Melting Furnace Research Articles

Nanophase transformation and strengthening - Toughening mechanism of the Cu–15Ni–8Sn alloy during aging

The Cu–15Ni–8Sn alloy ingot was prepared in the medium-frequency induction melting furnace. The hot extruded alloy was treated by solid solution at 840 °C for 60 min and aging at 400 °C for different times (0 miñ480 min). The effect of aging time on the evolution of the nanophase of Cu–15Ni–8Sn alloy and the strengthening-toughening mechanism were studied. The results show that at the beginning of aging, the alloy undergoes spinodal decomposition, the wavelength of the modulated structure is approximately 3∼7 nm, the ordered phase transformation of D022 and L12 occurs simultaneously, and the ordered phase size is approximately 5 nm. With the extension of aging time, the modulated structure became coarser, and the wavelength of the modulated structure increased to 5–9 nm. At the same time, the D022 ordered phase changed to the L12 ordered phase, and a continuous distribution of elliptical discontinuous precipitation appeared at the grain boundary. The ratio of the long and short axes of the discontinuous precipitation was approximately 4.7. In the late aging period, the D022 ordered phase was basically transformed into the L12 ordered phase, and discontinuous precipitation, which is incompatible with the matrix, extended into the crystal. After 120 min of aging at 400 °C, the hardness, strength, and elongation of the alloy are 105.4 HRB, 839.8 MPa and 9.6 %, respectively. The peak-aging states D022 and L12 coexist in an orderly phase at the nanoscale, and this nanoscale strengthening phase is completely integrated with the matrix, which improves the strength and toughness of the alloy. The research results can provide support for the development of high-performance copper alloys in the ocean.

Characterization of firebricks used in copper smelting furnaces of the 19th century, Atacama, Chile

In the 19th century, mining in northern Chile was of great economic importance. Today, the ruins of the copper smelters and abundant fragments of refractory bricks from their furnaces remain. The refractory materials have not been previously studied. the origin, physical and chemical properties, and compressive strength of 10 different samples of historical refractory bricks collected on-site were investigated. The characterization results showed that the bricks are silico-aluminous, unlike the magnesium-chromium bricks used by current foundries. It was determined that 90% of them were produced in the UK and 10% were manufactured in Chile. The phases present are mullite, quartz, cristobalite, and tridymite, and the chemical composition corresponds mainly to SiO2. The compressive strength of the historical bricks is similart to those currently used,. These results may contribute to the knowledge of the 19th century mining and metallurgical historical heritage of Chile and the UK.

Justification of an acceptable modern energy-efficient method of obtaining sodium silicate for production in Kazakhstan

Sodium silicate is used in various industries. Sodium silicate is a basic component in the production of silicate adhesives and paints, silica gel, welding electrodes, corrugated packaging, and geopolymer concretes and cements. All this is currently not produced in the Republic of Kazakhstan. The article discusses the methods of production of sodium silicate and substantiates the possibility of organizing production in the Republic of Kazakhstan. The authors have studied all the available experience in the production of sodium silicate, both now and in the past. At this stage of the research, an analysis was made of the experience in the production of serial and pilot sodium silicate in the USSR in the past and in countries where development has not been suspended at the present time. All possible sources of raw materials of technogenic and natural origin were studied. Business trips and expeditions to natural deposits were carried out and samples of raw materials from various natural and man-made sources were delivered. Studies have been carried out to determine the available volumes of raw materials. Various technologies for melting sodium silicate have been studied, incl. by unconventional schemes, such as smelting in cyclone furnaces. For melting in electric furnaces, various schemes of energy-saving methods for melting sodium silicate were analyzed. Promising ones have been identified. The following types of sodium silicate production were analyzed in the study: traditional smelting (carbonate method), wet method, sodium chloride sublimation method, sulfate method, cullet smelting. The optimal variant has been chosen, which makes it possible to reduce the cost of electricity by several times when introducing a highly efficient innovative technology of electric melting into practice.

