Investigation of shot blasting and thermal stress relieving processes on residual stresses and corrosion behavior of X60 steel gas pipelines

Corrosion is one of the most common complications in some industries. Two main factors causing corrosion are tensile stress and a corrosive environment, both of which require careful control. The purpose of this research is to achieve an optimal method of increasing corrosion resistance and also reducing tensile residual stress in API X60 gas pipelines. In the present study, residual stress has been examined in samples which have undergone either shot blast or heat treatment operations or both of them. In this research, 4 samples have been studied including: shot blasted, firstly heat treated then shot blasted, firstly shot blasted then heat treated and heat-treated using API-X60 steel pipe to indicate the best method of resistance to corrosion and stress. To investigate these properties, residual stress of these components has been examined by using the Contour Method and corrosion resistance has been studied through the Cyclic Polarization Resistance method. The results showed that the best corrosion resistance happen by the heat-treated sample (almost twice as much as the other methods) and also the most compressive residual stress observe in the firstly shot blasted and then heat-treated sample.