Research On Laser Welding Procedure Of Stainless Steel Sheet

Stainless steel sheet are more and more widely applied in industry, especially in theautomotive and aerospace industry. In the welding of stainless steel sheet, adopting thetraditional arc welding may easily cause welding deformation, which can’t meet theindustrial requirement. In order to reduce deformation in the process of thin stainless steelwelding, generally the laser welding with high energy density, and TIG welding with smalllinear energy are adopted. In this paper, we study the welding of thickness to1mm ofSUS304stainless steel sheet with pulse laser welding, the influence of weldingparameters on weld, analysis of the causes and prevention measures of welding defectsoccurred during pulsed laser welding of SUS304stainless steel sheet. The microstructureand mechanical properties of welded joint are researched, and the pulsed laser weldingprocess of stainless steel sheet is optimized, basic data are provided in order to obtain thecomprehensive performance of high quality welded joint.Relations and restrains exist between pulsed laser welding process parameters,appropriate parameter combination is needed to obtain qualified welding joint. In variousprocess parameters, the pulse frequency has the greatest influence on the quality of theweld, the selection of appropriate pulse frequency is particularly important. In the weldingof stainless steel plate, in order to get better formed weld, the selection of processparameters should follow the principle of the small current, high pulse frequency, bigpulse width and high welding speed.Improper welding process settings can easily lead to welding defects such as porosity,spatter, undercut and welding deformation. For1mm of SUS304stainless steel sheet,when the pulse frequency is15Hz and30Hz, the technical porosity can’t be completelyeliminated. the shape of the hole is conical, irregular and spherical. And when the pulsefrequency is45Hz, whatever the value of welding current, welding speed and pulse widthvary, no technical porosity occurs. When the welding current is180A, it is prone to weldspatter. Reducing the current below160A, can effectively reduce the welding spatter.When the welding speed is800mm/min, the weld is prone to undercut. Slowing down thewelding speed appropriately, can reduce the tendency of undercut.During the pulse laser welding of stainless steel sheet, the weld microstructureusually have obvious stratification. The region near the fusion line is long and thin dendrites, these dendrites point to weld center along the surface of weld. Away from theweld fusion line are dendrites in disorder, in the weld center is small and fine cubic.For1mm of SUS304stainless steel sheet, the coke can take-1mm, welding currentcan take120A~130A, pulse frequency can take50Hz~60Hz, the pulse width can take2.5~3.0ms, the welding speed can take600mm/min to720mm/min, the well matchedparameters can get better weld joint both in forming and mechanical performance. Amongthem the fifth experimental specimen’s performance of weld joint is optimal, the specificprocess parameters: take1mm from the coke, welding current is130A, pulse frequencyof50Hz, pulse width is3.0ms, the welding speed is600mm/min.