The service life of blast furnace is largely determined by the erosion of carbon brick. The experiments were carried out to investigate effects of sulfur and titanium interaction in molten pig iron on erosion of carbon brick. The experimental results show that the erosion of carbon brick was enhanced when the sulfur content increased separately in molten pig iron, however, this effect could be made up by addition of titanium in molten pig iron. The control standard of sulfur content and titanium content in molten pig iron was proposed, which was combined with the operation to delay the erosion of carbon brick. The quantitative relationship between the erosion rate and sulfur and titanium interaction at 1773 K was obtained based on experimental data, when sulfur content increased by 0.01%, the increment of titanium content by 0.015% would be needed to compensate for the effect of sulfur content on the erosion. The mechanism of sulfur and titanium interaction was analyzed through the erosion process of carbon brick, the difference between the influences of two elements on the surface tension and viscosity of molten is the essential cause of the interaction.

For the purpose to describe the change of the viscosity properties of the converter slag during smelting reduction process using aluminum ash as reductant and provide basis for technology development, the viscosity of CaO–MgO–SiO₂–Al₂O₃–FeO slag system at a fixed basicity of 3 was measured with the various ratio of A/(A+F) (w(Al₂O₃)/w(Al₂O₃+FeO)) by the cylinder method, and the structural of the melt was analyzed based on the FTIR and Raman spectroscopy to further explain the evolution behavior of viscosity. The results showed that viscosity of the slag was increased with increasing the ratio of A/(A+F). When this ratio increased from 0.17 to 0.5, the simple network units of the molten slag were polymerized into more complex network structure, resulting in a slow increase in viscosity from 0.65 dPa·s to 0.91 dPa·s at 1873 K. With further increasing this ratio to 1.0, the main structure was converted from silicate structure to aluminate structure. In addition, the polymerization degrees of aluminate units and silicate units both increased, which eventually led to an rapid increase in the viscosity from 0.91 dPa·s to 1.94 dPa·s.

Information of the coke packing condition and its size distribution in the deadman is critical for understanding the blast furnace hearth phenomenon. In this study, a commercial blast furnace was frozen and dissected. It was found that the upper part of the deadman below the taphole was mainly filled with coke and slag. In the area from the height of about 912 mm below the taphole and downward, the hearth was mostly consisted of coke and hot metal and the depth was about 2320 mm. The bottom part of the hearth with a height of 214 mm was coke free and filled only by hot metal. A multi-feature analysis method based on comprehensive image-processing technique was used for measuring the size of the coke and the voidage of the deadman. It was found that the mean sizes of coke in the upper and lower parts of deadman were 34.39 mm and 32.12 mm respectively. The overall mean size of coke was 33.3 mm. The size of the coke in the deadman was reduced by 36% comparing with its original size. At the edge of the deadman, the voidage increased rapidly from 10.7% to 41.1% at the depth of 1.0 m to 2.2 m below the taphole centerline. In the centre of the deadman, the voidage increased slowly from 16.6% to 31.3% and then decreased. The average voidage of the edge and the centre areas were 38% and 25% respectively.

Developments in blast furnace (BF) ironmaking have long focused on low-coke operation. In this study, high-carbon metallic briquettes (HCMB) were prepared using ultrafine iron oxide powders and coal fines for BF application. The preparation conditions were optimized, and the binding mechanism of the briquette was analyzed. The gasification behavior of the optimally prepared HCMB was investigated under conditions simulating the in-furnace environment of the BF, and its application in BF was evaluated through numerical simulations. The results showed that the optimal preparation condition was m_hematite/m_coal = 2.0. The optimally prepared HCMB had a carbon content of 25.6 wt%, cold strength (CS) of 1300 N/briquette, and crushing strength after reaction (CSR) of 2500 N/briquette. The high strength of the briquette was attributed to the iron network binding. The threshold temperature and activation energy of the briquette gasification in the blast furnace were 973 K and 166 kJ/mol, respectively. Simulation results on the HCMB application in a BF of 2500 m³ indicated that mixing HCMB of 5% into the ore burden could save approximately 12.5 kg of coke for producing one ton hot metal from the ore.

