Combining the calculation of resistance to deformation of rolled piece with the based finite element calculation of elastic deformation of roll system, the model of shape control in rollingsilicon steel thin-gauge strip with Sendzimir 20-high mill was established.By calculating the deformation resistance of the rolled piece based on the preset shape and iteratively calculating the elastic deformation between the roll system under the rolling force of the rolling mill, the influence laws of the support roll gap shape adjustment (ASU) and the taper change of the No.1 intermediate cone roll on the shape of the rolled piece were determined.The adjustment of ASU in the middle of the support roll mainly affects the area of 0.6 m at the center of the width of the rolled piece, and has almost no effect on the area of 0-0.2 m at the edge. The adjustment of ASU at both ends of the support roll has an impact on the edges of the rolled piece, and also on the middle part of the rolled piece. Increasing the taper of the intermediate roll has a significant effect on improving the strip crown at a distance of 0-0.15 m from the edge of the rolled piece. By optimizing the calculation of the ASU of the roll system and the axial shifting amount of the intermediate roll, the average difference of transverse of the same silicon steel thin-gauge strip rolled by Sendzmir 20-high is reduced by more than 25%,and the shape control of the 0.25 mm thickness strip reaches below 8 IU, effectively improving the shape control capability of the Sendzimir 20-high mill for silicon steel thin-gauge strip.

Aiming at the challenge of integrated control of key indicators such as shape, properties, and surface quality in the production of high-quality sheet and strip, the achievements of China in the integrated control technology of shape-property-surface for high-quality sheet and strip were introduced. The strip shape control technologies of multi-modal information fusion detection and multi-stand and multi-process coordination were briefly described from the aspects of straightness detection of hot rolled strip, intelligent prediction system of roll and strip shape state, comprehensive control model of roll bending and axial shifting, and strip shape feedforward control of cold and hot rolling process. The control technologies of hot rolling process and mechanical properties based on large model were briefly described from the aspects of microstructure parameters and mechanical properties control model of hot rollingprocess and pre-control of microstructure properties of hot continuous strip rolling. The intelligent simulation and control technology of high-quality strip surface characteristics was briefly described from the aspects of unsupervised classification detection algorithm for surface defects and comprehensive control of surface defects and characteristics. On this basis, the field applications of these technical achievements were described, and the development of comprehensive control of high-quality sheent and strip was prospected.

The development history of heavy plate production in China was sorted out, and the development of heavy plate in China was divided into five stages, i. e, initial stage, accumulation stage, development stage, maturity stage and optimization stage, The characteristics of each stage were analyzed from the aspects of mill specification, equipment level, capacity scale and so on; The technical progress and development of key processes and equipment for heavy plate, such as hot delivery and hot charging, reheating furnace, rolling mill and leveler were described; The development, application and advancement of typical heavy plate products, such as special shipbuilding steel and offshore engineering steel were elucidated; The future development of heavy plate in China was prospected and suggestions were put forward.

The development history of heavy plate production in China was sorted out, and the development of heavy plate in China was divided into five stages, i.e, initial stage, accumulation stage, development stage, maturity stage and optimization stage, The characteristics of each stage were analyzed from the aspects of mill specification, equipment level, capacity scale and so on; The technical progress and development of key processes and equipment for heavy plate, such as hot delivery and hot charging, reheating furnace, rolling mill and leveler were described; The development, application and advancement of typical heavy plate products, such as special shipbuilding steel and offshore engineering steel were elucidated; The future development of heavy plate in China was prospected and suggestions were put forward.

Marine engineering equipment faces significant challenges in achieving a coordinated design that integrates lightweight and properties with high strength and toughness under harsh service environments, such as those characterized by high salinity, high humidity, and impact loading. Traditional steel used in offshore platforms struggle to effectively balance the requirements of lightweight and mechanical properties. In contrast, Fe-Mn-Al-C lightweight high strength steels have emerged as highly promising alternative materials due to their lower density (10%-20% lighter than traditional steel), excellent strength and good weldability. Currently, under the "rolling + solution treatment" process route, the appropriate design of Al element content plays a crucial role in enhancing the properties of Fe-Mn-Al-C lightweight high strength steels. By employing characterization techniques, including optical microscopy(OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD), the influence of Al element content on the microstructure and mechanical properties of the experimental steels during the staged preparation process was investigated. The results indicate that when the mass fractions of Al element are 5%, 8% and 12% respectively, the microstructure of the experimental steels after rolling treatment consists of austenite and ferrite phases. As the Al content increases, the morphology of austenite transitions from equiaxed to acicular, and the proportion of high-angle grain boundaries increases from 57% to 89%. When the Al element mass fraction is 8%, the rolled experimental steel exhibits the optimal strength-ductility balance, with a tensile strength of 747 MPa and an elongation of 28.3%. After solution treatment at 1 000 ℃, the comprehensive properties of the experimental steel with Al element mass fraction of 8% are further enhanced, achieving a tensile strength of 701 MPa, yield strength of 612 MPa, and elongation of 38.3%. Its fracture surface displays characteristic dimple patterns indicative of ductile fracture. Through optimization of Al element content and process control, precise design of the dual-phase microstructure in Fe-Mn-Al-C lightweight high strength steels have been realized, laying theoretical foundations for developing marine engineering steels.

This paper examines the evolving trends in the digital transformation of the steel industry and provides a systematic overview of the research and engineering achievements of the State Key Laboratory of Digital Steel (DSL) in the domain of steel rolling. A series of high-fidelity digital twin models integrating data, physical mechanisms and empirical domain knowledge have been developed for critical production processes, including hot rolling, cold rolling and heat treatment. Intelligent optimization methods tailored for industrial production environments have been designed and implemented in large-scale steel enterprises both domestically and internationally. These innovations have yielded significant improvements in quality metrics, particularly in three-dimensional dimensional accuracy, microstructure, and mechanical properties. Finally, the paper outlines the future research and application prospects of "AI + steel rolling".

