A large amount of flue gas will be produced in the production process of the converter, and the flue gas has a high temperature and a large number of dust particles. Therefore, the cooling and dust removal of the converter flue gas and the recovery of the waste heat in the high temperature flue gas of the converter are the key to environmental protection, low carbon and cost reduction and efficiency of the converter process. The treatment methods of converter flue gas were summarized. It also points out the defects of the traditional waste heat recovery and dust removal methods, introduces and analyzes the new waste heat recovery method, and proposes three technical routes of converter flue gas and product treatment application. Currently, the capability of collecting waste heat from medium and low-temperature converter flue gas is limited. Traditional OG method and LT method have problems with gas recovery quality, heat loss and poor dust removal effect and have been unable to meet the technical requirements of low-temperature converter flue gas waste heat recovery. Vaporization cooling pipeline coal injection dry waste heat recovery method and chemical molten salt energy storage method for low-temperature converter flue gas waste heat recovery provide a new technical way. According to the existing flue gas treatment process, the technical route with the low-temperature waste heat recovery of flue gas, the diversified utilization of converter gas and steam and the intelligent smelting as the core in the future was put forward, so as to make the efficient use of energy and reduce the energy consumption.

The rapid dissolution of lime in molten slag to improve the slag basicity contributes to the efficient dephosphorization and energy saving during steelmaking. The comparative study on the dissolution and dephosphorization behavior of lime and limestone in slag was conducted through high-temperature dissolution experiments and slag-metal reaction dephosphorization experiments. Results show that lime dissolved rapidly in the initial stage after added into molten slag, followed by a gradual decrease in dissolution rate and almost stagnation in the later stage. In the initial stage of limestone dissolution, a large amount of CO₂ generated by the decomposition of CaCO₃ hinders the contact between the slag and the surface CaO layer formed by CaCO₃ decomposition, thereby hindering the penetration of slag into the lime layer and the dissolution of lime. The CO₂ generated by later decomposition plays an important role in accelerating the dissolution of lime. There is an important correlation between the dephosphorization reaction and the rapid increase in CaO content in the slag. Due to the slow dissolution of lime in the later stage, the dephosphorization rate is lower, and the phosphorus content in the liquid metal is relatively higher. During the dissolution of limestone for dephosphorization, the CaO content in the slag increases more slowly than lime due to slow dissolution in the early stage, which leads to a slightly slower mass transfer coefficient of dephosphorization reaction in the early stage compared with the test of lime. In the later stage, because of the accelerated dissolution of limestone, the mass transfer coefficient in the dephosphorization reaction increases by about 11.6 times compared with that in the early stage and about 6.6 times higher than that in the test of lime.

The mechanism model of converter smelting has developed rapidly, but there are still many problems, such as the disconnection between model parameters and actual blowing and feeding conditions, and the inconsistency between predicted results and actual situations. The establishment of metallurgical models based on mechanism analysis methods such as multiple reaction zones in the converter melt, minimum Gibbs free energy theory, thermodynamic and kinetic coupling reactions has gradually become a consensus in the industry. Changes in the composition of molten steel and slag during the converter melt reaction process were studied and demonstrated the common issues of metallurgical laws in the smelting process. The analysis of the important characteristics of the molten pool reaction was also conducted. Moreover, the mechanism of synchronous changes in FeO accumulation and consumption during the smelting process, the equilibrium state of the reaction interface layer, and the slag-forming route of slag material in the smelting process were proposed. Based on the theory of multiple reaction zones in the converter, the molten pool was divided into“gas-steel liquid” jet impact zone,“slag-metal droplets-furnace gas” emulsification zone, and“slag-steel liquid (metal droplets)” slag zone. An oxygen allocation model for dynamic regulation of three reaction regions with values ranging from 10%~20%: 45%~65%: 40%~25% was established. Application of the model based on the mixing and stirring of the melt pool in the three reaction zones of the converter showed that when the comprehensive stirring energy was in the range of 0.60~0.75, the variation range of the equivalent mass transfer coefficient at the reaction interface was 1.019~1.024.

