Journal of Mining and Metallurgy, Section B: Metallurgy

The impact of hot roll temperature on the microstructure and corrosion resistance of super duplex stainless steel, which is used to coat mild steel in seawater environments

2025-07-31T15:20:23+02:00

A new material that can be used to replace single steel in high-strength tanks is mild steel cladding Super Duplex Stainless Steel (SDSS). The method of producing multilayer Super Duplex Stainless Steel (SDSS) is the cladding of mild steel. Many processes are carried out such as welding Plasma Direct Energy Deposition (DED), laser, and electro-slag strip. In the manufacturing industry, hot rolling is a simple process. Because the procedure is quick and uses inexpensive, traditional equipment, it is referred to as a simple method. The use of seawater was chosen because salty conditions favour corrosion. In this work, the effects of temperatures of 900°C, 1000°C, and 1050°C on the microstructure and corrosion resistance of hot rolled materials are investigated. The investigation of corrosion resistance by examining the microstructure and material properties using metallography, X-ray diffraction, Electrochemical Impedance Spectroscopy (EIS), and Scanning Electron Microscope (SEM) is the main goal of this work. The results of the study demonstrated that when the hot rolling temperature was increased, carburization and decarburization occurred and the corrosion resistance decreased.

Effect of equal channel angular pressing process on drawability of DC04 steel sheets

2025-07-31T15:20:24+02:00

Equal channel angular pressing (ECAP) is a severe plastic deformation processing (SPD) technique that induces significant changes in the crystalline structure of the material, resulting in improved mechanical properties. The objective of this experimental work is to study the influence of this process on the drawability of DC04 steel sheets. A pack of six sheets placed in sandwich were deformed at room temperature with an inside channel angle of 120° for 1 passe. A characterization by hardness measurement and tensile test was conducted. In addition, optical microscope observation and X-ray diffraction (XRD) analysis were performed. A finite element simulation using Abaqus was implemented to allow a thorough analysis of the process. Finally, the Erichsen test was used to assess the drawability of the sheet that present the best mechanical propriety, A finite element simulation also was used with Abaqus to allow a better analysis of the process. The results showed an increase in microhardness, reaching up to 64%. The microstructure study showed a grain refinement of about 70% with the appearance of a slight texture and without phase change. The tensile test showed an increase in yield stress (Re) and the ultimate tensile strength (Rm), and a diminution of elongation (A%) and the Strain Hardening Exponent (n) were observed. The Erichsen test showed a slight decrease, of the order of 10% of the Erichsen cupping index (IE), therefore, it should be noted that the sheets have retained a good suitability for deep drawing.

Hydrothermal leaching behavior of complex polymetallic secondary sulfide concentrate enhanced by ultrasonic

2025-07-31T15:20:25+02:00

Complex polymetallic secondary sulfide concentrate is difficult to efficiently be utilized because of its special mineral phase structure and high content of lead and iron. A novelty process proposed in this study, hydrothermal leaching without acid enhanced by ultrasonic, could achieve eco-friendly and selective separation of copper and zinc from complex polymetallic secondary sulfide concentrate, inhibiting production of hazardous material plumboferrite contained in leaching residue. The influence of controlling parameters on the leaching efficiency and the mineral phase composition and structure of the obtained leaching residue were studied. The obtained results showed that, without sulfuric acid, the leaching efficiency of copper was the best under the conditions of temperature of 180 ℃, oxygen partial pressure of 1.0 MPa, stirring speed of 600 r/min, ultrasonic power of 360 W, liquid-solid ratio of 10:1 and mass ratio of lignosulfonate to raw material of 0.2%. Under the above optimal conditions, the leaching efficiency of zinc, copper and iron reached 99.88%, 99.12% and 19.46%, respectively. Ultrasonic enhancement increased the copper leaching efficiency by 10.02%, and promoted the leaching efficiency of iron decreased by 5.20%. The leaching process conformed to the unreacted contraction core model under mixed control, the activation energy was 71.76 kJ/mol, and the macroscopic kinetic equation related to stirring rate, oxygen partial pressure and ultrasonic power was 1-(1-X)^1/3 -1/3ln(1-X) = 40.457 e^(-8630.19/T)t。

High-strength and high-conductivity Cu-0.7Mg-0.1Ca alloy fabricated via heat treatment and severe plastic deformation

2025-07-31T15:20:27+02:00

In this research, the effect of annealing in combination with severe plastic deformation (SPD) by the MaxStrain component of the Gleeble thermo-mechanical testing device on the microstructural characteristics, tensile behavior, and electrical conductivity of a Cu-0.7Mg-0.1Ca (wt%) alloy was investigated. The as-cast material was subjected to two treatments: annealing at 923 K for 15 min, followed by cooling in air, and annealing at 923 K for 75 min, followed by quenching in agitated water, which resulted in irregular and partially spheroidized Cu5Ca particles. Subsequent MaxStrain deformation resulted in a remarkable grain refinement by dynamic recrystallization (DRX), in which the annealed and quenched sample exhibited a higher DRX fraction than the annealed and air-cooled sample. As a result, the annealed and quenched samples showed a better synergy between strength and ductility, while these improvements were accompanied by only ~1% reduction in electrical conductivity. Accordingly, the present work demonstrated that annealing and subsequent SPD processing is as an effective method for processing high-strength and high-conductivity (HSHC) copper alloys.