Influence of high strain rate deformation on the microstructure and mechanical behavior of NiCoCrFe high entropy alloy

The paper reported a high-entropy alloy, NiCoCrFe, which was produced in a Vacuum Induction Melting (VIM) furnace. In order to homogenize the microstructure, the as-cast ingot was rolled, annealed and machined to appropriate dimensions. Then the Split Hopkinson Pressure Bar (SHPB) was used to evaluate the specimens under various strain rates. True stress–strain curves of this test showed similar patterns in all strain rates, with two peaks that can be assigned to the competition between strain hardening and thermal softening. Modified Johnson–Cook model applied to characterize flow behavior of the alloy. X-ray diffraction results indicated that the alloy was single-phase with FCC crystal structure at the casting condition, after thermomechanical operation and after high-strain rate tests. The specimens were further examined by EBSD. The results indicated the impressive presence of twins in the samples deformed at strain rate of 1500 s−1, confirms the significant contribution of twinning in the strengthening process; Regarding the low SFE of the mentioned alloy, it can be said that Twin-Induced Plasticity (TWIP) has occurred. By strain rate enhancement to 3000 s−1, finer and elongated grains were observed while twinning decreased because of SFE increase as a result of temperature elevation due to adiabatic heating during deformation. According to KAM map, there was strain gradient in mentioned sample, which results in production of GNDs and GNDs pile-up leading to strain hardening by creating obstacles to further slip. Moreover, in the hat-shaped samples, which used for shear localization resistance evaluations, bundles of nano-twins were observed whose formation largely prevented strain localization and make the above alloy suitable for applications exposed to high-speed impacts.

Determination of Optimal Modifier Level for Eutectic Silicon Phase in Hypoeutectic AlSi7Mg0.3Cu0.5 Cast Alloy

Silicon particles in as-cast aluminum alloys can be modified using various modifiers, with Strontium (Sr) and Sodium (Na) being the most employed in the aluminum casting sector. However, their concentration diminishes (fades) during the melting furnace process. Modifier fading within the melt can result from three principal chemical reactions: vaporization of the modifier under high vapor pressure conditions at melting temperatures, oxidation driven by a significant affinity for oxygen, or interaction with other elements in the melt leading to the formation of intermetallic compounds. Given the very low vapor pressure of both Na and Sr, their vaporization from the aluminum melt was excluded as a reason for the modifier's fading. Oxidation seems to be like the primary chemical reaction leading to the fading of Na and Sr from the aluminum melt. This study examined the effect of Sr and Na fading on the modification level of silicon particles in the AlSi7Mg0.3Cu0.5 (356) aluminum alloy. The cooling curve analysis has been utilized to quantify modifier fading. Approximately 105 ppm of Sr in the form of master alloy (AlSr10) and 67 ppm of Na in the tablet form were separately added to the melt. Both modifiers were kept in the melt for approximately 200 minutes to monitor their fading. The present paper aimed to quantify the fading of Na and Sr in an AlSi7Mg0.3Cu0.5 alloy. The depletion of modifiers (Na and Sr) while the melt is retained in a furnace can be quantitatively determined through equations derived from existing literature. The surface reaction rate constant (ks), once calculated, serves as a tool for predicting the extent of modifier loss during the melt-holding process in both industrial and laboratory furnaces.

New insights into the influence of hydrogen on important parameters of blast furnace

In the pursuit of curbing carbon dioxide emissions, hydrogen is being explored as a substitute for coke in the blast furnace smelting process. This research delved into the potential of hydrogen to mitigate carbon emissions, employing a hydrogen-rich blast furnace model for calculations. A novel approach for preheating hydrogen through blast furnace injection was proposed, accompanied by a more scientifically rigorous CO2 assessment method. This approach encompassed not only CO2 generation during blast furnace smelting but also factors in CO2 emissions from the hot blast stove and hydrogen preheating stove. Simulation outcomes underscored the significant carbon reduction potential of hydrogen. However, it's noteworthy that introducing preheated hydrogen into the blast furnace didn't guarantee lower CO2 emissions. For hydrogen volumes below 300 m³/THM, CO2 emissions rose as hydrogen temperature increased. Conversely, when hydrogen injection surpasses 300 m3/THM, elevated hydrogen temperatures correspond with decreased CO2 emissions. The most significant reduction in CO2 emissions, amounting to 26.1%, occurred when hydrogen at 1250 °C was blown at a rate of 350 m³/THM. These findings contribute to a more comprehensive understanding of hydrogen's potential for emissions reduction, underscoring the importance of intricate factors in optimizing its implementation in the blast furnace smelting process.

