The influences of SO₂ in the recirculation flue gas on the sintering process are studied through simulating the flue gas recirculation with sinter pot test at room temperature. The results show that, with the increasing concentration of SO₂, the SO₂ is absorbed by CaO,the surface of CaO particles will generate CaSO₄ which affects the formation of binding phase, so the sinter yield and particle size will decrease. The residual sulfur in sinter ore will increase obviously when SO₂ concentration is higher than 500ppm, the residual sulfur of middle sinter ore in 2000ppm is 1.54 times higher than that in 500ppm. Meanwhile, the SO₂ peak concentration in flue gas is enriched, which is conductive for the end-of-pipe treatment of SO₂. The RI of sinter ore is increased and softening and melting properties become better, because the consumption of CaO affects the formation of calcium ferrite and increases the reduction rate and melting point of sinter ore, another reason is that the decomposition of CaSO₄ leads to an increase in the porosity in the sinter, and the higher porosity makes the sinter expose more surface area to the reduced body, and the RI of the sinter increase. Therefore, adding an appropriate amount of SO₂ in the sintering process can improve the quality of the sinter, and if the SO₂ content is too high, it will affect the formation of the binder phase and reduce the strength and yield of the sinter.

To investigate the factor that cause the variation in friction coefficient by sliding conditions in commercially pure titanium coated titanium oxide film, in-situ observation of sliding interface during ball on block test and EBSD analysis of a sliding cross-section were performed. At the vertical load of 0.1 N, the friction coefficient stabilized at a low level of approximately 0.12. However, at 0.5 N, the friction coefficient varying widely in the range of 0.20–0.80. At 2.0 and 4.0 N, the friction coefficient stabilized at a high level, approximately 0.30 and 0.40, respectively. At the vertical load of 0.5 N, the friction coefficient was negatively correlated to the Taylor factor for the uniaxial compression of the titanium grains directly beneath the film . Thus, it can be presumed that the ploughing term of friction coefficient increased due to the enhancement of compressive strain of titanium. On the other hands, at vertical loads of 2.0 and 4.0 N, the ball is always in contact with multiple grains due to the larger contact area. As a result, it is considered that the influence of Taylor factor was equalized and the variation of friction coefficient got smaller.

The amount of martensite in austenitic stainless steels produced during plastic deformation at low temperatures is related to the reduction in hydrogen embrittlement resistance. A pre-strain at 4 K was employed in this work to produce strain-induced martensite (SIM) in the microstructure of SUS316L and its weldment to verify the changes in hydrogen embrittlement susceptibility through slow strain tensile (SSRT) tests in a high-pressure hydrogen environment. As the base metal specimens, the weld metal specimens, manufactured by gas tungsten arc welding (GTAW or TIG) were pre-strained at different levels (5%, 10%, and 15%) for comparison with the non-pre-strained condition. Analysis of the most degraded samples tested from -150 °C to 0 °C is conducted through fracture surface observations, lateral crack length measurement, and crack densities. It was possible to indicate that the pre-strain effect induced earlier crack nucleation in comparison to the situation observed in the non-pre-strained material. Moreover, the pre-existing martensite produced by the pre-strain at 4 K is responsible for earlier crack nucleation, leading to a loss in the hydrogen embrittlement resistance for the SSRT pre-strained base metal specimens.

For the analytical model of rolling force of ultra-thin strip, the iterative conditions of the exit plastic zone are improved to solve the convergence problem of the Fleck model in small reduction rolling. The nonlinear law of friction coefficient in multi-pass rolling is analyzed, and the friction coefficient database for sample data is established through the friction coefficient calculation model, which is used GWO-KELM neural network training friction coefficient prediction model, the Fleck rolling force prediction model based on the modified friction coefficient is established ultimately. A comparative analysis of prediction errors is conducted on three different specifications of strip steel using actual production data from a multifunctional 280 mm 20-high mill. The results show that the best performing MSE, RMSE, MAE, MAPE and R2, with values of 170.48, 13.06 kN, 9.01 kN, 3.30%, and 0.989, respectively. The accuracy of the modified rolling force prediction model is significantly improved, and the data scale of friction coefficient database can be continuously expanded, so the accuracy of the rolling force prediction model can be continuously improved.

