Effect of Hot-Bending Process on Microstructure and Mechanical Property of K65 Submerged ARC Welded Pipe

Dong, Liming; Pan, Xin; Wang, Yinbai

doi:10.1007/978-3-319-48765-6_88

Cited by 1 publication

(1 citation statement)

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“…To increase transport efficiency and to lower the costs of pipeline construction, longitudinally submerged arc welded (LSAW) pipes with larger diameters and thicker walls have been increasingly used by the pipeline industry. [1][2][3][4] For example, in Russia, the LSAW pipeline in the Bovanenkovo-Ukhta project 2 was recently constructed with K65 steel (the highest grade of the Russian natural gas pipeline), which is similar in specifications and yield strength requirement (550 MPa grade) to API X80 but has a stricter low temperature toughness value of 60 J at −40°C (compared to −20°C for API X80 grade 5,6 ) due to the extreme Arctic environment. In that project, in which over 1.8 million tonnes of pipe were used, the target capacity is 50 billion m 3 /year, and the length of the main line is 2600 km.…”

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confidence: 99%

Investigation of the microstructure and toughness of 550 MPa grade pipeline after the hot-bending process

Wang

Tsai

Yang

et al. 2016

Materials Science and Technology

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In this work, the effects of the hot-bending process on the microstructure and low temperature (−40°C) toughness of weld metal of pipeline K65 (the highest grade of the Russian natural gas pipeline) were studied. The weld metal from the longitudinally submerged arc welding (LSAW) pipe making process was compared with that subsequently treated by the hot-bending process. It was found that the latter process led to serious deterioration in toughness, which obviously degraded the sound properties achieved in the original weld metal of LSAW pipes. Microstructural characterisation revealed that the weld metal, which originally consisted mainly of acicular ferrite in the as-deposited condition, became predominantly composed of bainitic ferrite after hot bending. It is clear that reaustenisation caused a smaller austenite grain-sized matrix, which brought about a very high volume fraction of bainite. Consequently, the low temperature toughness was deteriorated, in contrast to the excellent toughness achieved in the as-deposited weld metal.

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