Nihon Kikai Gakkai ronbunshu (Aug 2022)
Studies on Deformation Behaviour of Thin Carbon Steel Plate by Laser Quenching and its Mechanisms
Abstract
Laser quenching is a partial quenching method that significantly reduces deformation associated with heat treatment compared to conventional methods such as furnace quenching and induction quenching. However, thin parts such as brake disk and miniature-guide rail are subject to large deformation even by laser quenching. To expand the laser quenching applications, we proposed “dummy irradiation method” to complete heat treatment and deformation correction only by laser irradiation. Although the effectiveness of this method has been confirmed in our previous study, more detailed studies on the deformation of thin steel plate caused by laser irradiation are necessary to achieve highly accurate correction by dummy irradiation method. Therefore, laser irradiation experiments were conducted under various laser powers on three types of S50C plates with thicknesses of 2.5 mm, 3.0 mm and 3.5 mm, and the detailed deformation behaviors and the mechanism of the deformations were investigated. By the laser irradiation, the downward convex deformation (positive deformation) was caused in the direction perpendicular to the laser scanning direction, regardless of the laser power or plate thickness. In the laser scanning direction, both positive and negative deformations occurred depending on the laser power. Positive deformation occurred at low laser power and negative occurred at high laser power. Positive and negative deformations occurred at different times during the laser irradiation process: the positive deformations occurred during or immediately after the laser irradiation, while the negative occurred during the cooling process. It was found that the negative deformation in the laser scanning direction that occurs at high laser power could be related to the bending moment generated by the positive deformation in the direction perpendicular to laser scanning. From this result, it was considered that the plate width would affect the deformation caused by laser quenching. In order to correct the deformation by dummy irradiation, it is necessary to consider the plate width of the object as well as the laser irradiation conditions such as laser power and scanning speed.
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