No abstract

The effect of the time taken to add the alloy and the gas injection mode are significant factors for fast decarburisation. Industrial experiments and thermodynamic calculations are adopted to show the transition of the main factors and reaction sites with time. The results indicate that adding steel scrap and alloy are not recommended in the first 7 min in order to keep good thermodynamic and dynamic conditions. The gas injection mode is more critical for reducing the chamber pressure to 67 Pa in 8.5 min and the gas volume should be less than 10 m 3 in the first 4 min after the reaction begins. This method is effective in improving the decarburisation rate and decreasing the carbon content at the end of decarburisation. For 69% of the site tests the final carbon content was kept to about 10 ppm within 15 min.

It is of great significance to improve the yield of ferroalloy for steelmaking to reduce cost and save energy. In this paper a kind of loss mechanism of micro-carbon ferromanganese which has micro content of carbon during RH refining of interstitial free steel was investigated. The flow field of argon gas in the RH degassing vessel was investigated through numerical simulation. Through force analysis and particle tracking of the micro-carbon ferromanganese, it was found that microcarbon ferromanganese with size smaller than the critical value of 1.01 millimeters has a large probability to be carried away into the RH vacuum pipeline. The micro-carbon ferromanganese of small particle was easily lost into the vacuum pipe by the upward flow of argon gas. Industrial experiment was conducted and a novel mechanism was confirmed that increasing the vacuum pressure during addition of the micro-carbon ferromanganese could improve the yield greatly.