Abstract
The weldabilities were investigated during 10 kW high-power fiber laser welding of 304 stainless steel with the shielding gases of 100% Ar, 80% Ar + 20% CO2 and 100% CO2, respectively. As the proportion of CO2 in shielding gas increased from 0% to 20% then to 100%, the molten pool became unstable and the optional parameter range for obtaining a good weld appearance became narrow. The defocused distance was more negative during the CO2 shielded welding, where the weld joint without apparent defect, the maximum penetration, and a necking of weld width were formed. Porosity has been suppressed and eliminated in the CO2 shielded weld joint. The highest microhardness was obtained from the Ar + CO2 shielded weld joint, because the denser δ-ferrite appeared in the Ar + CO2 shielded weld joint. The microhardness of CO2 shielded weld joints was relative low because of the oxidation of the elements of C, Si, Mn, and Cr, which reduces the solid solution hardening tendency during the welding process.
Highlights
As an advanced welding technology, high-power fiber laser welding of thick plate stainless steel has been widely researched
When the types and proportions of mixed shielding gases were changed during laser welding, the rules of absorption and scattering for the laser beam were studied through theoretical calculations [5]
The results showed that a small amount of O2 in the shielding gas could combine with C in the base metal to form CO2
Summary
As an advanced welding technology, high-power fiber laser welding of thick plate stainless steel has been widely researched. The investigations demonstrated that weld defects, including spatter, porosity, and hump, were generated during laser welding of thick plates, due to its complex and volatile metallic vapor flow and molten pool [1,2]. The complex welding process was affected by various factors, such as power density, defocused distance, welding speed, and so on. Among these factors, the shielding gas was one of the most influential on the quality of welding [3,4]. When the types and proportions of mixed shielding gases were changed during laser welding, the rules of absorption and scattering for the laser beam were studied through theoretical calculations [5].
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