| 摘要 |
PURPOSE:To improve oxidation resistance to high temp. steam, by cold working the inner surface of heat resisting steel pipe made of high Cr steel or austenitic stainless steel through which high temp. steam is communicated, then irradiating laser beam and rapidly cooling the surface. CONSTITUTION:The inner surface of a pipe material 1 for passing high temp. steam such as heat transfer pipe of boiler for thermal power generation made of high Cr heat resisting steel contg. >=13% Cr or Ni-Cr austenitic stainless steel, etc., is subjected to cold workings such as roller finishing, shot blasting and shot peening. Tightly closing plates 4 having an inlet 2 and an outlet 3 for gas are attached to both ends of the pipe 1, gaseous Ar is fed in the pipe 1 from the inlet 2 and exhausted from the outlet 3 to obtain gaseous Ar atmosphere. Successively, a laser beam 5 is introduced in the pipe 1 through a crystal lense 6 made of KCl, inner surface of steel pipe is irradiated with a reflecting mirror 7 to heat it to 800-1,050 deg.C. The surface is locally melted and water cooled from outer part of steel pipe. Inner surface of the pipe 1 is made amorphous or fine grain layer is formed to improve oxidation resistance to high temp. steam.
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