药芯焊丝脉冲TIG增材制造倒Y形电弧光电特性分析

Analysis of Inverted Y-Shaped Arc Photoelectricity Characteristic of Flux-Cored Wire Pulsed TIG Additive Manufacturing

在药芯焊丝脉冲TIG电弧增材制造过程中,发现了电弧“骑”在成形件两侧的现象,该电弧被称为倒Y形电弧。倒Y形电弧对成形件两侧均有加热作用,其偏移导致成形件两侧受热不均,影响熔覆过程稳定性。按照点阵法测得的光谱数据利用Stark展宽方法计算了倒Y形电弧拖曳部分的电子密度,本研究试验条件下有部分区域(侧壁以外2 mm左右,Z方向0位置以下1.5 mm左右)符合局部热力学平衡条件。利用光谱诊断的Boltzmann图法来计算电子温度,将各点的数据拟合得到完整电弧温度场,分别从平行和垂直于焊枪运动方向分析了熔敷过程中倒Y形电弧的温度场。结果表明,从两个方向光谱诊断得到的倒Y形电弧钨极轴线处的温度最高值均大约为14000~16000 K,分布在钨极端部下方0.5~1.5 mm范围内,电弧拖曳部分的温度大约为5000~8000 K。在垂直于焊枪运动方向上,当钨极轴线与熔敷层中心重合时,正常倒Y形电弧及其温度场关于钨极轴线对称分布。当钨极轴线偏移熔敷层中心左侧1 mm时,倒Y形电弧向左发生偏移且温度场也向左发生了偏移,熔敷层左侧温度明显高于右侧温度。在平行于焊枪运动方向,倒Y形电弧温度场扭曲较小,熔敷过程中焊丝从钨极前(左)侧送入,扰动电弧且吸收电弧热量,导致电弧前(左)侧的尺寸和温度均小于后(右)侧,电弧拖曳部分出现了收缩现象。通过分析钨极轴线与熔敷层中心重合以及钨极轴线向左偏移熔敷层中心1 mm的电信号,发现前者的均值电压、基值均值电压、峰值均值电压均小于后者。利用电信号结合高斯热源模型进行分析,在成形件左侧壁相同位置,正常倒Y形电弧的温度和热流密度小于偏移的倒Y形电弧,在成形件右侧壁相同位置则相反,这与光谱诊断得到的温度场分布关系吻合。研究结果对于建立电弧增材制造过程中新的热源模型和过程监控具有重要意义。

In the process of flux-cored wire pulsed TIG arc additive manufacturing,the phenomenon of the arc riding on both sides of the formed part was found.The arc was called the inverted Y-shaped arc.The inverted Y-shaped arc had a heating effect on both sides of the forming part,and its deviation caused uneven healing on both sides of the forming part,which affected the stability of the cladding process.The electron density of the trailing part of the inverted Y-shaped arc was calculated using Stark broadening according to spectral data measured by the point matrix method.Under the experimental conditions of this study,some areas(about 2 mm outside sidewall,about 1.5 mm below 0 positions in Z direction)conformed to local thermodynamic equilibrium.The electron temperature was calculated using the Boltzmann diagram method of spectral diagnosis,and the complete arc temperature field was obtained by fitting the data of each point.The temperature field parallels to,and perpendicular to the moving direction of the welding torch in the deposition process was analyzed.The results showed that the maximum temperature of the inverted Y-shaped arc at the tungsten electrode tip was about 14000~16000 K,distributed in the range of 0.5~1.5 mm below the tungsten electrode the temperature of the trailing part of the arc was about 5000~8000 K.In the direction perpendicular to the moving direction of the welding torch,when the tungsten electrode axis coincided with the center of the deposited layer,the normal inverted Y-shaped arc and the temperature field were symmetrically distributed along the tungsten electrode axis.When the tungsten electrode axis shifted by 1 mm to the left of the center of the deposited layer,the inverted Y-shaped arc shifted to the left,and the temperature field also shifted to the left.The temperature on the left side of the deposited layer was significantly higher than that on the right.In the direction parallel to the moving direction of the welding torch,the temperature field distortion of the inverted Y-shaped arc was small.During the deposition process,the welding wire was fed in from the front(left)side of the tungsten electrode,which disturbed and absorbed the arc’s heat.As a result,the size and temperature of the arc’s front(left)side were smaller than those of the rear(right)side,and the arc contraction.By analyzing the electrical signals of the two cases where the tungsten electrode axis coincided with the deposited layer center and shifted by 1 mm to the left of the deposited layer center,it was indicated that the mean voltage,the base voltage average and the peak voltage average of the former were less than those of the latter.Based on the analysis by combining the electrical signal and the Gaussian heat source model,it was found that the temperature and heat flux of the normal inverted Y-shaped arc were smaller than those of the offset inverted Y-shaped arc at the same position on the left side of the formed part.In contrast,the opposite results were obtained at the same position of the right side of the formed part,which was consistent with the temperature field distribution obtained by spectral diagnosis.The results of this study were of great significance for establishing a new heat source model and process monitoring in the arc additive manufacturing process.