FEATURES OF THE FRACTURE OF SPECIMENS OF LOW-CARBON STEELS UNDER IMPACT AND STATIC LOADING CONDITIONS

The ductile-to-brittle transition temperatures of 20 and 09G2S low-car bon steels, which are used as petroleum and gas pipe materials, were d etermined. In determining the ductile-to-brittle transition temperatur e together with the traditionally used recorded values of impact stren gth and share of fibrous structure of the fracture a fractographic par ameter of similarity, the relative length of the stable-growth crack, was used. In this case the zones reflecting the behavior of the materi al in different local stressed conditions were revealed and measured. It was established that to evaluate the ductile-to-brittle transition temperature it is desirable to use the relative stable-growth crack le ngth. To provide reliability of piping this characteristic may be take n as 0.1-0.2 mm.