Medium-manganese (Mn) steel (MMS) has remarkable characteristics of high strength, strong work-hardening capacity, and wear resistance, being a promising third-generation advanced high-strength steel with lower raw material cost compared with other generations of advanced high-strength steel. The chemical composition and processing route play critical roles in determining the microstructural evolution of the MMS, and the microstructure composition significantly influences the mechanical, corrosion and wear properties of the steel. Hence, a lot of research work focus on exploring the direct relation between microstructural evolution and mechanical/corrosion/wear properties, and the progress has the following crucial aspects: (1) alloying design on the phase composition and carbide precipitation, (2) processing route on regulating microstructure evolution and twinning-induced plasticity and/or transformation-induced plasticity strengthening mechanism, (3) work-hardening, corrosion, and corrosion resistance of the regulated MMS, and (4) fracture and failure mechanism of MMS under tensile, corrosion and wear damages, as well as the improvement strategies.

Basic oxygen steelmaking (BOS) is the most frequently used method to produce molten steel, which is being developed to meet the requirements of being safe, efficient, clean, and intelligent. During the BOS process, splashing events cause undesirable consequences, such as casualties, low efficiency, environmental pollution, and uncontrollable operation. The causes of three types of splashing (eruptive, foaming, and metallic splashing) were unraveled and it is concluded that inappropriate foaming is the root cause of splashing. A variety of monitoring techniques for splashing have been developed to measure real-time slag foaming in a basic oxygen furnace (BOF). The audiometry technique with flexible operation and high accuracy was comprehensively introduced with a practical application. Based on the formation mechanisms, the countermeasures for the three types of splashing were proposed to regulate slag foaming in a BOF by integrating diverse measures in terms of raw materials, slag forming, blowing pattern, and the use of splashing regulating agents. Future work should emphasise an automatic action for these prevention measures in response to the splashing risk from the monitoring technology, promoting the progress of intelligent steelmaking.

In order to precisely control the final temperature of molten steel in RH (Ruhrstahl Heraeus)-TOP blowing refining, the final temperature prediction models of molten steel in RH-TOP blowing refining process for Interstitial Free (IF) steel production were established under the condition of oxygen blowing and non-oxygen blowing respectively. The results show that the beginning molten steel temperature of refining and the amount of added scrap were influential factors, the baking temperature in vacuum chamber was a factor that had small influence. When the model was operated, the hitting probability was above 95% (under the condition of both oxygen blowing and non-oxygen blowing) of prediction deviation of ±10 ℃. The accuracy is analyzed.

Aiming at the limitations of rapid fault diagnosis of blast furnace, a novel strategy based on cost-conscious least squares support vector machine (LS-SVM) is proposed to solve this problem. Firstly, modified discrete particle swarm optimization is applied to optimize the feature selection and the LS-SVM parameters. Secondly, cost-conscious formula is presented for fitness function and it contains in detail training time, recognition accuracy and the feature selection. The CLS-SVM algorithm is presented to increase the performance of the LS-SVM classifier. The new method can select the best fault features in much shorter time and have fewer support vectors and better generalization performance in the application of fault diagnosis of the blast furnace. Thirdly, a gradual change binary tree is established for blast furnace faults diagnosis. It is a multi-class classification method based on center-of-gravity formula distance of cluster. A gradual change classification percentage is used to select sample randomly. The proposed new method raises the speed of diagnosis, optimizes the classification accuracy and has good generalization ability for fault diagnosis of the application of blast furnace.

Corex is an alternative ironmaking process and raceway is one of the important areas to maintain the stability of the furnace. The raceway parameters are well established for blast furnace operation. But for Corex process, it has not yet been established and optimized. Thus, a mathematical model was developed to determine various raceway parameters such as RAFT (raceway adiabatic flame temperature), tuyere gas velocity and kinetic energy. The model provides an idea about the raceway geometry, zone temperature and kinetic energy accumulated in tuyere gas. Besides, all the raceway parameters have been analyzed to find out their effects on the Corex process. It is found that RAFT influences the gasification reaction kinetics and higher RAFT generates more CO in reduction gas, which improves the metallisation degree of the DRI in shaft. It is also found that increased gas velocity and kinetic energy generate more fines and demand more coke to maintain char bed permeability. High coke rate increases the production cost and lowers the production of hot metal.

The temperature distribution of iron ore pellet bed in grate has a significant effect on pellet production and quality control, but the related work is scarce. A well-designed test was successfully carried out by means of tracking measurement and the temperature distribution and variation in pellet layers were obtained. The effects of blast temperature, blast velocity and oxidation reaction on the pellet layer temperature were studied. According to the analysis, the inlet air temperature in the up-draught drying zone (UDD) and blast temperature in the Preheating I (PH I) zone should be raised, and the length of the down-draught drying zone (DDD) should be properly increased.