The viscous behaviors of CaO-SiO₂-11.00wt%MgO-11.00wt%Al₂O₃-43.00wt%TiO₂ slag systems were investigated by the rotating cylinder method in this paper, and the effects of CaO/SiO₂ on the viscosity, break point temperature and activation energy for viscous flow of slag were analyzed. Meanwhile, the slag structural characterizations were studied by Fourier transformation infrared (FTIR) spectroscopy and Raman spectroscopy, and the phase compositions of pre-melted slags were detected by X-ray diffraction (XRD) analyses. The results show that, when the CaO/SiO₂ increases from 0.20 to 0.80, the viscosity, break point temperature and activation energy for viscous flow of slag decrease. FTIR and Raman spectroscopy results indicate that the complex viscous units in slag are gradually depolymerized with the increase of CaO/SiO₂, which improve the fluidity of slag. The depolymerization mechanism of silicate networks can be expressed by . The complex O–Ti–O deformation units are depolymerized into the simple structural units ( monomers, chains and Ti–O stretching vibrations in 6-coordinated Ti⁴⁺) and the [AlO₄]- tetrahedrons are simplified to the [AlO₆]- octahedrons. In addition, the relative amounts of low melting point complicated pyroxene in the pre-melted slag increase, improving the meltability of slag and decreasing the break point temperature.

The effects of MgO, Al₂O₃ and basicity on the heat capacity and enthalpy change of CaO–SiO₂–MgO–Al₂O₃ slags at 1673 K and 1773 K as well as the thermal stability were investigated. The enthalpy change at 1773 K increased with the addition of Al₂O₃ and MgO, but decreased with increasing basicity. Thus, the higher basicity helped to reduce the heat consumption and fuel ratio of blast furnace. With increasing MgO content, the fluctuations of the temperature and viscosity caused by the reduction of the slag heat quantity decreased. Furthermore, the slag will have a better fluidity and thermal stability when MgO content is greater than 8 mass%. The increase of Al₂O₃ content deteriorated the fluidity and thermal stability of the slag to some extent. When the reduction of the slag heat quantity was fixed, as the basicity increased, the slag temperature increased obviously and the viscosity significantly decreased. Also, the fluctuations of slag temperature and viscosity became less pronounced with increasing basicity. The increase of the basicity was favorable to improve the fluidity and thermal stability of the slag. For the slag system of this experiment, the suitable basicity was 1.10–1.15.

The paper presents a study on the decarburization of pig iron droplets in synthetic BOF slag. The effects of droplet size and slag composition were studied. The results show evidently that the decarburization is very fast in general. One gram of pig iron is mostly decarburized within one minute. The reaction is shown to be faster when many small droplets were employed instead of one big droplet with equal total mass. This is explained by the bigger interfacial area between the liquid slag and the pig iron of the many small particles. It is also interesting to see that the decarburizing reaction in the slag having lower dynamic viscosity and higher FeO activity is slower than in the slag with higher viscosity and lower FeO activity. The slower reaction could be explained by the longer incubation time in this slag.

Transient phenomena during tundish transfer practices have shown to be detrimental for the significance of clean steel production. These have become a distress for steelmakers; for this reason, there is opportunity for innovation in molten steel transfer devices, such as the dissipative ladle shroud. In the present modelling study the performance of this devise is fully analysed in order to quantify its efficiency in the reduction of the emulsification phenomenon and the slag aperture areas using a mathematical model to simulate a real steel-slag-air multiphase system during the ladle change-over practice. The most relevant results show that the convectional ladle shroud delivers a very turbulent steel flow generating strong mixing patterns, entrapping massive amount of air and slag into the tundish bath promoting a continuous emulsification and a permanent aperture of the slag layer. These phenomena are significantly reduced by using the dissipative ladle shroud technology since this innovative design reduces the emulsification phenomenon in more than a 50% and could decrease the steel re-oxidation by the reduction of the slag layer aperture in about 80%, all in comparison to the conventional ladle shroud; these will represent a diminishment in the amount of declassed steel to a less demanding application.