With the increasing demand for lightweight and safety in the automotive industry, the use of steel/aluminum/magnesium/aluminum/steel composite plates instead of pure steel plates can not only achieve weight reduction, but also utilize the property advantages of composite plates to meet the strength requirements of automobiles steel. Steel/aluminum/magnesium/aluminum/steel five-layer composite plates were successfully prepared by rolling process. The effects of rolling temperature (400 ℃, 450 ℃ and 500 ℃) on the interface microstructure, interface bonding strength, tensile properties, and fracture mechanism ofthe plate were studied by optical microscope (OM), scanning electron microscope (SEM) and tensile test machine. The results show that the composite plates prepared with a rolling reduction rate of 45% and a rolling temperature range of 400-500 ℃ can achieve good bonding effects. The steel/aluminum interface is flat and straight. The aluminum/magnesium interface is wavy, and the fluctuation degree increases with the increase of rolling temperature. As the rolling temperature increases, the grains in magnesium layer gradually undergo dynamic recrystallization and grow, and the precipitation content of silicides in the aluminum layer increases. The bonding strength of steel/aluminum interface increases, while the bonding strength and tensile properties of aluminum/magnesium interface show a trend of first increasing and then decreasing.At the rolling temperatures of 400 ℃、450 ℃ and 500 ℃,the bonding strength of aluminum/magnesium interface is 77.54 MPa, 88.63 MPa, and 81.14 MPa, respectively; the tensile strength is 310 MPa, 324 MPa, and 278 MPa, respectively; the elongation after fracture is 39.9%, 40.9%, and 22.3%, respectively. The comprehensive mechanical properties of the composite plate are optimal at a rolling temperature of 450 ℃.

With the development of automotive steel towards thin-gauge and high-strength, phosphorus is added to steel as a strengthening element to improve its strength. Compared with ordinary steel, the mechanical properties of phosphorus-containing steel are changed due to the addition of phosphorus element, and the rolling force is changed. In order to explore the effect of phosphorus content on the rolling force of phosphorus-containing steel, under the premise of fully considering the performance characteristics of phosphorus-containing steel, Zwick tensile machine was used to carry out tensile tests on phosphorus-containing steel with different phosphorus content under the same reduction amount, and a large number of actual production data were regression analyzed to obtain the calculation formula of carbon equivalent of DN0160E4 phosphorus-containing steel. The deformation resistance model and the relationship between phosphorus content and cold tandem rolling force were established. Finally, taking the first stand of 1 420 mm tandem cold rolling unit of a steel plant as an example, the actual rolling parameters are substituted into the model for calculation and analysis. The results show that the addition of phosphorus can increase the tensile strength and yield strength, and decrease the elongation of steel. The rolling force required by DN0160E4 phosphorous steel is larger than that of ordinary steel under the same reduction, and the rolling force increases linearly with the increase of phosphorus content in phosphorous-containing steel.

Front-end warping and bending of slab during hot roughing rolling is a common asymmetric shape defect. Traditional control methods typically adopt an integral control strategy for the slab head, which may result in excessive warping, leading to slab collisions with production line equipment and disruptions in rolling rhythm. To address this issue, a segmented control method for slab front-end warping and bending was developed and validated through finite element simulations. The proposed method consists of two stages,i.e. the sled coefficient action stage and the upper/lower roll speed reversal stage. Using machine vision technology, the amount of warping or bending between passes is detected, and the corresponding adjustment value is calculated through the segmented control strategy in combination with the front-end warping and bending monitoring and control system. The adjustment command is then automatically applied before the next rolling pass, thereby realizing automatic control of slab front-end warping and bending. Application results demonstrate that the segmented control method reduces the slab head warping height by 77.04% compared with integral control, significantly mitigating front-end warping and bending defects and enhancing the stability of product quality.

Aiming at the problems of long roll changing time and low reliability of roll changing device in the continuous cold rolling production line at present,the structure and principle of work roll changing device of 4-high skin pass mill were introduced. Through comprehensive analysis of work roll changing steps and time sequence, some of the series operation steps were optimized to parallel operation or lap operation. It was found that the key factor affecting the work roll changing time was the running speed of AGC cylinder, and then the servo hydraulic system was optimized with constant power pump characteristics to improve the running speed of AGC cylinder and greatly reduce the work roll changing time. In order to improve the reliability and stability of the work roll changing device, the structure design, the selection of detecting elements and the installation accuracy of the device were optimized and improved. After adopting above measures, the work roll changing time is greatly compressed from more than 120 s to less than 90 s, and the operation reliability and stability are significantly improved, which lays a foundation for the continuous and stable production of the cold rolling production line and the improvement of product quality.

In view of the problem of surface and internal cracks that were prone to occur when producing 304L austenitic stainless steel plate with high Cr and Ni content using continuous casting billets,effect of chemical composition and heating process on the microstructure and thermal plasticity of hot rolled 304L austenitic stainless steel plate was investigated. The results showed that with increasing of Ni element content, the ferrite transformation to austenite are more difficult of 304L austenitic stainless steel, and result in more large-sized ferrite phases distributed continuously at a certain angle to the rolling direction in the hot rolled plate, which deteriorated the bad thermal plasticity of the plate and formation internal cracks. With decreasing of Cr element content, the ferrite content is reduced, and result in the size and quantity of large-sized ferrite that is continuously distributed at a certain angle to the rolling direction in the plate and the thermal plasticity of the plate is improved further more. Higher heating temperature and holding time of the casting billets accelerated the transformation of residual ferrite to austenite during the hot rolling process, thereby the occurrence of large-sized ferrite that is continuously distributed at a certain angle to the rolling direction in the hot rolled plate is reduced, and the thermal plasticity of the plate is improved.

During the rolling process of medium and heavy plates, various types of plane shape defects may occur, which severely affect product quality and yield, thereby constraining performance and production line efficiency. As a critical technical aspect for ensuring the dimensional quality of final products, planar shape control has long been a key focus in the field of steel rolling. The development of planar shape control technologies for medium and heavy plates are systematically reviewed, covering the evolution from fundamental theories and experimental studies to engineering applications, with concise analysis, comparison, and commentary. Furthermore, recent advances in intelligent equipment and data-driven control technologies are summarized, and future research directions are discussed in the context of the steel industry's ongoing shift toward intelligent manufacturing. The aim is to provide theoretical support and practical insights for the continued optimization and upgrading of planar shape control technologies.

