A dephosphorisation technology using CaO-based flux during the tapping process of basic oxygen furnace (BOF) converter was developed by metallurgists. In order to understand the dephosphorisation mechanism during this process, laboratory experiments were carried out using industrial BOF crude steel and some CaO-based fluxes. It was found that the dephosphorisation behaviour of CaO in BOF crude steel differs from that of the dephosphorisation processes of hot metal. Owing to the lack of liquid phase, the efficiency of dephosphorisation using pure CaO is relatively low. The formation of 2CaO•SiO 2 phase is also crucial, but the low Si content in BOF crude steel restricts the formation of 2CaO•SiO 2 -3CaO•P 2 O 5 (C 2 S-C 3 P), thus affects the dephosphorisation efficiency. Kinetically, suitable addition of SiO 2 and FeO x can accelerate the dissolution of the flux; and thermodynamically, the addition of SiO 2 is helpful for the formation of C 2 S-C 3 P, resulting in a better dephosphorisation efficiency.
A novel technology for the removal of fine inclusions has been put forward using a dispersed in situ phase induced by an explosive reaction of a composite ball of slag forming materials. A composite ball with this function has been designed and prepared using a laboratory model batch type balling disc (at 12 rev min 21 ) and the composite ball has been fed at the end of Ruhrstahl-Heraeus refining. The results indicate that feeding composite ball in Ruhrstahl-Heraus ladle is a novel technology and the inclusion in the interstitial free molten steel can be removed effectively. Compared with conventional inclusion removal technology, the number of the oxide inclusions can be decreased to a lower level and the inclusion size becomes finer. Using this novel technology, the total oxygen in the as cast slab can approach to 5 ppm and the steel production cost for per ton can be reduced by 5-12 RMB.
In the present work, a new ladle dephosphorization process has been developed using the dispersed in situ phases induced by an explosive reaction of the composite balls with slag forming materials. A composite ball with this function has been designed and prepared using a laboratory model batch type balling disc (at 12 rev min −1 ) and then has been fed during the convert tapping process. The results indicate that the explosion reaction of a composite ball at steelmaking temperature can take place and plenty of fine powders have been released. Feeding composite ball during converter tapping is a new process and the phosphorus in the molten steel can be removed effectively. Using this technique, the average dephosphorization rate is about 50% and the lowest phosphors in the molten steel can approach 40 ppm. Furthermore, there is no phosphorus reversion phenomenon occurred after the following procedures. Further study is recommended.
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