China is the world's largest producer and consumer of vanadium （V）, with approximately 88.7% of V derived from V-bearing steel slag, a byproduct of V-titanium （Ti） magnetite （VTM） smelting. This paper reviews the industrial status of VTM smelting in China from two aspects, blast furnace （BF） and Non-BF. BF smelting is the mainstream mode, and resource recovery rate of Ti should be improved simultaneously while gradually advancing low-carbon transformation of industry. Among Non-BF processes, the hydrogen-based direct reduction combined with electric arc furnace melting separation process has the most promising application prospects. Subsequently, the common problem of increasing V content in V-bearing hot metal faced by various processes is analyzed, i.e., how to increase the V content in hot metal under the same smelting rhythm without compromising the stability of the smelting system and without significantly increasing production costs. Limited by the symbiosis of V and Ti, the core principle of "controlling Ti and preserving V" should be maintained from the thermodynamic perspective, while the multi-directional constraints on increasing V content in V-bearing hot metal composed of reaction rate, interfacial mass transfer and process coupling should be comprehensively considered from the kinetic perspective. Suggestions such as optimizing raw material ratio, precisely controlling reaction temperature and slag phase composition, and enhancing interfacial mass transfer efficiency are proposed. Meanwhile, the paths of increasing V content in V-bearing hot metal for different processes are discussed. Finally, the application prospects of artificial intelligence （AI） technology in solving the problem of increasing V content in V-bearing hot metal are analyzed, and a comprehensive solution integrating ironmaking big data analysis, AI, expert experience, and process theory is proposed for BF conditions. This solution aims to address the dynamic balance between the V burden entering the BF and the smooth operation of the BF from two directions, increasing the V content of V-Ti sinter and increasing the charging proportion of V-Ti sinter, so as to maximize the vanadium content in hot metal on the premise of stable BF operation. This paper provides theoretical guidance for the future development of VTM smelting in China, and the proposed scheme is expected to offer technical reference for the BF smelting of VTM and related industries.

To address the dual demands of the tightening supply of high-quality pellet feed and the low-carbon transition of ironmaking, hematite-limonite, which is abundant and relatively low-cost, is becoming an important supplementary raw material for oxidized pellet production. This paper reviews the sources and basic characteristics of hematite-limonite, systematically summarizes its effects on key stages of pellet production, including green pellet preparation, drying, preheating, and induration, and further outlines recent research progress, industrial application practices, and the main strengthening approaches for increasing its proportion in pellet blends. Existing studies indicate that the high specific surface area, developed pore structure, and certain self-bonding ability of hematite-limonite are beneficial to pelletizing and can reduce binder consumption. However, its high crystal water content, high loss on ignition （LOI）, and lack of oxidation exotherm tend to lower the decrepitation temperature, aggravate cracking and powdering during drying and preheating, and increase the difficulty of induration and thermal profile control. Through grinding pretreatment, optimization of ore blending structure, reconstruction of the drying-preheating-induration schedule, and regulation of flux system, basicity, and MgO content, the insufficient consolidation caused by high-LOI raw materials can be compensated to some extent, thus enabling the stable application of hematite-limonite in different pelletizing processes. The key to increasing the proportion of hematite-limonite lies in establishing a whole-process coordinated control system. Future studies should focus on dehydration behavior, pore and crack evolution, and induration mechanisms, so as to promote its high-proportion and stable application.