The raceway has been studied extensively both theoretically and experimentally. The raceway boundary is coarse and fragmentary, but all of previous studies are based on Euclidean geometry, which regards the dimension of raceway as an integer. The fractal method of calculating raceway size, which describes boundary with extremely irregular or fragmentary characteristic, is brought forward in physical model. The fractal theory is used to calculate the fractal dimension of raceway boundary and the precise surface area of ellipsoidal raceway boundary. The result shows that the surface area based on fractal is larger than that based on Euclidean. And the surface area increases with the rise of blowing rate.

The development of continuous casting technology of electrical steel was analyzed. The technologies and products characteristics of conventional continuous casting, thin slab continuous casting and rolling, middle thin slab continuous casting and rolling and twin-roll thin strip were compared. Conventional continuous casting technology was widely adopted in producing electrical steel; thin slab continuous casting and rolling and middle thin slab continuous casting and rolling technology industrialized electrical steel; and study of twin-roll thin strip casting technology was focused on fundamental experiments.

Abstract： Baivumebo iron ore is special magnetite containing fluorine, kalium and sodium elements, and the main raw material for ironmaking of Baotou Iron and Steel (Group) Co. The effects of basicity and ratio of Al2O3 to SiO2 (A/S) on the formation of silico-ferrite of calcium and aluminium (SFCA) in Baivumebo low silica sinters were studied by means of mini-sintering, XPF-500 optical mineralogical microscope and CSS-88000 electronic universal testing machine. The results show that it is beneficial to the formation of complex calcium ferrite to enhance the basicity of Baivumebo low silica sinters. The acicular SFCA-I was increased with the enhancing basicity and reached the peak at basicity 28, then the columnar or platy SFCA formed and the bonding strength decreased. Alumina is beneficial to the formation of acicular complex calcium ferrite in Baivumebo low silica sinters. But the residual unfused Al2O3 reagent came into being when A/S was 035, while complex calcium ferrite still remained to be acicular. There is a common rule about mineralogy components affected by basicity and ratio of A/S, that is, SFCA is increasing accompanied with hematite and porosity reduced, but the content of glass phase is stable.

According to the ion and molecule coexistence theory, the activity model of FeSiB ternary system was established, and the influence of ratio xSi/xFe, boron content and temperature, etc on the activity of the melt compound was investigated. The results show that the FeB activity is high in the liquid iron, when xSi/xFe is 05; the activity of boron increases with increasing the boron content for different contents of xFe and xSi, and the activity of boron at the ratio xFe=04 is about one order of magnitude higher than that for the xFe=08; The activities of the melt compound were also affected by temperature, but the influencing extent was little. The equal activity diagrams of silicon and boron were drawn for the first time according to the model results.

Surface roughness is commonly used to characterize material microstructure during processing, and accurate measurement of surface roughness is the premise and foundation of machining. Therefore, online non-destructive measurement of surface roughness based on the laser speckle method has become a hot issue in recent research. The improvements in surface roughness measurements based on the laser speckle method are systematically reviewed. Theory of speckle formation is introduced. The statistical properties of the speckle patterns including first-order statistical properties and second-order statistical properties are directly related to surface roughness. Surface roughness measurements based on the laser speckle method are roughly divided into the speckle contrast method, speckle correlation method, and fractal method. The three methods are described in detail, and an extensive comparison among all the methods is presented. The recent progresses and application of surface roughness measurements are reviewed. Finally, surface roughness measurements based on the laser speckle method are prospected and summarized.

Driven by the double carbon policy, the iron and steel industry urgently needs to implement a new development concept to strengthen the use of solid waste resources from ironmaking and steelmaking and effectively enhance the economic benefits of recycling resources in order to reduce the accumulation of solid waste resources in the iron and steel industry. The iron and steel production process produces more than 600 million tons of solid waste annually, including metallurgical dust sludge, blast furnace slag and steel slag, etc. From the perspective of environmental friendliness, the efficient utilization of ironmaking and steelmaking solid waste resources through innovative cross-industry technologies is of great significance to the low-carbon, green and high-quality development goals of the iron and steel industry.
  The utilization of solid waste resources in the iron and steel industry mainly involves the resource utilization of ferrous metallurgical solid waste, blast furnace slag, converter slag, metallurgical dust sludge, the used refractory materials and the extraction of valuable components from solid waste resources. Therefore, to present and summarize the comprehensive utilization technologies of solid waste resources in iron and steel industry and promote the development of the field, a special issue on ‘‘Resources Recycling of Solid Wastes from Ironmaking and Steelmaking’’ was organized by Journal of Iron and Steel Research International. As the guest editors, we would like to sincerely thank everyone who has contributed to this special issue, including all the authors, reviewers, and editors. We hope this special issue will be helpful to researchers and readers who are interested in this field.

