Abstract
High-strength steel has been required from the viewpoint of reduction in cost and environmental deterioration in recent years. However the probability of delayed fracture caused by hydrogen increases with steel strength. As universal mechanism of hydrogen embrittlement, hydrogen enhances the dislocation mobility and local plasticity and so stabilizes and increases vacancies. From these behaviors of hydrogen, high-strength steel with high resistance to delayed fracture was developed to suppression dislocation mobility and vacancy formation. Pre-strain and ageing method enable to improve the delayed fracture property of high-strength steel. The property of the delayed fracture was evaluated and the mechanism was examined.