The rapid development of industries such as automotive, shipbuilding, cryogenic pressure vessels, and aerospace has imposed increasing demands on steel materials. As a new generation of materials, Fe-Mn-Al-C lightweight steels have attracted significant attention over the past two decades due to their combination of high strength, high ductility, high toughness, and low density. Depending on the varying additions of C, Mn, and Al, the microstructure of Fe-Mn-Al-C lightweight steels can be categorized into ferritic, austenitic, and dual-phase types. Differences in composition, microstructure type, precipitates, stacking fault energy, and testing conditions result in distinct deformation mechanisms among these steels. Based on the microstructural and structural characteristics of Fe-Mn-Al-C lightweight steels, this paper systematically reviews the deformation mechanisms of ferritic, austenitic, austenite-based dual-phase, and ferrite-based dual-phase lightweight steels. In ferritic lightweight steels, deformation mechanisms evolve with increasing Al content and the degree of B2/DO₃ ordering, leading to enhanced dislocation slip resistance and a transition from single curved dislocations to paired long straight screw dislocations. In austenitic lightweight steels, the deformation mechanism shifts with increasing stacking fault energy in the sequence of transformation-induced plasticity （TRIP） → twinning-induced plasticity （TWIP） → dislocation slip （dislocation type）. Based on the interaction between dislocations and ordered structures, mechanisms such as dynamic slip band refinement （DSBR）, microband-induced plasticity （MBIP）, and shear band-induced plasticity （SIP） have been proposed. The deformation mechanism of dual-phase lightweight steels is primarily governed by the deformation behavior of the matrix phase, while also being influenced by precipitates and ordered structures. High flow stresses induced by low-temperature and high-strain-rate deformation promote TWIP effects in both austenite and ferrite. Finally, future research directions on the deformation mechanisms of Fe-Mn-Al-C lightweight steels are outlined based on current progress.

High-strength stainless steel is widely used in key structural components of nuclear power equipment because of its excellent combination of strength, plasticity, and corrosion resistance. The stability of its passive film under harsh corrosive environments with high temperature, high pressure, and chloride ions directly affects the service safety and lifespan of nuclear power equipment. Grain boundary characteristics serve as a core parameter for regulating the microstructure and corrosion behavior of stainless steel and play a decisive role in the structure of the passive film and pitting corrosion resistance. This paper took 15Cr-7Ni high-strength stainless steel fabricated by laser powder bed fusion （LPBF） as the object and investigated the influence mechanism of microstructure evolution on passive film stability under different solution treatment temperatures. The results show that the direct aged specimen exhibits fine grains, a high proportion of high angle grain boundaries, and a high density of dislocations and sub grain boundaries. Increasing the grain boundary density promotes effective chromium diffusion, leading to the formation of a dense passive film with high chromium content and low carrier concentration, thus achieving the best corrosion resistance. As the solution treatment temperature increases, the grains continuously coarsen, the grain boundary density gradually decreases, and the martensite content first increases and then decreases. The specimen solution treated at 1 000 ℃ followed by aging has the highest martensite content, where the two phase interface easily forms a micro galvanic couple, causing anodic dissolution of the martensite region. Simultaneously, the continuous coarsening of grains and the decrease in the proportion of grain boundaries result in a lower chromium content in the passive film and a significant increase in defect density, giving the worst corrosion resistance. After high temperature solution treatment at 1 200 ℃ followed by aging, the matrix structure becomes more homogeneous, and the martensite content decreases. However, during the aging process, a large number of nanoscale copper rich phases precipitate, forming chromium depleted zones around them, which impairs the integrity of the passive film. The corrosion resistance of this specimen is slightly improved compared to the 1 000 ℃ treated specimen, but it remains lower than that of the direct aged and 800 ℃ solution treated plus aged specimens. By elucidating the intrinsic relationship between microstructure evolution and the corrosion resistance of the passive film, this study provides theoretical support for optimizing the heat treatment process of this type of material and ensuring its safe service under harsh corrosive environments.