Iron ore sintering process is the main CO2 emission source throughout the integrate steelworks, which primarily comes from the combustion of solid fuels. Improving the combustion efficiency and reducing the solid fuel consumption are important ways to reduce the CO2 emission in the sintering process. Around the efficient combustion of fuel, the migration behavior and combustion characteristics of solid fuel in the granulation process were investigated. The results indicated that during the granulation process, fuel particles with size less than 0.5 mm mainly migrated into the granules with grain size of 1–3, 3–5 and 5–8 mm; fuel particles with size of 0.5–1 mm mainly migrated into granules of 1–3 mm; fuel particles with size of 1–3, 3–5 and 5–8 mm mainly entered the granules with the same grain size. With the increase in fuel particles grain size from - 0.5 to ? 8 mm, the combustion efficiency exhibited a firstly-increasing and then decreasing tendency, while the NOx exhibited a decreasing tendency. Potential reason can be described that finer fuel particles (- 1 mm) easily distributed in the outer layer of the granules, which combusted fiercely due to its larger specific surface area, leading to the development of incomplete combustion and the conversion of fuel nitrogen; the combustion efficiency of larger fuel particles was restricted by the inner diffusion of O2, which then contributed to the reduction of NOx under the inadequate combustion atmosphere.

The use of low-grade, refractory and composite paragenetic mineral resources is necessary for overcoming the shortage of iron ore resources in China. As a solution to the treatment of such iron ores, the direct reduction of carbon-bearing pellets can ensure complete iron removal and the effective enrichment of other high-value elements. Thus, this technology enjoys a broad application prospect. However, there are several problems with low-temperature reduction, such as low iron ore reaction efficiency, long reaction time, and high energy consumption. To improve the low-temperature carbothermic reduction efficiency of iron ores, a static magnetic field with magnetic induction intensity of 1.0 T was introduced. An isothermal reduction experiment was conducted at 1223 K to study the low-temperature self-reduction characteristics of carbon-bearing pellets of Bayan Obo lean iron ores in the static magnetic field. Also, the acting mechanism of the magnetic field was explored from the perspective of the reduction process, reaction efficiency, phase composition, microstructure changes, and dynamic behavior of iron ores. The results showed that the magnetic field can increase the low-temperature reduction rate of carbon-bearing pellets of Bayan Obo lean iron ores. Under the conditions of reduction temperature of 1223 K, magnetic induction intensity of 1.0 T, and reduction time of 60 min, the reduction degree was 92.42%, 1.65 times that without a magnetic field. The magnetic field promoted the replacement of Ca²⁺ and Fe^2+, so that the hard-to-reduce iron-bearing silicates were reduced in the order of Fe₂SiO₄ →(Ca, Na)FeSiO₄ → FeO → Fe. The magnetic field enabled loose minerals, more pores and cracks, and changes in the growth morphology and distribution position of metallic iron. Compared with the case under the non-magnetic condition, the metallic iron precipitated from the slag phase in a foliated shape, separated from the matrix iron oxides, and grew up at the junction of the slag phase and coke. The magnetic field significantly increased the interfacial chemical reaction rate of the carbothermic reduction of iron ores and reduced the internal diffusion resistance of gas in the product layer. Specifically, the interfacial chemical reaction rate increased by 138% and the internal diffusion coefficient increased by 309%. Therefore, the effect of the magnetic field on the internal diffusion resistance was the main cause for strengthening the low-temperature reduction of iron ores.

The effects of Mn addition (0.005, 0.01, 0.03, 0.05, and 0.07 wt.%) on microstructure, shear mechanical behavior, and interfacial thermal stabilities of SAC305 joints were investigated under isothermal aging temperatures of 170 °C with different aging time (0, 250, 500, and 750 h). It is found that Mn addition can increase fracture energy of joints without decreasing the shear strength. And the microstructures have transformed from the eutectic net-like structure in SAC305 solder joints into the structures based on β-Sn matrix with intermetallic compounds (IMCs) distributed. By doping 0.07 wt.% Mn, the Cu₆Sn₅ growth along the SAC305/Cu interface during thermal aging can be inhibited to some extent. During isothermal aging at 170 °C, the maximum shear force of solder joint decreases continuously with aging time increasing, while the fracture energy rises first and then decreases, reaching the maximum at 500 h compared by that with the microstructure homogenization. Cu₃Sn growth between Cu₆Sn₅/Cu interface has been retarded most at the aging time of 250 h with 0.07 wt.% Mn-doped joints. With the aging time prolonging, the inhibition effect of Mn on Cu₃Sn IMC layer becomes worse. The strengthening effect of Mn can be explained by precipitation strengthening, and its mechanical behavior can be predicted by particle strengthening model proposed by Orowan.

