Continuous laser process of welding and heat treatment for stress improvement joining Available to Purchase

This paper proposes a continuous process of laser welding and laser heat treatment to reduce stress in joints. As the high-carbon material tends to form cracks during the cooling period after welding, the method is designed to provide a low cooling rate and region-limited heat treatment in a single session of work clamping. This process was adapted for industrial-line operation to attempt the joining of parts made of dissimilar materials (cast iron and stainless steel) used in automobile engine exhaust components. In the welding process, pulse irradiation using a laser with optimized power minimized the heat-affected zone (HAZ). After welding, the process parameters were changed and the laser was made to scan the processed region (containing the HAZ) continuously. Observation of the weld specimen showed that this laser process changed the formations of high-carbon martensite into troostite in the HAZ of the cast iron. The hardness of the HAZ was reduced from 900 HV (with welding only) to 550 HV, causing the tensile strength of the weld joints to increase from 343 MPa to 408 MPa.