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Characteristic Analysis of Processing Defects in Stainless Steel After Laser Cutting
L-J. Yang, Y. Ding, Q. Li and Y. Wang

Millisecond laser machining has been widely applied to meet the demands for increasing efficiency and accuracy in the manufacturing industry. But, the residual heat affected zone (HAZ), recast layer and internal microcracks represent a serious impediment to further application. Experiments were conducted to analyse these machining defects for a millisecond pulsed Nd:YAG laser cutting operation of AISI 304 stainless steel using O2 as the assist gas. Metallographic tests were adopted to investigate the characteristics and structure of HAZ, as well as recast layer. The formation mechanism of the recast layer, the HAZ and microcracks were explained. Based on the energy spectrum of the kerf surface, electrochemical corrosion with acid solution was employed to remove the recast layer above the HAZ layer-by-layer. Through subsequent ultraviolet (UV) nanosecond laser processing of the crack region it can be verified that microcracks not only exist in the recast layer, but also penetrate deep into the HAZ from the perspective of the upper and sectional view of the kerf.

Keywords: Nd:YAG laser, ultraviolet (UV) laser, AISI 304 stainless steel, laser cutting, heat affected zone (HAZ), recast layer, microcracks, electrochemical corrosion, millisecond, nanosecond

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