Steel Melt Research Articles

Plasma-arc skull melting and casting of austenitic steel with super equilibrium nitrogen content

Plasma-arc skull melting and casting of austenitic steel with super equilibrium nitrogen content

Feasibility of Preparing Steel Slag–Ground Granulated Blast Furnace Slag Cementitious Materials: Synergistic Hydration, Fresh, and Hardened Properties

Steel slag and GBFS are wastes generated during the steel and iron smelting process, characterized by their considerable production rates and extensive storage capacities. After grinding, they are often used as supplementary cementitious materials. However, the intrinsic slow hydration kinetics of steel slag–GBFS cementitious material (SGM) when exposed to a pure water environment result in prolonged setting times and diminished early-age strength development. The incorporation of modifiers such as gypsum, clinker, or alkaline activators can effectively improve the various properties of SGM. This comprehensive review delves into existing research on the utilization of SGM, examining their hydration mechanisms, workability, setting time, mechanical strengths, durability, and shrinkage. Critical parameters including the performance of base materials (water-to-cement ratio, fineness, and composition) and modifiers (type, alkali content, and dosage) are scrutinized to understand their effects on the final properties of the cementitious materials. The improvement mechanisms of various modifiers on properties are discussed. This promotes resource utilization of industrial solid wastes and provides theoretical support for the engineering application of SGM.

New approach to evaluating the thermodynamic consistency of melts in the ‘metal-slag’ system based on interatomic interaction parameters

The article presents a new approach to evaluating the thermodynamic state of the ‘metal–slag’ system during metal smelting in oxidizing-reducing conditions. The interaction between the metal and slag is analyzed using the model of the structure of metallurgical melts, which considers cooperative ion exchange processes and interatomic interaction parameters. As a result of analyzing experimental data on the compositions of reacting melts during pig iron and steel smelting, criteria were developed for assessing the degree of achieving the equilibrium in the system regarding sulfur. The charge state parameters of the metallic system ZY and the slag system Δe, the slag stoichiometry index ρ, and the charge state parameter of the melt components Zi were used. The regularity of a consistent formation of metallic and slag melts has been established, which is evidenced by a significant correlation between the chemical equivalent of the metal composition ZY and the slag Δe. Analytical dependences were obtained in the form of ZY = f(Δe,ρ). The identified patterns and criteria can be integrated into automated process control systems for regulating the slag regime and producing high-quality pig iron and steel.

Spatial distributions, behaviors, and sources of PCDD/Fs in surface water and sediment from the Yangtze River Delta

The Yangtze River Delta (YRD), one of the most economically developed and industrialized regions in China, is confronted with challenges arising from rapid urbanization, particularly environmental pollution. The collection of surface water and sediment samples from forty-nine sites in the YRD was conducted to analyze 2378-substituted polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) congeners. The detected concentrations of PCDD/Fs were 0–5.3 pg TEQ/L in water and 0.12–1493 pg TEQ/g dw in sediment. The PCDD/Fs contamination in the sediment was widespread in the YRD. There were variations in the congener characteristics of PCDD/Fs in surface water and sediment. The proportion of OCDD was significantly lower in surface water samples compared to sediment, while the less chlorine-substituted homologs were found in larger proportions. To understand the partitioning and behavior of dioxins within the water-sediment system, we calculated the organic carbon normalized partition coefficients and fugacity fraction (ff) of PCDD/F congeners. The results revealed that the PCDD/Fs had not attained a state of distributional equilibrium, and the non-specific hydrophobic effect seemed minimally influential on their partitioning between sediment and water. The average ff values, which varied between 0.06 and 0.63, indicated differing migration directions for the PCDD/F congeners. Source identification analysis provided evidence that the dioxins in the river water were primarily attributed to industrial thermal processes. Iron and steel smelting, along with pesticide production and use, were likely responsible for the sediment contamination. This comprehensive analysis underscores the complex nature of PCDD/Fs pollution in the YRD and highlights the necessity for targeted environmental management strategies.

