Effect of Laser Power on Microstructure and Tensile Properties of Laser Welded DP۵۹۰ Steel Joints

This study investigated the effects of varying laser power on the microstructure and tensile properties of DP۵۹۰ steel joints. Three joints were prepared using three different laser power levels (۴۰۰W, ۴۵۰W, and ۵۰۰W), while keeping all other factors constant. The results indicated that laser welding resulted in the formation of martensite in the fusion zone, leading to a notable increase in hardness. However, with increasing the laser power, the hardness increment decreased due to the presence of acicular ferrite and Widmanstatten ferrite alongside martensite. The heat-affected zone (HAZ) of all welds exhibited a region where hardness dropped below that of the base metal (BM) due to partial tempering of martensite. This softening effect intensified with higher laser power. The sample welded with a laser power of ۴۰۰W failed early in the tensile test due to lack of penetration. Conversely, the other two samples failed within the softened zone, showing yield strength values similar to the BM and high joint efficiency values (۹۲.۵% for ۴۵۰W and ۸۹.۵% for ۵۰۰W) but with a noticeable reduction in elongation. Both DP۵۹۰ steel and welded joints exhibited a two-stage work hardening behavior consisting of a transient stage followed by a stage III hardening.

کلیدواژه ها:

Dual-Phase steel ، Laser welding ، laser power ، Microstructure ، tensile properties