| 摘要 |
A metal structure product excelling in resistance to cracking as experienced by metal structure products under stress loading disposed in corrosive environment, namely, environmental cracking; and a method of enhancing the environmental cracking resistance. At a place of metal structure product where the environmental cracking thereof is a problem, a surface layer of 50 mum thickness from the surface is constituted of a stratiform structure composed of crystal grains whose major axes are parallel to the surface. Preferably, the ratio of, with respect to the crystal grains of the stratiform structure, length in the direction of major axis to length in the direction of minor axis is 5 or higher. This can be attained by applying ultrasonic shock to the surface of the place of metal structure product where the environmental cracking thereof is a problem. Preferably, after the ultrasonic shock treatment, a quality assurance inspection for inspecting the occurrence of plastic deformation at the zone extending from the surface to a thickness of 50mum is conducted.
|
