The sintering process constitutes a crucial stage in the blast furnace ironmaking technology,but it also generates significant amounts of pollutants. In the context of ultra-low emissions,steel enterprises urgently need to upgrade and transform their existing desulfurization and denitrification processes to address the problems that exist in their practical applications. Based on the current status of flue gas desulfurization and denitrification technologies in sintering processes of steel enterprises,mainstream desulfurization and denitrification technologies applied in China's sintering flue gas treatment field are systematically introduced. Meanwhile,an outlook is provided for the removal technologies of sulfur dioxide and nitrogen oxides in sintering flue gas that are widely applied in steel enterprises currently. Selecting mature desulfurization and denitrification processes based on flue gas characteristics will become the main path for the steel industry to complete ultra-low emission transformation. The semi-dry desulfurization technology needs to actively develop technologies for the harmlessness and resource utilization of desulfurization ash, and at the same time apply automation and intelligentization technologies to address the problem of desulfurization efficiency under changing operating conditions.The research focus of SCR denitrification is low-temperature SCR technology, especially the development of low-temperature catalysts with anti-water and anti-sulfur poisoning ability.The simultaneous desulfurization and denitrification process of active coke should be studied more in the aspects of preventing crystallization plugging,system corrosion and standardized operation.
Hot metal pretreatment dephosphorization process is an important measure to improve the quality of steel products and expand the variety of smelting. Different process methods have been developed at home and abroad. The characteristics and key technologies of hot metal pretreatment dephosphorization process that form productivity are summarized and analyzed, which can provide reference for solving the technical details of the current process mode and developing new processes. The development status of hot metal pretreatment dephosphorization process and its automatic control technology at home and abroad is summarized. The process characteristics and application of dephosphorization process commonly used in hot metal pretreatment at home and abroad are sorted out and analyzed, and the application, advantages and disadvantages of the above technology are emphatically summarized. Hot metal ladle dephosphorization is more suitable for stainless steel production line, and there are still technical details to be solved in dephosphorization converter. The research progress and development trend of automatic control of hot metal pretreatment dephosphorization process are expounded. Rational use of industrial data to establish process control model will be an important direction. The hot metal pretreatment dephosphorization process and its automatic development approach and prospect are prospected, which can provide reference for achieving automated and precise control, as well as intelligent process flow, in the subsequent dephosphorization process of molten iron pretreatment.
Under the background of the "dual carbon" era, the EAF mini mill steelmaking process is regarded as an effective carbon reduction technical route. More and more EAF steelmaking capacity has been further expanded in the world. The study on the global layout of EAF steel production capacity reveals that according to the output of EAF steel in major countries, which can be divided into five echelons. The layout of production capacity is affected by six factors, which are trade circulation, energy conditions, economic development, technological innovation, environmental protection policies, and market demand in the world. The analysis of more than 210 existing enterprises with EAF equipment in China shows that nearly 200 enterprises are located on the east side of the "Hu Line". The layout of production capacity mainly presents four characteristics, which are resource supply, energy reliance, green orientation, and group model. There are problems such as weak cost competitiveness of short-process enterprises compared to long-process enterprises in the same region, serious product homogeneity among enterprises in the region, and insufficient green environmental protection advantages. Based on the current status of the layout of EAF steel production capacity in China, four optimization directions for the existing layout are proposed, along with two development trends for future layouts. The layout of EAF steel production capacity is prospected from aspects of location, production capacity and time. It is essential to manage both the existing and incremental EAF steel capacity well to fully utilize the crucial role of EAF steel in the green and low-carbon transformation and development of the steel industry. It is suggested that the development of EAF mini mill steelmaking process should not be decided in isolation. A comprehensive judgment should be made on the strategies for the layout of EAF steel production capacity in different periods.