High alumina slag is widely found in pyrometallurgical extractions of ferronickel, ferrochromium, and platinum group metals. The effects of MgO, Al₂O₃, and CaO/SiO₂ on the sulfur distribution ratio between high-alumina CaO–SiO^₂–MgO–Al₂O₃ slag and carbon-saturated iron were investigated. The slag consisted of Al₂O₃ content in the range of 27.61–40.00 wt.%, CaO/SiO₂ ratio of 0.8–1.1, and MgO content of 8–16 wt.%. The theoretical liquid areas of CaO–SiO₂–MgO–Al₂O₃ slag were analyzed through the phase diagrams. The sulfur distribution ratio was measured via the slag–metal equilibrium technique at 1500 ºC. It was observed that the sulfur distribution ratio increased with higher MgO content and higher CaO/SiO₂ ratio largely due to the increase in free O^2- ions and the decrease in activity coefficient of sulfur ion in slag, but slightly decreased with the increasing Al2O3 content because of the decrease in free O^2-.

A procedure for evaluating the susceptibility of raw materials for the process of sintering of ironore mixes is presented. The procedure relies on the evaluation of the amount and quality of the finest grain fraction. The method is based on determination of particular grain fractions. For the grain less than 015 mm, the determination of the amount is performed using an IPS (Infrared Particles Sizer) grain size analyzer and for the grain larger than 015 mm, the fraction is determined using the (wet and dry) screening methods. This allows for quantity assessment of the quality of material in terms of its susceptibility to selfpelletizing by calculating Total Ability for SelfPelletizing (TASP) index fT. The presented method, in combination with the grain size and chemical analyses, can serve for evaluation of suitability of raw material and mixes for the sintering process. Furthermore, the TASP index for 10 types of iron ores and concentrates was determined. The usability of the TASP index was verified by determination of its impact on yield of sintering process both in laboratory and in industry scale.

Municipal sludge is produced in large amounts and is difficult to treat. Incineration is the most direct and thorough treatment method. In order to study the feasibility of sintering for municipal sludge treatment, the municipal sludge reforming process was studied under high-temperature oxidation conditions. The results showed that the sludge reforming process could be divided into four stages: the precipitation and evaporation of adsorbed water, the precipitation and combustion of the volatile, the combustion of the residual volatile and solid carbon, and the decomposition of salts and the melting of sludge. An increase in the heating rate resulted in more intense sludge combustion and improved the sludge reaction capacity and combustion performance. After burning at 1300 oC, Si, Ca, Mg, Al, K, Na, and Cu formed new phases and entered the slag. 75% of P remained in the slag. 80% of the S formed SO₂ and entered the flue gas. Cl formed gaseous chlorides like HCl upon combustion and entered the flue gas. As sintering is a feasible method for treating municipal sludge, care must be taken to limit the amount of P that ends up in the ore.

Many problems appear in the sintering process of vanadiumbearing titanomagnetite, such as high energy consumption and low productivity; sinter quality is also very poor for its low tumble strength and high reduction degradation. Sinter productivity and quality are dominated by bed permeability and mineralogy structure, which are highly influenced by the thermal state of sintering bed, so the sintering process of titanomagnetite is researched by bed dissection in this work. Temperature evolution curves of sinter materials were measured, and the results show that melting duration, peak temperature duration and sintering temperature of different layers differ greatly from each other; flame front speed and vertical sintering speed of bed lower region are much smaller than those of bed upper region. Simultaneously, sinter samples were collected from different layers, and their mineralogy characteristics are analyzed; sinters from bed lower region have poor mineralogy structure, and the amounts of perovskite and dicalcium silicate increase intensively, which are bad for sinter strength and reduction degradation property. Measures are proposed to improve the quality and productivity of titanomagnetite sinter.

Excessive sintering of mould fluxes can readily cause defects and sticker breakouts in continuously cast strands. Studying the sintering property is important to minimize problems related to sintering arising from the use of mould fluxes in continuous casting. An effective method of measuring the apparent sintering temperature has been developed in this study. The method is based on monitoring the formation of cavities caused by melting of samples. For monitoring, the differential pressure of an inert gas flow was measured through a set volume of sample (mould flux A) held in a furnace tube. The apparent sintering temperature was defined in this test to determine sintering process. The sintering properties of fluxes with various contents of carbon black were examined along with identification of mineralogical phases and the nature of the sinter for samples of mould flux A held for one hour at different temperatures. The experimental results indicated that the apparent sintering temperature (AST) was a useful parameter to assess the threat of problems related to sinter.