To clarify the austenite grain growth behavior of P92 heat-resistant steel during normalizing and its effect on impact toughness, confocal scanning laser microscopy （CSLM） was employed for in situ observation, and combined with the Sellars model to characterize the austenite grain growth behavior in different temperature intervals and to analyze the grain growth mechanism together with the impact toughness in the tempered condition. The CSLM results show that, during heating, grain boundary migration is not obvious in the temperature interval of [950, 1 050] ℃, whereas it becomes significantly enhanced when the temperature is further increased to the interval of （1 050, 1 150] ℃. During holding, no obvious migration of austenite grain boundaries is observed with increasing holding time at 950 and 1 050 ℃, while pronounces grain boundary migration occurred during holding at 1 150 ℃. Based on the Sellars model, austenite grain growth models are established for the temperature intervals of [950, 1 050] ℃ and （1 050, 1 150] ℃, and the predicted results agree well with the experimental data. Further analysis indicates that undissolved VX precipitates restricted grain boundary migration at 950 and 1 050 ℃, whereas the precipitates are nearly dissolved at 1 150 ℃, leading to a marked weakening of the restriction effect. Impact tests show that the specimens with grain sizes of 9.2 and 13.9 μm exhibite relatively high impact toughness, whereas within the coarse-grained range of 132.3-192.8 μm, no obvious correspondence is observed between grain size variation and impact toughness. Instead, the variation in impact toughness is related to the area fraction of microstructures corresponding to the strongest preferred orientation. This study provides a theoretical basis for predicting and interpreting austenite grain growth during normalizing of P92 steel, and supports the coordinated regulation of creep resistance and impact toughness in the design of post-weld normalizing and tempering treatments.

Due to the presence of a high density of dispersed nano-oxides,oxide dispersion strengthened（ODS） alloys exhibit excellent radiation resistance,corrosion resistance,and high-temperature stability, and are therefore regarded as promising candidate structural materials for nuclear applications. However,a key technical challenge at present is how to achieve reliable welded joints while maintaining a high density of dispersed nano-oxides in the weld metal,so as to fully exploit the performance advantages of ODS alloys. To address this issue, the effects of tungsten inert gas （TIG） welding and resistance spot welding （RSW） on the weld metal of 9Cr-ODS steel were comparatively investigated, and the microstructure and mechanical properties of the weld metal under different welding processes were systematically analyzed. The results show that the weld metals produced by both methods exhibit martensitic structures. However, the martensite in the TIG weld is relatively coarse, and the porosity in the weld is high, the pore size is large, and the pores are enriched along the fusion line and the upper surface. In contrast,the martensitic structure in the RSW is finer and more uniform, and the coarsening and clustering of oxides are effectively suppressed,thereby better preserving the dispersed distribution characteristics of nano-oxides. In terms of mechanical properties,the average hardness of the RSW metal is 545HV,whereas that of the TIG weld metal is only 432HV. In addition,tensile test results indicate that the strength of the RSW metal is significantly higher than that of the TIG weld metal. Compared with TIG welding, RSW causes less microstructural degradation in ODS steel and results in a lower degree of damage to nano-oxides,thereby achieving superior mechanical properties in the weld metal. The findings of this study provide an important reference for the optimization and development of welding processes for ODS steels,and contribute to promoting their engineering applications in advanced fields such as nuclear energy.

Structural materials for the spallation target in accelerator-driven subcritical systems serve in harsh environments characterized by high temperatures, heavy irradiation, and intense corrosion. A new low-activation high-Si martensitic heat-resistant steel （SIMP steel） is considered the preferred structural material due to its excellent comprehensive properties. However, residual ferrite still exists in the microstructure of industrial hot-rolled SIMP steel after normalizing at 1 000 ℃,which is inconsistent with thermodynamic calculation results. To clarify the mechanism of this phenomenon and optimize the heat treatment process, the austenitization process of hot-rolled SIMP steel at 1 000 ℃ and 1 050 ℃ was dynamically observed in situ using high-temperature in-situ confocal laser scanning microscopy. Meanwhile, the micro-strain distribution, local chemical composition partitioning, and carbide precipitation behavior within the as-rolled microstructure were systematically characterized by electron backscatter diffraction （EBSD） and energy dispersive spectroscopy （EDS）. The results show that during the holding process at 1 000 ℃, the austenitization of SIMP steel is incomplete due to the constraints of the initial hot-rolled microstructure, and a volume fraction of approximately 14.6% residual ferrite is retained in the microstructure after cooling. When the normalizing temperature is raised to 1 050 ℃, the sample achieves complete austenitization, and a desirable fully martensitic structure is obtained after cooling. EBSD results reveal that significant heterogeneities in strain and composition exist in the hot-rolled microstructure. The ferrite exhibits low internal strain because it undergoes high-temperature recovery after hot rolling, whereas the surrounding martensitic matrix accumulates a high density of micro-strains due to the diffusionless shear phase transformation, which exerts a mechanical constraint on the reverse transformation from ferrite to austenite during subsequent heating. Meanwhile, carbon atoms partitioned into the martensitic matrix during the cooling process after hot rolling, leading to a carbon-depleted and chromium-rich state in the ferrite regions. Concurrently, the chromium-rich M₂₃C₆ carbides do not completely dissolve 1 000 ℃. They precipitat along the phase interfaces and exert a pinning effect, thereby weakening the chemical driving force for the reverse phase transformation. When the temperature is raised to 1 050 ℃, the martensite releases more of the accumulated strain energy, and the mechanical constraint is removed. Meanwhile, the carbides are thoroughly dissolved, which eliminated the interface pinning effect. It is concluded that the heterogeneities of strain and composition are the kinetic barriers that suppress complete austenitization during 1 000 ℃ normalizing, and the actual normalizing temperature for industrial hot-rolled SIMP steel should not be lower than 1 050 ℃.

