Experimental studies of crack growth kinetics and bearing capacity of steel pipes of underground water distribution systems

Abstract

It was established that the value of the critical stress SK for all experimental steels increases with the increase in the service life, and the impact viscosity decreases, which indicates the structural embrittlement of the pipe steels associated with their sudden flooding. It is shown that the new 20 FA steel has the highest visco-plastic properties and resistance to brittle fracture, which is economically modified with a carbide-forming element (vanadium) and has a fine-grained structure and a low conten to fharm fulimpurities (sulfur, phosphorus). The microstrain of the α-Fe crystallattice, as well as the quantitative decay of cementite andt here distribution of carbon between ferrite and pearlite, were estimated by X-ray diffraction methods. The new steel grade 10FA is recommended for use in the construction of oil and gas pipelines and, for example, bridge structures, which are constantly under cyclic loads with simultaneous contact with a corrosive and aggressive environment. For the first time, the influence of thes ervice life of oil pipelines on the hydrogen content and microcracks in pipe steels of oil pipelines was determined.