A reuse approach of grinding sludge: Analysis of corrosion and mechanical properties of oxyacetyline torch melted Fe and Cu alloy

This study mainly focuses on investigating the feasibility of utilizing grinding sludge, a by-product of grinding steel plates, as an alternative raw material by filtering and compressing the sludge, removing impurities, adding copper wire bits, and analyzing the resulting samples for improved hardness and corrosion resistance. To improve the hardness and convert the sample to a definite shape, copper wire bits are added to the separated Fe particles during melting. These copper wire bits, which are common scrap available during electrical maintenance, are melted together with Fe particles using the oxy-fuel steel cutting torch at a temperature range of 1539–1600 °C. The melted samples are then characterized using XRD, optical, and scanning electron microscopy analyses. The XRD results confirm the presence of a body-centered cubic lattice structure. Optical and scanning electron microscopy analyses reveal the formation of grains and the mixing of Cu with Fe. Further investigations are conducted to analyze the strength and corrosion properties of the samples. Micro-hardness and electrochemical analysis are performed, and the results show that the addition of copper wire bits improves the corrosion resistance and micro-hardness of the Fe. The fact that the addition of copper wire bits during the melting process improved the corrosion resistance and micro-hardness of the Fe means that the samples can now be sent to the cupola furnace for melting and reuse. This is a sustainable approach that will allow for the responsible disposal of the materials, while also potentially reducing the need for new materials in future production processes.

Effect of solid solution tungsten on the radiation-induced amorphization in bulk M23C6 fabricated by vacuum induction melting

To provide a mechanistic understanding of the stability of the M23C6 phase under irradiation, the crystalline to amorphous (c-a) transition behavior in bulk M23C6 specimens with a variation in tungsten (W) content subjected to helium ion irradiation was investigated. The Cr-W-C ternary ingots with a W concentration range of 0–11.6 at.% were fabricated by vacuum-induced furnace melting. Microstructure characterization revealed that the dominant phase in the ingots was M23C6 regardless of the W concentration, and a small amount of metallic-Cr, (Cr, W), and W-rich carbide co-existed as the minor phase. The lattice parameter of M23C6 increases with an increase in W concentration, and the maximum value is 1.083 nm when the W content is 11.6 at.%. Based on this, the chemical formula of the M23C6 particle in F82H steel was represented by Cr20W3C6 or Cr19W4C6 because its lattice parameter was estimated to be 1.08–1.09 nm. From the grazing incident X-ray diffraction analysis before and after irradiation, the amorphous peak was only observed in the specimen of W concentration 11.6 at.% after irradiation, which was further confirmed by transmission electron microscopy analyses. It is clarified that the c-a transition behavior in M23C6 is dependent on the W content, the amorphization of M23C6 can be mitigated when the W concentration is 6.8 at.% or less under the present study condition.

Corrosion behavior of CaO–Al2O3–SiO2–MgO-Cr2O3 slag on MgO refractory brick for smelting of chromite

The MgO bricks were generally used as the refractory linings in electric furnace smelting of chromite ore. The reaction mechanisms between the MgO refractory and CaO-Al2O3-SiO2-MgO-Cr2O3 slags were experimentally investigated. The elemental distribution and phase compositions at the contact surface between slags and refractory bricks were studied using thermodynamic calculations and SEM-EDS techniques analysis. The main phase of the refractory brick was MgO, while the main phases of slag were pyroxene ((Ca, Mg) AlSi2O6), chromium spinel (Mg (Al, Cr)2O4), and magnesium olivine (2MgO·SiO2). The EDS analysis showed that the main phases at the contact surface of slag and refractory brick were calcium magnesium olivine and magnesium olivine, and the proportion of calcium magnesium olivine phase increased with the increase of slag basicity. Furthermore, the thermodynamic calculation indicated that the melting temperature and the slag viscosity decreased with the increase of slag basicity, and then the molten slag more easily penetrated the pores of refractory brick and caused brick corrosion.