Temperature distribution in CrMnNi steel-Mg-PSZ functionally graded material during FAST/SPS

Within the scope of this study, the macroscopic temperature distribution in the steady-state temperature condition during Field Assisted Sintering Technique/Spark Plasma Sintering (FAST/SPS) in functionally graded materials (FGM) was investigated. The sample material exhibited a diameter of 50 mm and a thickness of 9 mm. The FGM samples were composed of steel X2CrMnNi 16-7-6 and Mg-PSZ ceramic (MgO partly stabilized ZrO2). By varying the sintering tool setup, a specific modification of the macroscopic temperature distribution within the sample material and the sintering tool was achieved. The aim of the modifications was to optimize the temperature gradients in order to allow for the simultaneous compaction of all FGM layers under ideal circumstances. This involves achieving enhanced ceramic densification without inducing steel melting. Finite element method (FEM) simulations were carried out to get information about the temperature distribution within the sample material and the sintering tool. Furthermore, for this propose, thermocouple temperature measurements were conducted at various measurement points on pre-sintered FGM within the specific sintering tool setup. Additionally, all findings regarding the temperature distribution within the sample material and the sintering tool were compared with results concerning the temperature distribution from the microstructural and mechanical characterization of the center and edge regions of the FGM samples. The FGM samples exhibited a significant increase in temperature from the center to the edge in the radial direction depending on the used sintering tool setup. While the FGM samples showed only minor vertical temperature gradients in the center, the highest vertical temperature gradients were determined at the edge of the FGM sample using an asymmetric sintering tool setup.

Experimental Investigations in the Processing of AISI H11 Powder Blends Enriched with Tungsten Carbide Nanoparticles for the Additive Manufacturing of Tailored Hot Working Tools in the Directed Energy Deposition (DED-LB/M)—Impact of Tungsten Carbide Nanoparticles on Microstructural and Mechanical Characteristics

In this study, the DED-LB/M process of AISI H11 tool steel powder blends modified by adding WC nanoparticles (WC-np) in concentrations of 1, 2.5 and 5 wt.-% was the object of scientific investigations. For this, 30-layer cuboid specimens were manufactured. The overall scientific aim was to examine how the WC-np interact with the steel melt and in the end, influence the processability, microstructure and mechanical properties of produced specimens. The examinations were carried out on both as-built and thermally post-processed specimens. An advanced microstructural analysis (SEM, EDS, EBSD and XRD) revealed that due to the high solubility of WC-np in the molten steel, most of the WC-np appear to have dissolved during the ongoing laser process. Furthermore, the WC-np favor a stronger distortion and finer grain size of martensite in the manufactured specimens. An increase in hardness from about 650 HV1 for the H11 specimen to 780 HV1 for the one manufactured using the powder blend containing 5 wt.-% of WC-np was observed in as-built conditions. In the same way, the compression yield strength enhanced from 1839 MPA to 2188 MPA. The hardness and strength increasing effect of WC-np remained unchanged even after heat treatments similar to those used in industry.

Steel degassing in continuous steel melting units

The requirements for the quality of steel products dictate the need to increase the share of evacuated steel. In addition, the growing cost of fuel, as well as the desire of society and the state to decarbonize various industries, including ferrous metallurgy, requires companies to reduce fuel costs and switch to more modern and cleaner technologies. Reducing the specific fuel consumption, and, accordingly, emissions, is possible due to the transition to continuous production, minimizing the cost of heating the equipment and maintaining the set temperature in the degasser during technological downtime. The article deals with the issues of steel melt degassing in U-type continuous degassers in continuous steel making units. Aim. To consider the influence of rarefaction of a gas bubble on the characteristic size over the melt, speed and time of its surfacing in a U-type degassing unit. Based on the obtained dependences, to determine the characteristic size of a vacuum chamber and energy effect of switching to a continuous vacuumization. Methods.. Results. The authors have determined a bubble characteristic size in a steel melt under vacuum of different degrees. They studied the effect of vacuum on vacuumization speed and the degassing unit dimensions. The energy effect of switching to continuous vacuumization was determined. The proposed methodology is valid for liquid media, the calculations are presented on the example of molten steel. Based on the conducted calculations, the depression influence on molten steel vacuumization was determined. The vacuum chamber dimensions, comparable with RH-vacuum cleaners presented at the market of similar productivity and quality of finished products, as well as reducing energy consumption for steel degassing in a continuous vacuum degasser, compared with the existing circulating installation, were determined.