With the rapid development of China's industry,higher requirements are put forward for high-speed and heavy-load railway tracks,stable and safe mechanical bearings,efficient and environmentally friendly mining. At the same time,it also leads to a rapid increase in the consumption of materials in the corresponding field in terms of wear failure,resulting in huge economic losses. As an important engineering material,bainite wear-resistant steel can obtain excellent strength,toughness and wear resistance by adding low-cost alloy elements and simple heat treatment process. It has broad application prospects in mining,railway,machinery and other fields. The research results of bainite wear-resistant steel in China are reviewed from the aspects of composition design,heat treatment process and microstructure on wear resistance. It is expected to provide reference for the design,preparation and application of bainitic wear-resistant steel by analyzing and summarizing the research status of various aspects. Finally,combined with the current research results,the development trend of bainite wear-resistant steel and the research direction that needs to be paid attention to in the future are discussed.
Hydrogen embrittlement is a complex phenomenon in materials science and engineering,which can lead to a decrease in the mechanical properties of high-strength age-hardened aluminum alloys and seriously affect the service life of aluminum alloy products. Firstly,the forms of hydrogen entering the material are introduced,including hydrogen absorption introduced during the manufacturing process,hydrogen exposure,hydrogen absorption caused by corrosion,and artificial hydrogen charging. Secondly,the interaction between hydrogen and microstructure is summarized,focusing on the effects of precipitates,dislocations,and grain boundary states on hydrogen embrittlement in alloys with different aging tempers. Finally,the relevant mechanisms of hydrogen embrittlement are discussed,including hydrogen-enhanced decohesion mechanism,hydrogen-enhanced localized plasticity mechanism,adsorption-induced dislocation emission mechanism,and mixed mechanism. Future research work in this field is also prospected,in order to provide a theoretical reference for the design of hydrogen-embrittlement-resistant aluminum alloys and hydrogen storage aluminum alloys.
Direct reduced iron (DRI) is an important process product for achieving deep decarbonization, which can be used in EAF, converter or electric melting furnace. The chemical composition and quality of DRI, as well as the use of fuel reducing agents, have a significant impact on the application of DRI in next process and carbon reduction. An overview of the current production status of direct reduced iron is summarized, the application of direct reduced iron and the quality requirements for direct reduced iron, the current situation and development of reduction gas used in direct reduction are analyzed, and the processing and application of iron ore used in direct reduced iron production, as well as the preparation of reduction gas are analyzed and considered. EAF and converter require DRI with high iron grade, low gangue, and high metallization rate, while electric melting furnaces can use DRI with relatively low grade and high gangue content. At present, the EAF process has large production capacity and mature technology, while the electric melting furnace process is in the research and development stage. In addition, from the perspective of carbon reduction, the direct reduced iron from low grade and high content gangue has a significant impact on the power consumption and carbon emissions of both EAF and smelting furnace processes. Therefore, iron ore used for direct reduction should reduce the content of gangue and improve its grade as much as possible during the source selection stage, in order to produce high-quality direct reduced iron. The traditional direct reduced iron production mainly uses natural gas as energy and reducing agent. Natural gas is a fossil fuel, and China's natural gas resources are scarce and expensive. Therefore, the application of coke oven gas or CO+H2 mixed reduction gas from CO2 conversion can ensure the reduction rate of iron ore, increase the content of direct reduced iron C content, and reduce carbon emissions.
Reasonable blast furnace burden structure is a fundamental factor for high quality smelting of blast furnace, which is very important for stabilizing blast furnace running, improving smelting efficiency, reducing energy consumption and cost. In view of the conditions of the blast furnace burden for Zenith Steel Group Company Limited, the experiments on the softening and melting droplet performance of the comprehensive burden were carried out, at the same time, a comprehensive technical index accounting model based on the energy-quality balance was constructed, and the entropy weight method was used to calculate the evaluation indexes of each group of charging schemes, so as to give the comprehensive evaluation value of the schemes to obtain the optimal solution. The research results show that the integrated A-1 scheme(Sinter∶Baosteel Pellets∶Nantong Pellets∶PB Lump Ore=76∶5∶6∶13) has the highest comprehensive evaluation value, which reduces iron cost by 6.97 yuan/t, reduces carbon emission of iron by 6.36 kg/t, and improves the total amount of iron in the batch by 0.29 t compared with the baseline scheme, at the same time, the softening start temperature is 1 245 ℃, the drop temperature is 1 462 ℃, and the molten drop characteristic value is 1 121.46 kPa·℃, which is better for the softening and molten drop performance. In conclusion, the decision-making method of the comprehensive burden scheme built for the comprehensive burden performance and blast furnace technical indicators can play a certain guiding role for the optimization of the furnace burden structure in the blast furnace process of the iron and steel enterprises.
