No abstract

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.

No abstract

Comparative experiments on different decarburisation processes of Fe-C alloys in Ar-CO-CO2 and Ar-H2O-H2 atmospheres were carried out. The fundamental principles of carbon distribution, migration, and conversion are elucidated during decarburisation in both atmospheres. The completely decarburised layer of 2-mm-thick strip in Ar-CO-CO2 atmosphere appeared about 20 min later than the decarburisation in Ar-H2O-H2 atmosphere. Compared with the decarburisation in the Ar-H2O-H2 atmosphere, the carbon-rich phase dissolution zone is wider and the solid solution carbon content in the centre side is lower in the Ar-CO-CO2 atmosphere. The concentration gradient of solid solution carbon on the centre side of the interface of austenite zone in Ar-CO-CO2 atmosphere is smaller than that in the Ar-H2O-H2 atmosphere.