To solve the corrosion problem of steel used as mine hydraulic support due to the complex service environment, the microstructure, mechanical properties, corrosion behavior and mechanism of four commonly used steels(S890 steel and 30CrMnSi steel developed in China,andForeign Ⅰ、Foreign Ⅱ steels developed in foreign) for hydraulic support used the same heat treatment process were studied, and the suggestions for improving the corrosion resistance of S890 steel were put forward. The results show that the microstructure of S890 steel after quenching at 840 ℃ for 2 hours and tempering at 480 ℃ for 1 hour are tempered sorbite and martensite, and the yield strength, tensile strength and -20 ℃ impact energy are 855 MPa, 905 MPa and 195 J, respectively. The mechanical properties of S890 steel are better than that of similar materials developed at home and abroad. After total immersion corrosion (3%NaCl+5%HFAE solution, 3%NaCl and 5%HFAS solution), the annual corrosion rate of S890 steel in 5%HFAE emulsion is 0.36 mm, which is superior than 30CrMnSi steel and similar to that of the Foreign Ⅰ and Foreign Ⅱ steels. After analyzing the corrosion resistance of S890 steel it can be seen that the corrosion pits mainly occur in the CaS-Aloxide-MnS complex inclusions, which seriously accelerate the corrosion of the steel. Therefore, the content of S, P, Ca elements of S890 steel should be strictly controlled to reduce the quantity and density of composite inclusions. Meanwhile, the heat treatment process and the uniformity of the microstructure of S890 steel should be improved to increase its corrosion resistance.

When the traditional 20-high rolling mill is used to expand the ultra-thin specifications during the rolling of silicon steel, the evaluation of equipment capacity and the selection of process parameters are based on experience and field trials. The lack of theoretical support leads to a high risk of equipment damage and high trial and error costs. At the same time, the product quality cannot be guaranteed after the specification expansion. In response to the above problems, fully considering the equipment and process characteristics of the 20-high rolling mill, combined with actual rolling data on site, and taking into account rolling stability and strip surface defect control, a 20-high rolling mill rolling capability evaluation model and technology was established and corresponding rolling ability accounting software was developed. This software can be used to accurately calculate rolling capacity of a 20-high rolling mill for silicon steel. It was applied to a cold rolling plant for silicon steel of a steel company. Through comparative analysis of the calculated minimum product thickness and the actual export product thickness, it was found that, under the premise of ensuring hourly output and considering rolling stability and defect control capabilities, the calculated minimum product thickness is smaller than the actual product thickness, and the product thickness specification has room for expansion in a thinner direction, which laid a theoretical foundation for the subsequent product quality control and rolling process development of high-grade non-oriented silicon steel and oriented silicon steel to expand to thinner specifications.

In order to improve the qualification rate of ultrasonic testing for continuous casting extra thick slab, reduce the production cost of heavy plates, and prevent quality defects such as "white spots", "hydrogen embrittlement", and "point segregation", and overcome the difficulties of traditional experimental methods for detecting hydrogen diffusion in extra thick slab, a numerical simulation method was used to study the process of reducing hydrogen concentration in steel to a safe range through stacking cooling, and good results were achieved. Due to the thickness of the continuous casting slab reaching 400 mm, it takes a long time for hydrogen to diffuse from its core to the surface. Ordinary stacking slow cooling cannot meet the hydrogen removal effect of the slab. Therefore, using slow cooling pits and slow cooling pit heating methods for stacking slow cooling can further improve the insulation effect of the slab and make the hydrogen diffusion of the slab more sufficient. Therefore, a mathematical model for hydrogen diffusion in slab was established based on three stacking methods. The effects of ordinary stacking, slow cooling pit stacking, and slow cooling pit heating on hydrogen diffusion in slab were compared, and the hydrogen content and hydrogen removal rate at each position of the slab were obtained. Under the three stacking modes of ordinary stacking, slow cooling pit stacking, and slow cooling pit heating, the hydrogen removal rates of the bottom slab were 58.93%, 67.63%, and 71.98%, respectively. The slow cooling pit stacking method and slow cooling pit heating method are not only more conducive to the hydrogen diffusion in extra thick slab but also can make the hydrogen diffusion on the upper and lower surfaces of the extra thick slab more uniform.

Driven by the "dual-carbon" strategy, the transformation of 82B wire rod production processes from traditional long-process to electric furnace short-process has become inevitable. However, there is still a lack of systematic research on the causes of abnormal martensite structures near the core of wire rods produced by short-process technology. To address this, this study investigated the causes of abnormal martensite structures in 82B wire rods produced by recycled steel materials+electric furnace short-process through metallographic observation, quantitative analysis of macro/micro-segregation, and thermal simulation tests, combined with comparative analysis of 82B wire rod structures produced by traditional long-process technology. The results show that the segregation levels of Mn and Cr elements near the core of short-process 82B wire rods are more severe than those of long-process 82B wire rods. This segregation, along with the higher residual Ni content, shifts the C-curve of 82B steel to the right, reduces the critical cooling rate for martensite formation from 7 °C/s to 3 °C/s. As a result, the martensite content of short-process 82B wire rods under the same cooling rate is higher than that of long-process 82B wire rods. Based on experimental results, process adjustments were applied, including increasing the soaking temperature of billets from (1 120±10) ℃ to (1 160±10) °C and maintaining the heating and soaking holding times at 100-120 min. These adjustments significantly improved macro-segregation and suppressed the formation of abnormal martensite structures.

Microstructure analysis is an important analysis method in the research and development process of iron and steel materials. At present, it is mainly judged manually by experts with rich experience, which is time-consuming and easily affected by subjective consciousness. Therefore, an intelligent analysis method for microstructure based on the residual neural network structure is studied. By improving the residual network model, an improved residual network model based on transfer learning and a deep residual shrinkage network model based on the attention mechanism are proposed. Two different convolutional neural network models are used for verification on the microstructure test set of 20 steel materials. The experimental results show that the accuracies of the two models reach 95.36% and 95.79% respectively, with strong generalization ability, and the shortest average prediction time is only 1.66 s per image. The two models have certain advantages in the classification of microstructure features of iron and steel materials, realizing the automation and intelligence of microstructure type classification.