Control of non-metallic inclusion is the core issue in the quality control process for producing high-quality steel products. During the continuous casting process, ladle filler sand is used to isolate the liquid steel and the slide plate, serving the functions of automatic teeming and protecting the slide plate. However, it also introduces a large amount of exogenous non-metallic inclusions into the liquid steel. Electromagnetic induction controlled automated steel teeming (EICAST) replaces the traditional application of filler sand in the ladle tapping process, thus avoiding the secondary contamination during continuous casting and providing a novel approach to improving the cleanliness of the liquid steel. The application of EICAST technology requires the adjustment of various process parameters, among which the selection and configuration of power supply parameters are crucial for improving the heating efficiency and achieving the automatic teeming for ladle treatment. The current work utilizes a simulation-based methodology coupling the multiple physical fields including electromagnetic field, temperature field, and solid-liquid phase transition, to investigate the influence of different power supply parameters on the heating efficiency of the blocking layer. The obtained results indicate that a minimum current of 550 A is required to achieve a 1 mm critical melting width at a specific frequency of 200 kHz. Based on the obtained results, the exploration of the nonlinear matching relationship among parameters likecurrent intensity, frequency, etc., can be extended to a general longitudinal magnetic flux induction heating model. It indicates the mechanism of electromagnetic induction heating and clarifies the interrelationships among different power supply parameters, laying the foundation for the further widespread application of EICAST in the steel industry.

To solve the problem of converter burn-through and steel leakage, a new model of monitoring and forecasting the residual thickness of converter lining was proposed. The erosion mechanism and influencing factors of the converter lining was analyzed to clarify the mechanical damage and chemical erosion effect of the smelting environment on the lining. Meanwhile, the feasibility of using infrared image analysis technology to detect the residual thickness of converter lining was clarified, and the research scheme of the residual thickness prediction model was designed based on infrared image recognition. Then, the image algorithm was adapted to realize the mutual conversion of infrared image and temperature, which effectively reduced the difficulty of analyzing infrared image data, and the factor analysis method was used to reduce the dimensionality of the network input. GA-BP neural network was finally employed to predict the lining spalling amount in a single smelting, and then the residual thickness of the lining was calculated. The proposed model is highly accurate, with 98% of the predictions having an error of less than 1 mm and 85% of the predictions having an error of less than 0.5 mm. This model filled the technical blank of detecting the lining residual thickness with infrared technology, expanded the application prospect of infrared technology in steel industry, and provided new ideas as well as methods for solving safety problems of converter lining.

To address the inadequate uniformity and notable temperature differences within the steel flow of a five-stream induction-heated tundish (IHT) at a steel plant, a novel channel outlet structure is proposed to optimize the tundish′s flow dynamics. Through orthogonal experimental design, various configurations for the channel outlet structure are explored, yielding residence time distribution (RTD) curves for each scheme. By integrating range analysis with empirical water model experiments, the optimal configuration for the channel outlet is determined, as proposed in Trial 3. This configuration features an aperture of 90 mm for outlet 1 with vertical and horizontal inclinations of 15° and 20°, respectively, while outlet 2 has an aperture of 80 mm with a horizontal inclination of 20°. The channel diameter is set at 100 mm. Under this design, the dead zone proportion is reduced to 18.61%, marking a 17.77% improvement over the prototype structure. Furthermore, the standard deviation of the average residence time is reduced to 8.36 s, representing a 66.64% enhancement over the original tundish. Computational fluid dynamic (CFD) simulations are conducted to model the flow field and temperature distribution for Trial 3, demonstrating that the tapered bifurcated channel structure facilitates efficient material and energy exchange within the tundish, thereby significantly improving flow field uniformity and temperature distribution. A robust theoretical foundation for optimizing the physical characteristics of channel IHT is provided.