With the continuous advancement of the China Fusion Engineering Demonstration Reactor（CFEDR） project, higher electromagnetic loads are expected during fusion magnet operation, placing higher demands on the cryogenic strength and toughness of coil structural materials, including the CICC jackets and coil cases. CHSN01, a high-strength, high-toughness, non-magnetic steel for cryogenic service independently developed in China, exhibits excellent cryogenic temperature properties and can meet the project requirements. However, the jacket and coil case require welding for fabrication, and the performance of the welded joint currently falls short of the target. Hence, a matching filler material for CHSN01 CICC jackets were developed through composition design, melting, hot rolling, and drawing in this study. The welded joint was then fabricated using the tungsten inert gas （TIG） welding process. To simulate the actual fabrication process of the jacket, the welded joint was subjected to cold deformation at room temperature and aging heat treatment at 650 ℃ for 100 h. Subsequently, the welded joint was characterized by optical microscopy （OM）, scanning electron microscopy （SEM）, X-ray diffraction （XRD） and electron backscatter diffraction（EBSD）, and tensile tests were carried out to evaluate its mechanical properties. The results show that a sound welded joint is obtained. No obvious grain coarsening is observed in the heat-affected zone （HAZ）. The weld metal is fully austenitic without obvious precipitates, and contains non-metallic inclusions with an average size of approximately 1 μm, mainly composed of Al₂O₃ and MnO. Moreover, the welded joint exhibits excellent low-temperature tensile performance, and all tensile specimens fractures in the weld metal. The 4.2 K yield strengths （YS,R_p） of the samples at the face and corner positions reach 1 555 MPa and 1 597 MPa, the ultimate tensile strengths （UTS,R_m） are 1 797 MPa and 1 777 MPa, and the elongations （EL,A） after fracture are 23% and 22%, respectively. These values approach the CFEDR project performance targets （yield strength of 1 500 MPa, tensile strength of 1 800 MPa, and elongation of 25%）. No deformation-induced martensite is detected near the tensile fracture region at low-temperature. The decrease in stacking fault energy with decreasing temperature promoted deformation twinning, which becomes the dominant deformation mechanism at cryogenic temperature.

