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Assessment Of Heat-Affected Zone Softening Of Hot-Press-Formed Steel Over 2.0 Gpa Tensile Strength With Bead-On-Plate Laser Welding, Kwangsoo Kim, Namhyun Kang, Minjung Kang, Cheolhee Kim
Assessment Of Heat-Affected Zone Softening Of Hot-Press-Formed Steel Over 2.0 Gpa Tensile Strength With Bead-On-Plate Laser Welding, Kwangsoo Kim, Namhyun Kang, Minjung Kang, Cheolhee Kim
Mechanical and Materials Engineering Faculty Publications and Presentations
High-strength hot-press-formed (HPF) steels with a fully martensitic microstructure are being widely used in the fabrication of automotive body structure, and 2.0 GPa-strength HPF steel has recently been commercially launched. However, heat-affected zone (HAZ) softening is unavoidable in welding martensitic steel. In this study, the HAZ softening characteristic of 2.0 GPa HPF steel was investigated by applying a high-brightness laser welding process, wherein the heat input was controlled by varying the welding speed. Microstructural evaluation and hardness test results showed that the base metal with a fully martensitic microstructure was changed to the same type of fully martensitic microstructure in …
Contamination Of Coupling Glass And Performance Evaluation Of Protective System In Vacuum Laser Beam Welding, Yongki Lee, Jason Cheon, Byung-Kwon Min, Cheolhee Kim
Contamination Of Coupling Glass And Performance Evaluation Of Protective System In Vacuum Laser Beam Welding, Yongki Lee, Jason Cheon, Byung-Kwon Min, Cheolhee Kim
Mechanical and Materials Engineering Faculty Publications and Presentations
Vacuum laser beam welding enables deeper penetration depth and welding stability than atmospheric pressure laser welding. However, contaminated coupling glass caused by welding fumes in the vacuum space reduces laser transmittance, leading to inconsistent penetration depth. Therefore, a well-designed protective system is indispensable. Before designing the protective system, the contamination phenomenon was quantified and represented by a contamination index, based on the coupling glass transmittance. The contamination index and penetration depth behavior were determined to be inversely proportional. A cylindrical protective system with a shielding gas supply was proposed and tested. The shielding gas jet provides pressure-driven contaminant suppression and …