The solubility of nitrogen in Fe-C-B-N system was measured at 1 758 K, and the computational model on activity (action concentration) of nitrogen and boron was established based on phase diagram and the coexistence theory about metal melt structure model. Comparing the computed results with the experimental results, satisfactory conclusion can be obtained. The result shows that BN and B4C can exist in Fe-C-B-N molten metal at high temperature, which consequently restrains the nitrogen removal from the melt. However, B4C content is extremely low. Before graphite is precipitated, the influence of carbon on activity of nitrogen in melt is higher in ternary system than in binary system; however, this effect is contrary to that after graphite is precipitated.

The effect of As content on the hot ductility of steel with 0.17 wt.% Cu was investigated at 700–1100 °C using a Gleeble- 3800 thermal–mechanical simulator. The results showed that increasing the As content from 0 to 0.15 wt.% obviously widened the hot ductility trough and pushed the trough into the high-temperature regime. Meanwhile, when the As content exceeded 0.10 wt.%, significant hot ductility deterioration was found. In the ferrite-austenite two-phase regions of 700–800 °C, the fracture appearance changed from dimple ductile to intergranular ductile or from intergranular ductile to intergranular decohesion with increasing As content. The inhibition formation of proeutectoid ferrite and austenite grain coarsening were responsible for the slight hot ductility deterioration by As in the two-phase region. In the austenite singlephase region above 850 °C, the fracture appearance changed from dimple ductile to intergranular decohesion with increasing As content, especially at 850–950 °C. Suppression of dynamic recrystallization and grain boundary segregation of As resulted in serious damage of the hot ductility and widened the ductility trough in the single-phase region.

The free surface waves of a molten lowmelting point Sn32%Pb52%Bi alloy under the imposition of an AC and a static magnetic field were visualized and recorded by use of a laser displacement sensor and a high speed video camera. The Fourier analysis method was used to analyze the oscillation characteristics. The results show that at the center of the free surface, the azimuthal and radial oscillation mode can be found simultaneously owing to AC magnetic field. With increasing coil current intensity, the amplitude and the main frequencies of the oscillations increase, and the azimuthal fluctuation at the center of the free surface is also enhanced. The fluctuation characteristics are closely related to the turbulent flow induced by the alternating electromagnetic force. A series of regular traveling waves can be observed on free surface, and the main frequencies of oscillations at threephase points decrease owing to superposing AC and static magnetic field. The static magnetic field can remarkably control the unstable swinging behavior of free surface. With increasing static magnetic flux density, the amplitude of oscillations at the center of free surface decreases firstly, and then increases, but the fluctuation amplitude at the triplephase point always reduces and keeps within 1 mm, and the azimuthal waves at the center of free surface are weakened. Especially at 144 T, the radial waves are dominant. The static magnetic flux density should be controlled in an appropriate range to obtain more stable free surface. With compound magnetic field, even if the static magnetic flux density is above 10 T, the free surface still vibrates with lower amplitude and dominant frequency.

Inclusion has an important effect on quality of high speed rail steel. In consideration of the lower acceptance percentage of the inclusion and its constraint against the requirement for large scale production of 350 km/h high speed rail steel in Panzhihua Iron and Steel (Group) Co, the technology of nonmetallic inclusion control for 350 km/h high speed rail steel was studied. An optimized model of the argon-blowing in ladle furnace (LF), the control of the components of the ladle slag, and the technique of calcium treatment for the molten steel was brought forward. Using the researched technology, the removal ratio of the inclusion was increased and the components, distribution, and shape of the inclusion in the rail steel were changed, which resulted in a reduction in the average total oxygen content to 10. 17×10-6 and an increase in the comprehensive acceptance percentage of the nonmetallic inclusion from 48. 21% to 98. 1%. Test has shown that this metallurgical technology can meet the requirement for large scale production of 350 km/h high speed steel in Panzhihua Iron and Steel (Group) Co.

Chemical heterogeneity in high-temperature austenite is an effective way to tune the austenite-to-martensite transformation during cooling. The effect of quenching temperature on microstructure evolution is investigated when the high-temperature austenite is heterogeneous. After fast austenitization from partitioned pearlite consisting of Mn-enriched cementite and Mn-depleted ferrite in Fe–0.29C–3.76Mn–1.50Si (wt.%) steel, quenching to room temperature and quenching to 130 °C followed by 400 °C partitioning are both applied. With increasing quenching temperature from 25 to 130 °C, the amount of heterogeneous microstructure (lamellar ghost pearlite) increases from 10.6% to 33.6% and the thickness of Mn-enriched retained austenite film is increased from 31.9 ± 5.9 to 51.5 ± 4.4 nm, indicating an enhancement of chemical patterning. It is probably ascribed to the reduction in driving force for austenite-to-martensite transformation, which requires a lower Mn content for austenite retention.

