With the blast furnace coal injection system taken as the research object, a modified equivalent heating value (Q_e) calculation model was established based on Hess's law and thermochemical principles which effectively quantified the heat expenditure effects of processes including organic decomposition, moisture gasification, desulfurization, and ash slagging. The results showed that constrained by the reducing atmosphere and endothermic reactions, the actual effective heat contribution of coal powder was only 45%~50% of its total theoretical heat release. Particularly, ash composition exerted a significant non-linear influence on slagging heat consumption. For high-silica-alumina acidic coal with acidic ash, large amounts of flux were required, resulting in a slagging heat penalty approximately 3.6 times that of low-ash coal. Furthermore, a Q_e-based cost-performance index (k) showed that pulverized coal economy was governed by effective heat contribution, slagging heat from ash, grindability, and overall cost. High-volatile bituminous coal, though lower in calorific value, remained economical due to low ash, easy grinding, and low slagging heat. Some high-calorific anthracites lost value from higher slagging and grinding costs. This provides a theoretical basis for steel enterprises to optimize coal blending based on use value, thereby achieving cost reduction and efficiency improvement.

With the deepening advancement of China's "dual carbon" goals, scrap steel resources, as the only raw material in the steel industry that can be scaled up to replace iron ore, have become a key link in building a low-carbon circular industrial system through their efficient utilization. Currently, the utilization of scrap steel resources in China is at an important stage of rapid growth and strategic transformation. Based on the current industrial situation, the production scale and future trends of scrap steel resources are reviewed, the technical characteristics and application advantages of different steelmaking processes are analyzed, and on this basis, the path recommendations and policy outlooks centered on the high-quality, standardized, and large-scale development goals of scrap steel resources during the "15th Five-Year Plan" period are proposed, aiming to provide a reference for industrial transformation and policy formulation.

Aiming at the problems of low oxygen content in the flue gas circulation system of sintering machines and uneven heat supply between the upper and lower layers of thick material layer sintering, homogeneous sintering technology for reducing emissions and carbon consumption was developed. After the application of this technology, the circulation volume of sintering flue gas reached over 30×10⁴ m³/h, synchronously reducing the total amount of flue gas entering the activated coke device through the main exhaust fan. The consumption of sintering solid fuel was reduced by 1.5 kg/t, the productivity of sintering machine was increased by 0.08 t/ (m²·h), the sintering drum index (+6.3 mm) was increased by 0.07%, and the output increase was increased by 6%. Thus, the comprehensive goals of emission reduction, carbon reduction, output increase, and quality improvement in the sintering process were achieved.

Aiming at the problems of high failure rate caused by frequent operation of the 35 kV high-voltage circuit breaker in the LF refining furnace during the steelmaking process and the difficulty in determining the online status after offline maintenance, an offline detection device was developed. Adopting a modular design, the device integrates power supply, control, indication, and output modules. By simulating actual opening and closing scenarios, it achieves accurate detection of the circuit breaker's functions and contact status. After application, the device showed advantages such as low cost, simple operation, and strong adaptability, which could shorten the fault troubleshooting time by 58%, reduce the online failure rate after maintenance to 3.2% and save 3.86 million yuan in costs per year. Thus, the continuity and safety of steelmaking production were effectively ensured.

To address the technical challenge of excessive TiN inclusions formed by residual Ti in 35MnB steel during preparation, which lead to excessive class D coarse-series non-metallic inclusions, three industrial trials were conducted on 200 mm × 240 mm section billets. The JMatPro thermodynamic software was used to calculate the solidus and liquidus temperatures of the molten steel, and the kinetics mechanism of TiN inclusion precipitation in the solid-liquid two-phase zone was analyzed to clarify the intrinsic relationship between the Ti-N solubility product and the inclusion precipitation behavior. Through macroscopic low-magnification and optical microscopy characterization, the steelmaking and rolling process parameters were optimized specifically, and the influence of process adjustments on the purity of molten steel, microstructure evolution, and mechanical properties was systematically investigated. The results showed that precisely controlling the Ti content within 0.025% to 0.030%, eliminating the RH refining nitrogenation process, and extending the vacuum holding time to more than 15 minutes could effectively reduce the amount and size of TiN inclusions, making the D-class coarse inclusions grade meet the strict requirement of ≤1.0 grade in the technical agreement. The control level of non-metallic inclusions and the stability of the end quenchability of the optimized test steel were significantly improved, and all core technical indicators such as chemical composition, low-magnification structure, and hot upset forging met the agreement requirements. The relevant test data and process experience provided engineering practice and theoretical reference for the precise control of inclusions and process optimization of high-strength wear-resistant MnB steel for construction machinery.

The effect of different normalizing and tempering temperatures on the microstructure and mechanical properties of plastic mold steel 3Cr2NiMo was studied. The results showed that after normalizing at 810 ℃ and 840 ℃, the martensite lath was short and fine needle shaped with uniform structure, and the original austenite grain size was Grade 11. After normalizing at 900 ℃, the microstructure became coarse, and the original austenite grain size was Grade 9. The normalizing hardness increased first and then decreased with the increase of temperature. It was determined that the appropriate normalizing temperature of the test steel was 840 ℃. When the tempering temperature ranged from 450 ℃ to 500 ℃, the microstructure was tempered troostite, and the lath structure maintained the original martensite orientation. When the tempering temperature was increased to 650 ℃, the microstructure was tempered sorbate without obvious orientation. Subsequently, the carbides became spherical, aggregate and grow, while remaining uniformly dispersed. Moreover, the lath boundaries appeared blurred. The hardness of the test steel decreased with the increase of tempering temperature.

