Degradation of steels used in gas main pipelines during their 40-year operation

The degradation of the mechanical and corrosion properties of grade 17G1S steel in gas main pipelines after their 28–40-year operation is studied. A simultaneous decrease in their strength and hardness on the one hand, and impact toughness, fracture toughness and resistance to hydrogeninduced cracking, on the other, is observed. The influence of damages to the steel on the degradation of its properties is analyzed.