METHOD OF DETERMINING RESISTANCE TO RUNNING DUCTILE FRACTURE FOR HIGH-STRENGTH PIPE STEELS

摘要

This invention pertains to the material testing sphere and may be utilized to determine resistance to running ductile fracture (RDF) for high-strength pipe steels of K65 grade or higher grades with the impact toughness exceeding 2.5 MJ/m2. The method of determining resistance to RDF for high-strength pipe steels mostly with impact toughness exceeding 2.5 MJ/m2 includes the preparation of a pipe blank, manufacture of transverse specimens, performance of impact bending tests and subsequent determination of steel resistance to RDF using impact toughness value. The distinctive feature of this method is that several blanks are extracted from one pipe and subjected to provisional straining by compression that doesn't exceed 45 %. Then at least three transverse specimens are manufactured from each blank and tested for impact bending. Subsequently, the correlation between the relative impact toughness and provisional plastic strain values is determined, while resistance to RDF is determined using the provisional plastic strain value indicating the start of intense impact toughness decrease.