Evaluation method of delayed fracture property and overcoming techniques of delayed fracture of high strength steels

Abstract

The evaluation methods of the delayed fracture properties of high strength steels and the methods which improve the delayed fracture resistance of steels have been reviewed. The evaluation method which is crucial for the development of steels with high strength has yet to be authorized. However, a new evaluating method which adopts the critical hydrogen concentration for fracture and the hydrogen concentration which is absorbed from the environment as parameters has been proposed. It was verified that evaluation using this method showed good agreement with exposure tests of bolts in the service environment, and this method is being applied not only to delayed fracture but to other hydrogen embrittlement problems. To improve the delayed fracture properties of steels, the hydrogen trapping phenomenon in alloy carbides such as VC, Mo2C and TiC, and the TMCP process have been researched extensively. By using these methods, the development of high strength steels with excellent hydrogen embrittlement resistance has progressed.