Implementation of Pipe Steel Grade X52M Manufacturing According to API-5L Requirements Applied to Hot Rolling Mills “1700”

For the first time at rolling mill 1700 facilities, PJSC “Ilyich Iron and Steel Works” of Mariupol, the technology has been developed and the batch of hot-rolled coils (8 × 1260 mm) of steel grade X52M has been produced by the method of thermo-mechanical controlled rolling for further manufacturing of electric-welded pipes in accordance with API-5L. This paper confirms the advantages of the thermo-mechanical rolling method due to special features of the chemical composition and lower strength level during the production in comparison to other rolling methods, and the possibility to apply this method at the equipment that was not designed for manufacturing the products of such strength categories. The positive influence of Nb on microstructure forming and rolling products properties has been confirmed with the thermomechanical rolling method. Additionally, during the production, the controlled air cooling of coils has been applied up to 450 °C after coiling. This ensures the reduction of air scale layer thickness and improves the surface quality, including the surface quality during further manufacturing of electric-welded pipes. The developed technology makes it possible to ensure the production of coils which meet the present-day world requirements and meet the demands of domestic and foreign producers of electric-welded pipes. Next stages of the research to improve the quality and for further development of rolled products production for manufacturing of electric-welded pipes in accordance with API-5L have been determined.