It is an essential prerequisite to understand the basic physical properties and process mineralogical characteristics of smelting-separated titanium slag from vanadium-titanium magnetite for the efficient recovery and utilization of titanium resources. In this paper, titanium slag containing 39.91% TiO₂ was prepared from iron concentrate, titanium concentrate and magnetite via pelletizing, roasting, hydrogen-based reduction and high-temperature smelting separation. The cooling crystallization behavior, melting properties and process mineralogy characteristics of the slag were systematically studied by means of FactSage 7.0 thermodynamic simulation, melting point and melting rate measurement, mineral liberation analyser（MLA）, scanning electron microscopy-energy dispersive spectroscopy（SEM-EDS） and automated mineral identification and characterization system（AMICS） techniques, aiming to reveal the occurrence, dissemination and liberation laws of titanium-bearing minerals and provide theoretical support for the efficient recovery of titanium resources from such slags. The results indicate that anosovite is the preferential high-temperature crystalline phase that starts to form at 1 380 ℃, with a maximum crystallization amount of 51.257 g, and serves as the dominant titanium-bearing phase in the slag. Silicate gangue minerals concentrate in the medium-low temperature range of 1 190-1 220 ℃, tending to form eutectic and encapsulated intergrowths with anosovite, which provides a thermodynamic basis for the adjustment of cooling regimes and optimization of mineral separation. The smelting-separated titanium slag exhibits a flow temperature of 1 426 ℃ and a melting interval of 422 ℃. It is characterized by a high melting temperature and a wide melting range, leading to difficulty in melting and gradual softening, as well as poor high-temperature fluidity. This behavior is attributed to its high TiO₂ content and low CaO content. Titanium is mainly enriched in the elongated grains, with 75.51%（mass fraction） of titanium is hosted in anosovite, while silicon, calcium and aluminum are predominantly concentrated in the silicate gangue matrix, showing a distinct elemental separation feature. Mgnesium and iron elements are uniformly dispersed throughout the entire slag sample without preferential association with either titanium-bearing or silicate phases. There are four distinct dissemination forms exist between titanium-bearing minerals and gangue, namely penetration, encapsulation, contiguity and dispersion. Among them, encapsulated intergrowth and fine-grained dispersion are the main factors restricting mineral liberation. The single mineral liberation degree of anosovite is only 43.09%. It forms a stable "encapsulated-intergrowth" composite structure with glass phase, which is the primary cause of its poor liberation performance. A staged grinding and classification separation process was proposed as the optimal pretreatment method. This method can realize gradual liberation of encapsulated titanium minerals and prevent the overgrinding of fine particles, thereby facilitating the efficient recovery of titanium resources.

Low-nickel stainless steel features favorable cost advantages, while inclusions in molten steel are critical to its product quality. This study conducted industrial experiments to investigate the production process of low-nickel stainless steels. The quantity, size, and composition of inclusions were analyzed during the stainless steel smelting process, with a particular focus on the influence of the ladle furnace （LF） refining on inclusions. The results show that inclusions during the stainless steel smelting are mainly CaO-SiO₂ and SiO₂-MnO. The number density, maximum diameter, average diameter, and area fraction of inclusions decrease overall. During the smelting process, large-sized inclusions of approximately 35 μm appeared and then gradually are removed, with the average diameter of the inclusions being 5 μm. At the beginning of LF refining, the average diameter, maximum diameter, and area fraction of inclusions increase. As the LF refining process proceeds, the number density, average diameter, maximum diameter, and area fraction of inclusions gradually decrease. A comparison between the AOD-LF-tundish process and the AOD-tundish process shows that although the AOD smelting condition is favorable, LF refining still helps to further optimize the molten steel composition and promote the removal of large inclusions. However, the improvement in overall statistical indicators such as inclusion number density and average size is relatively limited. The final results show little difference between heats with LF refining and those without LF refining. Finally, a kinetic model was developed to simulate the LF refining using FactSage Macro Processing. Evolutions of the composition of the molten steel, slag, and inclusion during the steel-slag reaction were calculated. The calculation results show that during LF refining, the TAl mass fraction in the molten steel decreases from 0.003% to 0.002%, while the TO mass fraction decreases from 0.004% to 0.001 8%. The slag composition remained basically stable, with CaO mass fraction of 60%, Al₂O₃ mass fraction of 2%, SiO₂ mass fraction of 35%, and MnO mass fraction of 2%. The main component of the inclusions is CaO, which decreasing from 47.3% to 38.5%. The Al₂O₃ mass fraction is relatively low and increases slightly, with the calculated value of 20% being slightly higher than the measured value of 10%. The MnO mass fraction is approximately 20%, with an overall slight increasing trend. The SiO₂ mass fraction is approximately 20%. Therefore, the developed kinetic model can effectively predict compositional evolution in the LF refining process and provide guidance for inclusion control.

