2002 Volume 88 Issue 8 Pages 450-457
The decarburization mechanism of stainless steel in the low carbon region was investigated using a water model and a 178 ton combined blowing converter. The results obtained may be summarized as follows.
1) In the water model experiments, the slag-metal interfacial area increased in proportion to the stirring energy of the top blowing gas by a factor equivalent to the 1.2 power.
2) In comparison with conventional operation (without top blowing, CaO/SiO2=4.5) in the low carbon region, the decarburization rate increased by 1.7 times in operation with lowered slag basicity (CaO/SiO2=4.5→2.5, without top blowing ). The decarburization rate increased by 1.5 times in operation with nitrogen top blowing.
3) A new mathematical model which considers stirring by top blowing and the slag composition was developed. In an analysis with this model, it was found that the gas-metal interfacial area increased in proportion to the stirring energy of the top blowing gas by the 0.86 power. It was possible to calculate the decarburization rate under various top blowing conditions using this relationship.
4) The effect of lowering the slag basicity on the decarburization rate could be explained by the slag-metal interfacial area.
5) In order to explain the effect of top blowing with nitrogen on the decarburization rate, it was necessary to consider not only the slagmetal interfacial area, but also the gas-metal interfacial area.