In the production process of hot-rolled strip, the control accuracy of finishing rolling temperature directly affects the microstructure and mechanical properties of the strip, which is a key factor in ensuring dimensional accuracy and good flatness of the strip. Due to the complexity, multivariability and strong coupling characteristics of rolling process, traditional mechanism models have obvious deficiencies in prediction accuracy, which is difficult to meet the requirements for high-precision and high-performance products control.To this end, this article combines a domestic 2 250 mm hot strip mill with the GBDT algorithm and mechanism model to develop a predictive model for the finishing rolling temperature of hot-rolled strips that integrates both mechanistic models and data.This model has both the physical interpretability of a mechanism model and the ability to fully develop GBDT algorithm's advantages in data mining, enabling continuous learning and adjustment of historical data and real-time feedback, thus maintaining the stability and reliability of the model's predictive performance;At the same time, it has self-training and closed loop control functions to achieve automatic closed loop control.After applying the model online, the deviation of long-term genetic prediction for finishing rolling temperature has decreased from 14.55 ℃ to 9.85 ℃. The results show that the model has high calculation accuracy and can meet the requirements for finishing rolling temperature control under different steel grades and working conditions, thereby improving the stability of strip rolling and the precision of head finishing rolling temperature control, enhancing product competitiveness.

Q355D angle steel is the key material of transmission tower under extreme cold conditions, and its low temperature impact toughness is strictly required. The microstructure and fracture morphology of Q355D angle steel specimens with different chemical compositions were analyzed by stereomicroscope (SM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), optical microscope (OM) and transmission electron microscope (TEM). The initiation and propagation behavior of impact cracks were clarified. The results show that the content of carbon and nitrogen in the chemical composition of Q355D angle steel will significantly affect its low temperature toughness. The high content of carbon and nitrogen elements will cause the increase of cluster pearlite structure and the increase of interstitial solute dissolved in the lattice of metal materials, resulting in the deterioration of plasticity and the increase of brittleness of angle steel. In addition, there is also a banded structure in the sample with higher carbon content, which also leads to the deterioration of the plasticity of the angle steel. In the samples with unqualified impact properties, the phenomenon of Al₂O₃ inclusions and second phase particles enrichment and growth is also found. Due to the above reasons, the brittle fracture of the samples is caused. Therefore, the mass fraction of carbon in Q355D angle steel should not exceed 0.16% to reduce the content of pearlite and improve the segregation of pearlite clusters. In its production, deoxidizer should be accurately added and calcium treatment process should be optimized to avoid excessive aluminum residue reacting with oxygen to form Al₂O₃ inclusions. Continuous casting adopts digital electromagnetic stirring process and soft reduction process to improve banded structure and central segregation. After adopting the above measures, the stable production of Q355D angle steel is realized.

Aiming at the problems of cold cracking, heat affected zone softening,toughness decreasing, and residual stress in the welding of high-strength steel for automobiles, the Q960E automobiles high-strength steel has been taken as the research object, the laser composite welding test method has been used to study the effects of different heat treatment parameters such as preheating temperature, quenching temperature, and tempering temperature on the microstructure and mechanical properties of the welded joint. The research results indicate that the welded joint of Q960E high-strength steel consists of a welding base material, a weld seam, a fusion zone, an overheated zone, and a normalized zone, at preheating temperature of 100 ℃, quenching temperature of 900 ℃, and tempering temperature of 400 ℃, the base material is tempered martensite, the weld seam is fine bainite, the fusion zone is fine bainite and coarse martensite, the overheated zone is coarse bainite, and the normalized zone is a recrystallized crystal composed of bainite and martensite. As the quenching temperature increases, the tensile strength and yield strength of the welded joint show a trend of first increasing and then decreasing, and the elongation at break shows a trend of first decreasing and then increasing. As the tempering temperature increases, the tensile strength and yield strength of the welded joint show a gradually decreasing trend, while the elongation at break shows a gradually increasing trend. When the preheating temperature is 100 ℃, the quenching temperature is 900 ℃, and the tempering temperature is 400 ℃, the tensile strength of the welded joint is 1 150 MPa, the yield strength is 1 075 MPa, and the elongation at break is 10.56%, the comprehensive performance is superior, and it is the best heat treatment processes for Q960E automotive high-strength steel.

Nickel (Ni) is an important alloying element widely used in steel, which not only significantly enhances the corrosion resistance and heat resistance of stainless steel, but also improves the strength, ductility, and toughness of alloy steel. Nickel-based alloys are also applied in the manufacturing of high-temperature aerospace structural components due to their high strength and good heat resistance. Although nickel has been fully utilized in steel and alloys, especially in improving the toughness/cryogenic toughness of steels, the physical metallurgical mechanism of nickel in enhancing the toughness of steel has not been fully understood. In this paper, the application and research progress of nickel in steel and alloys are first briefly reviewed, and then the mechanism study of nickel in improving the impact toughness and welding toughness of steel are summarized. It is emphasized that the improvement of impact toughness of steel by nickel is mainly achieved by grain refinement, dislocation movement promotion, increment of high-angle grain boundaries, and stabilizing austenite, while the welding toughness is enhanced by effectively increasing the content of acicular ferrite and reducing the harmful phase of martensite-austenite islands (M/A). As a new approach to strengthening and toughening steel, the research status of Ni-Cu alloying in low-alloy high-strength steel are briefly described. Finally, the development trend of Ni-containing steel is provided.