It was very difficult for the smelting of vanadiumbearing titanomagnetite by blast furnace because the content of TiO2 of blast furnace slag could amount to 20%-25%. After long term development and continuous improvement, special intensified smelting technologies for vanadiumbearing titanomagnetite by blast furnace were obtained and improved gradually. With the improvement of beneficiated material level and equipment level, smelting intensity has been increased gradually and the highest comprehensive smelting intensity reached 145 t/(m3·d). Technicaleconomic indexes of blast furnace have also been increased remarkably. The highest utilization coefficient exceeded 27 t/(m3·d) on the condition that the burden grade was only about 50%.

A study on the production of low phosphorus steel by double slag operation in 210 t converter was carried out. A phosphorus content of less than 0. 005% (mass percent) was obtained before tapping. About 80% phosphorus could be removed by the first slag after 5 min. High Fe3+ content and high basicity in the first slag were in favor of dephosphorization. On the other hand, Fe3+ content had less effect on dephosphorization during second slag treatment. In the second slag period, the fraction of dephosphorization increased with the increase of basicity up to a basicity of 6. Further increase of basicity of the second slag had very little effect on dephosphorization. The tapping temperature had great impact on dephosphorization. It was impossible to get phosphorus less that 0. 005% when the tapping temperature was higher than 1 943 K. The optimum operation conditions were suggested. On the basis of these conditions, the amount of the second slag and the effect of the remaining first slag were estimated.

The effect of oxygen on the microstructure evolution and glass formation of Zr-based bulk metallic glasses (BMGs) was studied in detail. It was found that oxygen did not form oxides or dissolve in glass matrix, but induced the precipitation of α-Zr which has the high affinity and solubility of oxygen in the Zr-based bulk metallic glass (Zr-BMG). With the precipitation of α-Zr, the remaining melts contain much lower oxygen content and have strong glass formation, resulting in the formation of α-Zr/BMG composite. The findings provide an important insight into the mechanism of the oxygen on glass formation, and give us a useful guideline to avoid the oxygen detrimental for designing new BMGs.

To achieve high-efficiency utilization of complex and unmanageable iron-containing minerals, the effects of oxygen enrichment on productivity, yield, flame front speed, exhaust gas peak temperature, and desulphurization reaction of the vanadium–titanium magnetite sintering process as well as sinter tumble index and mineralogy were clarified, with oxygen enrichment concentrations ranging from 21 to 29 vol.%. Results indicated that with increasing the oxygen enrichment concentration from 21 to 27 vol.%, the flame front speed increased from 30.3 to 40.0 mm min-1, the yield enhanced from 72% to 77%, and the productivity augmented from 1.83 to 2.67 t m-2 h-1; in the meantime, the tumble index was improved from 73.7% to 77.9%, and the exhaust gas peak temperature rose from 376.4 to 484.8 °C. The main reason for the improvement in sintering properties was the increased combustibility of fuels and the generation of proper liquid phase that improved the permeability of the packed bed. The improved sinter strength is mainly due to the increase in the phase fraction of silico-ferrites of calcium and aluminium. In addition, oxygen enrichment sintering could significantly increase the desulphurization level of vanadium–titanium magnetite sinter and the rate of desulphurization reaction during sintering process.

The cross-section profile is a key signal for evaluating hot-rolled strip quality, and ignoring its defects can easily lead to a final failure. The characteristics of complex curve, significant irregular fluctuation and imperfect sample data make it a challenge of recognizing cross-section defects, and current industrial judgment methods rely excessively on human decision making. A novel stacked denoising autoencoders (SDAE) model optimized with support vector machine (SVM) theory was proposed for the recognition of cross-section defects. Firstly, interpolation filtering and principal component analysis were employed to linearly reduce the data dimensionality of the profile curve. Secondly, the deep learning algorithm SDAE was used layer by layer for greedy unsupervised feature learning, and its final layer of back-propagation neural network was replaced by SVM for supervised learning of the final features, and the final model SDAE_SVM was obtained by further optimizing the entire network parameters via error back-propagation. Finally, the curve mirroring and combination stitching methods were used as data augmentation for the training set, which dealt with the problem of sample imbalance in the original data set, and the accuracy of cross-section defect prediction was further improved. The approach was applied in a 1780-mm hot rolling line of a steel mill to achieve the automatic diagnosis and classification of defects in cross-section profile of hot-rolled strip, which helps to reduce flatness quality concerns in downstream processes.

