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60th anniversary of RosNITI JSC
ArticleName Quality index improving of the electric-welded K55 pipes
DOI 10.17580/chm.2021.01.07
ArticleAuthor R. V. Sulyagin, M. N. Mozzhegorov, A. O. Struin, A. G. Varnak

RusGazShelf Ltd. (Moscow, Russia):

R. V Sulyagin, Candidate of Engineering Sciences, Head of the Welding and Materials Department, E-mail:


Russian Scientific and FResearch Institute of Tube Industry – RusNITI JSC (Chelyabinsk, Russia):

M. N Mozzhegorov, Researcher, E-mail:


TMK Overseas (Houston, USA):

A. O. Struin, Candidate of Engineering Sciences, Quality Manager, E-mail:


TMK GIPI LLC (Sohar, Sultanate of Oman):

A. G. Varnak, Senior Engineer, E-mail:


The pipes manufacturing process with using the high frequency welding process (HFW) is widely applied for the producing of casing pipes, pipes for infield, supply and main pipelines. One of the criteria for meeting pipes to customer requirements is to provide the necessary mechanical properties of the pipe body and the welded joint. The analysis of forming, welding and local heat treatment of the welded joint was carried out during mastering of K55 pipe production. Metallographic researches of the base metal and welded joint were carried out. Pipes acceptance tests have been performed in accordance with API 5CT requirements. Based on the results of the researches and tests, the key factors influencing on the microstructure of the welded joint were identified. The technology of thermomechanical treatment of the welded joint has been developed. New modes of forming and welding have been applied, which make it possible to reduce the effect of the actual anisotropy of metal in terms of the yield strength and ultimate strength on the quality of the finished product. This article describes one of the possible options for obtaining a set of mechanical properties in accordance with the requirements of the API 5CT for HWF pipes.

keywords Welding, high frequency current, quality, fracture toughness, yield strength, tensile strength, thermomechanical treatment, heating

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