The twenty-high rolling mill is core equipment for high-precision metal material rolling. As a key component for its load-bearing and transmission,the backing bearing is required to be installed in groups on the mandrel to constitute the support roller. In a certain steel plant,the outer rings of the backing bearing in the twenty-high rolling mill frequently exhibited failures such as cracks and spalling,resulting in a service life of only about one month for new bearings,with an average of five times of use. This situation has increased spare parts costs and operation and maintenance pressures,and has severely restricted production efficiency and product quality stability. Existing research on metal fatigue and roll fatigue is generally based on experiments,simulations, and traditional classical phenomenological theories,and limited achievements are available for engineering practice and for guiding the maintenance of backing bearings in twenty-high rolling mills. To address the above problems,the structural characteristics of the equipment and the actual rolling process parameters of the steel plant's twenty-high rolling mill were fully integrated, and a calculation model for the fatigue layer of the outer ring of backing bearing was developed. Firstly, the contact forces between the rolls were solved through an elastic deformation model of roll system,and a modified load calculation model for the backing bearing was established by further considering the notch effect in the contact area between the intermediate rolls and the support roller, so that the load calculation was highly consistent with the actual working conditions on site. Secondly,the normal contact stress and shear stress were calculated based on Herz elastic contact theory and Mindlin theory,and the stress field distribution in the bearing contact area was obtained through coupled calculation to identify the stress causes of defect initiation. Finally, a fatigue damage layer accumulation calculation model suitable for this type of bearing was established based on damage mechanics theory. The key parameters of the model were calibrated on site through regression analysis of material basic mechanical tests and historical failure detection data,and the model was verified in new roll tests. The results show that the model can accurately predict the fatigue life of the bearing,the deviation between the predicted value and the actual measured value is less than 5%. The successful development of this technology is conducive to accurately controlling the service status of the backing bearing on site, effectively optimizing the roll change timing,avoiding waste caused by premature replacement or failures caused by delayed replacement,reducing bearing wear,and ultimately achieving the comprehensive benefits of improving production efficiency, reducing operation and maintenance costs,and ensuring product quality stability.

Stainless steel-carbon steel composite rebar coil, referred to as composite coiled rebar, possesses excellent properties including high strength, high toughness, and corrosion resistance, offering broad application prospects. However, the current hot rolling process still faces issues of unclear bimetal deformation behavior and uneven cladding layer distribution. This study selected 316L stainless steel seamless tubes as the cladding material and HRB400E carbon steel round bars as the core material, using a clean interface and oxidation free technology for billet assembly. Industrial hot rolling trials were conducted to produce ϕ12 mm composite coiled rebar, obtaining round pass profiles from rough rolling （P6）, intermediate rolling （P12）, pre finishing rolling （P18）, and the finished product （FP）. Testing shows that FP exhibits no obvious yield point, with average values of ultimate tensile strength （UTS,R_m）, elongation after fracture （A）, and elastic modulus （E） are measured at 716.7 MPa, 27.84%, and 188 GPa, respectively. Machine vision technology was applied to analyze the P6, P12, and P18 samples. The total reduction rates （R_tot） are 52.63%, 79.26%, and 88.53%, respectively, while the average cladding thickness reduction rates （Fd¯） are 50.67%, 75.33%, and 87.33%, respectively. The deformation discrepancy between the stainless steel cladding and the core carbon steel exhibits a trend of first increasing and then decreasing. The stainless steel cladding area fraction for the P6, P12, and P18 samples are 15.27%, 17.31%, and 16.88%, respectively, showing an initial increase followed by a decrease. This study discoveres for the result that during the intermediate and finishing rolling stages of composite coiled rebar, the two metals do not deform synchronously in equal proportions. This finding provides critical supporting data for understanding the asynchronous deformation behavior of bimetals in hot rolling.

