To study the decarburization behavior of cast iron sheets, a series of gas-solid experiments were carried out. The treatment was carried out under Ar-H 2 -H 2 O mixed gas atmosphere. Results show that P H 2 O/P H 2 in the gas mixture determines the oxidation of iron at a given temperature and the critical value of P H 2 O/P H 2 to produce ferric oxide rises with temperature. The oxidation of iron take place when the ratio of P H 2 O/P H 2 > 0.62, 0.66, 0.7 at 1293 K, 1353 K, 1413 K, respectively. The gassolid decarburization reaction of cast iron sheets follows first-order kinetics. Cross-sectional microstructure images indicate that graphitization of cast iron sheets occurs at 1353 and 1413 K. The depth of the decarburized layer increases gradually with temperature and time, the square of depth has a near linear relationship with time. The activation energies of the decarburization reaction calculated by two different ways are similar to that for internal carbon diffusion.

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The gas–solid reaction decarburisation of cast iron strips is a direct steel production method with low production costs. In this study, the decarburisation kinetics of Fe-C alloy strips in an Ar-CO-CO2 atmosphere were investigated. Fe-C alloy strips with 4.2 wt.% C and different thicknesses (1, 1.5, and 2 mm) were used for the decarburisation experiments under temperatures of 1293, 1353, and 1413 K. The results indicate that, under appropriate mixed gas conditions, rapid decarburisation can be achieved. With an increase in the decarburisation temperature, the decarburisation rate increases significantly. Under the same decarburisation temperature and time, thinner Fe-C alloy strips exhibit a better decarburisation effect. The decarburisation process includes three rate-limiting stages, namely gas and surface reaction, carbon diffusion, and cementite decomposition. The microstructure of the decarburised strips comprises a complete decarburised layer and a partial decarburised layer, and the thickness of the complete decarburised layer increases with decarburisation time. The decarburisation of the Fe-C alloy strip is an apparent first-order reaction with an activation energy of 124.7 kJ ∙ mol−1, and the activation energy for the growth of the complete decarburised layer is 132.3 kJ ∙ mol−1. The results of this study can help develop more efficient and cost-effective steel production methods.

The average carbon content after decarburization is an important criterion in judging the feasibility of the solid-state steelmaking process. To investigate the change mechanism of the average carbon content, the gas-solid decarburization of 2 mm iron sheet in weak oxidizing atmosphere (Ar + H2 + H2O) at 1293, 1353, and 1413 K is studied. The influences of decarburization time and temperature are considered. Increasing both the temperature and time can enhance decarburization. The gas-solid decarburization reaction of 2 mm iron sheets is nearly a first-order reaction, and the activation energy of the decarburization reaction is 144.9 kJ/mol. It was found that the diffusion of carbon from the interior of the sheet to the reaction interface is the rate-controlling step. The relationship between decarburization time, temperature, and average carbon content is precisely described by an empirical formula. A new segmented heating method is developed. With this new method, 0.28 mass% C sheets can be produced from 4.15 mass% C sheets with thickness of 2 mm in 70 min.