For the collapse of the working layer of dry vibrating material during preheating, the four-strand tundish of a steel plant was taken as a prototype for numerical simulation. The software ANSYS was used to calculate the temperature field and stress and strain field on the working layer under three preheating stages through the indirect coupling method. The results show that during the preheating process, the temperature field distribution on the hot surface of the working layer gradually develops toward uniformity with the increase in preheating temperature. However, the temperature gradient between the cold and hot surfaces increases subsequently, and the highest temperature between the cold and hot surfaces reaches 145.31 °C in the big fire stage. The stress on the top of the working layer is much larger than in other areas, and the maximum tensile stress on the top reaches 39.06 MPa in the third stage of preheating. Therefore, the damage to the working layer starts from the top of the tundish. In addition, the strain of the area near the sidewall burner nozzle in the casting area is much larger than that in the middle burner area with the increase in preheating temperature. Thus, the working layer near the sidewall burner nozzle is more prone to damage and collapse compared with the middle burner nozzle.

In 2022, China produced 1.018 billion tons of crude steel, with steel slag accounting for 10–15% of the output. The presence of 10–20% f‐CaO in steel slag causes volume instability, hindering comprehensive utilization. The generation of f‐CaO is closely associated with the dissolution of quicklime during the converter slag‐forming procedure. This study focuses on investigating the evolution of the lime–slag interface and the variations in lime dissolution rate under different slag conditions using the electron probe microanalyzer and ImageJ. The results reveal that the formation of the CaO–FeO solid solution, (Ca, Mg, Fe) olivine, and low‐melting point (Ca, Mg) olivine at 1400 °C. As the FeO content decreases, a dense and high‐melting‐point 2CaO·SiO2 layer is formed. A maximum thickness of the 2CaO·SiO2 layer is precipitated at a dissolution time of 180 s. Additionally, the average dissolution rate of lime in different slags shows an initial increase followed by a subsequent decrease. Among the slag studied, the highest average dissolution rate is in slag A3 at 2.24 × 10−6 m s−1, while the lowest rate is in slag A4 at 1.49 × 10−6 m s−1. The presence of the 2CaO·SiO2 layer hinders the mass transfer, thereby further inhibiting the reaction.

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