Formation mechanism of porosity in high power YAG laser welding
Formation mechanism of porosity in high power YAG laser welding
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DOI：
10.2351/1.5059433
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发表时间：
2000
期刊：
影响因子：
--
通讯作者：
S. Katayama;N. Seto;M. Mizutani;A. Matsunawa
中科院分区：
文献类型：
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作者：
S. Katayama;N. Seto;M. Mizutani;A. Matsunawa
为了研究气孔的形成机理，获得良好的焊缝质量，采用高功率YAG激光焊接A5083铝合金和304钢，研究了气孔形成的条件，并利用X射线透射成像系统对激光焊接过程中小孔、气泡、气孔和液体流动等进行了观察。除304型在N2气中焊接外，在Ar、He和N2气中焊接的3.5kW YAG激光器焊缝中形成了大量的气泡和气孔。即使在He和Ar气体中，304型钢在高焊接速度下的气孔也会减少。金属从小孔底部蒸发形成大量气泡，并在固液界面前向上流动。在低速焊接时，A5083合金熔池表面的气泡消失，但大部分气泡被捕获在焊道的凝固前沿。保护气体也包括在孔隙中。这一机理与大功率CO2激光焊接机理相似。在He、Ar或N2保护气体中，A5083合金和304钢的焊接熔池均出现了从小孔底部到熔池后上部、从熔池表面附近的后部到前部以及从小孔后面的顶部到底部的快速流动。为了研究气孔的形成机理和获得良好的焊缝质量，研究了A5083铝合金和304钢在高功率YAG激光焊接时气孔的形成条件，并对小孔的行为进行了分析。通过X射线透射成像系统，使用标记观察激光焊接过程中的气泡和孔隙以及液体流动。除304型在N2气中焊接外，在Ar、He和N2气中焊接的3.5kW YAG激光器焊缝中形成了大量的气泡和气孔。即使在He和Ar气体中，304型钢在高焊接速度下的气孔也会减少。金属从小孔底部蒸发形成大量气泡，并在固液界面前向上流动。在低速焊接时，A5083合金熔池表面的气泡消失，但大部分气泡被捕获在焊道的凝固前沿。保护气体也...
With the objectives of clarifying the formation mechanism of porosity and producing a sound weld bead, welding conditions of porosity formation were investigated in A5083 alloy and Type 304 steel welded with a high power YAG laser, and the behavior of a keyhole, bubbles and porosity as well as liquid flows were observed during laser welding through X-ray transmission imaging system using markers. It was confirmed that a lot of bubbles and pores were formed in 3.5 kW YAG laser weld beads produced in Ar, He and N2 gases except Type 304 in N2 gas. Porosity was reduced at high welding speed in Type 304 steel even in He and Ar gases. A lot of bubbles were formed by the evaporation of metals from the bottom tip of the keyhole and flowed upwards in front of the solid-liquid interface. Some bubbles disappeared out of the molten surface especially in A5083 alloy welded at low welding speed, but the majority of bubbles were trapped at the solidifying front of the weld beads in most cases. The shielding gas was also included in the porosity. This mechanism is similar to that in high power CO2 laser welding. Fast liquid flows occurred circularly from the bottom keyhole to the rear upper part of the molten pool, from the rear to the front near the pool surface, and from the top to the bottom behind the keyhole in weld molten pools of both A5083 alloy and Type 304 steel in He, Ar or N2 shielding gas. Slightly different flows were noticed in the molten pool of Type 304 steel between YAG and CO2 lasers.With the objectives of clarifying the formation mechanism of porosity and producing a sound weld bead, welding conditions of porosity formation were investigated in A5083 alloy and Type 304 steel welded with a high power YAG laser, and the behavior of a keyhole, bubbles and porosity as well as liquid flows were observed during laser welding through X-ray transmission imaging system using markers. It was confirmed that a lot of bubbles and pores were formed in 3.5 kW YAG laser weld beads produced in Ar, He and N2 gases except Type 304 in N2 gas. Porosity was reduced at high welding speed in Type 304 steel even in He and Ar gases. A lot of bubbles were formed by the evaporation of metals from the bottom tip of the keyhole and flowed upwards in front of the solid-liquid interface. Some bubbles disappeared out of the molten surface especially in A5083 alloy welded at low welding speed, but the majority of bubbles were trapped at the solidifying front of the weld beads in most cases. The shielding gas was also...