SUS304 stainless steel strips are mainly produced by rolling forming processes. However, when the material thickness is reduced to the micron scale, challenges arise including significant thinning difficulty and high surface roughness. Electrochemical machining can serve as a subsequent process after rolling to achieve further material thinning and improve surface quality. Currently, NaNO₃ solution is the common electrolyte for this process, but it is classified as a controlled explosive precursor chemical. In contrast, NaCl solution, as a traditional electrolyte in the electrochemical machining field, is not a controlled chemical and imposes fewer restrictions on its use and disposal in industrial production. Therefore, this study proposed substituting NaCl solution for NaNO₃ solution in the electrochemical machining process following rolling of SUS304 stainless steel strips. This research systematically analyzed the electrochemical dissolution characteristics of SUS304 stainless steel in NaCl solution. Electrochemical test results show that SUS304 has no obvious passive region in flowing NaCl solution, with an open circuit potential value E_ocp of approximately -0.265 V （vs. SCE, means the potential versus the saturated calomel electrode）. Electrochemical machining experiments reveal that localized pitting first appears on the surface of SUS304 stainless steel, then expands across the entire surface, and finally forms a uniform honeycomb micro pit structure. The experiments also find that when the current density is below 10 A/cm², the current efficiency on the SUS304 stainless steel surface increases with rising current density. When the current density exceeds 10 A/cm², the current efficiency stabilizes at approximately 95%, and the material surface becomes smoother under high current density conditions. Based on these findings, an electrochemical dissolution model for SUS304 stainless steel in NaCl solution was established. Finally, electrochemical machining trials were conducted on SUS304 stainless steel strips. Compared with the initial specimens, the surface roughness values S_a and S_z（S_a is the arithmetic mean of the absolute heights of all measurement points within the evaluation area, and S_Z is the difference between the highest point and the lowest point within the evaluation area） after electrochemical machining decreased by about 36.3% and 47.7%, respectively. This confirms that the environmentally friendly NaCl solution can serve as the electrolyte for electrochemical machining of rolled SUS304 stainless steel strips, enabling high quality manufacturing of thin SUS304 stainless steel strips.

In order to optimize the heat treatment process of 35B cold heading steel and shorten the heat treatment time, the effects of intercritical heating temperature and subcritical holding time on the microstructure and mechanical properties of 35B cold heading steel were systematically studied. JMatPro calculations provide the phase transformation curves of 35B steel under equilibrium conditions, with A₁ （phase transition starting temperature） determined to be 715 ℃ and A₃ （end temperature of phase transition） determined to be 795 ℃. The samples were heated to intercritical temperatures of 735, 745, 755, 765 ℃ respectively, held for 0.5 h, then furnace cooled to the subcritical temperature of 685 ℃, held for 2, 4, 6 h respectively, and finally furnace cooled to room temperature. The results show that as the heating temperature increases and the holding time prolongs, the cementite in the microstructure first transforms from lamellar to granular. When the heating temperature is too high or the holding time is too long, the cementite further grows and coarsens, showing a tendency to re form a lamellar structure. With a subcritical holding time of 2 h, the microstructure mainly consists of incompletely broken lamellar pearlite accompanied by a small number of fine spheroidized cementite particles. The spheroidization rate is highest after 4 h of holding, but the average size of the spheroidized particles is relatively large at 0.66 μm, which is detrimental to the mechanical properties of the cold heading steel. When the holding time is further increased to 6 h, carbides aggregate and grow, and the lamellar structure coarsens, forming a coarse lamellar pearlite structure. Considering the entire process of cold heading forming and service performance, the optimal spheroidizing annealing process is heating at 755 ℃ for 0.5 h followed by furnace cooling to 685 ℃ and holding for 2 h. Under this process, the microstructure is a composite structure of incompletely broken lamellar pearlite and finely dispersed spheroidized cementite, achieving a favorable match between strength and plasticity. The microhardness reaches 154.97HV, the yield ratio decreases to 0.65, and the reduction of area increases to 67%, meeting the requirements for cold heading forming. Additionally, this process significantly shortens the spheroidizing annealing time and improves production efficiency.

