Product Code: ICAL08_P119

Continuous Laser Process of Welding and Heat Treatment for Stress Improvement Joining
Authors:
Ryoichi Kuwano, Polytechnic University; Sagamihara, Kanagawa Japan
Tsuyoshi Tokunaga, Chiba Institute of Technology; Narashino, Chiba Japan
Yoshiki Nagano, Saitama University; Saitama, Saitama Japan
Toshiyuki Miyazaki, Chiba Institute of Technology; Narashino Japan
Presented at ICALEO 2008

For welding cast iron, such is a kind of high carbon materials, a continuous process of laser welding and laser heat treatment is proposed. These materials tend to form cracks during cooling period after welding, therefore the process is designed to obtain low cooling rate and region limited heat treatment with once works clamping. This process is adapted to industrial line operation. Dissimilar materials parts of cast iron and stainless steel joining were tried. These parts were used in the exhaust components of automobile engines. On the welding process, pulse irradiation of a laser with the optimized power produces the minimize heat affected zone (HAZ). After the welding, changing process parameters and then the laser was scanning on the processed region (contain the HAZ) continuously. Observations of the weld specimen, the formations of high carbon martensite were transformed into troosetite in the HAZ of the cast iron by the continuous laser process. The HAZ hardness was decreased from 900HV (welding only) to 550HV, causing the tensile strength of the weld joints to increase from 343MPa up to 408MPa.