Detoxication and recycling of chromium slag and C-bearing dust via composite agglomeration process (CAP)-blast furnace method

The utilization of virulent chromium slag has always been a worldwide problem, and lots of C-bearing dust produced in steel industry has not been utilized efficiently. Sintering is a potential method to treat these two kinds of solid wastes, but it is limited by small treatment capacity, incomplete detoxification of Cr(Ⅵ) when they were directly added into sintering process. In this study, an innovative technology of co-processing chromium slag and C-bearing dust via composite agglomeration process (CAP)-blast furnace method was put forward and systematically investigated. In the CAP, the chromium slag and C-bearing dust were first made into composite pellets and added into the matrix feed for co-sintering. The results showed that, 20% chromium slag and 5% C-bearing dust could be co-disposed by the CAP without destroying the quality of the sinters. Cr(VI) was completely reduced to Cr(III) or metal Cr. 12.83% Cr existed as metal Cr, and the rest of Cr existed in spinel as (Mg, Fe)(Cr, Al)2O4 or in silico-ferrite of calcium and alumina as Cr(Ⅲ). After blast furnace smelting, 90.22% Cr in sinters entered stainless mother liquor to be recycled.

Numerical Analysis of Metals Under The Influence of Electromagnetic Field at Different Current Values

The primary factors of the widespread use of induction melting furnaces are uniform metal and heat distribution due to its mixing features, low alloy losses, excellent temperature and composition control, versatility in processing different materials, the ability to quickly start the process from a cold state when needed, and the absence of air pollution problems. In induction heating, not all sides of the part to be heated receive an equal amount of heat. Only if the part to be heated is of the type that conducts heat very well can all sides of the part be heated close to each other. Induction heating produces high heat on the surface, less on the inner parts, and least on the center of the material. This heating varies depending on the frequency of the current source and the penetration depth. In this study, a model was created in ANSYS numerical analysis program by taking the current, which is one of the electromagnetic and thermal parameters affecting the temperature distribution in the metalic material in induction heating, at different values. In the simulation model created, three-dimensional numerical analysis results of a cylindrical metallic material were obtained. In the simulation program, the power and frequency required for the design of the induction coil and the magnetic permeability, resistivity, heat transfer coefficient of the material and the position of the material in the inductor are determined as boundary conditions. Depending on these variables, the temperature and magnetic field distributions on the material were obtained. In addition to the numerical analysis, a cylindrical metallic material with known properties was placed in a specially manufactured induction coil and the temperature values on the material were measured to verify the numerical analysis. ANSYS modeling results with the same material dimensions, properties, and other parameters used in the experiment, were given and examined in comparison with the experimental results.

МОДЕЛЮВАННЯ ВІДБИВНОЇ ПЛАВИЛЬНОЇ ПЕЧІ, ОСНАЩЕНОЇ ВИХРОВОЮ КАМЕРОЮ З ДУГОВИМ ІНДУКТОРОМ

A scheme of a reverberatory furnace for melting aluminium waste in a vortex flow of melt created by a curve inductor in a separate cylindrical chamber is presented. The vortex chamber, which is connected to the furnace's melting bath by means of two channels, performs two functions in this furnace: it stirs the molten metal in the bath and creates a vortex funnel into which the pulverized charge is fed. A mathematical model for numerical research of electromagnetic and hydrodynamic processes in such a system is formulated. The influence of the angle of attachment of the suction and pumping channels to the side cylindrical surface of the vortex chamber on its parameters was determined. Such pa-rameters were the average speed of liquid metal in the furnace bath, the melt flow through the cross sections of the connecting channels and the average angular speed of the metal in the chamber. It was established that the angle of the connection of the suction channel has little effect on the operation of the chamber, in contrast to the angle of the pump-ing channel, which in order to achieve maximum efficiency of metal stirring in the bath should take minimum values, and to create the maximum vortex funnel should be more than 500. Considerations are given regarding the compromise values of this angle, which can ensure the necessary operation of the chamber, both from the point of view of the liquid metal stirrer in the furnace bath, and from the point of view of the rotating device of the metal in the chamber. Ref. 8, fig. 5. Keywords: reverberatory melting furnace, vortex chamber, curve inductor, liquid metal, modelling of electromagnetic and hydrodynamic processes, connecting channels, angle of connection of channels to the vortex chamber.

Nine types of iron smelting furnaces in southern Siberia in the first millennium AD: A review of archaeological and chronological data

This article systematizes all currently known archaeological data and radiocarbon dates related to iron-smelting furnaces from Southern Siberia. On the basis of 159 excavated and well-preserved furnaces, nine construction types can be identified. The analysis of a series of radiocarbon dates made it possible to revise previous models about emergence and development of iron metallurgy in Southern Siberia and neighboring regions. We conclude that iron metallurgy developed in the region not in the Scythian time, as has long been assumed, but in the subsequent Xiongnu period of the 2nd century BCE – 2nd century CE. During the 3rd–6th centuries CE, metallurgy flourished, which is expressed in the different types and numerous smelting furnaces that coexisting in the same region. This article raises for the first time the problem we have called the ancient Türkic metallurgy paradox. This inexplicable phenomenon describes the sudden and almost complete disappearance of iron metallurgy in Southern Siberia in the 7th century CE.

