A metallurgical evaluation of Grade 483 line pipe

CIM Bulletin, Vol. 75, No. 841, 1982

D.R. BELL, R.B. CASAULT and J.D. BOYD Physical Metallurgy Research Laboratories, CAN MET Energy, Mines and Resources Canada,Ottawa

Full-scale sections of three different types of Grade 483 line pipe have been evaluated extensively. The variations in chemical composition, optical microstructure, tensile properties, hardness and Charpy impact toughness with specimen orientation and location were determined. Significant variations in several properties, notably Charpy shelf energy, impact transition temperature, inclusion content andferrite grain size, were observed for different locations in the pipes. The results indicate that current specifications call for test samples for the most conservative locations, except for impact tests. Minimum Charpy impact values generally occur at the 1/2-width location, which may be a more appropriate specified test location than the present 1/4-width location. The anisotropy of impact toughness, and the importance of low sulphur content and inclusion shape control for adequate toughness in the transverse/rolling-direction orientation were demonstrated. The orientation of impact specimens is critical for spiral-weld pipe, and the current specification test is non-conservative in that it can give results which are two to three times higher than the minimum value for the steel.

Mots Clés: Physical metallurgy, Line pipe, Steel, Pipeline steels, Microstructure, Tensile properties, Hardness, Charpy impact toughness, Foothills Pipelines Ltd., Alaska Highway Pipeline