Recrystallization in directionally solidified columnar grain or single-crystal alloys significantly degraded alloy performance by introducing recrystallized grain boundaries perpendicular to the stress direction. Accordingly, recrystallization represented a critical concern during the manufacturing of aeroengine and gas-turbine blades. Serviceexposed directionally columnar grained blades were examined, and stresses induced at different production stages of blades were simulated to investigate recrystallization behavior during subsequent normalservice or slightlyovertemperature service conditions. The results showed that recrystallization occurred near the fillet between the blade airfoil and shroud, with a relatively large affected zone. Based on the size and number of recrystallized grains, recrystallized regions were categorized into two types: one consisted of one or several large recrystallized grains, while the other comprised numerous fine recrystallized grains. Analytical results showed that recrystallization had already formed inside the blades before service. Simulation results of directional solidification, machining and service processes for the alloy demonstrated that collisions during machining and handling, as well as uneven loading and excessive deformation during straightening, would cause plastic deformation of blades and further induce recrystallization during subsequent hightemperature heat treatment.

Electroslag remelting is a core metallurgical technology for preparing high-end special steels, which is of great strategic significance to ensure the autonomy of high-end equipment materials and promoting the high-quality development of the steel industry. The evolution of electroslag remelting technology is systematically reviewed based on its domestic and international development status and practical industrial cases. According to the iteration characteristics of each branch technology of electroslag remelting, the bottlenecks of technological iteration and the main development directions in the future are clarified. Efforts should be focused on high-end incremental markets such as superalloys and high-end bearing steels in the future,. A technological barrier should be estabilished through the combined process of vacuum electroslag remelting and rotating electrodes to promote the transition of the industry towards green, intelligent and high-end development.

Studying the influence of induction heating on the metallurgical transmission behavior was of great significance for improving the quality of castings. However, direct observation and measurement were difficult to conduct owing to the high temperature of the melt and the high cutting cost of ingots, which resulted in substantial experimental losses. Therefore, a multi-physical field coupling model of electromagnetic field-temperature field-flow field-solute field was designed by combining numerical simulation with experimental verification, and sampling verification was performed on a 700 kg ingot of 34CrNi1Mo steel. The influence of two induction heating layouts on the solidification process and solute transport behavior of the ingot were simulated, and the application scenarios of dif ferent coil layouts were analyzed. The results showed that the coil layout exerted a significant impact on the solidification behavior of the ingot. Magnetic fields from different layouts modified flow field patterns and mitigated solute segregation. The two layouts reduced the carbon segregation rate at the riser by approximately 47% and 52% respectively. It was confirmed that the induction heating technology was a feasible approach to achieve solute homogenization in the ingot and improve the quality of the ingot, providing a reference for the industrial application of induction heating of ingots.

Taking S355J2G4 locomotive steel produced by Ansteel ASP 2150 production line as the research object, the strength and toughness of the S355J2G4 locomotive steel were simultaneously improved through compositon design, thermomechanical control process. The law of organizational evolution was analyzed by using EBSD and other methods, and the relationship between microstructure and properties was revealed. The results showed that the final rolling temperature was 860 ℃, and the coiling temperature was reduced from 600 ℃ to 550 ℃, the microstructure changed from ferrite and pearlite to ferrite and bainite. The yield strength was increased by 31 MPa, the tensile strength was increased by 27 MPa, the elongation was decreased by 4.5%, and the impact energy at -40 ℃ was decreased by 96 J. The coiling temperature was 600 ℃, and the final rolling temperature was reduced from 880 ℃ to 860 ℃ with the microstructure composed of ferrite and pearlite. The yield strength was increased by 32 MPa, and the tensile strength was increased by 14 MPa. The elongation was increased by 1.5%, and the impact energy at -40 ℃ was increased by 18 J, realizing synchronous improvement of strength and toughness. The optimal production process for S355J2G4 was a final rolling temperature of 860 ℃ and a coiling temperature of 600 ℃, which provided reliable data support for the matching of the entire process involved in the actual production of hot-rolled strip steel products models in the field of metal materials.

The medium carbon low alloy ultra-high strength steel 24SiMn2TiB was selected as the research subject. Specific alloying elements (Cr, Ni, and Cu) were incorporated into the base composition of the steel, and the corrosion behaviors of both the original and modified steels in a simulated marine atmospheric environment were systematically evaluated by electrochemical measurements and salt spray tests. The results showed that the addition of 0.77% Ni, 0.72% Cr and 0.32% Cu significantly enhanced the corrosion resistance of 24SiMn2TiB steel under simulated marine atmospheric environment, with the corrosion rate reduced by 11.1% to 22.7% compared to the original steel. Further analysis revealed that Ni, Cr, and Cu facilitated the formation of stable corrosion products, particularly α-FeOOH, which contributed to the formation of a compact rust layer and thus further improved the corrosion resistance of the medium carbon low alloy ultra-high strength steel 24SiMn2TiB.