Interfacial reaction between AZ91D magnesium alloy melt and mild steel under high temperature

Interfacial reaction between AZ91D magnesium alloy melt and mild steel under high temperature

Study on interfacial morphologies of AA1060 and SS321 magnetic pulse welded joints

In this study, the application of magnetic pulse welding was employed for the production of tubular joints using 1060 aluminium and 321 stainless steel. Two crucial process parameters, the charging voltage, and the gap between the outer and inner tubes, were subjected to mechanical property tests and morphology analysis. The joints that exhibited favourable mechanical properties were obtained with a gap size of 1.25 mm and a charging voltage exceeding 3.5 kV. The presence of intermetallic compounds at the joint interface indicates the occurrence of fusion in the transition zone. The quantity of molten metal increased with an increase in the charging voltage. The aluminium content in the intermetallic compounds within the transition zone decreased as one moved from the 1060 aluminium side towards the 321 stainless steel side. The gap distance plays an important role in determining the efficiency of energy transformation at the joint interface during magnetic pulse welding (MPW). A smaller gap distance resulted in a substantial amount of energy being transformed into plastic deformation in the transition zone. Conversely, a greater gap distance led to a significant amount of energy from the electrical charging voltage being converted into thermal energy. The MPW joint consisted of bonding, mechanical interlock, and non-bonding regions. The mechanical properties of the joint were influenced by the composition of the intermetallic compound. Taking into account the impact of morphologies and elastic modulus of the transition zone, an increase in the melting of stainless steel during the welding process was found to be advantageous for the MPW of 1060 aluminium to 321 stainless steel.

Relation of nonmetallic inclusions to the cyclic properties of steel 42CrMo4 after steel melt cleaning by filtration and related processes

Nonmetallic inclusions (NMIs) detrimentally influence the steel properties. The application of metal melt filter systems promises to reduce NMIs in steel. In the current work, NMIs are analyzed from metallographic sections after metal melt filtration or cleaning by a related process of the steel 42CrMo4 using immersion filtration, flow-through filtration as well as filters floating on top of the melt. Analyses by automated scanning electron microscopy (ASPEX) as well as light optical microcopy (LOM) revealed the chemistry, size distribution, and morphology of NMIs. The filter systems had a significant effect on these characteristics of NMIs. The threshold value ΔKth against fatigue crack propagation was found to depend on the amount of NMIs within the steel. A higher amount of NMIs caused less crack deflection leading to less roughness-induced crack closure and in turn resulted in lower threshold values at a stress ratio of R = 0.1. The comparison of the present analysis of NMIs with fatigue data from previous work indicated that the analysis of NMIs from metallographic sections can be used to approximate the fatigue strength of a batch in the same way as the analysis of NMIs from fatigue fracture surfaces for single specimens, as suggested by Murakami.

SUSTAINABLE AND STRATEGIC SOFT-MAGNETIC Fe-Si-Al ALLOYS PRODUCED BY SECONDARY METALLURGY

In Slovenia, Fe-Si-Al alloys for non-oriented, silicon-steel sheets are designed and manufactured in a sustainable manner. Ferrous scrap is recycled, and, therefore, CO2 emissions are greatly reduced. However, sustainable technologies based on secondary metallurgy have many limitations. Impurities that cannot be effectively removed from the steel melt increase the complexity of the material’s behavior during processing and use. One of the most contaminating elements is copper (Cu). In this review, the focus is on phenomena related to the Cu impurity during the specific steps of the metallurgical processing of selected Fe-Si-Al alloys. The identified challenges concerning the efficiency of some technological phases related to the presence of Cu in Fe-Si-Al, non-oriented electrical steels might motivate further (inter)disciplinary research, basic or applied. In order to follow the set goals of the EU and achieve climate neutrality by 2050, silicon electrical steels produced with sustainable circular-economy approaches must be recognized as a strategic material for the EU.