This paper reviews studies on the prediction of ductile fracture during metal forming using an ellipsoidal void model and some other models proposed by the author and some relevant studies. Section 2 discusses the research on the theory of voids for predicting ductile fracture during metal forming. Section 3 summarizes the simulation method for predicting ductile fracture during metal forming using the ellipsoidal void model, and Section 4 summarizes the simulation result on the ductile fracture prediction during metal forming using the ellipsoidal void model. Section 5 shows the applicability of the ellipsoidal void model and the simulation result on the ductile fracture prediction during metal forming using some other models.

It is well known that Ni-advanced weathering steels considerably improve the protectiveness of rust layers and drastically reduce corrosion rate compared with the conventional weathering steels. However, unpainted Ni-advanced weathering steels are not suitable for use in high-chloride environments because of no formation of protective rust layers. To expand the application of Ni-advanced weathering steels, it is imperative to understand in detail their corrosion behavior in high-chloride environments. In this study, the effect of Ni addition on the atmospheric corrosion behavior of carbon steels was explored through a wet-dry cyclic corrosion test and potentiodynamic polarization measurements in a simulated high-chloride environment. In particular, the study focused on corrosion morphology and analyzed the distribution of corrosion depth after the corrosion test. During the corrosion test, the protective rust layers did not seem to form on all the specimens due to the high-chloride condition. Nevertheless, the corrosion rates decreased with increasing Ni addition to steels. Corrosion morphology analysis revealed that the Ni addition suppressed relatively uniform corrosions on the entire surface and the growth of deep hole-like corrosions. Anodic polarization curves showed that the Ni addition suppressed the dissolution of the steel matrix, which led to the atmospheric corrosion properties of 2.5Ni-WS and 5Ni-WS in inhibiting relatively uniform corrosion and the growth of deep hole-like corrosions. The change in the electrochemical properties of the steel matrix due to the Ni addition significantly affects the atmospheric corrosion behavior of carbon steels in high-chloride environments.

This study investigated the fundamental aspects of signal enhancement in arc-plasma-assisted laser-induced breakdown spectroscopy (AP-LIBS), as a crucial step towards its potential application for enhanced real-time compositional analysis in electric arc furnaces (EAF). By superimposing a sustained arc discharge with nanosecond laser pulses on molten iron, AP-LIBS achieved significant signal enhancement compared with conventional LIBS. Spatiotemporal characterizations revealed that the enhancement was most pronounced in the peripheral plasma region, characterized by larger plasma size and longer lifetime in AP-LIBS setups. The enhancement factor η, defined as the ratio of AP-LIBS signal intensity to the sum of individual arc and laser-induced plasma intensities, exceeds 10 for most emission species. Spatial distribution analyses show increased emission intensities at greater distances from the laser spot in AP-LIBS, in contrast to the decay observed in standard LIBS. Temporal analysis demonstrated extended high-intensity periods for AP-LIBS compared to the rapid decay in conventional LIBS techniques. The spatiotemporal behavior of the enhancement factor varies significantly among the emission species, thereby providing insights into complex plasma dynamics. Elements with low vapor pressure and ionic species generally exhibited higher enhancement, whereas elements with high vapor pressure exhibited limited enhancement, indicating minimal additional evaporation effects for high vapor pressure element. These findings provide valuable insights into plasma generation and maintenance mechanisms in AP-LIBS, suggesting its potential for improved sensitivity in elemental analysis for electric arc furnace applications.

Assuming that heat is transported by lattice vibrations (phonons) in silicate glasses, their thermal conductivity is correlated with the product of sound velocity, volumetric heat capacity, and phonon mean free path (MFP). The sound velocity and heat capacity have been studied extensively, but the origin of the composition-induced variation in the MFP remains unclear. The present study investigated MFP in M_2/nO–SiO₂ (Mⁿ⁺: Li⁺, Na⁺, Ca²⁺, Sr²⁺, or Pb²⁺) glasses with a variation of M_2/nO content. The MFP of the silica glass decreased with the addition of M_2/nO. The effect of the type of metallic cation on the MFP was minimal for the selected alkali and alkaline-earth silicate glasses. By contrast, the MFP of lead silicate glasses was higher than those of alkali or alkaline-earth silicate glasses when the metallic cation contents were comparable. Previous studies have demonstrated that alkali and alkaline-earth cations act as nonframework species that break the silicate network structure, whereas lead cations have inconclusive structural roles. Our data indicate that lead cations partly act as framework cations and that phonons tend to be scattered near nonframework cations in silicate glasses. Thus, the phonon MFP is a useful parameter for determining the structural role of metallic cations in silicate glass via phonon propagation.