Based on low carbon and Nb-Ti complex designing to trial-produce the two degrees ultra high strength automobile beam steels of 600 MPa grade (600L) and 700 MPa grade (700L), the produce processes and parameters of ultra high strength beam steels of 600 MPa grade and 700 MPa grade were also mentioned. Fatigue tests were performed on the steel sheets of both grades, along with bench fatigue tests on fabricated beam parts. The results showed that the fatigue limit of 700 L beam steel sheet was slightly higher than that of 600L beam steel sheet, while the fatigue ratio of 600L beam steel sheet was higher than that of 700L beam steel sheet. However, the bench fatigue life of the beam parts made from 600L beam steel sheet was much longer than that of 700L beam steel sheet. This indicated that the fatigue resistance of materials with different strength grades couldn’t be simply compared by fatigue limit alone. Instead, the fatigue ratio, by correlating the fatigue limit and static strength of materials, indirectly reflected the key characteristics of materials under cyclic loading, providing a more scientific and comprehensive characterization of the fatigue performance. The Cr+N micro-alloyed design in 600L beam steel sheet enhanced its fatigue performance through a triple mechanism of solid solution strengthening, fine grain strengthening and resistance improvement, which enabled the 600L beam steel sheet to achieve a stepwise improvement in fatigue performance.

A flexural loading test was used to study the influence of loading stress and H₂S coupling environment on the corrosion resistance of oil well pipes. SEM、LCSM and EPMA were used to analyze the influence of different loads on the corrosion morphology, corrosion resistance and corrosion depth of 110S oil well pipes, and to explore the migration mechanism of corrosive S ions in the rust layer. The results showed that the tensile stress produced by bending loading could significantly accelerate the corrosion, and the effect of loading stress was much greater than that of hydrogen sulfide. The maximum corrosion depth of the specimen surface was positively correlated with the magnitude of the tensile stress. With the increase of load, the circular corrosion pits on the specimen surface transformed into boat-shaped corrosion pits, and the length, width and depth of the corrosion pits increased with the applied load, as did the depth-to-width ratio. Under the coupling effect of loading stress and H₂S, the corrosion rate of oil well pipes significantly increased, and the depth of corrosion pits increased from 6.278 6 μm to approximately 131 μm. The superimposed blocked cell effect caused S ions to migrate continuously from the rust layer to the rust layer/substrate interface, which further increased the stress corrosion cracking tendency.

In coking production, the coke-pushing process was completed by the coordination of coke-pusher car, coke-guide car and the quenching car. Premature retraction of the cokeguiding grid by the coke-guide car may lead to red-hot coke falling accidents, which disrupted coking production and threatened the safety of operators. In order to solve this problem, the existing wireless communication network technology for coke oven locomotives was investigated and applied. On this basis, the retraction protection technology for the coke-guiding grid of the coke-guide car was developed. After the implementation of this technology, the coke-guiding grid could only retract after the coke-pusher car finished coke pushing and the coke-pushing rod withdrew from the coke-guiding grid, ensuring safe and orderly coking production.

By combining numerical simulation with experimental research and statistical datas from production sites, the effects of the ladle lid and thermal insulation blanket on the molten steel temperature in a 100 t ladle was investigated. Simulation results showed that, after 30 minutes of tapping, the central temperature drop of molten steel in a ladle with a lid was 17.9 ℃ lower than that without a lid. Production statistics indicated that, within 21~30 minutes after tapping, the average temperature drop of molten steel in a ladle with a lid was reduced by approximately 16.52 ℃compared to one without a lid, which demonstrated significant thermal insulation performance of the ladle lid. The results also revealed that a greater thickness of the thermal insulation blanket led to better heat preservation. At 72.32 minutes after tapping, the molten steel temperature with a 15.00 mm thickness thermal insulation blanket was 8.77 ℃ higher than that without any blanket, yielding a cost benefit of 1.26 yuan per ton.

Edge crack defects occur frequently during the hot rolling process of low-temperature oriented silicon steel, and remain one of the primary quality problems in hot-rolled coils of oriented silicon steel. Through methods such as microstructure observation, energy spectrum analysis, and thermal simulation experiments, the cause of edge crack formation was identified as decarbonization and coarsening of ferritic grain boundaries during prolonged high-temperature heating of the slab. During rolling, grain refinement through the γ→α phase transformation was impeded, and recrystallization was suppressed by low edge temperatures. The resulting coarse and elongated non-recrystallized microstructure exhibited high brittleness, and tearing during rolling led to the formation of microcracks, which further propagated into edge cracks in the finishing stage. By adopting optimized heating and rolling strategies such as seamless charging, lower heating temperature, shorter heating time, high reduction rough rolling, fewer-pass rapid rolling, heavy vertical edge rolling, and edge heater temperature compensation, the edge quality qualification rate of hot-rolled oriented silicon steel coils increased from 76.3% to 85.2%,