Features of secondary treatment and continuous casting of pipe steel grades with the requirement for resistance to hydrogen induced cracking

摘要

Vyksa Steel Works manufactures a wide range of pipe products for building oil, gas, water pipelines, heating systems, and for construction and other industries. A key requirement for the pipe products is the resistance to hydrogen induced cracking and sulfide stress cracking. It should be pointed out that there are features of corrosion-resistant steel grades production related to systems with casting and rolling combined (CRC) such as CSP (Compact Strip Production), ISP (In_Line Strip Production), Conroll (Continuous Thin Slab Casting and Rolling Technology),QSP (Quality Strip Production), FTSP (Flexible Thin Slab Casting), and DSP (Direct Strip Production Complex). Such features as ultra-low sulfur content in the final stage of secondary treatment, "narrow" axial zone of billet due to the peculiarities of the thin slab casting are the defining factors for resistance to HIC and SSC. The main activities of smelting process, secondary steelmaking and casting of corrosion-resistant steel grades are: 1. a narrow range for the desired carbon content in steel (EAF technological indicators of work); 2. the features of steel deoxidation in ladle (for the sulfur content of no more than 0.0010% before casting); 3. the technology of calcium modification; 4. the use of rare earth-containing modifier; 5. optimization of continuous casting of steel (soft reduction, secondary cooling, etc.). Introduction of new technologies of smelting process, secondary steelmaking and casting of corrosion-resistant steel grades has resulted in stability of resistance to HIC and SSC with additional requirements to charpy impact absorbed energy and shear area at -50C.