Studies of the Possibility of Improving the Quality of Iron Ores and Processing of Technogenic Composite Iron-Containing Waste of Metallurgical Production

Ferrous metallurgy has been and remains one of the main types of production activities that enables humanity to extract, process and produce basic equipment for all types of activities. The growth of ore production as well as the reduction in world reserves of the raw material base have lead to the search for effective methods of processing and preparation of waste for metallurgical processing. The mining and metallurgical sector of the Republic of Kazakhstan, which has its an integrated mining and metallurgical complex with its own coal, iron ore, and energy base, uses iron ores from several deposits. It also includes ash and sludge storage tanks, which store valuable metallurgical waste, such as converter production sludge, rolling scale, and others, the use of which is hindered by the presence of certain harmful impurities in the composition (a rather high content of non-ferrous metals, especially zinc, a high content of oils, etc.). These valuable technological wastes require additional research that may contribute to their use as a charge or as iron-containing components of the charge. Based on the urgency of the tasks of dephosphorylation of iron ores and utilization of human-made waste (converter sludge and rolling scale), studies were conducted to try to eliminate existing problems. The results of the research work make it possible to obtain metals based on prepared pellets with a significantly low phosphorus content; this will enable the use of an oiled rolling scale and converter sludge for the production of a metalized product for steel smelting. The resulting metalized products make it possible to dispose of scale and converter sludge by 70%, and the degree of iron extraction exceeds existing methods by 1–3.5% (92.1–94% vs. 95.6%).

Numerical modelling of high-power laser spot melting of thin stainless steel

Numerical modelling is an important scientific tool in laser materials processing to study different melting, evaporation, and solidification phenomena. It can assist in understanding why certain defects are formed, and thus may provide solution paths for how to decrease certain defects and to increase the quality of a product. Laser spot melting in heat conduction mode represents a simple case and is an excellent first step to build and test solvers prior to moving on to more complicated cases such as laser keyhole welding of thick plates. Modelling of laser spot melting requires only a limited computational domain and allows more complex physics to be added gradually. In this work, a thin 3.0 mm thick stainless steel plate was melted with high-power fiber laser and numerically simulated using a native and custom-build solver based on the VOF method within OpenFOAM. The process was captured with a high-speed imaging camera and simulation results are compared with the experimental results. It was found that temperature-dependent surface tension plays a vital role in controlling melt flow directions within melt pool.

Integrating Wire Arc Additive Manufacturing into Selective Paste Intrusion for Reinforced Concrete Elements: Effect of Temperature on the Mechanical Performance

AbstractThis research aims to integrate the Wire Arc Additive Manufacturing (WAAM) process into the Selective Paste Intrusion (SPI) process to enable the production of reinforced concrete elements with complex geometries. However, the high temperatures generated during the steel melting process in WAAM can locally lead to a full stop of hydration which consequently is linked to a decrease of the mechanical properties of the concrete in the bonding zone around the reinforcing bar. This study aims to determine the maximum allowable temperature at which concrete retains sufficient hardening conditions which allows strength development when combining SPI with WAAM. In practical application, this temperature limit can directly be affected by e.g. the protruding length of the WAAM‐reinforcing bar above the SPI particle bed or external cooling strategies. As continuation of previous research, this study establishes a link between actual and targeted temperatures in the steel bar to allow the combination of WAAM and SPI processes. Temperature limits without compromising mechanical performance are investigated, and the need for and extent of additional cooling measures are evaluated. The results show that temperatures of the concrete in the fresh state can reach up to 70°C without weakening its mechanical performance.