In recent years, microalloyed steel has garnered widespread attention due to its low cost and excellent performance, finding extensive application in numerous industries such as automotive and construction. The prediction of hot-rolled steel properties is a major direction in steel intelligent manufacturing and holds great significance for enhancing the stability of product performance. Consequently, predicting the mechanical properties of microalloyed steel is highly significant for optimizing the production process, improving product quality, and increasing production efficiency. Data preprocessing methods such as clustering, outlier rejection, and linear normalization were developed based on microalloy steel industrial big data, rolling process theory, and statistical principles. Combined with precipitation thermodynamics, the effective Ti content was calculated, and a forward selection-based method was employed for feature screening. The mechanical property prediction of microalloyed steel is established based on random forest, and the particle swarm optimization algorithm is utilized to optimize the hyperparameters of the random forest, thereby achieving high-precision prediction of the mechanical properties of Ti microalloyed steel. The results indicate that the model has a hit rate of 96.8% for yield strength and 98.9% for tensile strength within a relative error of ±6%, and the elongation has a hit rate of 97.9% within an absolute error of ±4%. It is verified that the developed model conforms to the laws of physical metallurgy and achieves good model accuracy in online prediction in the field.

The stiffness of rolling mill has an important influence on the control of plate thickness and shape and the stable operation of rolling. In order to study the stiffness of the rolling mill system and the change of rolling force during the actual rolling process of the 1850 Furnace Coil Rolling Mill, based on the finite element analysis, a thermal coupling model of the rolling process of the furnace coil rolling mill was established under the extreme rolling conditions while taking into account the influence of rolling temperature. Then, the stiffness, stress and strain of key parts during the operation of the rolling mill under the influence of multiple factors were calculated. Three sets of numerical simulation were carried out according to the maximum rolling force in the rolling schedule. The deformation of each part of the rolling mill fluctuates up and down with the change of rolling force. The real-time stiffness of the rolling mill system is calculated based on the rolling force and the total vertical deformation in the rolling process. Using the average rolling force and the average deformation, the stiffness of the rolling mill is 6 078, 6 089 and 6 077 kN/mm, respectively. The results show that even though the average rolling force and total deformation in the three rolling procedures are different, the stiffness values are basically the same.

In order to meet the high temperature performance requirements of high power density diesel engine block and cylinder head materials, changes of mechanical properties and microstructure of high strength vermicular graphite cast iron for diesel engine cylinder head after different thermal exposure temperatures of 350, 500 ℃ and different holding time of 0-1 000 h were studied. The results show that after thermal exposure, the tensile strength R_m of the compacted graphite cast iron test piece decreases with the increase of holding time, and the elongation A increases with the increase of holding time. The tensile strength R_{m(25 ℃)} and elongation A_{25 ℃} of the specimens at room temperature decreased by 20.0% and increased by 41.7%, respectively after thermal exposure at 350 ℃ for 1 000 h. The high temperature tensile strength R_{m(200 ℃)} and elongation A_{200 ℃} decreased by 20.2% and increased by 125% respectively compared with those without heat preservation. The room temperature tensile strength R_{m(25 ℃)} and elongation A_{25 ℃} of the specimens exposed at 500 ℃ for 1 000 h decreased by 46.7% and increased by 36.1%, respectively, compared with those without heat preservation. The high temperature tensile strength R_{m(200 ℃)} and elongation A_{(200 ℃)} decreased by 14.6% and increased by 50%, respectively, compared with those without heat preservation. With the increase of thermal exposure time, the amount of pearlite in the matrix of compacted graphite cast iron gradually decreases, and the amount of ferrite gradually increases, which is the main reason for the change of microstructure and mechanical properties.

Changes in the morphology and size of the γ′ phase of C-HRA-3 heat-resistant alloy after aging at 700 and 750 ℃ with respect to aging temperature and time were investigated. The coarsening kinetics of γ′ phase is derived, and an attempt is made to predict the γ′ phase size at 10⁵ h. The results show that the shape of γ′ phase is uniform spherical distribution after long term aging at 700 ℃/11 023 h in the C-HRA-3 alloy. The size of the γ′ phase increases and the shape changes from spherical to partially spherical after long term aging at 750 ℃/11 023 h. The size of the γ′ phase gradually increases with the increase in aging temperature and time, and the effect of aging temperature is more significant. The growth kinetics equation of the γ′ phase in C-HRA-3 alloy after aging at 700 and 750 ℃ was obtained, and the effective activation energy of γ′ phase growth, D_Eff, was calculated to be 260 kJ/mol. It was predicted that the average diameter of the γ′ phase would be about 140 nm and about 230 nm when aged at 700 and 750 ℃ for 10⁵ h, respectively.

