1985 Volume 51 Issue 12 Pages 2253-2258
A new measurement equipment was introduced which can measure the thermal properties and the optical absorptance of CO2 laser light by stepwise heating system using low power CO2 laser light as the heat source. Following results are obtained as to absorption characteristics of iron materials. (1) The absorptance μ increases as the CLA surface roughness σ increases. The relation between μ and σ is represented as μ∝ σ 0.35, where σ> 0.1 μm. (2) The absorptance on roughed surfaces considerably reduces by diminishing the surface defects through annealing. The main cause of absorptance increase on roughed surfaces would not exist in surface roughness itself but in residual surface strain which increases the DC electric resistance of specimen surfaces. (3) The asorptance make higher as the carbon content in the specimen increases. (4) When the oxidized layer over 0.1 μm thick is formed on the surface, the absorptance extremely increases. (5) The absorption characteristics under a high energy density condition of ca. 105 W/cm2 which is often generated in actual laser machining processes show a similar tendency to those of (1) - (4), so that the fundamental measurement of absorption by this stepwise heating method is usuful for analysing the laser machining phenomena and for selecting the machining conditions.
