Decarburisation of Fe-C alloy strips by gas–solid reaction in Ar-CO-CO₂

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.

Prospects for green steelmaking technology with low carbon emissions in China

“…Thus, a new ultrashort process, the S 3 process has been proposed. [93][94][95][96][97][98][99] Figure 15 shows the main steps of the S 3 process. The BF or molten reduced iron undergoes off-furnace pretreatment and alloying (hot metal dephosphorization, alloying, 2.0-3.8 wt% carbon), and is then directly solidified by a two-roll continuous caster or other thin strip continuous caster (e.g., 1.0-3.0 mm).…”

“…These inclusions and bubbles often originate from the decarburization and oxidation of liquid metal, and the oxygen content in liquid metal with a high carbon potential is low. Thus, a new ultrashort process, the S 3 process has been proposed 93–99 …”

Analysis of decarburisation mechanism of Fe-C alloy strip

“…Our team previously reported basic studies in two atmospheres, H 2 O-H 2 and CO-CO 2 [38][39][40][41][42], with a maximum decarburisation temperature of 1413 K. In this paper, the decarburisation effect under two atmospheres is studied, and the difference in the decarburisation mechanism is analysed. Although there was a carbon concentration gradient in the steel plate during the decarburisation process, there were different structures and phase compositions.…”