Image Number 4 for United States Patent #7651576.
The method of preventing cold-worked stress corrosion cracking in the iron steels and alloyed steels including stainless steels comprises removing a residual tensile stressed layer, optionally generating residual compression, through the impact of irradiation with the ultra-short femtosecond pulse and kW class high average-power laser, and removing a hardened surface layer extremely susceptible to stress corrosion cracking, whereby this susceptible hardened surface layer with many concentrated dislocation defects and the likes is removed without generating or introducing any of such hardened layer in the process of its removal. The method is free from the risk of damaging other equipment by peening with steel balls or other shaped shots, is almost unlimited in actual environment, effectiveness, work, place and other conditions for application, is inexpensive, and functions continuously for a much longer period than an ordinary nuclear reactor's service lifetimes.
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