The effects of an axial static magnetic field (ASMF) on the columnar to equiaxed transition (CET) during directionally solidifying GCr18Mo steel were investigated by experiment and numerical simulation. Experimental results show that the CET has been promoted by the increases of the magnetic field intensity and temperature gradient and the decrease of the growth speed. The corresponding numerical simulations verify that a thermoelectric magnetic convection in the melts and a thermoelectric magnetic force acting on the secondary dendrite neck are produced by the interaction between ASMF and a thermoelectric current. Compared the experimental results with the numerical simulations, the mechanism for the CET with ASMF demonstrates that the application of ASMF contributes to the transport of the fragments in the melts and detachment of dendritic side arms. Based on these results, we propose a process window for the CET of GCr18Mo steel with ASMF.

Both physical experiments and mathematical simulations were employed to investigate the transport phenomena involved during Horizontal Single Belt Casting (HSBC) of AA6111 aluminum alloy, using an inclined feeding system. Flow instabilities in the metal delivery system were first analyzed, and it was found that the first impingement gives rise to instabilities in the melt film falling from the slot nozzle of the head box. Meanwhile, this impingement also has the potential to result in air suction. Using the Eulerian multiphase method, the start casting stage is shown to be very short. Its predictions are similar to those from the Volume of Fluid (VOF) method, and both are confirmed by physical experiments. During steady state casting, one can classify the melt into four regions. The “wavy contour” in “Region I” is an instability largely induced by impingement on an inclined refractory piece. “Region II” demonstrates the buffer effect of the inclined refractory wall and the flow must be continuous within it. The resistance force induced by the melt that has flowed just earlier onto the belt, gives rise to “Region III”, which is a transition region. Its transient variations in width determine the quality of the strip’s edges. The thickness of “Region IV” is associated with both “Region II” and “Region III”.

Fluid flow of liquid steel in a slab mold influenced by three different submerged entry nozzles with the same bore sizes but different ports including rectangular, square, and round shape at immersion depth of 185 mm was studied. The analysis includes numerical simulations and physical modeling. The results show that the port shape has great effects over the fluid dynamics of the liquid steel inside the slab mold. The comparison among the three nozzle port designs indicates that the nozzle with square ports, (SEN-S), decrease the jets velocity, promote a symmetrical path inside the mold and decrease the bath level oscillations; representing the best choice to control the turbulence and decrease the quality problems.

The melt flow and bubble motion in a 230×1300 mm² continuous casting slab mold were investigated under different inclination angle, divergent angles and immersion depth of the submerged entry nozzle (SEN) and different argon gas injection rates using a volume of fluid (VOF) and discrete phase model (DPM) to avoid slag entrapment and enhance the removal rate of nonmetallic inclusions. Water-model experiments were conducted to validate the numerical models. Moreover, the optimized conditions were applied in a manufacturing plant. The results showed that the simulated steel/slag level fluctuation and argon bubble trajectories are consistent with the experimental results. The optimized SEN structure has an inclination angle of 20° and a divergent angle of 9°, which can improve the flow pattern in the steel/slag interface, alleviate the level fluctuations, decrease the chance of slag entrapment, and optimize the movement of inclusions. The immersion depth of SEN should be 150 mm, which is beneficial to the floating removal of non-metallic inclusions and reduce the level fluctuation at steel/slag interface. The optimal argon gas blowing rate to avoid slag entrapment near the SEN is 10 L/min. Furthermore, the rate of edge defects (ED) in the hot roll strip induced by slag entrapment is apparently reduced by applying the above conditions.

Shape defect such as bow and crossbow, is one of the major defects in hot rolled sheets. These defects arise due to non-uniform plastic strain (thermal and mechanical) due to improper rolling process. In-turn this non-uniform strain induces residual stress in the rolled material. Hence measurement of residual stress in early stage helps as a Go/No Go tool, while supplying material to customers to whom shape defects are very much problematic during its downstream process. In this paper a non-destructive testing (NDT) technique has been developed to predict the magnitude of bow/crossbow based on residual stress measurement using ultrasonic technique. The technique employs the relationship between residual stress distribution and its corresponding effect towards bow/crossbow formation. The paper also elaborates about residual stress measurement using ultrasonic measurement based on the acousto-elastic theory. It was demonstrated that there exists a distinct relationship between crossbow and residual stress for high strength hot rolled steel sheets experimentally.

