An integrated investigation into the causes of delayed and brittle fracture in the heat affected zone of high-strength 14H2GMR

A reduction in the mass of metal used in a welded construction is usually achieved by employing low-alloy steels of high strength, with proof stress in the range of R sub 0.2 =600-900 MPa. Any effective welding technology for these steels should ensure that the welded joints possess a high level of resistance to delayed and brittle fracture. Since in many cases constructions in high- strength steels are used at tow temperatures, the problem of raising the level of resistance of the welded joint to brittle fracture is of importance. The problem of the prevention of incidence of delayed fracture (the initiation of cold cracking) when welding low-alloy steels of high strength is also very real because the conditions favoring delayed cracking exist during the period of active diffusion of hydrogen, and of the development of the processes of thermal straining in the welded joints. In the opinion of many authors, a certain relationship exists between these two modes of fracture. In particular, an assumption has been made that an incomplete process of delayed cracking (which does not lead to cold cracking) may be the cause of reduced resistance to brittle fracture of the HAZ in l4H2GMR high-strength steel.