In order to satisfy the green and efficient rolling production, the double stands reversible breakdown rolling process was proposed, two layouts of double stands individual and tandem reversible breakdown rolling were analyzed and compared. In view of the high production flexibility of breakdown rolling for special-quality steel, it will be more advantageous to choose the double stands individual reversible layout. Based on the above, the roller grooving configuration mode and rolling pass arrangement for H-H double stands individual reversible breakdown rolling process were analyzed and discussed, the rolling temperature and parameters of typical steel grades in various pass were calculated and checked. Meanwhile, the deformation permeability in various pass of breakdown rolling was simulated and calculated by FEM software-ABAQUS. The results indicated that the spare parts of breakdown rolling mills could be unified if BD₁ and BD₂ rolling mills were selected by the same roller grooving configuration and the same mill type. Meanwhile, it was provided with good production flexibility that the roller systems of two rolling mill stands were exchanged by each other when the roller grooves should be turned again, or two rolling mill stands were chosen one to use and the other to maintain. For the production of typical steel grades, the overall temperature drop of the breakdownrolled billet could be controlled within 100 ℃ and the final rolling temperature could be maintained above 950 ℃, so that the hot processing temperature window control of corresponding steel grades and their treatment requirements of subsequent procedures could be satisfied, and also the temperature drop of delivering between two mill stands would be controllable. Moreover, the parameters of main motors and their overload capacity could be satisfied with the requirements of rolling parameters for typical steel grades. The good deformation permeability at the core of the billet could be obtained by applying larger reduction after the accumulated deformation by previous two passes. For the billet with the dimension of 300 mm×390 mm, the fine deformation uniformity for the small rolled billet with the cross section of 150 mm×150 mm could be achieved by breakdown rolling of more than 5 accumulated reduction ratio. Finally, the typical process layout of double stands reversible breakdown rolling for special-quality steel was introduced, and the application prospect for the breakdown rolling process mentioned above was forecasted in the base of wire rod and straight bar for special-quality steel.

This cost-effective stainless steel composite plate integrates the excellent hydrogen resistance of stainless steel with the high strength and wear resistance of low-alloy steel. Such composites offer a promising approach for developing commercial materials with superior resistance to hydrogen. However, the influence of the cladding microstructure on the hydrogen resistance of stainless steel/carbon steel composite plates remains poorly characterized. Consequently, base materials exhibiting contrasting deformation resistance (Q235 vs. 700L) were employed to control the cladding microstructure. This work characterizes the microstructure of stainless steel and carbon layers in 316L/Q235 and 316L/700L composite plates and evaluates its impact on hydrogen resistance. Results show that the 316L cladding layer in the 316L/700L composite plate preferentially recrystallizes, reducing its hydrogen embrittlement susceptibility index from 9.8% of 316L/Q235 composite to 5.9%. Recrystallization control elevated ∑3 twin boundary density in 316L cladding (316L/700L) from 0.79% of 316L/Q235 composite to 19%. This microstructure simultaneously impedes hydrogen crack initiation through twin boundary resistance and suppresses propagation by disrupting random grain boundary networks, collectively enhancing hydrogen embrittlement resistance.

To produce 9Ni steel plates with excellent microstructure, properties andplate shape in wide and thin gauge via a medium-heavy plate mill, the pack rolling process was investigated through experiments and numerical simulations. The chemical composition of 9Ni steel was designed, and the CCT curve of the tested steel was determined. Through pilot trials, 3 mm thick pack-rolled plates were obtained alongside suitable welding methods for stacking and spacer compound formulations. Finite element simulations were used to analyze stress and strain distribution patterns under different reductions to establish reasonable rolling schedules. Results indicate that uniform stress distribution at 10 mm reduction, while reductions greater than 15 mm caused non-uniform distribution with significant differences between the lower surface of the top plate and its upper surface.There is higher stress at edges but relative uniformity centrally. Industrial production on the medium-heavy plate mill implemented roughing rolling start at 1 150 ℃, finishing rolling start at 950 ℃, and finishing rolling end at 810 ℃. According to the CCT curve, cooling rates greater than 5 ℃/s yield fully martensitic microstructure. The Ac₁ and Ac₃ of the tested steel are 621 ℃ and 735 ℃, quenching temperature must exceed 735 ℃ for complete austenitization, while two-phase region quenching above 621 ℃ achieves reversed austenite. The 5 mm thick wide and thin gauge plates exhibited excellent comprehensive mechanical properties with flatness less than 3 mm/m, meeting standards and customer requirements.

With the implementation of the "dual carbon" strategy, the steel industry has put forward higher requirements for optimizing the electricity consumption required for hot rolling of medium and heavy plates. Aiming to achieve quantitative calculation and prediction of electricity consumption during hot rolling of medium and heavy plates, a theoretical electricity consumption calculation model was constructed and a set of electricity consumption calculation software for hot rolling of medium and heavy plates was developed. This software can formulate the rolling schedule according to the produced steel and target demand and accurately calculate the electricity consumption for each pass of rolling manufacturing and the electricity consumption per ton of steel of a single slab, which can provide data support for steel enterprises to quantify the electricity consumption in the medium and heavy plate rolling process and optimize the rolling process. By comparing with the manufacturing data of the steel mill, the calculation results of the software are basically consistent with the actual situation when the thickness hit rate is almost 99%,the deviation of electricity consumption in each pass of roughing rolling is kept within 10%, and the deviation of electricity consumption per ton of steel inrouging rolling is -3.12%-3.86%, which can accurately reflect the electricity consumption of the plate in the rolling process. After verification, this software can provide data support for developing new steel grade and new processes, scheduling manufacturing, selecting the main motor of the rolling mill, and so on, which helps steel enterprises further achieve energy conservation and emission reduction, and create economic benefits for them.

