ビーム偏光と吸収率に関する研究 : 第2報,偏光焼入れ時の吸収率の推定

Transformation hardening was performed on S40C steel by a linear polarized CO2 laser beam without the use of any additional absorbent coating. The depth and width of the hardened zone were measured at different incident angles of the beam. In addition, the relationship between the heat input of the laser beam and the characteristics of hardened zone, such as depth and width, was investigated by finite-element analysis. Absorptivities at different incident angles during laser hardening were deduced by comparing the relationship between the laser power and hardened depth, which was determined experimentally, with the relationship obtained by calculation. A pronounced absorptivity peak of approximately 58% was observed during laser hardening in air when the incident angle was approximately 74°. Absorption characteristics were also deduced in a different atmosphere. The results were compared with absorption characteristics calculated theoretically or measured calorimetrically to investigate the influence of surface temperature and oxidization on absorptivity. It was found that the peak absorptivity value increased when surface temperature rose or oxidization occurred.