Experimental investigation of the phase equilibria of CaO–Al2O3–TiO2 slag system at 1500 °C with p(O2)=10−3 atm

The phase diagram CaO–Al2O3–TiO2 slag system is of great importance for metallurgical processes, such as the utilization of Ti-bearing slag and optimization in Al–Ti alloy steel smelting process. In the present work, the high-temperature phase equilibrium experimental technique was adopted, and the type and composition of equilibrium phases were identified by Electron Probe Micro Analysis (EMPA) and X-ray diffraction (XRD). The iso-thermal section of CaO–Al2O3–TiO2 system at 1500 °C in Ar atmosphere was constructed for the first time. There are 10 three-phase fields (Liquid + CaO+3CaO·2TiO2, Liquid+3CaO·2TiO2+4CaO·3TiO2, Liquid + CaO·Al2O3+4CaO·3TiO2, CaO·TiO2+CaO·Al2O3+CaO·2Al2O3, CaO·2Al2O3+CaO·TiO2+CaO·6Al2O3, Liquid + Al2O3+Al2O3·TiO2, Liquid + CaO·TiO2+CaO·6Al2O3, Liquid + CaO·6Al2O3+Al2O3, Liquid + TiO2+Al2O3·TiO2, 4CaO·3TiO2+CaO·TiO2+CaO·Al2O3), 13 two-phase fields (Liquid + CaO, CaO+3CaO·2TiO2, Liquid + Al2O3, Liquid+3CaO·2TiO2, Liquid+4CaO·3TiO2, Liquid + TiO2, Liquid + CaO·TiO2, Liquid + Al2O3·TiO2, CaO·TiO2+CaO·2Al2O3, Liquid + CaO·6Al2O3, Liquid + CaO·Al2O3, 4CaO·3TiO2+CaO·TiO2, 4CaO·3TiO2+3CaO·2TiO2), 3 single-phase solid solution fields (4CaO·3TiO2(ss), 3CaO·2TiO2(ss), TiO2(ss)), and 2 independent single liquid phase fields. Besides, taking the Ti-bearing slag system as an example, the influence of oxygen potential on the activity of (TiOx) was discussed; furthermore, the reasonability of the valence state approximation of element Ti was farther evaluated.

New technological techniques for local repair of worn sections of the converter lining

The duration of converter campaigns has increased significantly due to improvements in steel smelting technology, quality of used refractories, lining design, as well as due to various ways of maintaining the lining in working condition during the campaign (hot repair).

Finite integral transform with homogenized boundary conditions solution of transient heat conduction applied to thermal plug and abandonment of oil wells

After the end of productive life of a geological oil reservoir, a set of operations for well Plug and Abandonment (P&A) is performed to recover the soil layers to its natural state. As traditional P&A techniques are expensive activities, alternative technologies are gaining renewed interest for capital expenditure reduction and leak risks mitigation. Hence, the Thermal Plug and Abandonment (TP&A) procedure is here investigated by focusing on the fulfillment of two intermediate milestones, combining new technology with conventional P&A practices. The first milestone consists in applying a thermite exothermic reaction to generate enough heat for melting the entire thickness of the production tube. The second milestone aims to determine if the resulting molten section has sufficient dimensions to allow for the passage of the cement pumped downhole, thus ensuring the complete sealing of the oil well's cross-section. The thermal investigation was conducted by applying a homogenized form of the Finite Integral Transform (FIT) analytical framework to solve the transient heat conduction equation in 2-D polar coordinates. The well assembly was geometrically discretized as a multilayered circular domain. The thermite reaction was modeled as a theoretical volumetric heat source profile dependent on both time and space, placed in the innermost layer. While a pure FIT approach may only be used to solve Neumann boundary conditions, the combined scheme applied here copes with any type of boundary condition. Hence, the integration of FIT with homogenization satisfies the Dirichlet condition requirement of the TP&A procedure. The methodology was verified through an equivalent Finite Volume Method (FVM) solution obtained using a commercial code. The results evidenced that within the 5 min duration of thermite reaction, the entire circumferential section of the production tube exceeds the steel melting temperature by at least 227 °C, thus fulfilling both milestones set. The research outcomes are part of a series of investigation steps to thoroughly analyze the new TP&A technology with regard to its compliance with the regulatory norms established to P&A operations.

