Influence of Microstructure Characteristics on the Toughness of High Strength Pipeline Steel Weld and Heat Affected Zone

Abstract: In order to research the influence of microstructure characteristics on the toughness of high strength line pipe weld and heat affected zone(HAZ), reduce costs of pipeline construction and ensure safety and reliability of service, a case study of X80 pipeline steel, the influence of austenite grain size, second phase particles, second phase structure of HAZ coarse grain zone on the toughness of weld and HAZ were analyzed. The analysis results showed that the effective ways to improve the toughness on welded and HAZ of high strength pipeline steel pipe were to control t8/5 and tH properly for guarantees the number and uniform distribution of the second phase particles and the uniformity and refinement of bainite in HAZ coarse grain area, and avoid the formation of the large-size angle-shaped M-A element of island chain. In addition, in the design and preparation of welding materials, achieve the subtle proportion and smelting of the content of the multi-alloy and micro-alloy to prevent forming inclusions and heterogeneous phases which influenced plasticity and toughness in the weld caused by the segregation of alloy elements.

Author(s): YUAN Xueting;LI Li; YANGJun; NIU Hui; LIU Haizhang; GUO Dan;