Assessment of Heat-Affected Zone Softening of Hot-Press-Formed Steel over 2.0 GPa Tensile Strength with Bead-On-Plate Laser Welding

Applied Sciences

Kwangsoo Kim¹  Namhyun Kang¹  Cheolhee Kim²  Minjung Kang² 

[1] Department of Materials Engineering, Pusan National University, Changjeon-Dong, Pusan 46241, Korea;Welding and Joining Research Group, Korea Institute of Industrial Technology, Songdodong Incheon 21999, Korea;

关键词: hot-press-formed steel;    high-strength steel;    2 GPa strength;    laser welding;    heat-affected zone;    softening;   

DOI  :  10.3390/app11135774

来源: DOAJ

【 摘 要 】

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 the weld metal, while relatively soft microstructures of tempered martensite and ferrite phase were partially formed in the intercritical HAZ (ICHAZ) and subcritical HAZ (SCHAZ) areas. In the tensile test, the joint strength was 10–20% lower than that of the base metal, and the fracture initiation was estimated at the ICHAZ/SCHAZ boundary, where the lowest hardness was confirmed by the nanoindentation technique.

【 授权许可】

Unknown