Principle of decarburization reaction of reduced iron powder

The carbon and sulfur in the reduced iron powder are impurity elements, and its high content directly affects the application of iron powder. Therefore, in the production, we reduce the sulfur content of iron powder by a reduction after desulfurization, and the sulfur content can be reduced to below the national standard after a second reduction. 

1 Decarbonization

The carbon in the sponge iron powder is mainly solidly dissolved in Fe to form cementite (Fe3C). In the process of the secondary reduction of iron powder, in addition to the oxygen and carbon in the iron powder self-reaction decarburization, there are mainly the following decarburization reactions.

〔C〕+2H2=CH4 + 10.8kcal/mol  (1)

〔C〕+H2O=H2 + Co -28.3kcal/mol  (2)

(1) The reaction is exothermic, which is very limited for iron powder with high carbon content relying only on dry H2 decarbonization. (2) It is endothermic reaction, so moistening H2 with more water vapor contributes to the high decarbonization of iron powder at high temperature. After decarbonization, the carbon content in reduced iron powder can be reduced to less than 0.03%