Currently, research and developments are underway for steel production using hydrogen-direct reduced iron and large-scale electric arc furnace (EAF). Fe₃C has attracted attention as a carburizing agent and clean source of iron for EAF steel production to lower the concentration of impurities. However, production capacity of cementite is low since the carbonization reaction rate of reduced iron pellet is limited by gas diffusion inside micropores in the pellet.

In this study, the carbonization reaction rate of porous iron whisker with approximately 95% of porosity was examined. The porous iron whisker can be produced through carbothermal reduction of fine iron ore and biochar mixture. The carbonization reaction rate of the porous iron whisker was approximately three times faster than that of fine iron particles. The porous iron whisker has advantageous for rapid cementite production compared to fine iron particles since the effective surface area is larger in the porous iron.

This study investigates the effect of P addition on the corrosion resistance of steels before and after rust formation. Electrochemical measurements and surface analysis of P-containing steels (Fe-0.5 mass% P, Fe-1.0 mass% P, and Fe-1.5 mass% P) were conducted to analyze the contribution of P to their initial corrosion resistance before rust formation. The results showed that the initial corrosion resistance of the steel worsened with increasing P content. According to the surface analysis conducted by SEM/EDS, more P segregations at the grain boundaries occurred with higher P content. Polarization measurements indicated that these P segregations became initiation sites for localized corrosion, resulting in a decrease in the initial corrosion resistance.

Although the initial corrosion resistance was worse with higher P content, the long-term corrosion resistance showed the inverse trend, improving with increasing P content. Atmospheric exposure tests at Miyakojima and surface analysis of the rust layers showed that P was incorporated into the rust layer, and it promoted the protective ability against corrosion.

Iron ore sintering is a high-energy-consuming industry, and its high dependence on fossil fuels and the low concentration of CO in the sintering flue gas conceal the truth of the large total amount of CO emissions, which leads to the continuous emission of CO in the sintering flue gas has been harmful to the atmosphere and human health, and it is facing the great pressure of CO emission reduction. On the basis of commercially applied sintering technologies, the mechanism and characteristics of CO emission from sintering flue gas are discussed, and feasible ways to control CO emission in multiple aspects of source control, process emission reduction and end-of-pipe treatment are summarized. The core of source abatement is to reduce the fuel ratio, process abatement is to improve the combustion conditions of fuels to enhance the conversion rate of CO to CO₂, and end-of-pipe treatment is to separate or oxidize CO to CO₂ by physical or chemical means. hydrogen sintering technology is the future development direction for source abatement, steam blowing sintering technology is introduced for process control, and catalytic oxidation technology has great prospects for removing CO from flue gas in end-of-pipe treatment. CO has great prospects, but efforts are needed to develop highly active catalysts with anti-poisoning and long-standing stability. Finally, feasible technical routes for sintering flue gas CO reduction and their challenges are analyzed, and a coordinated multifaceted control of source-process-end sintering technologies is proposed to achieve the goal of high-efficiency sintering flue gas CO reduction.

This work demonstrated that the silicon carbide addition to pre-alloyed Fe-Mo powder could result either in the formation of steel or iron microstructure depending on the added silicon carbide content. With 1.0 wt. % silicon carbide addition, slowly cooled sintered Fe-Mo-Si-C alloys showed steel microstructures consisting of proeutectoid ferrite and eutectoid transformation product in the form of ferrite + carbide mixture. With 2.0 wt. % silicon carbide addition, slowly cooled sintered Fe-Mo-Si-C alloys with Mo contents of ≥ 0.85 wt.% microstructures comprised ferrite + austenite constituents in the forms of either degenerate upper bainite or ausferrite. With ≥ 3.0 wt. % silicon carbide addition, ductile iron-like microstructures were developed in sintered Fe-Mo-Si-C alloys. The change of microstructures in experimental sintered alloys was attributed to the combined effect of alloying molybdenum, silicon, and carbon elements. Tensile strength and hardness increased with increasing added SiC content while ductility varied with microstructural components.