Based on the theory of metallurgical process engineering, this paper systematically expounded the important position of the general process layout in the modern steel manufacturing process. A scientific and reasonable general process layout is the physical basis for achieving the efficient coordination of "three flows" and constructing the process network nodes, and it is also the prerequisite for optimizing interface technologies. The general process layout determines the time-space distance of interface connection between processes, fundamentally presetting the operational efficiency of mass flow and energy flow. The ironmaking-steelmaking interface, as the intersection hub and core of mass flow and energy flow throughout the entire process, its optimization technology is an important approach to build a high efficiency, low consumption, and green manufacturing system. This paper focused on the hot metal transportation process and equipment to discussed the key technologies of the "one-ladle technology" process developed in Shougang Jingtang. A comparative study was conducted on the two different types of hot metal transportation processes of Shougang Qiangang and Shougang Jingtang. Production practice shows that the "one-ladle technology" mode based on a compact general layout, by optimizing the transportation route and technical equipment, significantly reduces the temperature drop and waiting time during the hot metal transportation process, realizes efficient and quasi-continuous production between the blast furnace and the converter, completely changes the traditional turnover mode of torpedo car, effectively improves the operational efficiency of ferrous mass flow, and significantly reduces energy dissipation. The research results show that optimization and continuous innovation of the ironmaking-steelmaking interface technology are of great significance for improving production efficiency, reducing process energy consumption, and achieving the green and intelligent development of steel plants. The collaborative optimization of the general process layout and interface technology is an important foundation for achieving high efficiency, high quality, low cost, and green and low-carbon development in the steel manufacturing process.

The two‑roll extrusion coating process with grooved rollers is widely used in the silicon steel industry, but surface defects such as double lines and missed coating lines are common. To improve the coating uniformity of steel strips and to deeply investigate the deformation behavior of the grooves under extrusion transmission and its correlation with coating defects, a three‑dimensional finite element model of the coating roller-acrylic plate extrusion transmission under fluid‑free conditions was established based on the structural principle of the roll coater. A visual experimental platform for observing the extrusion and rotation deformation of the coating roller was designed and built. By using image processing algorithms, the characteristic deformation values of the grooves under different loads and plate speeds were obtained, and a method for characterizing the three‑dimensional contact deformation of the grooves was proposed. The accuracy of the finite element method was verified by comparing the simulation results with the experimental ones. On this basis, the influences of operational and structural parameters on the groove deformation were systematically studied, and the physical mechanisms of coating defects in the absence of fluid effects were revealed. The results show that after loading, the land width increases nonlinearly from the center to the ends along the roller axis, while the cross‑sectional area of the groove flow channel decreases linearly. This axial non‑uniform distribution is the structural cause of the "thick in the middle, thin at both ends" coating defect. Under dynamic extrusion, the grooves at the roller center exhibit a "）（"‑shaped profile due to three‑dimensional rubber constraints, whereas those at the ends develop an "S"‑shaped distortion caused by the loss of boundary constraints and frictional coupling. This distortion leads to a sharp reduction in flow channel volume and cross‑sectional deformation, which is the key factor responsible for missed coating lines. An increase in the load intensifies the axial non‑uniformity of the groove deformation. As the pitch increases, the land width increases by 11.542%-20.886%, and the cross‑sectional area of the groove flow channel decreases by 20.270%-28.031%. At the roller ends, the land width increases by 3.458%-3.109% relative to the middle, and the cross‑sectional area of the groove flow channel decreases by 6.070%-2.084%. Increasing the pitch improves the axial uniformity of the groove deformation but accelerates groove wear. Changes in plate speed have a negligible effect on the groove deformation. Under actual industrial conditions, the coating roller with a large pitch exhibits the best axial uniformity of groove deformation. By appropriately combining the load, plate speed and pitch, the coating defects caused by groove deformation can be effectively suppressed, thereby improving the coating uniformity and production efficiency of the two‑roll extrusion coating process.