JOURNAL OF THE JAPAN WELDING SOCIETY
Online ISSN : 1883-7204
Print ISSN : 0021-4787
ISSN-L : 0021-4787
Studies of High Power CO2 Gas Laser as a Heat Source (Report 2)
Yoshiaki ArataIsamu MiyamotoTakeshi Yamada
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1971 Volume 40 Issue 12 Pages 1249-1260

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Abstract

Absorptance of various metals in polished surface condition at wavelength 10.6μ was evaluated at both room and fusion temperature, and as the results it was emphasized that the absorptance was too low. The authors proposed to improve the absorptance by the surface treatment. The surface treatments were divided into four groups; (a) roughened, (b) coated with non-metallic thin layer, (c) coated with fine powder and (d) created by the focused laser beam heating.
Conclusions obtained may be summarized as follows:
(1) The absorptance of metal sheet in the surface condition supplied by a commercial vender, which was highly polished, was proportional to a square root of the dc resistivity and agreed well with the theoretical values calcurated from Hagen-Rubens's equation at both room and fusion temperatures.
(2) Surface treatments such as superficial roughening or coating having a material of lower boiling point than base metal had little effect on the absorptance.
(3) When the focused laser beam impinged upon the aluminium specimen in the surface condition (b) or (c) for a long time, a part of the surface-treated layer remained so as to keep the considerably high absorptance. However, in the case of SUS27 stainless steel specimen absorptance decreased with beaming time, at last down to the polished one due to complete removal of the surface-treated layer.
(4) In the case of SUS27 there was large difference between the absorptance in different surface conditions, and coating with non-metallic fine powder had the largest effect on the absorptance. On the other hand, in the case of Al there was little difference between the absorptance in different surface condition except for coating with a material of very low boiling point.
(5) Though, in polished surface condition, Al was very difficult for CO2 laser processing in comparison with SUS27, surface treatment made the processing easier for Al than SUS27.
(6) In generel, the absorptance of metal had a tendency to increase with increasing the traveling velocity of the laser heat source and decreasing its power level in the surface conditions (b) and (c), but the tendency was completely contrary in the surface condition (d).

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