The copper was the main manufacturing material to produce the coherent lance for enhancing the cooling effect. Due to the low hardness of copper and high-temperature environment, the exit of Laval nozzle would be worn off, resulting in suppressing the impaction ability of supersonic oxygen jet. In order to investigate the effect of wear length on the behavior of coherent jet, both high-temperature experiment and numerical simulation have been carried out, and the axial velocity, total temperature and oxygen fraction were measured in the experimental test to verify the accuracy of simulation model. Based on the result, the overexpand phenomenon was generated due to the Laval nozzle exit wear off, which improved the shock wave intensity at the tip of Laval nozzle, resulting in a lower axial velocity at the velocity potential core. With a longer wear length, the vorticity of the coherent jet periphery is increased, which causes more thermal energy of combustion flame being released prematurely near the coherent lance tip, leading to a shorter velocity potential core.

Ferritic stainless steels are used for automobile exhaust parts because of their high heat and corrosion resistance. Among them, parts located upstream near the engine, so-called hot-end parts, for example, exhaust manifolds, are required to show excellent heat resistance. Since thermal fatigue is induced by repeating heating and cooling with mechanical strain restriction, thermal fatigue resistance is one of the most important properties of upstream exhaust-parts materials.

In this study, the effect of Al addition on thermal fatigue deformation morphology was investigated for high heat-resistant ferritic stainless steel SUS444 which has been used for automobile exhaust parts. In contrast with the steel without Al addition, which fracture morphology in thermal fatigue under the maximum temperature of 1,173 K was necking, cracking was predominant in the steel with Al addition without necking. Al addition has the effect to prevent necking in thermal fatigue under the maximum temperature of 1,173 K due to solid solution strengthening by Al.

In general, the stress-strain relationship of materials obtained by standard uniaxial tensile test, which can identify the hardening behavior only up to necking. Beyond necking, the material behavior is usually estimated by extrapolating or numerical modelling based on hardening behavior prior to the uniform elongation. This study investigated the post-necking hardening behavior of a fully martensitic steel by in-situ synchrotron X-ray diffraction during tensile deformation. From the in-situ results, the dislocation density, lattice strain and phase stress were calculated within the necked region and outside the necked region. A near steady-state flow with some hardening was observed within the necked region of a martensitic steel. However, beyond uniform elongation, outside the necked region the dislocation density and phase stress decreased slightly, suggesting stress relaxation. Steady-state flow and dislocation densities at large strains suggest dynamic recovery occurs in the martensitic steel at room temperature.

Thermal hysteresis in fusion welding causes significant weld deterioration in medium- and high-carbon steels. Therefore, the development of an effective alternative welding process is required. Friction stir welding (FSW) is a solid-state welding process performed in an atmosphere that reduces the risks associated with melting and solidification of metals, making it an effective alternative method. Furthermore, it facilitates a flexible in-process control of heat input, which can be achieved by controlling the welding parameters. Considering these, the authors conducted a series of studies to elucidate the characteristics of FSW for medium- and high-carbon steels, including high-strength tempered steels.

This paper presents the results of applying FSW to 1.4 GPa-grade tempered JIS-S55C steel plates. Five distinct weld types were created by varying the welding parameters, including tool rotation and welding speed. The temperature of the interface between the tool and in-process material was measured using a thermal imaging camera. The microstructure of the welds was evaluated using optical microscopy and field-emission scanning electron microscopy (FE-SEM) with an electron-backscatter diffraction (EBSD) measurement system. The mechanical properties of the welds were evaluated through Vickers hardness and tensile tests. Digital image correlation analysis was employed to analyze the local deformation during the tensile test.

