Acceleration of Decarburization in RH Vacuum Degassing Process.

Fundamentalexperiments were carried out in order to accelerate the vacuum decarburization rate in low carbon range.As the results, it became clear that enlargement of interfacial area was more efficient than increase in overall mass ttansfer coefficient.One of the most practical methodsto enlarge interfacial area was Ar injection into molten steel.Effect of Ar injection on decarburization rate was investigated in the 1 50 kg Vl F. Ar injection was effective on decarburization rate, and the apparent decarburization rate constant with a two-holed nozzle was larger than that with a one-holed nozzle, Next, effect of Ar injection into a vacuum vessel of RH was investigated with a water model, C02desorption rate was measuredto simulate decarburization rate.Gas injection nozzles were settled at the lowest part of the side wall in the vacuum vessel.The number of nozzles was I , 8, or 1 6.An experiment without gas injection was also carried out as a reference.Gas injection into the vacuum vessel was effective on the C02desorption rate.In particular, increase in the number of nozzles wasmore effective at a constant total gas flow rate.Finally, plant trials were carried out.Configuration of the nozzles was the same as the case of 8 nozzles in the water model.Gasflow rate into the snorkel for circulation was2 500N//min.Gasflow rate into the vacuum vessel was 800 N//min.Inner diameter of the nozzles was2 mmip.As the result, it became possible to decrease the carbon content from 200 to IOppm within I Omin.Interfacial area with Ar injection was evaluated to be I .6 times larger than that without Ar injection.