METAL STRUCTURE EXCELLENT IN ENVIRONMENTALLY CORROSIVE CRACKING RESISTANCE, AND METHOD FOR IMPROVING RESISTANCE TO ENVIRONMENTALLY CORROSIVE CRACKING OF METAL STRUCTURE

摘要

PROBLEM TO BE SOLVED: To provide a metal structure excellent in resistance to an environmentally corrosive cracking, that is the cracking caused under a corrosive atmosphere when a stress is applied to the metal structure, and to provide a method for improving the resistance to the environmentally corrosive cracking.;SOLUTION: In this metal structure, the surface layer of 50μm thickness from the surface of a portion having a possibility of causing the environmentally corrosive cracking made into a lamellar structure consisting of a grain whose major axis is parallel to the surface. Preferably, the ratio of a length of the major axis to the minor axis of the grain of the lamellar structure is defined as ≥ 5. This structure is obtained by applying an ultrasonic impact treatment to the surface of the portion having the possibility of causing the environmentally corrosive cracking. Preferably, after the ultrasonic impact treatment, a quality assurance inspection to inspect that the range of 50 μm thickness from the surface is plastically deformed is performed.;COPYRIGHT: (C)2004,JPO