Industrial naphthalene contains thionaphthene, quinoline, and their derivatives, which can cause catalyst poisoning during the hydrogenation process, significantly reducing catalyst lifespan. A two-step hydrogenation technology involving fixed-bed hydrofining and deep hydrogenation of industrial naphthalene was designed to produce decalin. The hydrofining process mainly removed sulfur and nitrogen impurities from industrial naphthalene. Using NiMo sulfide catalysts for hydrofining, sulfur content was reduced from 3 200ppm to below 34ppm, and nitrogen content from 102ppm to below 38ppm. Taking the hydrofining product as the raw material for deep hydrogenation, a Pt-Pd/SiO₂-Al₂O₃ catalyst was used in deep hydrogenation process and then both naphthalene and tetraline were completely converted to decalin, with the trans-decalin content in the product stabilized at approximately 87.2% and a maximum trans-/cis- of 6.8. Both catalysts exhibited excellent stability over a 1 000-hour test, showing no signs of deactivation.

The rapid recovery process of Ansteel 3200 m³ blast furnace after long-time shutdown was summarized. In response to the situations including long-time shutdown, suboptimal distribution of the shutdown charge, and severe heat loss in the hearth, effective thermal insulation measures of the blast furnace were implemented during the shutdown period. A recovery scheme was formulated based on rapidly reheating the hearth and discharging the cold slag and iron and then gradually restoring full blast volume. After the blast furnace recovery, the blast furnace restored its pre-shutdown production level within 36 hours by adding clean coke in appropriate quantities at optimal times and precisely controlling the opening and closing sequence of tuyeres.

Aiming at the cracking phenomenon of thick-gauge HSLA steel plate coils rolled by Hot Rolled Strip Steel Mill of Angang Steel Co., Ltd. after being used for tube making, composition and process analysis were conducted, and it was determined that the low charpy impact test result was the cause of the cracking. Using optical microscopy analysis, thin film analysis and replication method to test and analyze the cracking specimen, it was found that coarse second-phase precipitates existed in the plate coil, the overall microstructure was uneven, the grains were coarse and the upper and lower surfaces were asymmetrical, and there were coarse carbides (alloyized cementite) distributed in a chain-like or network-like pattern at the ferrite grain boundaries. Under the combined influence of these factors, the plate coil cracked after being subjected to tube making stress. By improving the composition design, optimizing the thermal regime, rolling temperature, cooling temperature, rolling deformation regime and so on, through the mass production of 6 000 tons of thick-gauge Q345B hot-rolled steel coils, the individual impact and average impact energy values exceeded 180 J. As a result, the cracking rate of steel coils during pipe manufacturing decreased from 25% to 0, completely resolving the technical challenge of coil cracking in pipe production.

_Aiming at the bright band color difference on the upper surface occurring during the production of wide low-carbon deep-drawing steel for automotive outer panels on the electro-galvanizing line, a systematic study was carried out by means of optical microscopy, SEM, EDS and metallographic analysis. The results showed that the defect was caused by abnormally coarse grains in the surface layer of the cold-rolled substrate, leading to abnormal crystallization during electro-galvanizing. The areas with abnormal electroplating crystallization appeared as small bright spot defects, and a large number of bright spots macroscopically manifested as bright band color difference. Through comprehensive defect inspection and process analysis, it was determined that the high hot rolling coiling temperature and excessive wrapper roll pressure during coiling resulted in coarse grains in the surface layer of the hot-rolled strip, and the heredity of the hot-rolled microstructure led to coarse grains in the surface layer of the cold-rolled substrate. By reducing the coiling temperature from 750 ℃ to 710 ℃ and optimizing the wrapper roll pressure parameters, the defect was successfully eliminated, and the process optimization had no significant effect on the microstructure and properties of the finished product.

To solve the surface sliver defect of threated steel, the macro morphology and micro composition of threated steel were detected by SEM scanning electron microscope and energy spectrum analyzer. The results showed that there were unilateral sliver defects of different sizes at the longitudinal and transverse ribs of the threated steel. The irregular inclusions of Al₂O₃, SiO₂ and Al₂O₃-SiO₂ were detected at the cross section of the sliver defects, with sizes ranging from 40~120 μm. These non-metallic inclusions caused a deterioration in the local plasticity of the threaded steel ingot, leading to the formation of cracks. As the rolling process progressed, these cracks gradually expanded and ultimately resulted in sliver defects. By implementing measures such as reducing the oxygen content at the converter endpoint and enhancing the air-tightness during pouring, the average oxygen content of the molten steel in the tundish was reduced to 25ppm. Consequently, the incidence rate of surface sliver defects in hot - rolled products decreased from 2.7% to 1.5%, effectively preventing the occurrence of sliver defects.

The soft collection chute in the finishing and collection area of the large bar production line at Lingyuan Iron and Steel is a core equipment in the bar packing and collection process. However, the original structure was affected by the frequent impact loads during the bar conveying process, resulting in frequent failures of the chain and the support bearing seats of the rotating sprockets. This not only directly led to production interruptions, but also significantly increased the maintenance difficulty and labor-hour costs due to the limited working space for chain restoration and the cumbersome disassembly and assembly procedures, seriously restricting the maintenance efficiency and the continuous operation ability of the entire production line. To address this production bottleneck, targeted improvement and optimization of the soft collection chute structure were implemented for the soft collection chute, including optimizing the force transmission path, enhancing the structural strength of key components, and conducting adaptive structural design. These measures fundamentally eliminated the problems of chain breakage, bearing seat damage and narrow operation space. After the improvement, the integrated operational stability of the equipment was improved by more than fivefold, while maintenance efficiency was enhanced by 80.0% to 83.3%. This was expected to generate annual direct economic benefits amounting to over 1 million yuan. It not only reduced the consumption of spare parts and maintenance costs, but also decreased the unplanned downtime, achieving a dual improvement in production efficiency and economic benefits.