Research of the kinetics of crack growth under the action of static and cyclic loads of pipe steel in a NACE corrosion-aggressive environment

Abstract

An analytical method for calculating and forecasting static hydrogen fatigue of pipe steels intended for operation in corrosive-aggressive environments containing hydrogen sulfide has been developed. Mathematical calculations correlate well with experimental results (deviations do not exceed 5-7%), which is allowed in engineering predictive calculations. The rate of crack growth in 06G2BA steels was investigated experimentally; graphs of crack growth curves and "load-elongation" curves for compact samples of economically modified steel 06G2BA with a low rate of deformation (ENSHD) in the NACE environment and in air under variable stresses are constructed. For the first time, static and cyclic fatigue curves for pipe steels 09Г2С and 17Г1С were constructed when tested in the NACE environment, which allows to calculate and predict their failure-free residual working life. For the first time, environment-accelerated crack growth for pipe-modified steel 06G2BA in the NACE environment was investigated, and calculations of the service life of pipe steels based on the mechanics of elastic-plastic failure were performed. It has been proven by experimental metallographic and mechanical studies that with the increase in flooding, which occurs during the long service life of the 06G2BA pipe steel, the cyclic strength increases sharply (by 2-3 times), which contributes to the extension of the working (failure-free) resource of the pipelines.