During the application of a thin-film epoxy-resin coating, line pipe may be heated to temperatures in the vicinity of 450 °F for as long as 1 hour. Because pipe-manufacturing processes, such as the U-O-E process, introduce significant plastic strain into the pipe, the pipe steel is in a condition in which it might undergo strain aging during coating application. Strain aging is a change in properties that occurs in many steels as a consequence of interstitial-related age hardening induced by cold working and time at a suitable temperature. The aging temperature is usually relatively low, only...
During the application of a thin-film epoxy-resin coating, line pipe may be heated to temperatures in the vicinity of 450 °F for as long as 1 hour. Because pipe-manufacturing processes, such as the U-O-E process, introduce significant plastic strain into the pipe, the pipe steel is in a condition in which it might undergo strain aging during coating application. Strain aging is a change in properties that occurs in many steels as a consequence of interstitial-related age hardening induced by cold working and time at a suitable temperature. The aging temperature is usually relatively low, only moderately above room temperature, but in highly susceptible steels, aging may occur even at room temperature. The change in properties generally occurs slowly at room temperature and more rapidly at somewhat higher temperature. Since thin-film coating involves elevated temperatures, the properties of pipe produced from a steel susceptible to strain aging are likely to be modified by the application of a thin-film epoxy-resin coating. The objective of the investigation described in this report was to measure the changes in properties in a typical X70 pipe that resulted from the application of a thin-film epoxy-resin coating.