Research and Application of Coupled Mechanism and Data-Driven Prediction of Blast Furnace Permeability Index

In order to ensure the stable operation of blast furnace production, it is necessary to keep abreast of the trends in the gas permeability index of the blast furnace. As one of the key parameters to be monitored in the process of blast furnace smelting, the gas permeability index directly reflects the performance of the blast furnace in the actual production of the furnace. Continuous monitoring of the permeability index is required in the actual production of the blast furnace in order to effectively guarantee the stable and smooth operation of the blast furnace. The aim of this study is to accurately predict the trend in the blast furnace gas permeability index by constructing an intelligent prediction model and utilizing a data-driven approach to monitor the gas permeability index and ensure the stable operation of the blast furnace. First, based on the actual production data of a #2 blast furnace of an iron and steel enterprise, an isolated forest algorithm is applied to detect and eliminate the outliers in the original data, and then a data driver set is constructed after normalization of the deviation. Second, by analyzing the coupling mechanism between the blast furnace permeability and gas flow, as well as Spearman correlation analysis and MIC maximum information coefficient (MIC) analysis, key parameters are screened out as feature variables from the data-driven set. Finally, a wavelet neural network algorithm is used to construct an intelligent prediction model of the blast furnace gas permeability index. Compared with a BP neural network (BP), a particle swarm-optimized BP neural network (PSO-BP), and XGBoost, the wavelet neural network shows obvious advantages when the error is controlled in the range of ±0.1, and the prediction accuracy can reach 95.71%. The model is applied to the actual production of a #2 blast furnace of an iron and steel enterprise, and the results show that the predicted value of the blast furnace permeability index is highly consistent with the actual value of real-time blast furnace production, which verifies its excellent characteristics.

Calculation of the Magnetic Field of a Current-Carrying System

With regard to the study of the characteristics of electrovortex flows occurring indirect current electric arcs and electroslag smelting furnaces, a method has been developed for calculating the magnetic field in a current-carrying medium based on the calculation of the Biot–Savart–Laplace integral. The developed technique is focused on the use of unstructured grids and does not require a priori information about the shape of the computational domain. The technique has been tested on problems that have an analytical solution, i.e., the calculation of the distribution of the magnetic field in the cylinder and the calculation of the magnetic field of the ring with the current. The distributions of the magnetic field are obtained for the two-dimensional and three-dimensional cases. We used NVIDIA CUDA technology on graphic processor units (GPUs) to speed up calculations. A comparison of the calculation times on various CPUs and GPUs is given.

Thermoelectric Performance of Ca2Si Synthesized by High-Temperature Melting

Ca2Si was successfully synthesized via a high-temperature melting furnace and a spark plasma sintering process, allowing its thermoelectric properties to be studied. High-temperature melting furnaces were utilized to inhibit the volatilization of Ca elements during the preparation stage, ensuring the production of high-purity Ca2Si. The resistivity of Ca2Si increased gradually with rising temperature and reached 12 mΩ·cm at 873 K, demonstrating semi-metallic characteristics. In the temperature range of 323 K–873 K, Ca2Si displayed relatively low total thermal conductivity, from 1.1 to 1.7 W·m−1·K−1. Nevertheless, Ca2Si attained a maximum thermoelectric figure of merit (ZT) of 0.1 due to the atypical behavior and electrical properties of semiconductors. In contrast, Mg2Si achieved a ZT value of 0.32 at 873 K, owing to its exceptional Seebeck coefficient.