Selective laser melting of a novel 13Ni400 maraging steel: Material characterization and process optimization

Selective laser melting (SLM) has attracted recent attention in building parts with improved functionality and properties. Accordingly, the present work attempts to fabricate a novel 13Ni400 maraging steel parts with maximum theoretical density by SLM. A Box Behnken Design response surface methodology (RSM) approach is used to evaluate the influence of critical process parameters (laser power, laser scan speed, layer thickness, and hatch spacing) on the relative density, micro hardness, surface roughness, and tensile strength. Both the powder and the fabricated parts were characterized for the structural and microstructural features using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The influences of energy density and other process variables are explored through careful parametric studies and 3-D surface plots. Analysis of variance (ANOVA) is carried out, which reveals that the laser power and layer thickness are the most dominant process parameters impacting the performance of the SLM process. A revolutionary preference ranking organization technique for enrichment evaluation (PROMETHEE) is adopted to convert the multiple responses into an equivalent net outranking flow and rank the alternatives. The PROMETHEE-based outcomes are further improved by using a cuckoo search (CS) algorithm. A confirmatory test is conducted on the optimum build conditions obtained by the hybrid methodology (combination of PROMETHEE and Cuckoo Search) to validate the proposed work. It is seen that the value of net outranking flow is enriched by ∼5 %. This work is proficient in producing defect-free parts, with maximum densification and with improved mechanical properties for a newly developed 13Ni-400 maraging steel.

Automated systems for monitoring the consumption of metal charge at factories by conversion metallurgy

The domestic factories engaged in conversion metallurgy use scrap as the main raw material for steel production (at least 70 % of the total charge). In difficult economic and geopolitical situation factories are cautiously considering the possibility of introducing new technologies that require high capital expenditures and modification of existing units. In this article automated control systems are proposed that help reduce the consumption of metal charge and energy resources during steel smelting: an electromagnetic scanner with an automatic control system that determines the presence of concentrations of non-magnetic substances in scrap at each point of the wagon or trailer of the road train and the bulk density of scrap; a neural network system for temperature control in electric furnaces and out-of-furnace processing (installation ladle-furnace and units for vacuuming). These systems will allow enterprises of conversion metallurgy (on the example of Pervouralsk Novotrubny Plant): to improve the quality of scrap metal by tightening the requirements for the quality of raw materials of scrap suppliers according to the interstate standard for secondary fer-rous metals; to increase the productivity of the electric furnace by reducing the time under current by 3 minutes, and to reduce the consumption of metal charge by 4.66%, electricity by 500 kWh for 1 melting cycle, the release temperature by 10 ℃ to reduce vacuuming time for 2 minutes. The proposed automated control systems require insignificant capital costs for installation and commissioning, and do not require the shutdown of existing production.

Research on carbon dioxide capture and mass transfer in hydro-jet cyclone

Steel smelting has a large amount of flue gas emissions and high carbon capture costs, making it one of the “heavy disaster areas” for carbon dioxide (CO2) emissions. This article develops a hydro-jet cyclone (HJC) by coupling the gas phase swirling flow field with the liquid phase jet flow field, and proposes a carbon capture technology for smelting flue gas. During the dispersion process of liquid phase microelements, there was simultaneous rotation and revolution of droplets, which enhances the gas–liquid mass transfer process. The surface renewal effect increases the effective specific interface area, and the interface oscillation effect was beneficial for reducing the mass transfer resistance on the liquid side. A model for the effective phase interface area (ae) of HJC was first proposed for different jet hole, with a maximum ae of 5358.95 m2·m−3.In the CO2-NaOH system, the absorption efficiency of CO2 was 88.9 %. This article supplements HJC's research on carbon capture and gas–liquid mass transfer by optimizing the size of the jet hole, which was beneficial for the development of efficient carbon capture equipment in the steel industry and further promotes the sustainable development of the steel industry.