In steel industry, product number recognition is necessary for factory automation. Before final production, the billet identification number (BIN) should be checked to prevent mixing billets of different material. There are two types of BINs, namely, paint-type and sticker-type BINs. In addition, the BIN comprises seven to nine alphanumeric characters except the letters I and O. The BIN may be rotated in various directions. Therefore, for proper recognition and accident prevention, end-to-end BIN recognition system that uses the deep learning is proposed. Specifically, interpretation and sticker extraction modules are developed. Furthermore, the fully convolutional network (FCN) with deconvolution layer is used and optimized. To increase the BIN recognition accuracy, the FCN was simulated for various structures and was transferred from the pre-trained model. The BIN is identified by the trained FCN model and interpretation module. If the BIN is sticker-type, it is inferred after the sticker region is extracted by the sticker extraction module. The accuracy of the proposed system was shown to be approximately 99.59% in an eight-day period.

The nitriding behavior of titanium sponges with nitrogen gas and the dissolution behavior of titanium nitride titanium sponges in titanium alloy melt were examined.

A titanium nitride sponge was produced using nitrogen gas. A high nitriding temperature corresponded to a longer nitriding time, and thus to a higher nitrogen concentration in the sponge. Both the titanium sponge and titanium nitride sponge featured a porous structure. Porous structures at both the surface layer and inside were formed at intervals of about 5.0 × 10⁻⁵ m. When the titanium nitride sponge was immersed into a titanium alloy melt, the melt permeated into the pores. The nominal dissolution rate of the titanium nitride sponge in the titanium alloy melt depends on the temperature of the melt. Higher melt temperatures corresponded to higher nominal dissolution rates. However, the concentration of nitrogen in the titanium nitride sponge had no influence on the nominal dissolution rate. Nitriding models of the titanium sponge with nitrogen gas, and the dissolution model of the titanium nitride sponge into the titanium alloy melt were proposed. These models considered the structure of the sponge; thus, the behavior of both the nitriding and dissolution sponges was predicted and confirmed.

Thermo-mechanical controlled process (TMCP) technology has been widely used to improve the mechanical properties of hot-rolled steel plate. Laminar cooling has been the main cooling form in the steel mills. However, the performance of laminar cooling is limited by its low cooling capacity, nonuniformity, and inefficiency. In this work, it was demonstrated that the air-atomized water jet can be applied in the hot-rolled plate manufacturing process with excellent cooling performance. The cooling efficiency of the steel plate (700°C) was significantly improved by applying air-atomized jet (AJ) with different water densities compared with impinging jet (IJ). Moreover, the local spray density, boiling curves at different positions and the corresponding average heat flux of both cooling methods were systematically investigated by mathematical correlations. The experimental data in this study would be beneficial for design and simulation of the cooling device to achieve better cooling rate and uniformity.

The modelling of the precipitation and growth behaviour of the sigma phase in super duplex stainless steel was investigated to clarify the quantitative effects of chemistry. The alloying elements of Cr and Mo useful for improving of corrosion resistance can promote sigma phase precipitation but that phase does not always grow rapidly. Therefore it is meaningful to clarify the effect of alloying elements on the kinetics of sigma phase growth to improve the trade-off relation between the corrosion resistance and avoiding harmful phase precipitation.

A physical model regarding sigma phase growth rate as a function of temperature and the parameters regarding the amount of allying elements in the steel was suggested on the basis of the traditional nucleation theory during isothermal heating process. It was confirmed that the physical model suggested in this work explains the experimental results of the effects of temperature and alloying elements of CR, MO and Won the growth rate of the sigma phase.

The time-temperature-precipitation (TTP) diagram called as C-curve of the sigma phase in duplex stainless steel was investigated to clarify the effect of each amount of alloying elements. Because of the trade-off between the improvement for corrosion resistance and avoiding the sigma phase precipitation regarding the increase of Cr and Mo, it is important to clarify the effect of each alloying elements on the nose temperature and time of the TTP curve which indicates the critical heating condition to be free from harmful phase precipitation.