Bronze producing tool of the first half of the 1st century BC from West Georgia

The Article is a discusses of the scientific research process of operating principles of bronze producing tools- crucibles discovered by archeologists in Sachkhere region, village Sairkhe, at Sakhoveli metallurgical spot in 1968. These artefacts always attracted attention due to their original form. But for scientists, it remained a mystery that despite of abundance of crucibles and cast bronze objects of different purposes revealed at Sairkhe site during the archeological excavations, the presence of high temperature producing furnace for metal melting, where these crucibles could have been placed, has never been discovered. As a result of multiple experiments and based on the reliable scientific arguments, we were able to determine that the metallurgists from Sairkhe possessed totally original method of bronze production. They created such type of crucibles that didn’t need big furnaces producing high temperature. Melting and alloying copper for producing bronze was possible with these crucibles themselves, thus making the most complicated and expensive metallurgical cycle, simple and cheap.

Antimony and gold substance flows analysis of pyrometallurgical process for antimony-gold concentrates

In this paper, substance flow analysis was used to analyze the production of antimony and gold in the pyrometallurgical process of complex antimony and gold concentrate. The comprehensive recovery and utilization of antimony and gold concentrate were studied in detail by establishing antimony and gold mass balance accounts and substance flow charts. The results showed that the resource efficiency of antimony and gold was 88.85% and 94.86%, respectively. The direct recovery of antimony in the blast furnace, gold smelting furnace, cupellation furnace and reverberatory furnace was 95.44%, 84.95%, 85.11% and 91.22%, respectively. The circular substance flow generated by the cupellation furnace accounted for 72.6% of the total circulation flow. One tonne of antimony accompanied 0.016 tonnes of antimony into water-quenched slag and 0.017 tonnes into the arsenic alkali slag. The proportion of gold entering antimony oxide, precious antimony, antimony matte and water-quenched slag in the blast furnace was 8.4%, 84%, 6.7% and 0.9%, respectively. The proportion of gold entering the gold-bearing products, antimony oxide and antimony slag in gold smelting furnace was 90.6%, 3.6% and 5.8%, respectively.

Improvement of blast furnace production using digital technology

The role of mathematical models in the improvement of the blast furnace smelting technology is shown. Examples include the new developments of the Institute of Metallurgy of the Ural Branch of the Russian Academy of Sciences in the field of digital models of blast furnace production, in particular, two-dimensional and three-dimensional mathematical models of the thermal state of various zones of the blast furnace, including analysis and forecast of phe-nomena of gas dynamics, heat exchange, recovery in blast furnace using a complex of mathematical models; monitoring of refractory lining state and hearth filling using three-dimensional mathematical model of thermal processes; forecast of silicon content and other elements in cast iron and slag based on neural network technologies; optimization of the composition and improvement of metallurgical characteristics of iron ore agglomerate and coke in order to increase the efficiency of blast furnace melting and analysis of the efficiency of blast furnaces based on the calculation of the minimum consumption of coke. These models are based on the consideration of physical, chemical and thermal phenomena occurring in the blast furnace, taking into account their two-dimensional nature implicit in the problem statement. The developed complex of models includes balance (equilibrium) model, models of gas dynamics, heat exchange, reduction, cohesion zone. New developments in the field of analysis and control of thermophysical and physicochemical phenomena occurring in different zones of the blast furnace allow to raise the technology and methods of blast furnace melting to a fundamentally new level, which saves fuel and energy resources. The possibility of using a digital model in tempo with a process using sensor readings through the blast furnace department management system of the enterprise is shown.

Numerical Simulation and Application of an Oxygen-Enriched Side-Blown Smelting Furnace for the Treatment of Electroplating Sludge

In the oxygen-enriched side-blown smelting furnace for the treatment of electroplating sludge, fluent was used to simulate the gas–liquid two-phase flow process. The relationship between the lance diameter, lance inclination, bath depth, and the bath evaluation indicators were studied, and the oxygen lance spacing was optimized. The results show that the high velocity and high gas rate areas were near the oxygen lance, while the stirring dead zones with low velocity appeared in the central and bottom areas of the molten pool. The key parameters were optimized using single-factor analysis and multifactor comprehensive optimization. The results showed that the bath evaluation indicators were all at good levels under the optimal parameter conditions. These were comprehensively obtained as the following: the lance diameter was 25 mm, the lance inclination was 15°, the lance spacing was 1050 mm, and the bath depth was 1500 mm. The industrial test carried out in an environmental protection enterprise in Guangdong achieved satisfactory results. The test shows that the electroplating sludge containing 7.24% Cu can be melted at 1300~1400 °C to obtain matte. Compared with industrial copper slag, the smelting slag has a higher CaO and a lower Fe content.