The materials used for penetrating warhead shells require high strength and toughness. Ultrahigh strength steel with low cost and excellent toughness has become the preferred material for penetrating warhead shells. The typical steel grades, composition, properties and development history of these materials were firstly reviewed, the strengthening and toughening mechanisms of typical ultrahigh strength steels were focused on and the need for performance of the materials was explored. Then, strengthening and toughening mechanisms of low-alloy ultrahigh strength steel and secondary hardening ultrahigh strength steel, “multiphase, metastable, multiscale” microstructure and nanocomposite precipitation were introduced, and the difficulties in the development of these materials were analyzed. Finally, the development directions of high purity, high microstructure uniformity, multiphase microstructure control and low cost were discussed.

Soft magnetic material is one of the key energy materials to realize the technological breakthrough in the important industries upstream of electronic components. The advancement and investigation of high-performance soft magnetic materials are paramount for energy conservation, consumption reduction, and the successful execution of the "Made in China 2025" initiative. High-entropy alloys have a wide range of adjustable magnetic properties due to the doping of magnetic elements such as Fe, Co and Ni. Therefore, high-entropy alloys are poised to emerge as superior soft magnetic materials. This review delineates the pivotal factors influencing the magnetic properties of high-entropy alloys, highlighting the magnetic properties of high-entropy soft magnetic alloys are very sensitive to the chemical composition, preparation process and parameters, and the phase structure. Heat treatment is identified as the primary strategy for refining microstructures of high-entropy alloys and optimize their properties. In addition, the intrinsic mechanism that affects the magnetic characteristics of high-entropy soft magnetic alloys is elucidated from the atomic scale based on the theoretical simulation method, which further defines the dependence relationship between the magnetic properties of high-entropy soft magnetic alloys and the magnetic domains. Finally, it condenses part of the scientific problems in the development of high-entropy soft magnetic alloys and briefly summarizes the directions that should be focused on in the future development of high-entropy soft magnetic alloys.

Argon injection in nozzle can prevent nozzle clogging during the continuous casting process, but it can also cause defects of subcutaneous bubbles in slabs and increase the risk of intensified fluctuations at the steel-slag interface. Herein, for the process of argon injection from the bowl of nozzle, a three-dimensional mathematical model of the tundish-nozzle-mold was established by coupling the DPM model and VOF model. A 1∶2 scaled water model experiment was conducted to verify the morphology of bubble plume and size distribution of bubbles in the mold. The effects of argon flow rate, casting speed, and submerged depth of nozzle on the flow field, size distribution of bubbles in varied regions and fluctuation behavior of steel-slag interface in the mold were investigated. The results show that with a low argon flow rate, the liquid steel flowing out from the nozzle ports separates into two streams: one rushes to the narrow face, and the other impacts the steel-slag interface. Large size bubbles are mainly distributed in the near-nozzle region of the 1/2 and 1/4 wide faces. With the increase in the argon flow rate, the impacting position of the stream on the narrow face move upwards, and the slag open eyes appear in the vicinity of the nozzle and gradually become larger. Moreover, the number of large size bubbles in 1/2 wide face first increases and then decreases, and the number of small size bubbles near the narrow face increases significantly. With a low casting speed, a single-roll flow pattern is formed in the mold, and the bubbles are concentrated near the wall of the nozzle with a large slag open eye generated here. An increasing casting speed is beneficial for the uniform spatial distribution of bubbles in the mold, and reduce the area of slag open eye, but will increase the number of small bubbles in the area near the narrow face. In addition, a low submerged depth is favorable for bubbles to float upwards in the near-nozzle region. Moderately increasing the submerged depth of the nozzle can decrease the number of small bubbles near the wide face.

