In this study, we investigated the relationship between the decarburization effect of the solid-state decarburization method for preparing silicon steel and the atomic diffusion behavior in the matrix, focusing on 1 mm thick Fe-0.18 wt% C-Si (1.5, 3.5 wt%) alloy strips as the research object. Solid-state decarburization experiments were carried out in an Ar-H₂O-H₂ atmosphere, and the self-diffusion behavior of C and Si in Fe-C-Si alloy system was simulated by molecular dynamics. The results show that the molecular dynamics simulation results are consistent with the decarburization experimental results. When the temperature is lower than 800 °C, the atoms maintain a compact bcc structure, so the migration rate of carbon is low. When the temperature rises, the atoms move violently, resulting in the destruction of the crystal structure. Because the atomic arrangement tends towards a disordered structure, the migration rate of C is high and the diffusion coefficient increases. The experimental results showed that the decarburization rate was accelerated. At the same temperature, the diffusion activation energy Q = 48.7 kJ·mol⁻¹ of carbon in an Fe-3.5 wt% Si-C alloy matrix can be calculated. The diffusion activation energy of carbon Q = 47.3 kJ·mol⁻¹ was calculated using a molecular dynamics simulation. When the content of Si is 3.5 wt% and 1.5 wt%, the diffusion series of Si can be expressed as D_{3.5Si, Si} = 8.54 × 10⁻¹⁰ exp(−33,089.7/RT) m²/s and D_{1.5Si, Si} = 2.06 × 10⁻⁹ exp(−46,641.5/RT) m²/s, respectively. When the Si content is 3.5 wt%, the diffusion coefficient of Si is larger. After diffusion to the near surface, it combines with the remaining O to form a continuous strip of SiO₂. When the Si content is 1.5 wt%, the diffusion coefficient of Si is small. The remaining O diffuses in the matrix and will oxidize when encountering Si; it cannot aggregate in a highly-dispersed distribution. The lattice transition from face centered cubic lattice austenite to body centered cubic lattice ferrite occurred in the matrix of the thin strip. The diffusion coefficient of C in ferrite is much larger than that in austenite. Therefore, the decarburization rate suddenly increases before decarburization stagnation. With the increase in Si content, the diffusion activation energy of C decreases, which promotes the decarburization effect.

The reduction of magnetite in H₂ and CO atmospheres was compared using a microwave-heating technique. The reduction of magnetite in a mixed H₂ + CO atmosphere was compared with respect to the effects of a microwave field and a conventional field. Microstructural changes were observed using an electron microscope. The results show that the metallization rate and reduction degree of the H₂-reduced magnetite are much higher than those of the magnetite reduced by CO at 900–1100 ℃. The Fe phase generated by H₂ reduction forms a cavity structure, and the Fe phase generated by CO reduction forms a dense block. Under conventional heating conditions, the higher the H₂ content in a pure CO atmosphere, the better the reduction effect. Under the effect of a microwave field, the atmosphere with the highest reduction rate was 50% H₂ + 50% CO. Compared with conventional heating, the bubble holes formed by reduced iron in microwave field are larger under the same conditions.

To investigate the effect of microwave irradiation on the rate of magnetite reduction while increasing the gas phase diffusion rate limit, the microstructure and kinetics of CO reduction of magnetite powder were studied. The investigation was conducted through microwave irradiation and conventional heating at 900~1100 °C. Under the two heating methods, the iron crystal is selectively reduced and gradually expanded along the direction normal to the length of the ore powder, forming a strip of iron crystal that penetrates the powder and expands outward across the width. The microwave field can effectively improve the sintering of minerals. The changes in Avrami exponents m and k in the reduction process were determined by combining the Johnson–Mehl–Avrami (JMA) model with the lnln method. The microwave field did not change the limiting step. Microwave irradiation proves to be the most effective means to enhance both the initial reduction rate and the rate during the primary iron crystal precipitation phase. The morphology of the iron crystal takes on a dense punctate shape, influenced by the rate of diffusion control.

This paper analyses solid-state decarburisation kinetics with the aim to clarify the transition rule of restrictive links in the process of decarburisation, providing a theoretical basis for regulating the solid-state-decarburisation rate. Experimental calculation of the Fe–Mn–C ternary alloy phase diagram using FactSage thermodynamic software, with medium manganese cast steel as the research object, experiments conducted at P H 2 O / P H 2 = 0.56 and a total gas flow rate of 1500 mL·min ⁻¹ .The results show that the increase in manganese content has little effect on the carbon equivalent of solid solution in the γ-phase. This is because the proportion of γ-phase in the manganese cast steel decreases as the manganese mass fraction increases, but the increase in the γ-phase-carbon mass fraction makes the change in the carbon equivalent of solid solution in the small manganese cast steel plate. At 950°C, the internal diffusion of carbon in a 1 mm manganese cast steel plate has an obvious limiting effect on the decarbonisation process. When the decarburisation temperature rises to 1090°C, the effect of carbon diffusion on the whole decarburisation process decreases. The limiting factors inhibiting the whole decarbonisation process are the surface chemical reaction, that is, the temporary surface chemical reaction, as well as the internal diffusion limit of solid carbon, which leads to cementite decomposition. In the entire process of solid decarbonisation, a higher manganese content is beneficial for improving the reaction rate because, at the temperature of this experiment, manganese carbide dissolved into solid carbon, thus reducing the restrictive effect of the cementite decomposition on the decarbonisation process.