Papers by Keyword: Induction Melting

Abstract: This study aimed to smelt high-entropy alloys (HEAs) composed of inexpensive and commonly available metallic elements using iron-based alloys, ligatures, and commercially pure metals, and to investigate their phase structure and heat-resistance. High-entropy alloys of the FeNiCrCuAl system were smelted in air using an induction furnace with a crucible lined with rammed neutral aluminum and magnesium oxides. The elements Fe, Ni, Cr, Cu, and Al were introduced via high-alloy cast iron, stainless steel grade GX10CrNiMn-18-9-1 (1.4541), industrial-grade low-carbon ferrochrome (FeCr70C1), binary Cu-33Al ligature, tough-pitch copper, and semi-finished nickel. Samples of the investigated alloys were prepared using lost foam and sand mold casting methods. Microstructural analysis revealed the presence of rounded dendritic branches, copper-rich interdendritic regions, and high-chromium carbides. The phase composition of the as-cast FeNiCrCuAl alloys consisted of multiple phases: solid solutions with a BCC structure ordered in the B2 type, an FCC structure, and complex carbides (FeCr)₇C₃. High-entropy alloys of the FeNiCrCuAl system, with increased aluminum and chromium content, can significantly outperform standard heat-resistant stainless steels in terms of oxidation resistance indicators – surface oxidation rate, and oxidation stability at 900°C and 1000°C. The specific oxidation of the high-entropy alloy FeNiCrCuAl, which contains at least 18 at. % chromium, was 0.1627 mg/cm² after a 4-hour exposure at 1000 °C. Under the same conditions, the specific oxidation of X2CrNi19-11 stainless steel (1.4306) was 0.6689 mg/cm².

Abstract: Fe-6.5wt%Si high silicon steel alloy was prepared using the vacuum induction melting method. Ordered phase formation in Fe-6.5wt%Si alloy was inhibited by adding trace Cu and induction cycle heating purification treatment. The microstructure and magnetic properties of high silicon steel were investigated. The results show that with the increase of Cu content, the alloy microstructure first changed from coarse grain to fine isoaxial crystal, followed by strip dendrite, with ordered cracking. The saturated polarization strength of the alloy decreased from 25.1 emu of the sample without adding Cu and heating once to 21.5 emu for seven cycles, the residual magnetic polarization increased from 0.0255 emu to 0.048 emu, the slope of the magnetization curve slowed down, and the coercive force increased from 2.4 Oe to 4.0 Oe. With the increase of cyclic heating times, the microstructure of the alloy without added Cu refined and transitioned from columnar to equiaxial crystals, from isoaxial dendrite to strip with the addition of 0.03 wt%Cu, and from strip to isoaxial structure with the addition of 0.05 wt%Cu. With the increase of cycle heating times, the saturation magnetization strength of the alloy without Cu and with 0.03 wt%Cu alloy increased, while the recalcitrant force reduced. Conversely, the saturation polarization strength decreased for the alloy with 0.05 wt% Cu, and the coercive force was also reduced.

Abstract: The main aspects of effective dephosphorization of steel under conditions of induction melting are presented. Regularities of scale growth on the surface of iron, as well as the conditions of its catastrophic oxidation, are considered. An industrial experiment was conducted to remove phosphorus from steel intended for brake discs.

Abstract: We report on preparation of Mg₂(Si,Ge,Sn)-based thermoelectric materials by a direct induction melting method in Al₂O₃ crucible. A 40 g ingot of Mg₂Si_0.8Sn_0.1Ge_0.1 was prepared after addition to the batch 10 wt% of Mg excess. Evolution of crystal structure of the induction melted sample upon annealing and spark plasma sintering (SPS) was tracked by room-temperature X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods. An evidence for the formation of Mg₂(Si,Ge,Sn) solid solution was obtained from the crystal lattice parameter of this phase which was found to be larger than that of undoped Mg₂Si. XRD and SEM indicated that alongside with the main phase of the Mg₂(Si,Ge,Sn) solid solution, an impurity phase of Mg₂Sn exists in the sample. Amount of the Mg₂Sn impurity phase is significantly reduced in spark plasma sintered sample.

