Influence factors of X80 pipeline steel girth welding with self-shielded flux-cored wire

Abstract

For girth weld of high-pressure oil and gas transmission pipeline, there is impact toughness values deviation phenomenon with self-shielded flux-cored semi-automatic welding technology. The macro-images, microstructure and mechanical performance of girth welding joint have been investigated by OM, SEM, TEM. The results show that there are several factors of impact toughness unqualified values of weld joints, such as welding heat input, coarse grain zone and a chain of M–A organisations, Al₂O₃ and Zr Precipitates particle sizes and distribution et al., which are the main unqualified reasons of welding impact toughness of the semi-automatic self-shielded core butt welding process of X80 pipeline steel.

Keywords:

• Girth welded joint
• Microstructure
• Mechanical properties
• Coarse grain and M–A mixing zone
• Heat input
• Precipitates

Acknowledgement

This work was supported by the Science research and technology development project of CNPC (No. 2014B-3416-0501) and Project of Natural Science Foundation of Shaanxi Province in China (2012GY2-23).