In the process of iron and steel smelting, the interfacial effects such as wetting, dissolution and chemical reaction between the refractory and molten steel (hot metal) will be affected by the electric field existing on the interface. In order to clarify the frictional electrification behavior between molten steel (hot metal) and refractory materials caused by relative motion, a low-temperature fluid flow charging experiment and a thermal simulation experiment were carried out. It can be seen from the low-temperature fluid flow and charging experiment that as the stirring speed increased, the electrostatic voltage generated by the friction between the fluid and the graphite container gradually increased. Due to the different density, viscosity, and the number of impurities and ions in different fluids, the static electricity generated by the flow varied significantly. From the thermal simulation test, it can be seen that frictional electrification occurred between the flowing molten iron and the refractory material, and as the speed of the molten iron flow increased, the generated static electricity increased. The magnitude of static electricity generated between different types of refractory materials and flowing molten iron was different, which was related to their physical and chemical properties.

According to the process of making composite roll by electroslag remelting with T-mold, consumable electrode ring welding and drawing, a three-dimensional finite element model is established by using ANSYS software. The distribution of potential, current density and temperature field in slag pool and the influence of electrode position change are numerically simulated. The method of thermoelectric coupling is used in the calculation, and the skin effect in the electric field model is considered. The results show that the strongest position of skin effect and the maximum current are concentrated on the surface of the consumable electrode. The high temperature zone is between the consumable electrode and the roll core. The change of electrode position has great influence on the current density distribution of slag pool. When the distance between the electrode and the roll core is increased by 10 mm, the maximum temperature in the slag pool is decreased by 20 K, and the average temperature in the upper slag pool is increased. Finally, the numerical simulation results are verified by experiments.

As a model of high voltage and high energy rechargeable batteries, magnesiumion batteries have become the focus of scientific research and market in the field of energy storage. Developing cathode active materials with good reversible cycle and good compatibility with electrolyte is the key to improve the comprehensive performance of magnesium ion batteries. It has been found that transition metal sulfides (TMDCs) are more conducive to the intercalation and extraction of magnesium ions between molecular layers, and exhibit better magnesium storage capacity. On the basis of introducing the working principle and key materials of magnesium ion batteries, the application of several twodimensional layered transition metal sulfides, including MoS2 and TiS2 with a layered structure, Chevrel phase with bulk stacking structure and other transition metal sulfides in cathode materials of magnesium ion batteries in recent years were reviewed and summarized. The existing problems, future research emphasis and development trends were expounded, which hope to be able to provide some reference for future research on improving the comprehensive performance of magnesium ion batteries.

Open indirect cooling water is the main form of the water system in iron and steel enterprises. It is necessary to study the relationship between water volume and water quality in the process of water supply and consumption for understanding the law of open indirect cooling water system. The concept of "effective water" was put forward by combining water volume and water quality indexes in the process of water use. Mathematical model and related analysis methods were established. A case study of the water supply and consumption in a steel enterprise showed that the change of water quality in both water supply and consumption would lead to the change of water replenishment efficiency of the system, and then the fresh water consumption and wastewater discharge of the system would be changed. Compared with the water quantity index, the concept of "effective water" and its analysis method can more scientifically evaluate the water use characteristics of the open cooling water system.

Highspeed steel is widely used in machining tools for largescale equipment manufacturing because of its high hardness, good red hardness and good wear resistance. However, it is easy to cause problems such as segregation of carbides in the large cross section during highspeed steel production process, affecting the mechanical properties and service life of the material. Through the comparison and analysis of the methods of mould casting, continuous casting, electroslag remelting and powder metallurgy, explores the factors affecting the segregation of carbides and the methods of improving the segregation of carbides are explored. The results show that the carbide segregation can be improved by adding inoculants, microalloying elements, mechanical agitation, and electromagnetic stirring. In addition, through comparative analysis, it is found that the use of electroslag remelting to produce highspeed steel can costeffectively control the carbide segregation, and electroslag remelting has become the main method for producing highspeed steel.

In order to improve the endpoint hit rate of basic oxygen furnace (BOF) steelmaking, a new prediction model of BOF endpoint is established to achieve the accurate prediction of the carbon content and temperature at the end of the converter. Knearest neighbor weighted based twin support vector regression (KNNWTSVR) is adopted for the model. A KNN weighted matrix is introduced to the objective functions, and the whale optimization algorithm is used to solve the objective functions to improve the performance of the algorithm. Then, based on the datasets of a 260 t BOF, the prediction model for converter steelmaking endpoint is established. The experimental results show that the predicted hit rates of the endpoint carbon content (error ±0.005 %) and temperature (error ±15 ℃) are 94% and 88%, respectively, and the double hit rate achieves 84%. Compared with the other two existing modeling methods, the proposed model obtains the best prediction effect. Therefore, it meets the requirements of the real production of converter steelmaking, and it is also suitable for mathematical modeling in other fields of metallurgy.

Due to the free- heating direct rolling process of continuous casting billet without the heating furnace, the energy and cost were saved and the emission was reduced compared with the conventional continuous casting- rolling process. The characteristics and key technologies of the free- heating direct rolling process were introduced, and the application of the narrow window control in the direct rolling process was analyzed. According to the improvement of the need for the product quality, the big data- driven direct rolling narrow window control technology was expected to emerge. With this technology, the lagging of the temperature and composition control system in the steel smelting- continuous casting- direct rolling process can be solved, which could be a revolutionary change to China’s steel industry.

The corrosion behaviors of the raw Q235 and hot- molten- aluminum- dipped (HMAD) Q235 steels were investigated in mass fraction of 3.5% sodium chloride solution. The surface morphologies of the samples before and after corrosion were detected using scanning electron microscopy (SEM). The corrosion rates of the raw Q235 and HMAD Q235 steels were studied by electrochemical impedance spectroscopy and a weight- loss method. The results showed that the corrosion rate of the raw Q235 among the three samples was the fastest with a value of about 0.11 mm/a (mm/year). The corrosion rates of HMAD Q235 steels with aluminum- dipping once and twice were 0.04 and 0.03 mm/a, respectively. The corrosion resistance of the raw Q235 steel was significantly enhanced after HMAD treatment, which indicated that HMAD was an effective way to improve the seawater corrosion resistance of Q235 steel.