To elucidate the impact of the solid solution process on the microstructure and mechanical properties of Cr−Mn−N austenitic stainless steel, comparative experiments were conducted with varying solid solution temperatures and durations. The results indicate that the grain size gradually increases with increasing solid solution temperature and duration. When the temperature reaches a high level (1120 °C) or is maintained at 1080 °C for an extended period (25 min), the smaller grains are progressively engulfed by the adjacent larger grains, resulting in a swift augmentation in grain size and heterogeneity. In the hot rolled specimens, a considerable quantity of precipitates with large sizes (200 nm) is observed. After the solid solution treatment, the precipitate dimensions are significantly diminished, and their volume fraction is significantly influenced by the temperature of the solid solution. EDS and HRTEM were used to determine that the main precipitated phases after hot rolling and solid solution treatment were Cr₇C₃, Cr₂₃C₆ and Cr₂N. With the increase in the solid solution temperature and time, the increment of grain boundary strengthening and dislocation strengthening decreases, while the contribution of precipitation strengthening initially increases before subsequently decreasing, which is the reason why the experimental steels with solid solution temperature of 1040 °C and solid solution temperature of 1080 °C held at 5 min still have the same mechanical properties despite the difference in solid solution treatment processes.

Insufficient defect data significantly limits detection accuracy in continuous casting slab production. This limitation arises from the data collection in fast-paced production environments. To address this issue, we propose LarGAN, a data augmentation approach that synthesizes similar and high-quality defect data from a single image. We utilize a progressive GAN framework to ensure a smooth and stable generation process, starting from low-resolution image synthesis and gradually increasing the network depth. We designed a Label Auto-Rescaling strategy to better adapt to defect data with annotation, enhancing both the quality and morphological diversity of the synthesized defects. To validate the generation results, we evaluate not only standard metrics, such as FID, SSIM, and LPIPS, but also performance, through the downstream detection model YOLOv8. Our experimental results demonstrate that the LarGAN model surpasses other single-image generation models in terms of image quality and diversity. Furthermore, the experiments reveal that the data generated by LarGAN effectively enhances the feature space of the original dataset, thereby improving the accuracy and generalization performance of the detection model.

Equipment wear and assembly clearances can change the longitudinal stiffness of hot strip mills and further affect roll-gap levelling accuracy and asymmetric strip profile control. In this study, the longitudinal stiffness of a 1580 mm four-high hot strip finishing mill was investigated by combining the analytical calculation of the hydraulic press-down system with a three-dimensional mill–strip finite element model. The effects of typical horizontal and vertical gap forms, including work-roll offset, same-side deflection, roll crossing, and unilateral vertical clearance caused by step-pad wear, on total longitudinal stiffness and stiffness difference between the two sides were analysed systematically. The results show that work-roll horizontal offset changes the longitudinal stiffness in a nonlinear manner, whereas work-roll rotation and roll crossing generally reduce the longitudinal stiffness and increase the stiffness asymmetry between the two sides. Unilateral vertical clearance also causes nonlinear variation in both total stiffness and side-to-side stiffness difference. The proposed method was further applied to the stiffness prediction module of the Guangxi BG 1700 mm hot strip mill production line, providing support for equipment maintenance, roll-gap levelling, and stable strip production.

The objective of this study is to investigate the effect of the solidification microstructure of CJ5L Recycled Stainless Steel in the cast state on its thermoplasticity. Therefore, the residual ferrite, solidification structure, and high-temperature thermoplasticity in both Recycled and Non-Recycled steel ingots are examined. The principal experimental techniques employed include SEM, OM, EPMA, and EDS. It was observed that the solidification microstructure underwent a gradual transformation from a dendritic structure with a skeletal shape to a worm-like dendrite as the thickness increased. This resulted in the formation of large equiaxed grains at the center of the steel ingots. The cooling rate decreased from 3~16 °C/s at the surface to below 0.8 °C/s at the center. The residual ferrite gradually transformed from a skeletal to granular and rod-like form with increasing depth, eventually forming a ferrite network at the center of the casting. In the Recycled steel, the composition segregation resulted in the formation of a network ferrite aggregation at the center of the steel ingots. The analysis of microstructure changes in conjunction with thermodynamic calculations revealed that the solidification mode of CJ5L stainless steel underwent a transition from the ferritic–austenitic (FA) mode to the austenitic–ferritic (AF) mode with increasing casting thickness. This resulted in an increase in the amount of residual ferrite from the surface to the center. The high-temperature thermoplasticity analysis of CJ5L stainless steel showed that at temperatures between 800 °C and 900 °C, the casting displayed optimal properties, minimizing crack formation during subsequent processing.

Non-metallic inclusions are preferential sites for pitting corrosion initiation in austenitic stainless steels. This study investigates the effect of magnesium addition on inclusion evolution and localized corrosion behavior of austenitic stainless steel using SEM–EDS, immersion testing, scanning Kelvin probe force microscopy (SKPFM), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). Magnesium addition modifies the inclusion population from coarse (Mn,Al)-O into finer MgO·Al₂O₃ spinel-based inclusions with improved distribution. Immersion testing in FeCl₃–HCl solution reveals delayed inclusion dissolution and reduced localized pitting attack in the Mg-treated steel. SKPFM maps, together with immersion observations, provide qualitative evidence of changes in the local electrochemical contrast between inclusions and the surrounding matrix. Electrochemical measurements in 3.5 wt.% NaCl further demonstrate improved corrosion resistance after Mg addition, as evidenced by an increase in pitting potential from 0.28 V to 0.52 V vs. SCE and charge-transfer resistance. The improved corrosion resistance is associated with inclusion refinement and modification of the local surface-potential distribution, which may influence inclusion-related localized corrosion processes. Overall, Mg microalloying modifies the inclusion characteristics of austenitic stainless steel and enhances its resistance to chloride-induced localized corrosion, demonstrating the potential of inclusion engineering as a strategy for improving stainless-steel corrosion performance.

Overcoming the strength–ductility trade-off at cryogenic temperatures is a key bottleneck for austenitic stainless steels. This study investigated the effects of Nb additions (0, 0.03, and 0.06 wt.%) on the mechanical properties and fracture behavior of 304 steel from room temperature (RT) to −196 °C. Within the investigated range, the 0.06 wt.% Nb steel produced the largest measured response. Compared with the Nb-free steel, the RT yield strength and elongation after fracture increased by ~5% and 2.4%, respectively; at −196 °C, they increased by 11.1% and 4.1%, and impact toughness by 31.8%, mitigating the low-temperature strength–ductility trade-off. Fractography revealed a transition from brittle cleavage/mixed fracture to dimple-dominated ductile fracture. The improvement in mechanical properties is consistent with the refined microstructure and the modified inclusion distribution, with the underlying mechanisms likely involving grain refinement and the solid-solution strengthening of the austenite matrix by Nb. It should be noted that, owing to experimental limitations, the deformation-induced α′-martensite was not quantitatively characterized in the present study, and no rigorous quantitative correlation has yet been established between inclusion characteristics and low-temperature impact toughness. Consequently, the relative contribution of each contributing factor to the observed performance enhancement remains unresolved. Nevertheless, this work provides experimental support for the microalloying design of ultra-low-temperature austenitic stainless steels.