By using 25/28%Cr duplex stainless steel containing various levels of Cr, Mo and W, the TTP curve was obtained experimentally via the microstructure observation test with an optical microscope after heating at various temperatures. The calculated TTP curves were also obtained from the physical model of sigma phase growth rate which has been proposed in the previous work by the authors of this work. Those calculated TTP curves almost agreed with the experimental results. It was possible to explain the influence of alloying elements of Cr, Mo and W on the TTP curve from the effect on the parameters in the kinetic model proposed.

Fusion zone microstructural evolution of Al-10% Si coated hot stamping steel during laser welding and its mechanical properties were investigated in this study. During laser welding, a liquidized Al-10% Si coating penetrated along the fusion boundary to form δ-ferrite. After hot stamping heat treatment, the final microstructure was composed of a martensite-ferrite dual phase. The dual phase formation causes mixed mode fracture (brittle fracture + ductile fracture) at the fusion zone due to the hardness difference between the martensite and ferrite phases. This issue can be addressed by applying filler wire or by changing the coating system from an Al-based coating to a Zn-based coating.

To investigate the effect of iron texture on the crystal orientation relationship between iron and zinc, Zn deposition was performed galvanostatically at 1500 A/m² at a charge density of 1.48 × 10⁴ C/m² onto high-purity electrolytic iron and cold rolled steel sheets in an agitated sulfate solution at 40°C. Fe with a large grain size showed an orientation relationship of {110}Fe//{0001}Zn. However, when the angle of inclination between the {110}Fe plane and the surface of electrolytic Fe was increased, the deviation in the orientation relationship {110}Fe//{0001}Zn increased. This result suggests that the orientation relationship of {110}Fe//{0001}Zn is difficult to maintain during the deposition when the inclination angle of the {110}Fe plane from the surface of electrolytic Fe increases. As a result, the epitaxial growth of Zn changes to random growth. Zn deposited on cold rolled steel sheets with a small grain size showed an orientation of {0001}, regardless of the orientation of Fe. This indicates that the orientation of the deposited Zn is more affected by the overpotential for deposition than by the orientation of steel sheets at the initial stage of deposition. Although strain was introduced into the high-purity electrolytic Fe with sandblasting, the orientation relationship of {110}Fe//{0001}Zn did not change remarkably, showing that the strain of Fe substrate has little effect on the orientation relationship between Fe and deposited Zn.

The decarburization experiments were carried out at different annealing temperatures, P_H2O/P_H2 and times. Under the annealing conditions in present work, the optimum annealing condition of decarburization was that annealing temperature was 1108 K under P_H2O/P_H2=0.317. The oxides morphology in oxidized layer was studied. The concentration distribution of silicon and oxygen along the oxidized depth was analyzed. The relationship between oxides phases, oxides morphology and concentration distribution of silicon and oxygen was established. Results showed four zones presented in oxidized layer from the atmosphere/steel interface to the steel matrix, which were enriched zone of oxides, depleted zone of oxides, spherical zone of oxides and lamellar zone of oxides in sequence. The oxidized layer of Fe-3%Si steel was composed of iron oxide, fayalite and silica. With the increase of oxidized depth, there was still some unreacted silicon atoms remained in the oxidized layer.

The microstructure and hardness of martensite in Fe–C and Fe–N alloys with up to 7.5 at% contents of carbon and nitrogen, respectively, were compared. Their difference in hardness was discussed based on four strengthening mechanisms. The martensitic structures of Fe–C and Fe–N alloys with equal contents of carbon and nitrogen, respectively, were nearly identical, except for the amount of retained austenite. Furthermore, Fe–C alloy was considerably harder than Fe–N alloy. This discrepancy gradually increased with carbon and nitrogen contents. The enhanced hardness of Fe–C alloy martensite was attributed to its higher dislocation density and the stronger pinning force of interstitial carbon atoms on dislocations.