In recent years, low energy consumption and low cost CSP short-process technology has been rapidly developed in Chinese iron and steel industry. However, compared with the traditional hot rolling process, the yield strength of CSP products is higher, which is extremely unfavorable for the formability of steel used in stamping.Therefore, the dynamic recrystalization behavior and cooling phase transformation of austenite of DC04 cold-rolled deep-drawing steel were analized through thermal simulation experiments, and the dynamic recrystalization model was established, which was used to guide the production practice of CSP production line, and the cold-rolled deep-drawing steel sheet with rich {111}texture was successfully trial-produced. The experimental results show that the dynamic recrystallization model of DC04 cold-rolled deep-drawing steel in CSP production line isZ=ε·exp[295.21/(RT)]. The judgment conditions of dynamic recrystallization are Z=1.94×10¹⁰exp(61.34ε_c) and Z=2.57×10⁸exp(24.99ε_s).Based on the 3D dynamic recrystallization diagram, it is determined that the thermal deformation of the strip at F₃ stand in actual production is in the austenite part recrystallization region. In the trial production using F₃ stand bypassing scheme, the microstructure of the obtained strip is mostly equiaxed grain with low strength. However, the grains of the strips produced by the conventional rolling process of F₃ stand non-bypassing scheme,the grains contact with each other at sharp or right angles, and the strength is about 30 MPa higher than former. The F₁and F₂ stands of CSP production line adopt high temperature, high reduction rate and low deformation rate rolling, which can make the strip microstructure undergo complete dynamic recrystallization, complete the transformation of columnar crystal to equiaxed crystal, and avoid the generation of mixed crystal. The performance of cold-rolled sheets produced using a 70% cold rolling cumulative reduction, bell annealing at 710 ℃, and the F₃ stand by passing and non-bypassing schemes were compared. The cold-rolled sheets produced with the F₃ stand bypassing scheme showed little difference in strength compared to those produced with the conventional non-bypassing scheme, but exhibited higher elongation A₈₀ and r values reaching 45% and 2.1. Additionally, the proportion of the favorable texture component {111} was higher, resulting in excellent deep-drawing performance.

In the production of medium and heavy plates, the thickness of the intermediate billet significantly impacts the plate's performance. Establishing an accurate temperature drop model for the intermediate billet not only enhances the stability of the plate's performance but also optimizes the rolling rhythm, thereby improving production efficiency. Therefore, using industrial production data as the foundation, the Python method was adopted to investigate the effects of factors such as the thickness and width of the intermediate billet of controlled rolled plates, the initial waiting temperature, the final waiting temperature and the ambient temperature on the temperature drop rate of the intermediate billet. The results indicate that there is a strong positive correlation between the waiting time and the thickness of the intermediate billet, a moderately negative correlation with the final waiting temperature, a weak negative correlation with the initial waiting temperature, and an extremely weak correlation with both the width of the intermediate billet and the ambient temperature. Based on these findings, a prediction model for the temperature drop law of the intermediate billet was constructed using a machine learning approach. The determination coefficient R² of the model reached 0.901 3. Through testing and verification, the temperature drop model demonstrated high prediction accuracy, with the absolute deviation rate of the temperature waiting time prediction at -6%-6%. This model provides valuable guidance for formulating processes and optimizing the rolling rhythm of the production line.

Aiming at the problem of excessive manual intervention of the existing cold rolling finishing unit, the control system and core database of the existing finishing unit were analyzed, and the technical scheme of automatic control and upgrading of finishing unit was formed. Secondly, the alternating control strategy of constant elongation and constant rolling force mode was determined, the automatic function of logic control and execution control module were improved, and the core database of the control system was expanded and refined. Finally, the process adjustment program of constant elongation and constant rolling force was optimized. The feed-forward preset parameters and the flatness feedback closed-loop control and adjustment mechanism of the finishing unit were established, and the automatic control function of the plate shape of the finishing unit was completed. This research is applied to the industrial production, and the automatic control function of the finishing unit based on the online data is realized. The automation rate of the unit increases to more than 90%, the manual operation and the scrap rate are reduced.

The roll gap calculation model of L₂ system is the foundation for controlling the thickness of hot rolled medium and heavy plates. Especially when employing the feedback pressure AGC control, the accuracy of roll gap calculation model of L₂ system directly affects the thickness of the head and the whole plate, consequently affecting the yield of medium and heavy plates. A 2 680 mm semi-continuous roughing rolling mill utilizes the pressure feedback AGC control system, but faces the problem of low thickness accuracy in rolling stainless steel medium and heavy plates. To address this problem, a multi-factor regression analysis was conducted using process data from the intermediate billet rolling process and actual thickness data measured by the thickness gauge. Sixteen indicators were selected for analysis to determine the correlation and path analysis of the thickness of the intermediate billet in cold state. The analysis results indicate a collinear effect of various factors on the thickness of the billet in cold state. The main influencing factors identified in the process of rolling medium and heavy plates are the roll gap, number of rolled pieces per unit of the roll, and slab discharge temperature. A multivariate fitting regression model was developed based on these key influencing factors to correct the roll gap of the R₇ stand during the rolling process. Extensive production practices have demonstrated that the application of the fitting regression model can significantly enhance the setting accuracy of the R₇ stand roll gap. This improvement has led to an increase in the overall thickness accuracy rate of medium and heavy plates from 84.47% to 98.92%.

In the production process of medium and heavy plates, the edge parts of plates often present irregular shapes. These irregular areas are generally unsuitable for further processing or application and need to be accurately cut off. To improve shearing efficiency and accuracy, an intelligent cut-to-length technology for segmented shearing of medium and heavy plates, which combines machine vision and PLC control, has been proposed.Firstly, the camera is accurately calibrated using Zhang Zhengyou's calibration method, and the spatial positional relationship between the camera and the shearing machine is determined. Then, the RGB color values of the image are extracted and further converted to the HSV color space, so that the image features are effectively extracted, and thus the endpoints of the plate head are accurately identified. Moreover, the distance between the endpoints in the world coordinate system is calculated by means of pixel coordinate conversion.When it is detected that the width of the plate head is stable and the number of endpoints is two, the system automatically determines that it is the regular position of the plate head. Subsequently, the system calculates the distance from the edge point of the length-measuring laser line to the regular position, so as to determine the target shearing position. The target position is sent to the PLC control system, and the roller table is controlled by the PLC to complete the shearing action.This intelligent fixed-length technology not only improves the accuracy of plate end-point recognition,but also significantly enhances the shearing accuracy and product quality, with the fixed-length accuracy controlled within ±5 mm.

