Laser forming of carbon steel sheets by cicled laser irradiation

Laser forming (LF) of sheet material is a progressive treatment process and have some benefits. Laser forming is a flexible process and needs no heavy metal-intensive equipment and tools. Materials with high rigidity, brittle, elastic materials can be treated by laser forming. Therefore, the investigation of LF is important task. An important point to study is repeatability of multipass laser forming of sheet materials and exploring of possibilities of stabilizing process parameters. Actually, this research is aimed at these issues. Results of heat process modeling during laser forming are shown. The modeling was carried out in specially developed software based on the three-dimensional non-stationary equation of heat conductivity. The analysis of transformations in carbon steels during forming cycles of laser irradiation is presented. The results of metallographic investigation of processed samples of steel 65G are presented, where occurrence of martensitic transformation is confirmed. Dependence of the deformation magnitude on the number of laser irradiation cycles and a comparison of the forming of samples without prior heat treatment and subjected to bulk hardening are shown. It is noted that collected heat during multi pass laser treatment causes expand heat affected zone decrease homogeneity of it and decrease maximal level of micro hardness on 100 HV. I is mentioned that previously hardened samples (by volume hardening) have higher level of bending angle compare to samples without previous heat treatment. Difference between mentioned options was more than 40% after twelve passes. It was recommended to use external cooling source to decrease level of collected heat in case of multipass laser forming process. High level of collected heat could initiate surface melting of treated samples.