抄録
Continuous process of welding and heat treatment using a laser is proposed. The process begins with the welding stage where the laser irradiates in pulse mode at the optimized power so as to minimize the heat affected zone (HAZ). Next, to improve the mechanical characteristics of the HAZ. The temperature during the heat treatment is controlled by the laser power, the scanning speed, and the number of laser scans. Therefore this is a continuous process completed in a short time. This process is applied in the joining of dissimilar materials (spheroidal graphite cast iron and ferritic stainless steel) that are used in the exhaust components of automobile engines. Observations of the weld specimen with a microscope showed the formation of high carbon hardened martensite in the HAZ of the cast iron. The ratio of the welding joint strength to the spheroidal graphite cast iron strength was 69% (343MPa). Then using the heat treatment, the martensite was transformed into troosetite. After the continuous processing (1 laser scan) the joint strength became 82% (408MPa). The trial weld of the car engine exhaust part passed the thermal fatigue test of the engine bench test.