Two-stage leaching of germanium from copper cake under subsequent non-oxidizing and oxidizing conditions

2025-07-31T15:20:27+02:00

Many world economies consider germanium as a critical raw material. Therefore, the development of its recovery from new sources is becoming more and more important. The leaching of copper cake, originating from the purification of zinc electrolyte, in sulfuric acid solution is presented in the paper. The cake contained 24.7% Cu, 21.2% Cd, 16.3% Zn, 4.50% Pb, 3.96% Ni, 3.22% Co and 231 ppm Ge. The leaching of wet and dried material was examined. It was found that the highest germanium recovery was achieved for a two-stage process composed of leaching under non-oxidizing conditions followed by pH adjustment with sodium carbonate followed by oxidizing leaching of residue from the first stage. In the first stage leaching in 12.5% sulfuric acid and later pH adjustment to >2.0 reduced germanium leaching yield to <10%. During oxidizing leaching of remaining residue in 15% sulfuric acid >99% of germanium was leached. The final solution contained 30 mg/dm³ Ge and 72.4 g/dm³ Cu. Germanium may be later recovered from the solution by precipitation with tannic acid or solvent extraction.

Study on the fabrication of active CaO from steel slag of the converter and its application in CO2 adsorption process

2025-07-31T15:20:28+02:00

Using an acetic acid leaching process to extract calcium components from converter steel slag, evaporation, and crystallization to obtain high-purity CaO material. The influence of leaching parameters on the CaO content of the material was investigated. The shrinking core model was applied to analyze the leaching rate in a weakly acidic solution. Finally, the CO₂ adsorption performance of the CaO material under different adsorption conditions was evaluated, and the adsorption process and reaction mechanism were investigated using XRD and SEM analysis. The results showed that leaching temperature and acetic acid concentration significantly impacted the CaO content. The optimal leaching parameters were found to be an acid concentration of 1 M, a solid-to-liquid ratio of 1:10, a leaching temperature of 70 °C, and a duration of 2 h, under which the CaO content reached a maximum of 86.3%. Kinetic results indicated that stirring shifted the rate-controlling step of calcium leaching from external diffusion and surface chemical reactions to internal diffusion. In the temperature range of 40-70 °C, the rate-controlling step was governed by internal diffusion. XRD and SEM results confirmed the high purity of the CaO material. CaO first transformed into Ca(OH)₂, which adsorbed CO₂ to form CaCO₃. The deposition of CaCO₃ on the material surface hindered the contact between Ca(OH)₂ and CO₂, reducing carbon adsorption efficiency. Increasing the CaO content enhanced adsorption performance significantly. In the adsorption temperature range of 0-100 °C, ensuring effective contact between Ca(OH)₂ and CO₂ was crucial. The calculated CO₂ capture capacities at 30 °C, 50 °C, and 70 °C were 0.32 g/g, 0.24 g/g, and 0.17 g/g, respectively. This study can provide a reference for the high-value utilization of steel slag and the reduction of CO₂ emission in iron and steel enterprises.

Effect of bottom argon blowing flow rate on evolution behavior of steel-slag interface

2025-07-31T15:20:28+02:00

In this research, the computational fluid dynamics (CFD) software FLUENT is used, which employs the finite volume method, to integrate discrete phase models and multiphase flow models in numerical simulations based on a prototype steel ladle from a particular facility. The simulations aim to investigate the slag entrapment phenomenon in bottom argon blowing. The slag layer is filled with DPM (Discrete Phase Model) particles whose densities are consistent with slag. These particles are used to simulate actual non-metallic inclusions in the slag. If the height of a particle is less than the minimum height of the slag layer, it is thought to have been entrained into the molten steel. By using the User Defined Function (UDF), the tracking of this particle is stopped. The simulation results reveal that the slag eyes have a tendency to increase in size as the argon flow rate increases. The slag eyes area is generally small when the argon flow rate is below 500 L/min. However, there is a noticeable increase in the slag eyes area when the argon flow rate exceeds 1000 L/min. The number of particles entrained into the molten steel increases as the argon flow rate increases; the number of particles entering the steel increases gradually below 1000 L/min and dramatically over 1000 L/min.