The hot rolling and cold rolling control models of silicon steel strip were examined. Shape control of silicon steel strip of hot rolling was a theoretical analysis model, and the shape control of cold rolling was a data-based prediction model. The mathematical model of the hot-rolled silicon steel section, including the crown genetic model, inter-stand crown recovery model, and hot-rolled strip section prediction model, is used to control the shape of hot-rolled strip. The cold rolling shape control is mainly based on Takagi-Sugeno fuzzy network, which is used to simulate and predict the transverse thickness difference of cold-rolled silicon steel strip. Finally, a predictive model for the transverse thickness difference of silicon steel strips is developed to provide a new quality control method of transverse thickness of combined hot and cold rolling to improve the strip profile quality and increase economic efficiency. The qualified rate of the non-oriented silicon steel strip is finally obtained by applying this model, and it has been steadily upgraded to meet the needs of product quality and flexible production.

To address the complex structures, large out-of-tolerance issues, and inconsistent quality of double-walled turbine blades, a mapping relationship between the structure and deformation was established based on a structural correlation study. Numerical simulations and pouring experiments were carried out based on the designed double-walled model, and a reliable displacement field model of the double-walled blade was established. A decoupling method for the displacement field of the double-walled blade castings was proposed, which decoupled the displacement field into bending, torsion, and expansion/shrinkage deformation vectors. Based on the displacement field analysis of the theoretical and physical models, an expansion/shrinkage model of double-walled blade structure castings was established. Furthermore, an experiment to determine the mapping relationship between double-walled construction and deformation was designed, which included the characteristic distribution distance and designed angle as structural parameters. The functional relationship between the deformation and the structural parameters was established based on a nonlinear regression method.

The utilization of highly reactive and high-strength coke can enhance the efficiency of blast furnace by promoting indirect reduction of iron oxides. Iron compounds, as the main constituent in iron-bearing minerals, have aroused wide interest in preparation of highly reactive iron coke. However, the effects of iron compounds on pyrolysis behavior of coal and metallurgical properties of resultant cokes are still unclear. Thus, three iron compounds, ie., Fe3O4, Fe2O3 and FeC2O4·2H2O, were adopted to investigate their effects on coal pyrolysis behavior and metallurgical properties of the resultant cokes. The results show that iron compounds have slight effects on the thermal behavior of coal blend originated from thermogravimetric and differential thermogravimetric curves. The apparent activation energy varies with different iron compounds ranging from 9485 to 11011 kJ/mol in the primary pyrolysis process, while lower apparent activation energy is required for the secondary pyrolysis process. Iron compounds have an adverse influence on the mechanical properties and carbon structure of cokes. Strong correlations exist among coke reactivity, coke strength after reaction, and the content of metallic iron in cokes or the values of crystallite stacking height, which reflect the dependency of thermal property on metallic iron content and carbon structure of cokes.

Modified mathematical models based on imaginary plane zone method in reheating furnace were developed in which non-gray radiation properties of gas were considered, and the Newton′s method and the finite difference method were adopted. Effects of productivity, fuel consumption, fuel-air ratio, calorific value of fuel and inserting depth of thermocouple on total heat exchange factor along the length of reheating furnace were investigated. The results show that total heat exchange factor increases with productivity or inserting depth of thermocouple, and it decreases when fuel consumption, fuel-air ratio or calorific value of fuel increases. The results are valuable for dynamical compensation of total heat exchange factor for online control mathematical models in reheating furnace.

The melting characteristics and wettability of the binding phase in high basicity sinter were studied. By changing nCaO∶nFe2O3 (molar ratio of CaO to Fe2O3) as well as the percentage of MgO, SiO2, and Al2O3, the melting characteristics and wettability of the binding phase were discussed. The results indicated that the characteristic melting temperature was the lowest and wettability was the best at nCaO∶nFe2O3=1∶1 (without addition); the addition of MgO increased the characteristic melting temperature and contact angles; when the percentage of SiO2 or Al2O3 was 3%, the characteristic melting temperature was the lowest, whereas the contact angles increased with an increase in SiO2 and Al2O3 contents.

A model of deformation resistance during hot strip rolling was established based on generalized additive model. Firstly, a data modeling method based on generalized additive model was given. It included the selection of dependent variable and independent variables of the model, the link function of dependent variable and smoothing functional form of each independent variable, estimating process of the link function and smooth functions, and the last model modification. Then, the practical modeling test was carried out based on a large amount of hot rolling process data. An integrated variable was proposed to reflect the effects of different chemical compositions such as carbon, silicon, manganese, nickel, chromium, niobium, etc. The integrated chemical composition, strain, strain rate and rolling temperature were selected as independent variables and the cubic spline as the smooth function for them. The modeling process of deformation resistance was realized by SAS software, and the influence curves of the independent variables on deformation resistance were obtained by local scoring algorithm. Some interesting phenomena were found, for example, there is a critical value of strain rate, and the deformation resistance increases before this value and then decreases. The results confirm that the new model has higher prediction accuracy than traditional ones and is suitable for carbon steel, microalloyed steel, alloyed steel and other steel grades.