Due to the volume change accompanying the fcc to bcc or bct crystal structures in steels, it is a common practice to determine phase transformation temperatures using dilatometry. The martensite start temperature (M_s) is often of particular interest. Experimentally, it is found that the start of the martensite transformation is not indicated by a sharp change in the slope of the dilatation curve as is predicted by the Koistinen – Marburger equation. Rather, there is a gradual change in the slope such that the martensite start temperature is ill-defined. The current work shows that this gradual change in slope can be related to chemical inhomogeneity in the steel caused by interdendritic microsegregation. It is shown that combining the Koistinen – Marburger equation with measured concentration profiles allows experimental dilatation curves to be well predicted.

The deformation behavior of an Advance High Strength Steel (AHSS) with a composition of 0.22C-1Si-2Mn was investigated by means of dynamic processing maps. The flow stress curves, which were determined by tensile tests within the temperature range of 1173 and 1573 K and at strain rates between 10⁻³ and 1 s⁻¹, were used for constructing the processing maps based on the Dynamic Materials Modeling approach (DMM). These maps were used to evaluate the optimum thermomechanical processing conditions by identifying the stable “safe” regions for plastic flow. Microstructure and fracture analysis of the test samples was performed and correlated to the processing maps. This analysis was used for determining the “safe” domains within the maps whereby plastic flow can be optimum for processing the material. This study will allow us in determining optimal industrial processing routes for producing these steels and to achieve the highest quality of the end product.

Fatigue crack initiation and propagation behavior of a water-quenched fully ferritic nitrogen steel were investigated by means of tension-compression fatigue tests. The Fe–0.011 mass% N steel showed no serrated flow associated with dynamic strain aging, and showed a fatigue limit of 150 MPa alongside a non-propagating fatigue crack. The major mode of crack initiation was at the grain boundaries, and the cracks propagated along the grain boundaries and interiors at and above the fatigue limit. The Fe–N steel did not exhibit a significant level of coaxing effect. The results were compared with our previous findings in Fe–0.006 and 0.017C steels, and the similarity and difference were discussed.

Soft magnetic powder compacts can suppress eddy current loss compared to conventional laminated cores. However, the compacts accompany greater hysteresis losses because the easy magnetization axes are not controlled in powders. In this study, a novel soft magnetic compact was prepared from a platelet-shaped iron powder with well-controlled easy magnetization axes and its effects on magnetic properties and crystal orientation of the compact were investigated. Such platelet iron powder was produced using a ball-milling process. During milling, the iron powder was subjected to the deformation, resulting in the shape change to the platelet. Simultaneously, a (001) fiber texture was formed preferentially, as it is characteristic of the deformed bcc metal. The powder was then compacted into a toroidal shape. The platelet surface of the powder was oriented so as to become parallel to the toroidal direction. Consequently, the easy magnetization axis, which lies along the platelet surface, was also oriented to the toroidal direction. The toroidal compact prepared in this way exhibited excellent magnetic properties. For example, the permeability was approximately 2.4 times higher than that of the compact prepared from a conventional iron powder.

Blast furnace sludge (BFS) is an industrial waste generated during ironmaking, which contains approximately 10% Zn, 25% Fe and 24% C and is a valuable secondary resource of zinc. In this study, ZnSO₄·7H₂O was produced using BFS by the combination of acid leaching, iron and calcium precipitation, concentration and crystallization. The effects of different factors and operation steps on zinc recovery were investigated, and the optimum parameters of the treatment process were obtained as follows: Acid leaching was carried out at 60°C for 10 min using sulfuric acid with the concentration of 150 g/L and a liquid to solid ratio at 3 mL/g; Iron precipitation was performed at 25°C using the liquid solution with pH value in a range of 4.0–4.4 and the H₂O₂ dosage of 60 mL/L; Calcium precipitation was conducted at 60°C for 40 min with the ZnF₂ dosage of 7.5 g/L. The recovery efficiency of zinc was approximately 95% and the purity of ZnSO₄·7H₂O in the product reached 99.57%. The obtained results indicate that the proposed process in this work can successfully recover Zn from BFS with high efficiency and short production route.