实验,验证了凝固速率与焊点背面直径之间的良好对应关系.该方法亦适用于其它热加工过程金属凝固速率的测量与分析.

Laser spot welding of mild steel was used to reveal the uniform retracting solidification process of the small-scale molten pool. A novel method for calculating the solidification rate of laser spot weld pool surface was presented. The surface temperature of weld pool during solidification process was measured by a point infrared sensor. Based on the difference in emissivities of the solid surface and liquid surface, the output data of infrared sensor, which can accurately reveal the liquidsolid transformation, was demonstrated, from which the solidification rates at different locations of the molten pool surface were obtained. Experiment result shows that the solidification rate is related to the bottom weld diameter. This method is also appropriate to measure the solidification rates of various metals in other heat processes.