The combined electromagnetic stirring technology is one of the key means to improve the homogenization level of continuous casting billets. In order to solve the problems of macrostructure white bright bands and large fluctuations in carbon segregation in φ600 mm 42CrMo large round billets, research on the homogenization of round billets based on combined electromagnetic stirring was carried out. Under the existing continuous casting process conditions, various process parameters of combined electromagnetic stirring were tested. By comparing the control effects on the homogeneity of large round billets, the influence of the synergistic effect of the three-stage electromagnetic stirring of M-EMS (Mold Electromagnetic Stirring), S-EMS (Strand Electromagnetic Stirring), and F-EMS (Final Electromagnetic Stirring) on the macrostructure and carbon segregation of 42CrMo was analyzed in depth. The results showed that M-EMS can solve the problem of negative segregation under the surface of round billets at a relatively low stirring intensity, S-EMS can significantly improve the positive segregation phenomenon in the CET (Columnar to Equiaxed Transition) zone, and the alternating stirring mode of F-EMS can successfully eliminate the traces of electromagnetic stirring in the equiaxed crystal region. Both M-EMS and S-EMS are helpful in increasing the equiaxed crystal ratio of round billets, and the equiaxed crystal ratio increases with the increase in the electromagnetic stirring current. The optimal combined electromagnetic stirring parameters for φ600 mm 42CrMo round billets are 150 A-1.5 Hz (M-EMS), 70 A-6 Hz (S-EMS), 950 A-6 Hz (50 s-3 s-50 s) (F-EMS). In general, a reasonable combined electromagnetic stirring can effectively improve the homogeneity of 42CrMo large round billets and significantly improve the macrostructure and carbon segregation conditions. The research results provide a practical reference for the reasonable selection of electromagnetic stirring parameters for large round billets.
To achieve high-speed casting under single-strand mode, a steel plant plans to upgrade its existing double-strand tundish continuous casting machine, requiring the tundish to have casting functions of both single-strand and double-strand and ensure the normal use of plasma heating. Different turbulence inhibitors and flow control devices were designed, and their influence on the flow field of the tundish were studied through physical models, and then the flow conditions of the molten steel were optimized. The research results indicate that the turbulence inhibitor of the double-strand tundish is not suitable for single-strand casting. After adopting a new turbulence inhibitor and appropriate modification wall in single-strand casting, various flow field indicators are significantly improved. The average residence time of molten steel increases from 383.7 s to 436.5 s, an enhancement of 13.8%; the response time extends from 36 s to 54 s, representing a delay of 50.0%; the peak time increases by 130.1%; the peak dimensionless concentration decreases by 44.6%. The industrial experimental results of single-strand tundish shows that during the single-strand casting process, the temperature difference between the blocking side and the pouring side of the tundish decreases from 16 ℃ in the original scheme to 6.5 ℃. Additionally, the residual steel in the tundish is reduced to 9.35 t, representing a decrease of 5.65 t compares to the 15 t in the original scheme. The novel combination of flow control devices improves the molten steel flow characteristics, which is beneficial for mass and heat transfer, compositional homogenization, and the flotation and removal of inclusions. This process not only enhances casting quality but also provides technical support for improving material properties and final product quality in steel production. Additionally, it offers valuable reference for future modifications of tundishes to meet flexible production needs and for the application of plasma heating.