High pressure roller grinding (HPRG) pretreatment can improve the quality of pellets, but its mechanical activation effect is affected by many parameters. The effects of HPRG pretreatment on the properties, pelletizing and roasting properties of vanadium-titanium-iron concentrate under different water contents were studied, and the suitable wetting degree for mechanical activation of vanadium-titanium-iron concentrate by HPRG pretreatment was determined. The results show that when the water content increases from 5.5 wt.% to 8.5 wt.%, the particle size of vanadium-titanium-iron concentrate decreases firstly and then tends to be stable after HPRG pretreatment, the specific surface area increases, and the hydrophilicity and billability are enhanced. However, the increase of water content is not conducive to the dissociation between iron ore and gangue, and the mineral liberation degree of titanomagnetite decreases. When the water content is 6.5 wt.%-7.5 wt.%, the mechanical activation of HPRG is the strongest. At this time, the grain size of titanomagnetite is the smallest, the lattice distortion rate is the largest, and the quality index of the prepared vanadium-titanium-iron concentrate pellets is the best. The suitable water content of vanadium-titanium-iron concentrate in HPRG pretreatment is 6.5 wt.%-7.5 wt.%. Correspondingly, the vanadium-titanium-iron concentrate needs to be wetted to a capillary water content of 4.4 wt.%-5.4 wt.% before HPRG pretreatment.

The utilization of relatively inexpensive and abundant hematite-limonite is of great practical significance for expanding the raw material source of pellets and promoting the green transformation of the iron and steel industry. For an imported hematite-limonite (AM), its wet milling-settling-filtering characteristics were investigated, and at the same time, laboratory trials and on-site industrial experiments were conducted on the roasting behavior, metallurgical performance and microstructural characteristics of pellets under simulated grate-rotary kiln process conditions, revealing the influence of the addition of AM on the raw material pre-treatment and pellet production. The results show that AM is an easy-to-grind ore, which is difficult to be settled and filtered after wet milling due to the presence of limonite, and it can be used with hard iron ore to strengthen the settlement and filtration performance in the actual production; when the milling fineness of AM(-0.074 mm content) is controlled at 70 mass%-80 mass%, and the specific surface area of the mixed concentrates is 1 500 cm²/g, qualified pellets(CCS≥2 500 N/pellet, RI＞60%, RDI_+3.15＞97% and RSI＜20%) can be prepared with AM ratios ranging from 0 to 40 mass%. However, with the increase of AM ratio from 0 to 40 mass%, the suitable preheating and roasting temperatures of pellets need to be increased by 50 ℃, respectively. The on-site industrial experiments further verified the laboratory results, under the condition that the thermal system of grate-rotary kiln pelletizing process is basically stable, the AM ratio should be controlled within 17 mass% to obtain good technical and economic indexes, and the energy consumption of the process will tend to increase if the AM ratio continues to be increased.

Iron coke is one of the main potential technologies for low-carbon ironmaking in blast furnaces. Evolution characteristics of the tensile strength, mechanical strength, and thermal properties of iron coke under different raw material ratios were analyzed. The mechanism of the influence of raw material ratios on the microstructure, pore structure, and carbon crystal structure of iron coke was analyzed using characterization methods such as optical microscope, SEM-EDS, BET, and XRD. The research results indicate that a lower porosity and a more uniform pore structure in iron coke contribute to enhancing its tensile strength. When the iron ore powder content exceeds 10 mass%, there is a significant decrease in the mechanical strength of the iron coke. Taking into account the mechanical strength and thermal performance of iron coke, the mass fraction of iron ore powder added should not exceed 15 mass%. By adjusting the addition of 1/3 coking coal to optimize the metallurgical performance of the iron coke, it is found that when the addition is between 20 mass%-22 mass%, the mechanical strength of the iron coke reaches the level of second-grade coke. The reactivity of iron coke exhibits a trend of initially decreasing and then increasing with the increasing in 1/3 coking coal content, and the underlying reason is the change in carbon structure and micropore structure.

