Production experiences with Mo-Nb line pipe steels

Abstract

Steelmakers are melting high-quality line pipe grades in conventional, high-volume production facilities. The basic oxygen furnace has become the mainstay for high-quality pipe production, but electric furnaces and open-hearth facilities are still utilized. To meet the requirements of high toughness at low temperature, oxygen lancing to reduce carbon content below 0.12% is also commonly employed in the electric and open-hearth furnaces. Hot-metal desulfurization (0.010% S or less) and / or inclusion shape control techniques are employed to enhance transverse ductility and notch toughness. The low-carbon Mo-Nb and Mo-Nb (V) steels are compatible with these new steelmaking, deoxidation and casting practices offering an economical approach to higherstrenth, tough steels needed for the production of heavy wall thickness A rctic and offshore submarine pipelines. The Battelle DWTT and Charpy results demonstrate the high toughness capability of these steels at temperatures of -40°C and below. Approximately 0.5 million metric tons of molybdenum-containing line pipe have been supplied, and this quantity is expected to double in 1976. Continuing production in North America, especially in Canada, and in Western Europe, especially in Italy, coupled with the production of several hundred thousand tons of Arcticquality, 1420-mm-diameter pipe by the Japanese mills will account for this high tonnage. The Mo-Nb/Mo-Nb (V) steel technology is playing an important role in Arctic and offshore, submarine pipelining throughout the world.