The difference of carbides in Fe-Mo-Cr-C alloy steels in terms of number, size and composition by different spheroidal annealing holding time was systematically investigated using scanning electron microscopy (SEM). The results show that the higher hardness of the specimens with longer annealing time is due to the dissolution of more eutectic carbides during austenitization and the precipitation of a greater number of secondary carbides of the M₆C (Fe₃Mo₃C) type with smaller sizes. The first-principle calculations show that Fe₃Mo₃C has the best overall performance, which is conducive to the improvement of the overall mechanical properties of the steel among the carbides of Fe-Mo-Cr-C alloy steels in the annealed condition. Different high and low energy levels and differences in orbital hybridization of Fe-d, Mo-d, C-d and C-p are responsible for the superiority of Fe₃Mo₃C over Fe₂Mo₄C, which is also a M₆C-type carbide, both in terms of structural stability and mechanical properties. The effect of carbides on mechanical properties of steel in spheroidal annealing was studied, which can provide a theoretical basis for other mold steel materials in the heat treatment process technology.

It was studied that the effects of solution temperature on heat-treated microstructure and resultant mechanical properties of a novel nickel based superalloy with a high content of γ′ precipitates by means of optical microscopy (OM), field emission scanning electron microscopy (FE-SEM) and mechanical experiments. The as-received hot-rolled microstructure undergoes static recrystallization during the solid-solution treatment completely. The recrystallized grains remain fine uniformly at 1 120 and 1 130 ℃, but become significantly coarser with a poor uniformity at 1 150 and 1 190 ℃. As the solid-solution temperature rises, the content of primary γ′ precipitates at grain boundaries decreases; while the number of secondary γ′ precipitates increases and their size decreases, until it exceeds the γ′ solvus (about 1 134.3 ℃). It is indicated that the mechanical properties of this alloy are jointly determined by the size of γ grains and the content and distribution of γ′ precipitates within γ grains. The tensile strength both at room temperature and 850 ℃ increases first and then decreases with the increase of solid-solution temperature. Compared with that of coarse-grained microstructure, the tensile plasticity of fine-microstructure is high at room temperature but poor at 850 ℃. The coarser the recrystallized γ grains, the longer the stress-rupture lifetime and the higher the stress-rupture plasticity under 850 ℃/350 MPa. The heat-treated microstructure with a solid-solution temperature of 1 130 ℃ obtains a higher high-cycle fatigue lifetime at 850 ℃.

With the development of the stainless steel industry, there emerges an urgent need to process large amounts of stainless steel dust and sludge. This stainless steel dust and sludge contains harmful elements such as K, Na, Pb, Zn, and S, which can negatively impact the environment when recycled back into the main production process. Effective removal of these harmful elements during the preparation of pre-reduced pellets from stainless steel dust and sludge can significantly reduce their presence in a closed-loop process, marking a significant step towards the resourceful utilization of stainless steel dust and sludge. Researchers draw on coal-based direct reduction processes to investigate the behavior of harmful element removal during the preheating, the oxidation roasting, and the coal-based pre-reduction of stainless steel dust and sludge pellets, and to optimize the parameters of the removal process. Under optimal pre-reduction conditions(C/Fe mass ratio of 2, the reduction temperature of 1 250 ℃, and the reduction time of 80 min) the removal rates for harmful elements K, Na, Pb, Zn, and S reached 95.47%, 55.14%, 98.13%, 94.27%, and 65.57% respectively. The pre-reduced pellets achieved a compressive strength of 555 N per pellet and a metallization rate of 86.48%, making them suitable as feedstock for stainless steel electric furnace smelting and achieving resourceful treatment of stainless steel dust and sludge.