Sintering is an indispensable link in the whole iron and steel industry production, the change of parameters in the sintering process will directly affect the quality and output of sinter. Taking the 150 m² sintering machine of a steel plant as the research object, the simulation software Fluent was used to simulate the sintering process parameters. By establishing a suitable physical and mathematical model, and based on on-site actual data, the temperature field changes in the material layer were simulated. Single factor analysis was used to study the effects of carbon content, porosity, material layer thickness, and suction negative pressure on timerequired to reach the sintering end point, and the optimal process parameters were determined. The research results show that increasing the carbon content shortens time required to reach the sintering end point, and the optimal sintering end point position is achieved when the carbon content is 4.23 mass%. When the porosity of the layer increases,time required to reach the sintering end point becomes shorter, and the sintering end point position is the best when the porosity is about 0.49. When the thickness of the material layer increased,time required to reach the sintering end point is extended. When the thickness of the material layer reaches 734.13 mm, the maximum vertical sintering speed reaches 0.321 mm/s.By increasing the suction negative pressure,time required to reach the sintering end point will be shortened. When the suction negative pressure reaches 15 kPa, the vertical sintering speed is optimal. Under the optimized process parameters, the quality and output of sintered ore are improved.

The effects of roasting temperature and basicity of pellets on compression strength of pellets were investigated by roasting experiments using horizontal tube furnace. The effect of pellets basicity, including natural basicity, 0.4, 0.6, 0.8, and 1.0, on the mineral composition of pellets were analyzed by using SEM-EDS techniques. The possible generators of Fe₂O₃-SiO₂-CaO system were calculated using FactSage software, and the above experimental results were analyzed and verified in combination with phase diagrams. The results show that for the pellets with basicity of 0.3-1.2, the compressive strength showes an obvious increasing trend with the increase of basicity, and a small amount of calcium-containing silicate minerals are firstly generated during the roasting of low-basicity pellet, and then calcium silicate minerals and calcium ferrate-based minerals are further generated during the roasting as the pellets basicity increased.

With the continuous promotion of the national“dual carbon” target, while developing emerging technologies in iron and steel industry, fuel diversification and resource efficiency are also the only way to achieve energy conservation and emission reduction. To explore the potential application of printer waste toner in the iron and steel industry, to explore the feasibility of the blast furnace injection process, the combustion behavior, performance, synergistic effects, and dynamic parameters of waste toner, pulverized coal used in blast furnace injection, and their mixed fuel in different proportions were investigated by thermogravimetric analysis to understand the fuel combustion mechanism and provide a theoretical basis for the injection of new fuels into blast furnaces. The results show that waste toner has excellent combustion performance, and its comprehensive combustion characteristic index, combustion stability, and flammability index are all better than those of pulverized coal. This suggests that waste toner can serve as an auxiliary fuel for blast furnace injection, potentially replacing a portion of pulverized coal. When the blending ratio of waste toner is 10%, the combustion performance of the mixed fuel is optimal, with a comprehensive combustion performance index, combustion stability, and flammability index of 21.97×10^-10 (min^-2·K^-3), 23.33×10^-6 (min^-1·K^-2) and 25.16×10^-6 (min^-1·K^-2), respectively. Through analysis of the ash content of waste toner, it was found that the mass fraction of Fe₃O₄ in the ash content of waste toner was as high as 84.99 mass%. Through the analysis of the synergistic effect between waste toner and pulverized coal, it was found that the blending of wastetoner and pulverized coal can promote combustion, and the synergistic effect parameter F is in the range of 0.80-1.15. Through dynamic analysis, it was found that the activation energy required for combustion of mixed fuels is lower than that of single fuels, and it generally decreases with the increase of the proportion of waste toner.

In the demand for a balance between high strength and high ductility of martensitic steel for automotive application, a new rapid tempering process was proposed. The research involved rapid tempering of newly designed medium-carbon martensitic automotive steel and comparison with that by conventional tempering approach to explore the impact on the steel′s microstructure and properties. Employing the techniques and equipment such as tensile testing machines, digital image correlation methods, X-ray diffraction, electron backscatter diffraction, and field emission scanning electron microscopy, the study revealed that the rapidly tempered specimen maintained high dislocation density and refined precipitated carbides, thereby preserving the martensite′s high strength. The results showed that the new processing successfully enhanced the material′s tensile strength and yield strength to 1 616 and 1 466 MPa, respectively, at a rapid tempering temperature of 400 ℃, leading to an increase of 10.2% and 12.5% over the conventional process while maintaining an elongation of over 10%. When tempered at 300 ℃, the martensitic automotive steel maintained a high elongation with a tensile strength near 2 000 MPa. These findings not only offer a new perspective on the preparation of high-strength martensitic automotive steel but also serve as a significant reference for material selection in future automotive industries.