To break through the long-standing technological blockade by foreign brands in the fields of conventional hot rolling automation mathematical models and main drive frequency conversion systems,the 1 580 mm hot rolling line in Lian Steel is introduced from four perspectives: production processes,equipment characteristics,intelligent systems,and quality metrics. From site selection to post-construction phases,the entire line was independently designed and constructed by Chinese. The process automation mathematical models,basic automation mathematical models,medium-voltage drive system,and main motor were innovations of Chinese engineers. The control models is accurate and reliable,and the drive system is efficient and stable,reaching world-class standard and advanced domestic level. It is the first fully localized 1 580 mm hot rolling line in China. Guided by advanced steel materials,the line achieves excellent quality indicators for low-temperature oriented silicon strip and high-grade non-oriented silicon strip,providing solid material support for building a stronghold of advanced manufacturing in the country.
In the marine environment,ship plate steel is prone to corrosion,which severely threatens the service safety of materials. To investigate the effect of rare earth Ce on the corrosion resistance of AH36 ship steel in a marine environment,the effects of Ce on the inclusions in AH36 steel and its corrosion behavior in simulated marine environment were analyzed by SEM,XRD,EPMA,and electrochemical tests. It is found that after treatment with Ce,the Al2O3,MnS,and TiN are converted into Ce-O and Ce-Ti-N-O-S inclusions,and the inclusion size decreases from 2.5-6.0 μm to 1-2 μm. Under the condition that the mass fraction of Ce is 0.009% and 0.034%,the inclusion number density in the experimental steel increases from 49 mm-2 to 54 mm-2 and 72 mm-2,and the proportion of inclusions smaller than 5 μm increases from 67% to 82% and 76%. The results of immersion experiments in 3.5%NaCl solution show that Ce can increase the proportion of α-FeOOH and Fe3O4 in the corrosion products. When the mass fraction of Ce is 0.009% and 0.034%,the ratio of the sum of the mass fractions of α-FeOOH and Fe3O4 to the mass fraction of γ-FeOOH (α*/γ*) in the corrosion products increases from 1.09 without Ce addition to 2.27 and 1.64. After 21 days of immersion,the corrosion current density of the samples with 0.009% and 0.034% Ce content decreases from 2.652 A/cm2 without Ce addition to 2.127 A/cm2 and 2.209 A/cm2,respectively. AH36 steel with a Ce mass fraction of 0.009% exhibits the best corrosion resistance.
TiN is typical non-metallic inclusion in superalloys,which will adversely affect the fatigue life and mechanical properties of the alloy. In order to study the wetting behavior between nickel-based superalloy and TiN and realize the effective control of TiN inclusions in nickel-based superalloy,the apparent contact angles between GH4169,GH4738,GH4720Li nickel-based superalloy and TiN substrate were obtained by sessile drop high temperature wettability experiment. The microscopic characteristics and element distribution of the wetting interface were observed by SEM-EDS,and the interfacial wetting process was analyzed by thermodynamic calculation. At 1 450 ℃,the final contact angles of GH4169,GH4738 and GH4720Li alloys with TiN substrate were 67.75°,51.39° and 106.13°,respectively,and no obvious reactants were formed at the interface. The alloy droplet penetrated into the substrate along the micropores of the substrate with the effect of capillary force. The average penetration depth of the substrate was 13.8,15.9 and 10.7 μm,respectively,which was consistent with the wettability order of the system. Under the influence of surface energy and density difference,TiN particles floated up to the surface to form a TiN particle layer,which increased the viscosity of the alloy droplet and hindered the spreading of the alloy on the TiN substrate to a certain extent. Finally,the apparent contact angle between GH4720Li and TiN substrate was greater than 90°.
