A Study on the Metallurgical and Mechanical ...（研究冶金和机械）.pdf

A Study on the Metallurgical and Mechanical Characteristics of the Weld Joint of X80 Steel Choong-Myeong Kim, Jong-Bong Lee, Jang-Yong Yoo Technical Research Laboratories, POSCO Pohang, Kyungbuk, KOREA ABSTRACT In order to respond the needs for high strength linepipe steel on these natural gas pipeline proj ects, POSCO has developed API-X80 grade Until recently X70 steel has been the generalized grade for linepipe steels with enhanced low temperature toughness. This paper describes steel. However, there is a need to use higher grade steels such as X80 the design concept and qualities of both base materials and weld joints or X100 for high transmission efficiency and lower construction of POSCO’s API-X80 steel pipes. costs.As X80 steel is manufactured by higher alloy addition and severe rolling reduction, weldability of X80 steel seems to be a more important issue than with previously-used lower grade steels. Several STEEL MANUFACTURING mill trials have been performed to optimize the production processes for X80 steel at POSCO. Field manufactured API-X80 grade plates Alloy design concept of API-X80 with a thickness of 15.6mm were found to have very high strength and toughness. It is thought that the high strength and enhanced low