Metal degassing in vacuum-chamber of circulating vacuum degasser of JSC EVRAZ NTMK

Abstract

For smelting of high-quality metal for transport purposes, it is necessary to limit the content of harmful impurities in it, including dissolved gases. For example, hydrogen content in the finished product should not exceed more than 2 ppm. In order to obtain low residual hydrogen content in steel in the converter shop of JSC EVRAZ NTMK, the transport metal is processed at circulating vacuuming plants. Circulating vacuum degasser is the last stage of steel processing before casting on continuous casting machine, so it is important to study and improve the technological processes in it. To investigate the physico-chemical processes occurring in this metallurgical unit, a hydrodynamic model of the system circulating vacuum degasser – steel ladle was created. Based on theoretical calculations and experiments conducted on a physical model, the main dependencies between the structural and technological parameters of the metallurgical unit were determined. The resulting equation makes it possible to determine the rate of metal circulation in vacuum chamber depending on gas flow rate supplied to inlet snorkel and its inner diameter at circulating vacuuming plants designed for metal processing in steel ladles with a capacity of 140 – 180 tons. Theoretical calculations were confirmed by practical smelting in a steelmaking unit. It is shown that during the wear of lining of the inlet snorkel vacuum chamber, in order to obtain stable residual hydrogen content, it is necessary to make changes in the technological process of vacuuming. Additionally, rational technological parameters of steel processing at the circulating vacuuming plant were determined on the basis of theoretical calculations.