The effect of Ce on the microstructure, mechanical properties and corrosion resistance of 27Cr-3.8Mo-2Ni super-ferritic stainless steel were investigated by FactSage 7.2. The results reveal that when the Ce content increases from 0.00 wt-% to 0.0498 wt-%, Al₂O₃ inclusions wrapped by irregular (TiNb)N are gradually modified into spheroidal CeAlO₃, Ce₂O₃, Ce₂O₂S and Ce-O-P complex inclusions, the rare earth inclusions are smaller than 1.0 × 10⁻⁶ m (1.0 μm) and dispersedly distributed. The diameter of recrystallized ferrite grain is decreased, the mechanical properties of super-ferritic stainless steels are well improved, impact fracture appearance transforms from pre-dominant cleavage to ductile fracture at 298 K (25°C), and the cleaving step of the fracture becomes smaller at 243 K (−30°C), the uniform corrosion resistance to H₂SO₄ of steels with is enhanced especially in 40 vol.-% H₂SO₄ at 333 K (60°C). In addition, the microstructure and properties could not be further improved with 0.0744 wt-% Ce content.

The service life of a blast furnace hearth is considered as a key factor limiting the service life of a blast furnace. The erosion of the hearth lining is generally inhomogeneous, and localized depression erosion often occurs. Since the conditions inside the blast furnace hearth cannot be directly measured, it is a common practice to use the existing thermal parameters to estimate the erosion, which can provide a basis for the safe production of the blast furnace. In this context, based on the anatomical data of the No. 2 commercial blast furnace, the three-dimensional erosion model is established, and the feasibility of the computational model is verified. Then, 15 computational models with localized depression erosion at different locations are established. The finite element method is used to simulate the heat flux of the cooling staves of each model. The results show that under normal cooling and heat transfer conditions, the remaining thickness of the hearth lining is inversely proportional to the heat flux of the cooling staves. The closer the localized depression erosion is to the cooling stave, the greater the effect on the heat flux of the cooling stave. If the localized depression erosion is far enough away from the cooling stave, it will have little effect on the heat flux of the cooling stave. On this basis, we summarized a method of judging the location of localized depression erosion according to the relationship between the localized depression erosion and the cooling stave heat flux. It should be noted that when the localized depression erosion is located at the junction of the cooling staves, the increase in heat flux will not be too large, which is easily overlooked. In order to prevent the occurrence of safety accidents, we should pay more attention to this situation.

The life of the hearth is the main limiting link of the campaign of a blast furnace. As the equipment for holding molten iron in the furnace, the high-temperature molten iron is in direct contact with the refractory, which makes the refractory have a larger temperature increase. If the temperature gradient inside the refractory is large, it generates large thermal stress and causes the refractory to crack. Blast furnace gas and molten iron intrude into the gap, which directly causes melting erosion and other chemical erosion with carbon bricks. It aggravates the erosion degree of the furnace and seriously affects the production life of the furnace. Therefore, the furnace often occurs with different types of severe depression erosion in the late service of the blast furnace. In this study, the calculation model of the thermal fluid-solid coupling considering the molten iron flow and the solidification of molten iron was established. This calculation model was applied to study thermal stresses in the furnace with severe erosion. Based on the calculation model, the effect of blast furnace production parameters and deadman condition on thermal stresses in the furnace with severe depression erosion were analyzed, including tapping productivity, tapping temperature, cooling intensity, and deadman geometry. The research results are of great significance for prolonging the safe production life of blast furnaces.

Hearths are an accident-prone component in blast furnaces. Accidents, especially hearth burnthrough, cause substantial economic losses and even casualties. Ensuring safe operations is a challenging task as it is impossible to directly observe the internal state of a hearth. Measured data from thermocouples arranged in the hearth lining are often used to evaluate the furnace safety status. However, thermocouples are easily damaged due to their long-term operation at high temperatures. This paper proposes an approach to assist in the safety monitoring of a hearth using heat flux from cooling staves. The method is proposed through a series of finite element simulations to construct the heat flux monitoring calculation model. The No. 3 blast furnace of an iron making plant is taken as an example. The three-dimensional finite element simulation method to calculate the monitoring value of the cooling stave heat flux is described in detail. The simulation results demonstrate that the heat flux monitoring of different cooling staves can vary. Even for the same cooling stave, the monitoring value varies with the increased lining erosion. To ensure safe operations, the monitoring value should be updated when the erosion profile of the lining changes significantly.

The blast furnace (BF) hearth is critical for determining the life of a BF. Irreversibly eroded hearths can be caused by high-temperature molten iron erosion, alkali metal corrosion, and thermal stress. When serious depression erosion occurs in the hearth, furnace protection measures can prevent the erosion from expanding and ensure the safe operation of the BF. At present, furnace protection measures and furnace protection strength are mostly selected based on engineering experience. In this paper, a three-dimensional (3D) computational fluid dynamics (CFD) numerical model of BF hearth with elephant-type depression erosion was established to predict and evaluate the effect of furnace protection measures. At the same time, the phase change behavior of hot iron solidification was also considered. A numerical model was used to analyze common furnace protection measures such as increasing furnace hearth cooling, closing the tuyere, reducing the tapping productivity, and reducing the tapping temperature. The calculation results are consistent with actual furnace protection experience.

The blast furnace hearth is the key position to determine the life of the blast furnace. To ensure the safety of the blast furnace hearth, when serious local depression erosion occurs in the hearth lining, necessary protection measures are taken to prevent the depression erosion from continuing to expand. At present, the measures and strength of furnace protection are mostly selected according to the engineering experience, lacking feasible theoretical methods to predict the effect of furnace protection. In this paper, a three-dimensional numerical model of thermofluid-solid coupling of blast furnace hearth with mushroom-type depression erosion was established. Taking hearth temperature and thermal stress as the evaluation indexes, the effect of furnace protection measures was predicted and evaluated. The influence of molten iron flow and the formation of a solidified iron layer on the temperature distribution of the refractory material was considered in the numerical model. We have verified the calculation model, and the calculated temperature value was in good agreement with the measured value. In addition, the numerical model was used to analyze common furnace protection measures such as increasing the furnace cooling, closing the tuyere, and reducing the smelting strength. The research results of this paper have guiding significance to select the type and strength of the blast furnace protection measures.