A New Approach in Solid State Steelmaking from Thin Cast Iron Sheets through Decarburization in CaCO_3 Pack

摘要

In the solid state steelmaking process used in recent researches, pig iron was directly casted and then decarburized in an oxidizing atmosphere in order to eliminate or reduce the amount of carbon. In the present study, the feasibility of solid state steelmaking from cast iron was investigated using limestone. For this purpose, white cast iron specimens were buried in a chamber containing CaCO_3 powder. Calcination of CaCO_3 produces CO_2 which participates in cast iron decarburization. In this technique, CO_2 reacts with the carbon content of sample according to Boudouard reaction which results in carbon consumption. Furthermore, effects of temperature and time on the decarburization process were investigated. White cast iron samples were decarburized at temperatures of 800, 900 and 1 000℃ for 10 and 24 h in the CaCO_3 powder pack. Very fine oxide layer was also observed to form during the decarburization process. Finally, samples were studied with optical microscope and SEM to measure the depth of the decarburized layer. However, secondary graphitization was occurred during the decarburization. Results showed that decarburization at 1 000℃ for 24 h has led to a completely decarburized layer of 420 μm thickness. In agreement, carbon analysis showed the reduction of carbon content from 3.16 wt% to 0.012 wt%. Kinetic studies revealed activation energy of 125 KJ/mol for decarburization of white cast iron using CaCO_3 powder pack.