Abstract
In 2005 I. P. Bardin Central Research Institute of Ferrous Metallurgy SSC FGUP developed and approved together with interested parties ТУ 14-1-5511 Technical Specifications “Rolled plates for 530-1,220 mm electric-welded pipes of К42-К60 strength grade” as part of improving К42-К60 strip for 530-1,220 mm electric-welded pipes performed in Ural Steel JSC. The above rolled products were successfully applied in projects on manufacturing of the Eastern Siberia – Pacific Ocean, Bovanenkovo-Ukhta, Sakhalin–Khabarovsk–Vladivostok pipelines and many others. Taking into consideration the vast experience of Ural Steel JSC in strip production for pipelines under national projects it was selected as the key supplier of Х70(К60) strip for manufacturing pipelines designed for arrangement of gasgathering systems in Yamal LNG gas plant within development of South-Tambey gas condensate field located on the Yamal Peninsula. When developing steel it was envisaged to impose stricter requirements on a number of technical characteristics for the purpose of increasing strip reliability and enhancing its performance. The enhancement captured non-metallic inclusion purity degree in terms of steel cold resistance improvement and raised impact strength requirements on Charpy specimen at negative temperatures down to -60 °С and extension of the grade mix for supplied 25- 28.5 mm thick strips due to severization of regulatory requirements to yield strength. The rolled steel under study, i.e. Х70(К60) strips produced in 2800 Mill at Ural Steel JSC, both ensured much better quality characteristics in pipelines and had more attractive prices compared to strips produced in 5000 Mill at other steelmaking plants. Ural Steel JSC is the only steelmaking plant in Russia which can produce Х70(К60) strip with a thickness of over 20 mm in 2800 Mill. Х70(К60) strips with improved cold resistance and weldability mastered in industrial production of Ural Steel JSC were offered to a wide variety of customers, including pipeline, fitting and components producing plants. Х70(К60) strips allow for manufacturing and operating high performance pipelines in the Far North regions.
Key words: corrosion resistance, hydrogen-induced cracking, sulfide stress cracking, controlled rolling, accelerated cooling, hightemperature tempering, microstructure.