窄间隙MAG立焊动态过程模拟及热物理特性

窄间隙MAG焊(NG-MAG)过程中电弧摆动和分时熔合技术是保证侧壁熔合良好的关键. 通过对摆动电弧移动过程中速度大小和方向不断变化规律的分析,在经典双椭球热源模型的基础上采用坐标变换法建立了NG-MAG立焊摆动电弧动态热源模型. 温度场模拟结果表明,NG-MAG立焊热循环曲线呈"多峰"现象,焊缝表面成形似"积木"而截面成形似"哑铃",与试验结果基本吻合. 分析认为"多峰"现象主要由电弧热源逐次逼近而后远离所致,而"积木"和"哑铃"的成形特点与移动过程中电弧速度(热输入)的周期变化及焊接熔池的动态变化高度相关,上述热特点对后续进行NG-MAG立焊组织演化研究提供技术支持.

Numerical simulation on dynamic process and thermal physical properties of narrow gap MAG vertical welding

In the process of vertical narrow gap MAG (NG-MAG) welding, arc-swinging and time-independent fusion technology is the key to ensure good sidewall fusion. Through analyzing the change rule about velocity and direction of arc-swing, the dynamic heat source model of NG-MAG vertical welding was established by using the method of coordinate transformation based on the classical double ellipsoid heat source model. Temperature field simulation results show that the welding thermal curves are "multi-peak", weld surface shape is "building blocks" and cross section is "dumbbell", which are in consistent with the test result of NG-MAG welding. The "multi-peak" phenomenon is mainly caused by the arc heat source moves near and then away from the side wall, whiles the formation of "building blocks" and "dumbbell" are highly correlated to the periodic change of arc speed (heat input) and weld pool during arc-swing. The above-mentioned characteristics provide the technical support for further research on microstructure evolution of high strength low alloy (HSLA) steel in NG-MAG vertical welding process.