Due to harsh production environment and numerous coupling factors of control system, the process of heating furnace is always a weak link in the automation degree of production line, which affects the intelligent and digital process of production line. With the continuous update and development of big data technology, it has gradually entered the field of metallurgical industry, aiming at using data mining technology to establish data-driven mathematical models, so as to break through the bottleneck of traditional models. This paper introduces the construction of intelligent control system of heating furnace combustion based on big data platform in a certain scene. Big data algorithm is adopted to carry out intelligent optimization control for heating furnace combustion process, improve the control precision of heating furnace. The intelligent furnace temperature control boasts an online rate not less than 93% and discharge slab temperature control accuracy (±12 ℃) of 93.2%, while reducing fuel consumption of 3.5%,achieving energy savings and improve product quality.

Carbon capture, utilization, and storage (CCUS) technology, as the only pathway to near-zero emissions of fossil energy at present, is crucial for reducing CO₂ emissions and supporting China′s "dual carbon" strategic goals. The large-scale, long-distance CO₂ pipelines, which connect CO₂ capture and storage sites, play decisive roles in ensuring the efficient operation of CCUS projects. In this work, the construction status of important domestic and international CO₂ pipeline projects is summarized basing on the phase characteristics and transport status of CO₂. The influence mechanisms of water content, impurity gas, and transportation technology on the corrosion behavior of CO₂ pipelines are summarized. The research progress on corrosion prevention methods such as corrosion-resistant pipeline materials, coatings, and corrosion inhibitors is reviewed. The future development direction of CO₂ pipelines is prospected. Compared with the demand of CCUS project and the mature CO₂ transportation pipeline technology in the world, there are certain gaps in the construction and experience of long-distance and large-scale CO₂ pipelines in our country, and it is urgent to deepen the engineering practice research of supercritical CO₂ pipeline transportation technology. At present, most studies on CO₂ pipelines are concentrated in the laboratory environment, and there are discrepancies in some research findings, which cannot effectively guide the construction and practical engineering application of CO₂ pipeline in China. Thus, it is urgent to establish pilot-scale experiment platforms and carry out massive experimental studies to reveal the interaction mechanism of multiple factors under actual complex working conditions. In addition, it is suggested to use cost-effective bimetallic composite pipes and develop novel types of efficient corrosion resistant coatings and corrosion inhibitors suitable for bimetallic composite pipes, in order to form a complete set of new protection technology for CO₂ pipelines.

In order to develop ultra-high-strength prestressed steel strands with higher development intensity and superior comprehensive performance, using 87Mn wire rod as the raw material, the evolution of the microstructure and properties of the steel wire during the nine-pass drawing process were studied, revealing its strength-ductility mechanism. The results showed that the equiaxed pearlite structure was elongated and refined along the drawing direction with the drawing process, showing obvious directionality, and finally forming a typical fibrous drawing structure. The dislocation density inside the steel wire increases with the increase of drawing strain, and the growth rate is faster in the early drawing stage, from 2.35 × 10¹⁴ m^-2 to 4.59 × 10¹⁴ m^-2, and the growth rate of dislocation density gradually slows down in the middle and late drawing stages. After 9 passes of drawing, the tensile strength of 87Mn wire rod increases from 1 170 MPa to 2 085 MPa, and the elongation decreases from 12.56% to 7.20%. The change of mechanical properties during the drawing process is mainly divided into three stages:in the early stage of drawing, dislocation strengthening and boundary strengthening work together, and the strength contribution of dislocation strengthening growth is obvious, from 189 MPa to 460 MPa. At this stage, the strength of the steel wire increases with the increase of the drawing strain, and the plasticity decreases significantly. In the middle of drawing, dislocation strengthening and boundary strengthening work together. The strength contribution of boundary strengthening is significant, from 600 MPa to 806 MPa, and the growth rate of dislocation strengthening decreases. At this stage, the plastic decline trend of steel wire slows down and the strength continues to increase. In the late stage of drawing, a large number of cementite dissolved, and the strength contribution of solid solution strengthening was enhanced to 149 MPa. At this stage, the combined effects of boundary strengthening, dislocation strengthening and solid solution strengthening worked together. The strength growth rate of steel wire was obviously accelerated, and the plasticity decreased slightly.

During the hot rolling process, the precise positioning of steel billets is of paramount importance, as it enables automated billet inspection, which in turn enhances both production efficiency and quality control. However, the actual production process is arduous due to the harsh conditions of the billet production environment, which presents challenges for plate inspection. To address the problems mentioned above, a robust Yolov8 algorithm for billet detection is proposed. A hybrid attention mechanism network is proposed to solve the problem of shallow feature loss in pyramid networks, enhancing the model's ability to learn local features and improving detection accuracy while maintaining model lightweightness. The implementation method involves the introduction of attention modules into the network with the objective of enhancing the preservation of detailed image feature information, thereby improving the overall detection accuracy of the targets. Subsequently, the NPANet feature fusion structure is designed to enhance the network's ability to fuse multi-scale features of images. This is achieved by refining the convolution modules to make the network model lighter. Finally, the loss function is improved to enhance the algorithm's regression performance and reduce the error in stable box generation. The experimental results demonstrate that the improved NDS-yolov8 model, in comparison to the initial network structure, exhibits a reduction in the weight file size from 6.2 MB to 4.6 MB, a decrease infloating-point performance from 8.1 GFLOPS to 6.4 GFLOPS, and an increase in the mean average precision (P_mA@[0.5:0.95]by 0.5% at different I_oU values. Compared to actual values in real-world scenarios, the NDS-yolov8 network model demonstrates significantly reduced error margins relative to the original Yolov8 network model. It achieves more accurate estimation of the billet's real-time position, thereby effectively enhancing the performance of billet detection and localization.

The rolling force prediction model is the core of the cold rolling set control system. For a long time, the traditional rolling force theoretical model has exhibited low prediction accuracy and a strong dependence on empirical parameters due to the complex influencing factors in the cold rolling process, such as multivariable interactions, strong coupling, nonlinearity, and time-dependence. These limitations have hindered its ability to meet the production requirements of high-precision cold-rolled ultra-thin-gauge strips. The setting of the rolling force primarily depends on the calculation accuracy of deformation resistance and the friction coefficient. By analyzing the classical Bland-Ford-Hill cold rolling force theoretical model, inverse calculation formulas for deformation resistance and the friction coefficient were established, thereby obtaining their true values. Subsequently, a least squares support vector machine (LSSVM) model optimized by the differential evolution (DE) algorithm (DE-LSSVM) was constructed. By inputting the true values of deformation resistance and the friction coefficient into the DE-LSSVM for training, corrections were made to these parameters, thus optimizing the rolling force theoretical prediction model. Experimental results demonstrate that, compared with the traditional rolling force theoretical model, the deviation of the rolling force prediction model based on optimization of deformation resistance and friction coefficient is controlled within 5%.

