발간논문

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Vol.22, No.4, 361 ~ 370, 1984
Title
Temperature Gradient and Hysteresis Effect of C -steel During the Surface - Hardening by CO2 Laser
김도훈T . H . Kim, 윤영주Y . J . Yoon
Abstract
The rapid heating rate by the irradiation of CO₂laser on the C-steel induced the increase of A_f temperature by about 250˚K. The desirable laser power density for the surface-hardening of medium C-steel for 5 second varied from 1.7×10³W/㎠ to 4.1×10³W/㎠ depending upon the hardened thickness. The calculated temperature gradient in the hardened layer was about 160˚K/min. Thus the desired thickness can be controlled by the selection of appropriate laser power density. When cold-worked medium C-steel was irradiated with a relatively higher laser power, the softened region with minium hardness was located between the hardened layer and the matrix. Meanwhile if the laser power was not enough to transform the laser-irradiated area into austenite, the softening of structure resulted from the relief of work-hardening. Although the turn-off of the laser irradiation caused the self-quenching of low C-steel, the cooling in air was not rapid enough to reach the critical value at which the martensite could be obtained.
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