Remelting rejected electrolytic manganese metal (EMM) scrap was investigated by electroslag remelting (ESR) process through industrial experiment. The results indicated that the ANF-6 slag (70 wt.% CaF₂ + 30 wt.% Al₂O₃) and deoxidizer could promote the desulfurization of ESR manganese in an air atmosphere. Under an air atmosphere, the sulfur in the ingot decreased to 0.0534 wt.% with a desulfurization ratio of ESR manganese of 53.2% by using ANF-6 slag and water-cooled copper electrode electroslag remelting rejected EMM scrap, suggesting its efficient removal. The electroslag ingots exhibited uneven chemical composition in an air atmosphere and cooling condition of the ESR process. The metal manganese could be oxidized by electroslag remelting of rejected EMM scrap in an air atmosphere with MnO content in the final slag of 21.9 wt.%. Besides, the activity of MnO in slag increased with increasing remelting temperature, resulting in a reduction in the slag–manganese sulfur partition ratio and desulfurization ratio. Moreover, with the accumulation of sulfur in slag and the oxidation of metallic manganese liquid, the slag showed a lower cleanliness and more oxidation, leading to an increase in sulfur and oxygen content in the electroslag ingot with the increase in ingot height.

The effects of the content of rare earth elements on the microstructure and properties of hot-dip Zn–5Al alloy steel wire for bridge cables were investigated. The microstructure of the hot-dip coating was analyzed using an optical microscope and a scanning electron microscope equipped with an energy-dispersive spectrometer. The bonding force between the hot-dip coating and steel wire was determined by the winding test. The corrosion resistance of the steel wire hot-dip coating was tested by the electrochemical workstation. The hot-dip Zn–5Al alloy coating has a corrosion-resistant structure composed of a zinc-rich phase and an aluminum-rich phase. Due to the enhanced bonding force, the microstructure of the hot-dip coating of the Zn–5Al alloy with rare earth elements is more compact and uniform than that without rare earth elements. The addition of rare earth elements improves the corrosion resistance of Zn–5Al alloy coated steel wire. Due to the rare earth segregation, which prevents the corrosion of the grain boundary and enhances the anti-intergranular corrosion performance, steel wire exhibits the optimum corrosion resistance when the content of rare earth elements is 0.08 wt.%.

How to manufacture the high magnetic induction grain-oriented silicon steel (Hi-B steel) by the process featured with the primary recrystallization annealing was demonstrated, during which nitriding and decarburizing were simultaneously realized in laboratory. By the techniques of optical microscope, scanning electronic microscope and electron backscattered diffraction, both the microstructure and the texture in the samples were characterized. The samples had been subjected to nitriding to different nitrogen contents at two specified temperatures using the two defined microstructural parameters: the grain size inhomogeneity factor σ* and the texture factor AR. The former is the ratio of the mean value to standard deviation of grain sizes; the latter is the ratio of the total volume fraction of the harmful textures to that of beneficial textures including {110}<001>. When the N content increased from 00055% to 00330% after the annealing at both 835 and 875°C, the resultant recrystallized grain size decreased but σ* changed little; whilst the rise of annealing temperature from 835 to 875°C resulted in the increase in both grain size and σ*. Moreover, either the injected N content or temperature had insignificant influence on the components of primary recrystallization texture developed during annealing. However, the increase of temperature led to the decreases in both intensity and volume fraction of {001}<120> and {110}<001> textures but increases in the {114}<481> and γ fiber textures and the resultant decrease of AR.

The cold-rolled 5% medium Mn steel was butt-welded using a fiber laser. The microstructure, distribution of micro-hardness, and tensile properties of the base metal (BM) and welded joint were investigated. The results showed that the fusion zone of the welded joint had the highest microhardness due to the formation of 100% martensite. A finely mixed microstructure of martensite, ferrite, and austenite was formed in the heat-affected zone, and there was no softened zone in this area. The tensile test results indicated that the ultimate tensile strength and yield strength were higher for the joint than for BM. The joint efficiency was approximately 100%. All samples of the welded joint failed at the location of BM during tensile deformation. The fracture surfaces of the BM and welded joint were mainly ductile fractures. The BM and welded joint exhibited strain rate independence of the tensile strength and yield strength at strain rates of 0.01–1 s^-1, while the yield strength of the BM and welded joint increased rapidly when the strain rate reached 5 s^-1 due to changes in the dislocation movement mechanisms. The uniform elongation of the BM and welded joint decreased with increasing strain rate.