Crown is one of the critical quality indicators for medium and heavy plate products, and its control level is a testament to an enterprise's production capacity and market competitiveness. With the vigorous development of artificial intelligence (AI) technology, intelligent control has become the core strategy driving the development of the iron and steel industry. However, there is still a lack of relevant research on how to apply AI technologies such as big data to improve product quality, especially in enhancing the plate crown control level during the medium and heavy plate rolling process. This study focuses on the plate crown control technology of medium and heavy plate mills. By combining mechanism models with data-driven models, an intelligent prediction model for heavy plate crown is established, achieving a hit rate of 83.04% for plate crown within the range of ±80 μm. Meanwhile, based on the theoretical framework of this model and big data analysis technology, the roll contour curve of the finishing mill work rolls is optimized. This optimization not only improves the crown control capability of medium and heavy plate mill products, but also extends the rolling cycle of work rolls, and increases both the mill productivity and product yield.

Hot-rolled galvanized high hole expansion steel possesses both high formability and high corrosion resistance, which can significantly improve the service life of automotive chassis parts to meet the requirement of new energy vehicles. However, due to the addition of annealing and galvanizing processes, the precipitation behavior and changes in microstructure and mechanical properties of hot-rolled galvanized sheets are more complex compared to pickled sheets, and require further research. The effect of coiling temperature on microstructure and properties of 580 MPa grade Nb microalloying hot-rolled galvanized high hole expansion steel was studied by using optical microscope (OM), scanning electron microscope (SEM), tensile testing machine and forming testing machine. The results show that compared with high-temperature coiling at 570 ℃, the hot rolled steel produced by low-temperature coiling at 450 ℃ had relatively smaller grain size and remained more defects such as dislocations, resulting in higher energy storage. Therefore, during subsequent annealing process, the driving force for recrystallization was greater and there were more nucleation positions, making the galvanized steel has a finer grain structure. Low temperature coiling suppressed Nb precipitation during the hot rolling stage, allowing most Nb to dissolve in the ferrite matrix or be in a critical precipitation state. In the subsequent annealing and galvanizing process, more small-sized and uniformly distributed Nb-containing precipitates were obtained, which not only contributed positively to yield and tensile strength, but also significantly improved the hole expansion rate. The galvanized sheet used the hot rolled strip of coiled at 450 ℃ possessed excellent mechanical properties and local formability. Its longitudinal yield strength, tensile strength and total elongation was 503 MPa, 602 MPa and 20.5%, respectively. The average hole expansion rate reached 95%.

For large size hot rolled H-beams with a web height H≥1 000 mm and a flange thickness h≥40 mm, the rolling load is relatively high in production and it is difficult to improve the product's microstructure and properties through traditional low-temperature and large reduction technology on existing production equipment. In order to achieve the localization of large size hot rolled H-beams, thermal simulation experiments, optical microscopes, scanning electron microscopes, transmission electron microscopes, tensile and impact tests were used to study the effect of rolling temperature on the microstructure and properties of Q420 grade HN1 109 mm×461 mm×21 mm×40.5 mm H-beam flanges. The results show that when the universal rolling temperature is reduced from1 000 ℃ to 900 ℃, the flange yield strength increases, the impact toughness first decreases and then increases, and the grain size is refined to a certain extent, the amount of V carbonitride precipitation increases, and its size gradually decreases. When the universal rolling temperature is controlled at 900 ℃ or 1 000 ℃, the microstructure and properties of Q420 grade large size hot rolled H-beam match well.

Currently, the production of 690 MPa grade marine platform steel plates usually adopts offline heat treatment, which not only wastes a large amount of heat but also takes a long time. This paper improves the existing heat treatment process and adopts the full-process online heat treatment (i.e., online quenching + online tempering) process. The microstructure of the plates after online heat treatment is observed by OM, SEM, TEM, and EBSD, and the yield strength, tensile strength, and impact energy are tested by a universal testing machine to explore the laws of microstructure evolution and property changes of the steel plates under different online quenching temperatures. The results show that the microstructure of the experimental plates after heat treatment is mainly composed of tempered martensite, ferrite, and carbides. With the increase of quenching temperature, the amount of martensite and the width of laths in the microstructure increase, the amount of carbide precipitation increases, the proportion of high-angle grain boundaries decreases, the yield strength and tensile strength increase, and the impact energy decreases. After online quenching at 850 ℃, although the yield strength of the experimental plates is lower than that at 900 ℃, the yield-to-tensile ratio and impact toughness are higher than those at 900 ℃, and the comprehensive mechanical properties are the best. The research results provide theoery support for the technology optimization of E690 plate.

The strip crown plays a crucial role in determining the quality of products in strip hot rolling. Hence, achieving precisely hot-rolled strip crown diagnosis is important to improve the control capability of hot rolling. Since the hot rolling process features nonlinearity, heredity, and strong coupling, the diagnosis of strip crown is an imbalanced problem with complex decision boundaries. Existing crown prediction models tend to learn more information from the majority class, but ignore the data of the strip with unqualified crown. To overcome this limitation, a hot-rolled strip crown diagnosis model based on the fusion of hybrid resampling and cost-sensitive is proposed, and the cost-sensitive factor is obtained by artificial hummingbird algorithm. Some advanced machine learning models are selected as comparison models. The experimental results demonstrate that the proposed model outperforms all comparison models with the A_UC of 0.889 and defect recall of 0.870. Moreover, the testing time of the proposed model is only 0.0059 s. After the madel was applied to online diagnosis,the detection rate of defect crown strips increased from 82% to 88%,and the crown compliance rate of strips improved from 59% to 71%.