With the soaring prices of Ni and Mo, it is necessary to develop new high-performance and Ni- and Mo-saving stainless steel. Based on the composition of the S32654, a new type of super austenitic stainless steel (SASS) with 24.5% Cr-17% Ni-5% Mn-6.3% Mo-0.7% N was prepared by pressure metallurgy and element synergistic control methods. The precipitation behavior and mechanical properties of the steel were studied. The results indicate that during isothermal aging at 800-1 050 ℃, as the temperature increased, the cellar precipitates composed of Cr₂N and σ phases first increased and then decreased, and 900 ℃ was confirmed to be the precipitation nose temperature of the steel. The ultimate tensile strength (UTS), yield strength (YS) and elongation of solid solution sample (1 200 ℃-30 min) can reach 958 MPa, 517 MPa and 77.4%. With the prolongation of aging time at 900 ℃, the cellular precipitates underwent nucleation and growth, which promoted intergranular cracking, resulting in a decrease in UTS and elongation (797 MPa and 13%, respectively, after aging for 120 min), and the yield strength (YS) first decreased and then increased. After 5 min of aging, the formation of intergranular precipitates consumed solid solution strengthening elements such as Cr, Mo, and N, leading to the reduction of YS to 492 MPa. After aging for 30 min and longer, the number and size of cellular precipitates increased, leading to an increase in YS (535 MPa, after aging for 120 min).

The effects of Mn content and solution treatment temperature on the microstructural evolution and mechanical properties of 17Cr-2Ni-0.2N-xMn duplex stainless steel were investigated by utilizing microstructural characterization and mechanical testing methods. The results indicate that while Mn, among the austenite-forming elements (Mn, Ni, N), exerts the least influence on the austenite-ferrite phase equilibrium temperature, it significantly enhances austenite stability. An increase in Mn content decreases the amount of quenched martensite and suppresses deformation-induced martensitic transformation, thereby improving the steel′s ductility and toughness. Notably, with an Mn mass fraction of 3%, the steel attains a desirable balance of mechanical properties, including 35.5% elongation, 944 MPa tensile strength, and 139 J impact energy at room temperature. Furthermore, an appropriate alloy composition enables the formation of a nearly equiaxed dual-phase microstructure in the 17Cr type duplex stainless steel after high-temperature solution treatment. The studied 17Cr-type duplex stainless steel exhibits excellent overall mechanical properties, with a maximum tensile strength exceeding 1 200 MPa in the solution-treated state, elongation after fracture greater than 50%, an impact toughness of 204 J at room temperature, and 99 J at -10 ℃.

The fatigue limits and S-N curves at 25, 200, and 315 ℃ were measured by using the QBWP-10000 cantilever rotary bending fatigue testing machine. The slow, stable, and fast crack propagation rate curves at different temperatures were tested using a universal testing machine. Based on the fact that fatigue cracks in M50 bearing steel mainly originate from carbides in the steel, a local damage life model related to temperature and time was established by combining the temperature dependent variation of parameters such as elastic modulus and Poisson's ratio with the hardening effect caused by cyclic stress at the carbide interface. Research has found that the stress intensity factor of fatigue defects such as carbides in M50 bearing steel is the amount of fatigue damage; the increase in temperature shortened the crack initiation time and accelerated the crack propagation rate, thereby reducing the fatigue ultimate strength of M50 bearing steel; the main factors affecting the initiation life are the number of cycles, temperature, fatigue defects, and local hardening of carbide interfaces caused by applied cyclic stress.