The competition between the ferrite and austenite for nucleation in the melt can result in various solidification sequences in the Fe-based alloy. This study demonstrates that the austenite solidification was initiated by metastable ferrite nucleation followed by ferrite-austenite transformation even in Fe-22mass%Mn-0.7mass%C, where the austenite is the primary phase in equilibrium. Time-resolved X-ray diffraction measurements were performed using a time-resolved X-ray tomography apparatus to identify the metastable ferrite nucleation followed by the austenite solidification. X-ray radiography was performed to observe the microstructure evolution through the metastable ferrite nucleation followed by the austenite solidification. The metastable ferrite nucleation was preferably selected when the completely melted specimen was cooled. During subsequent cooling, the ferrite massively transformed to the austenite in the solid state, and multiple austenite grains were produced in a single ferrite grain through ferrite-austenite transformation. The ferrite-austenite transformation was immediately followed by the coarsening of multiple austenite grains. When the ferrite-austenite transformation occurred in a semisolid state consisting of the ferrite and liquid phase, the liquid phase, which isolated the austenite grains, suppressed the coarsening of austenite grain. The typical austenite grain size ranged from 100 to 500 μm. Thus, the present results suggest that the ferrite-austenite transformation following the metastable ferrite nucleation has the potential to control the austenite grain size in as-cast microstructures.

Fe-9 mass%Ni alloy is widely used as a cryogenic steel owing to its excellent low-temperature strength and toughness. However, Ni is an expensive element, with medium-Mn steel considered an inexpensive alternative. Considering the Fe-10%Mn-0.1%C alloy is brittle at low temperatures, the application of intercritical annealing with two-step hot rolling could lead to toughening. Herein, the effect of intercritical annealing on the toughness of a Fe-10%Mn-0.1%C alloy with elongated prior-austenite grains (PAGs) formed via a two-step hot-rolling process was investigated. Intercritical annealing was performed on the specimens with and without two-step hot rolling. For both specimens, intercritical annealing resulted in softening of α'-martensite and an increase in the amount of retained austenite. In the specimen not subjected to the two-step hot rolling process, the fracture morphology transitioned from ductile to intergranular with a decrease in the temperature. Intercritical annealing improved the toughness when ductile fracture occurred. In the case of intergranular fracture, the effect of intercritical annealing on the toughness was negligible. In the two-step hot-rolled specimen with elongated PAGs, the fracture morphology transitioned from ductile to separation fracture with ductile fracture, and intercritical annealing improved the toughness at all temperature ranges. The improvement in toughness during separation fracture is attributed to the expansion of the plastic zone owing to ductile crack progression and the formation of sub-cracks, which promote the strain-induced transformation of retained austenite and ε-martensite.

The effect of MnS inclusions on the localized corrosion of low-alloy steel in a 0.5 mol/kg (3 %) NaCl solution was investigated to propose countermeasures for inhibiting localized corrosion initiated by MnS inclusions. Low alloy steels without MnS inclusions did not corrode in a 0.5 mol/kg (3 %) NaCl solution, regardless of the addition of Cu. That is, no matrix improvement effect due to solute Cu was confirmed. Slight corrosion occurred in the Cu containing steel with MnS inclusions; however, the MnS inclusions remained. Cu_7.2S₄ precipitated on the MnS in contact with a 0.5 mol/kg (3 %) NaCl solution. Therefore, Cu_7.2S₄ precipitates on the MnS inclusions during immersion, which could suppress the localized corrosion initiated by the MnS inclusions because Cu sulfide is not dissolved based on potential-pH diagram. The addition of Cu in a 0.5 mol/kg (3 %) NaCl solution does not improve the corrosion resistance of the matrix due to solute Cu but does suppress localized corrosion initiating from MnS by precipitating Cu sulfide on MnS.

Under certain conditions, the whole roll flatness meter outputs a bimodal waveform signal, which is clearly different from the conventional unimodal waveform signal. Since detection relies on the extraction of crest values and the values of the two waveforms do not have the same linearity, the presence of the two waveforms of different channels will clearly give rise to errors in the calculated flatness distribution. To develop an effective extraction method, it is necessary to accurately analyze the evolution of the waveforms. In this paper, the finite element method is used to calculate the load of the sensor, the stress distribution of each analysis surface and the deformation of the sensor mounting hole during the real-time detection to analyze the mechanism of the waveforms. The results show that unimodal and bimodal waveforms are produced under different strip tension and wrap angle conditions. In addition, the radial stress of the roll surface always presents two stress wave distributions. With increasing strip tension or wrap angle, the phase difference between the two waves increases. The stress distribution will change the deformation trend of the mounting hole and affect the stress distribution state of the sensor. When the phase difference of the stress waves exceeds the covering range of the sensor, the output signal changes from a unimodal waveform to a bimodal waveform. Finally, by setting up an experimental platform with variable tension and wrap angle, the relationship between the output waveforms and the working conditions in the simulation is reproduced.

