万瓦级激光-电弧复合焊接焊缝成形特性分析

Analysis on Characteristics of Weld Formation with 10 kW Level High Power Laser⁃Arc Hybrid Welding

为探究万瓦级激光-MAG复合焊接焊缝成形特性,在不同的激光功率下,对比分析了三种不同复合焊接方法在焊缝成形、等离子体形态方面的差异性及关联性。结果表明:随着激光功率变化,焊缝的特征尺寸及波动与等离子体的特征尺寸及波动具有一定的对应关系,具体表现为:随着激光功率增加,等离子体面积及其波动都增加,焊缝熔深、熔宽及其波动均增加;当激光功率增加到20 kW时,等离子体面积及其波动的增量开始减小,焊缝尺寸的增量也开始减小,焊缝成形质量开始变差。激光-单丝MAG复合焊接方法在20、25、30 kW激光功率下的平均熔深增量相比5、10、15 kW下的减小了71.64%。在相同的工艺参数下,与激光-单丝MAG复合焊接相比,激光-单丝MAG复合填丝焊接下的等离子体面积及其标准差显著增加,熔深减小,成形变差,而激光-双丝MAG复合焊接下的等离子形态、焊缝成形变化均不明显。随着激光功率增加,不同的添丝方式体现在焊缝成形及等离子体形态等方面的差异性逐渐增强,当激光功率增加到20 kW时,焊缝熔深以及影响熔深的等离子体面积及其波动的增量有所减小。

Objective Ultrahigh-power laser welding is an important development direction for plates with medium-thickness welding.The laser-arc hybrid welding method has obvious advantages in improving the appearance,quality,and efficiency of the weld.Therefore,the 10 kW level high power laser-arc hybrid welding technology has developed rapidly.However,when the laser power reaches more than 10 kW,the vaporization behavior of the materials,the interaction between the laser beam and plasma,the stable state of the molten pool flow,the mechanism of heat transmission,and the metallurgical behavior of the weld all change to different degrees,which will affect the stability of the welding process,leading to a poor appearance of the weld and generation of weld defects,and seriously limiting the popularization and application of 10 kW laser welding.The variation in the plasma morphology during the welding process indirectly reflects the stability of the welding process.In this study,the characteristic parameters are collected,which reflect the plasma morphology and appearance of welds of three different hybrid welding methods with different laser powers:laser-MAG single-wire hybrid welding,laser-MAG single-wire hybrid welding with filler wire,and laser-MAG double-wire hybrid welding,to seek the characteristic parameters for predicting the quality of welds and providing reference values for ultrahigh-power laser-arc hybrid welding with different heat sources.Methods Three welding methods were adopted in the present study:laser-MAG single-wire hybrid welding,laser-MAG single-wire hybrid welding with filler wire,and laser-MAG double-wire hybrid welding.The weld width and penetration were extracted when the laser power increased from 5 kW to 30 kW.Then,the plum and spatter,which were produced in the welding process and investigated by a high-speed camera,the plasma diffusion height,area,and plasma splash area with different laser powers were extracted for the three welding methods.The goal is to explore the relationship between the size of the weld and the morphological characteristics of the welding plasma for different welding methods and laser energy,which lays the foundation for 10 kW high power laser-arc hybrid welding.Results and Discussions As shown in Figure 4,the weld face of the three welding methods becomes worse with the increase in laser power,especially when the laser power is 20 kW.The appearance of the weld changes differently,and the differences among the three welding methods are gradually highlighted.The increase in the feature size of the weld is proportional to the increase in the laser power,but the relationship is not linear.Before and after the laser power reaches 20 kW,the increase in the weld feature size decreases slightly,and concave-convex points appear in the size curve;when the power is the same,the penetration of the laser-MAG single-wire hybrid welding is small,while that of the laser-MAG single-wire hybrid with filler wire is large.The former increases slightly with an increase in laser power,whereas the latter increases significantly.The variation law of the weld width with laser power is similar to that of penetration,and the weld size curve of the laser-MAG double-wire hybrid welding method is always in the middle position,as shown in Figure 6.For the three welding methods,the plasma area and the fluctuation increase with an increase in the laser power,and the variation trend of plasma fluctuation is the same as the fluctuation of penetration and the fluctuation of plasma spatter,but the fluctuation of weld width is smaller,as shown in Figures 9 and 11.v Conclusions Three different welding methods were used to explore the regular appearance of the weld and plasma morphology with different laser powers.The results showed that when the power was increased,the plasma area and fluctuation of the three welding methods increased,and the weld width,penetration,and fluctuation values increased.When the power was increased to 20 kW,the increment in the plasma area and fluctuation decreased,the increment in the weld size decreased,the maximum increment of weld penetration for laser-MAG single-wire hybrid welding decreased by 71.64%compared with the other two welding methods,and the appearance of the weld worsened.In addition,when the power was constant,compared with laser-MAG single-wire hybrid welding,the plasma area and standard deviation increased,the penetration depth decreased,and the appearance of the weld deteriorated.When laser-MAG double-wire hybrid welding was adopted,the changes in the plasma morphology and appearance were not obvious.When the power was increased to 20 kW,the increment in the amplitude of the variation decreased.In addition,there is a correlation between the appearance of the weld and plasma morphology.The plasma morphology is related to the laser power and wire feeding mode:when the laser power increases or the filler wire is added,the plasma concentration in the incident direction of the laser increases,the stability worsens,and the attenuation and interference of the laser enhance,which leads to a decrease in penetration and an increase in the spatter.Therefore,the change in plasma shape can be used as a reference to predict the appearance quality of the weld.