Contribution to the study of toughness in creep resistant steel welded joint

2025-07-31T15:20:28+02:00

Steel P91 is widely used in power stations due to its goоd creep resistance and predictable performance. The aim of this work was to compare the toughness values of different zones in the weld joint with a sample subjected to a simulated thermal cycle. The workpieces were welded using Gas Tungsten Arc Welding (GTAW) for the root pass and Manual Metal Arc (MMA) for the filler deposition. Post Welding Heat Treatment (PWHT) was carried out at 740 °C for 2 hours. The welded joint was tested for microstructure, macrostructure, hardness, strength and toughness. The macrostructure showed all typical zones with a tempered martensite microstructure. The difference in the carbide distribution, which were confirmed by the hardness measurements, are the result of variations in the chemical composition. The tensile strength and the fracture which occurred in the base metal, indicate good properties of the welded joint. The crack initiation energies determined were similar in the Base Metal (BM), Heat-Affected Zone (HAZ), and Weld Metal (WM), while the crack propagation energy was lowest in the WM. This indicates that carbides control the crack initiation energy, while their distribution influences the crack propagation. The simulated HAZ samples showed lower toughness compared to the welded specimens, which can be attributed to the differences in the performed thermal cycles. During welding, the HAZ undergoes several thermal cycles in each pass, resulting in smaller austenitic grains compared to the simulated HAZ. Lower values of toughness indicate that the simulation provides a conservative approach, i.e. the measured toughness is lower than the toughness in a real welded butt.

Evolution behavior of oxide inclusions in Si-Mn deoxidized steel during billet heating process

2025-07-31T15:20:28+02:00

To reduce the harm of oxide inclusions to the quality of Si-Mn deoxidized steel products, the effects of heat treatment temperature and isothermal heating time on the composition and morphology of inclusions are studied. The Si-Mn deoxidized steel LX82A billets are isothermal heating at 1000 °C, 1100 °C, 1200 °C for 8h, 10h and 12h, respectively. The results show that the inclusions change from oval to round gradually with the increase of heat treatment temperature. When the heat treatment temperature rises to 1200 ℃, the oxide inclusions completely transform into MnO-SiO₂-Al₂O₃ system. With the increase of heat treatment temperature, the MnO content in inclusions increases significantly. The SiO₂ content increases first and then decreases. The CaO and Al₂O₃ content decreases obviously at 1200 ℃. The MgO content does not change significantly during the heat treatment process. When the heat treatment temperature is 1000 and 1100 ℃, the average composition of the oxide changes the most when the holding time is 10 h. When the holding time is 10 h, the average content of SiO₂ increases and the average content of CaO decreases. Under the condition of heat treatment at 1100 ℃ for 10 h, the average content of MnO increases. When the heat treatment temperature reaches 1200 ℃, with the extension of holding time, the average content of the five components in the silicon-manganese deoxidized steel basically does not change.At a heating temperature of 1200°C, calcium treatment is facilitated, and the formation of a Mn-depleted zone occurs, thereby improving the steel quality and enhancing its performance. Moreover, oxide inclusions exhibit better deformability and lower melting points. Therefore, the heat treatment temperature should be maintained around 1200°C to optimize these properties.

Study of drying kinetics and moisture diffusivity in iron ore briquettes after using different drying techniques

2025-07-31T15:20:30+02:00

This study aimed to investigate the drying kinetics, effective moisture diffusivity and thermal degradation properties of iron ore briquettes using hot air drying, microwave drying, and infrared drying methods. The results showed that in both hot air and infrared drying, drying occurs gradually, starting with drying of the outer surface and gradually moving towards the inner core of the briquette. In microwave drying, the iron ore briquette is heated from the inside out. The moisture diffusion capacity is moderate at 100 W, lower at 180 W, and very high at 300 W. In both hot air and infrared drying, the moisture diffusivity is low at 105 °C, and the maximum strength is observed at 120 °C. The compressive strength was analyzed after applying the different drying methods, and the highest strength of 4.195 N/mm² was measured at 120 °C in the infrared chamber. The kinetic drying curves for the hot air, microwave, and infrared methods were analyzed using five different moisture ratio (MR) models: Newton, Henderson and Pabis, Logarithmic, Diffusion, and Wang & Singh. This research will provide valuable insight into the degradation of iron ore briquettes after the optimal removal of approximately 90% of the moisture from the sample. This approach will also guide the production of high quality dried products and assist in the production of green briquettes with lower carbon emissions. In this work, heat induration is used for drying as opposed to techniques such as sintering and nodulation where the agglomerates are heated at high temperatures of about 1100 °C and higher carbon emissions are produced.

A qualitative study of multiphase steel microstructure developed in four different steel alloys

2025-07-31T15:20:33+02:00

In this work, quench and partitioning (Q&P) heat treatment was performed on four different steel alloys in order to obtain multiphase steels having a microstructure containing ferrite, martensite, bainite, and retained austenite. The four alloys are SS1672, 38MnVS6, R350HT and SS2244. They are chosen to study the effect of increasing the Mn/Si ratio and the Cr effect on the microstructure. Multiphase steels with retained austenite of different fractions and morphologies in a ferritic-bainitic matrix have been obtained depending on the Cr and Si amounts. Detailed characterisation of the microstructural evolution of Q&P heat-treated four steel alloys by optical microscopy (OM) was done only to provide a qualitative understanding. Despite these limitations, the OM micrographs were sufficient to confirm and identify the formed phases, especially the bainite phase. It is found from this work that high Si levels are not strictly necessary to prevent pearlite formation during the Q&P treatment of medium and eutectoid steels, due to the presence of manganese. A Mn/Si ratio greater than 2 is found to be necessary to prevent pearlite formation. Also, a lower martensite start temperature (Ms) leads to a significant refinement of the microstructure components bainite and retained austenite.