From the viewpoint of expanding the allowable P limit, the effect of warm tempforming on delayed fracture resistance was evaluated for 0.09% P-doped 0.4%C–1%Cr–0.7%Mn–0.2%Mo steel (mass%). The P-doped steel was warm tempformed at 500 °C with a caliber-rolling reduction of 78% and annealed at 550 °C for 1 h. This thermomechanical treatment created an ultrafine elongated grain structure with a strong <110>// rolling direction fiber texture, in which P definitely cosegregated with Mn and Mo at grain boundaries. The slow-strain-rate-test and immersion test demonstrated that warm tempforming markedly enhanced the delayed fracture resistance of the P-doped steel at a tensile strength of 1100 MPa level, in contrast to conventional quenching and tempering treatment.

Knowledge of the viscoelastic properties of suspensions is essential for many industrial processes. Although oscillation and creep testing are widely used to measure the viscoelastic properties of complex fluids, few studies on the correlation between the viscoelastic properties measured using these methods have been published. This study aims to provide insights into the differences between these methods and determine which method is better suited for a particular application. The room-temperature viscoelastic properties of a suspension composed of polyethylene beads dispersed in a silicone oil matrix were measured by oscillation and creep testing and compared. The results of oscillation testing indicated that the suspension showed weakly elastic deformation, whereas the results of creep testing revealed that the suspension was relatively elastic, with the liquid phase showing lower viscosity. In addition, the viscosity measured by oscillation testing was lower than that measured by creep testing. When the imposed flow causes microstructural changes, such as when the shear flow and particle‒particle contact induce aggregation, the analyzed flow property considerably differs between testing methods.

The interfacial tension between the liquid steel and molten slag is one of the key properties to control the entrapment of mold flux in molten steel in the continuous casting process. A dynamic change of the interfacial tension is observed when deoxidized iron and silicate slag are in contact, which can be explained by the oxygen absorption and desorption at the iron/slag interface. However, the dynamic change of the interfacial tension is influenced by other surfactant components of the molten iron and slag. Fluoride ions are fundamental component of mold flux, and recognized as the surface active component of molten slag. The effect of fluoride ions in slag on the interfacial tension has not been critically evaluated. Here, the effect of fluoride ions in slag on the interfacial tension between molten iron and molten silicate slag was evaluated at 1823 K, where the fluoride-containing slag compositions were designed to exhibit the same SiO₂ activity and slag viscosity as those of the fluoride-free slag. Compared with the case of molten iron and fluoride-free slag, the interfacial tension between the molten iron and fluoride-containing slag was initially lower. Except the effect of oxygen adsorption, fluoride ion was considered to directly decrease the interfacial tension. However, as the fluoride content in slag was higher, the interfacial tension tended to show the higher value at the final state. This behavior was attributed mainly to fluoride vaporization as SiF₄, which reduce the SiO₂ activity in slag and thus equivalent oxygen content at the iron/slag interface.

A novel integrated constitutive equation of the flow curve for Ti–6Al–4V alloys is proposed by incorporating the effects of phase fraction in the hot-forging temperature range. The flow curve was obtained using hot-compression tests in the temperature range of 750–1050 °C and strain rate range of 1–25 s^-1. The effects of friction and deformation heat generated during compression were corrected using the inverse analysis method to identify the ideal uniaxial flow curve. The obtained stress parameters were satisfactorily regressed using the rule of mixtures on the α and β phases considering changes in the phase fraction. The integrated flow curve equation incorporating the rule of mixtures of the two phases effectively expressed the flow curve throughout the investigated temperature range. The internal microstructural observation showed that the continuous dynamic recrystallization of the α phase is dominant in the α+β two-phase region, while the deformation of the β phase becomes dominant just below the β transus. The constitutive equation presented here is in good agreement with the temperature dependence of the microstructure.