With the increase of industrial activities such as aluminum smelting, coal utilization and mining, the production of solid waste such as aluminum ash, cinder and red mud is increasing year by year, which seriously affects the sustainable utilization of ecological environment and resources. This study aims to explore and evaluate the synergistic treatment effect of three industrial waste residues, secondary aluminum ash, cinder and red mud, in the process of high temperature roasting, aiming to realize the resource utilization, harmlessness and by-product of valuable alumina powder. The effects of different roasting temperature, holding time and liquid-solid ratio on the leaching rate of alumina powder were investigated by high temperature roasting experiment, and the three-phase roasting conditions were optimized by orthogonal experiment. The results show that, under the conditions of calcination temperature, holding time and liquid-solid ratio of 1 100 ℃, 40 min and 11∶1, the three solid wastes can effectively promote the formation of alumina, and the recovery rate of alumina in the calcined product can reach 89.88%. If the temperature is too low, harmful substances are difficult to volatilize. If the temperature is too high, liquid phase will appear in the clinker, which will affect the recovery rate of alumina. Under the optimal process conditions, 89.88% of alumina powder can be recovered for every 1 g of secondary aluminum ash, 1 g of cinder and 2 g of red mud consumed. In the whole process, harmful substances volatilize into the waste gas, and silicate phase substances such as MgO, SiO2 and CaSiO3 are formed in the leaching residue. This process realizes the transformation of hazardous waste into ordinary solid waste, so as to achieve the purpose of treating waste with waste, which lays a foundation for the resource and reduction of solid waste.
Under the background of "double carbon" goal, the utilization of metallurgical process for resource treatment of municipal solid waste has shown broad application prospects. As a typical urban solid waste, waste tires contain rubber and valuable metal elements, and need to be properly disposed to avoid negative impact on the environment. Waste tires were used as raw materials to produce pyrolytic carbon by pyrolysis at different temperatures, the effects of pyrolysis temperature on the yield and composition of pyrolytic carbon were analyzed, the physicochemical properties of pyrolytic carbon were studied, and its application potential as a substitute for reducing agent used in rotary hearth furnace was evaluated. The results have shown that the optimum temperature for preparing pyrolytic carbon from waste tire is 450 ℃, the fixed carbon mass fraction is 86.89%, the volatile mass fraction is 5.13% and the ash mass fraction is only 6.63%. The ash of pyrolytic carbon is dominated by ZnO, the content of SiO2 and Al2O3 is much lower than that of coke powder, and the content of alkali metal is low. The specific surface area and pore structure of pyrolytic carbon are significantly better than that of coke powder, with complex microstructure, rich functional groups on the surface, better comprehensive combustion performance, and higher REDOX activity at high temperatures. Pyrolytic carbon begins to reduce iron oxide at 407 ℃, and the initial reduction temperature is lower than that of coke powder. During the reduction process, more hydrogen can be generated to promote the reduction reaction, and the reduction effect is significantly higher than that of coke powder. When pyrolytic carbon and coke powder are used to prepare carbon-containing pellets with iron and zinc dust mud, the metallization rate and zinc removal rate of pyrolytic carbon reduced pellets are higher. Therefore, pyrolytic carbon has the potential to replace coke powder as a low-carbon reducing agent in rotary hearth furnace, which can reduce the use of fossil fuels and carbon emissions, and realize the effective collaborative utilization of carbon reduction in steel industry and urban solid waste resources.
The blast furnace permeability index is a key indicator of gas flow within the furnace and plays a critical role in assessing furnace conditions. Early prediction of the permeability index can provide essential support for operational decisions. Real-time production data from a steel plant's smart center were first preprocessed,and key parameters for predicting the permeability index were determined preliminarily by combining expert knowledge and the LightGBM algorithm. Redundant parameters were then eliminated using correlation analysis,and the time lags between parameters were also analyzed. For the highly fluctuating permeability index time series,variational mode decomposition (VMD) is employed to decompose the series into modal components with reduced noise. Subsequently,temporal features were extracted via a temporal convolutional network (TCN) and then input into a gated recurrent unit (GRU) network to capture the long-term dependencies among furnace parameters,ultimately enabling accurate predictions of the permeability index one hour in advance. Simulation results demonstrate that the proposed VMD-TCN-GRU prediction model outperforms simple models such as XGBoost and GRU across all evaluation metrics. Under an allowable error range of ±0.5,the prediction hit rate reaches 97.83%,with a goodness of fit as high as 0.968. These findings indicate that the proposed model is more robust in handling complex fluctuations and multi-lag correlations of the permeability index,thus assisting operators in making timely adjustments to ensure stable and efficient furnace operation.