Abstract:

Aluminum-Multiwalled carbon nanotubes (Al-CNTs) composite was fabricated using air induction melting technique. The nanotubes were dispersed in molten aluminum using innate string action of induction heating at 760 °C. A heavy fluxing condition was used to avoid oxidation of the nanotubes and molten aluminum. The nanotubes were satisfactorily dispersed in the matrix as observed during metallographic examination using scanning electron microscope.
 
  The tribological properties (i.e. coefficient of friction and wear rate) of the Al-CNTs composite were investigated using ball-on-disk machine under dry wear condition at 2 cm/sec speed and 3N load. It was observed that both of the tribological parameters exhibited decreasing trends with increasing contents of the nanotubes, which was due to the self lubricating and structural features of the nanotubes. Improved tribology of the composite was the attribute of appreciable dispersion of the nanotubes in the matrix besides their exceptional mechanical properties and reinforcement.

Abstract: The method ofinduction cladding was adopted to make nickel-base layer on the surface ofsteel components in this test, and microstructure morphology, rigiditydistribution of the alloy layer made by cladding were analyzed and studied. Theresults shows that there is obvious bright white transition zone between thecladding alloy layer and the body, which forms an excellent metallurgicalbonding, microstructure of the alloy cladding layer is eutectic structure ofaustenite + carbide (austenite dendrite can be seen at individual parts), axialand radial rigidity are evenly distributed; bonding strength of cladding alloylayer is high without air hole and slag inclusion, with high flatness ofcylindrical surface, small machining allowance and low cost, etc.

Abstract: The temperature and velocity distribution of melting pool fields is very important effect to the silicon purification in vacuum induction furnace. A numerical model for the electromagnetic-thermal hydrodynamic coupling field has been developed by using the finite element method (FEM) and a two-dimension numerical simulation for temperature of metallurgical-grade silicon melting in vacuum induction furnace was carried out by using a software Multi-physics Comsol 4.2 in this paper. The results showed that the temperature field was dependent on induction heating times and melting pool position and the maximum temperature grads was 400K in constant temperature stage. With the silicon was molted gradually two vortexes were come into being for electromagnetic stirring in the smelting poor.

Abstract: The effects of technical parameters on initial silicon melting in cold crucible continuous casting were studied. These parameters include the materials, the shape and the position of the base, the mass of the silicon that set on the top of the base. Through experimental and theoretical analysis, the optimized parameters were finally given: the base graphite with obconical shaped should be put at the level of the second turn of the coil, and the initial silicon with 10g should be put on the base. The mechanism of these parameters affecting on the initial melting are discussed and revealed.

Abstract: Sn-filled and Fe-doped CoSb3 skutterudites were synthesized by encapsulated induction melting. A single δ-phase was obtained by subsequent annealing, as confirmed by X-ray diffraction. The as-solidified ingot consisted of mixed phases of -CoSb, -CoSb2, δ-CoSb3 and elemental Sb. The phases could be transformed by annealing, and the phases of the as-solidified ingot annealed at 773 K for 24 h transformed to δ-CoSb3. The temperature dependence of the Seebeck coefficient, electrical resistivity and thermal conductivity were examined from 300 K to 700 K. The positive Seebeck coefficient confirmed p-type conduction. The electrical resistivity increased with increasing temperature, which showed that the SnzCo3FeSb12 skutterudite is highly degenerate. The thermal conductivity was reduced by Sn-filling because the filler atoms acted as phonon scattering centers in the skutterudite lattice. The thermoelectric figure of merit was enhanced by Sn filling and its optimum composition was considered to be Sn0.3Co3FeSb12.

Abstract: Te-doped CoSb3 was prepared by the encapsulated induction melting, and its doping effects on the thermoelectric properties were investigated. Single phase d-CoSb3 was successfully obtained by the subsequent annealing at 773K for 24 hours. Tellurium atoms acted as electron donors by substituting antimony atoms. Thermoelectric properties were remarkably improved by the appropriate doping. Dimensionless figure of merit was obtained to be 0.83 at 700K for the CoSb2.8Te0.2 specimen.