Intermediate Frequency Induction Furnace Research Articles

Microstructures and properties of Ni-Si precipitation strengthened phosphor bronze

To strengthen phosphor bronze, this work attempted to form precipitate nanoparticles in the matrix by adding alloying elements. First, Ni and Si were identified as alloying elements through mixing enthalpy analysis. Then, Cu-8Sn-0.1P, Cu-8Sn-0.1P-0.5Ni-0.12Si, Cu-8Sn-0.1P-1Ni-0.24Si, and Cu-8Sn-0.1P-2Ni-0.48Si alloys were prepared by intermediate frequency induction furnace. After that, the microstructures of these alloys were characterized and their properties were tested. Experimental results indicated that Ni31Si12, Ni2Si, and Ni5P4 phases are newly formed in the as-cast microstructure after adding Ni and Si. At the same time, the eutectoid size of α-Cu and Cu41Sn11 in the as-cast microstructure of Ni-Si added phosphor bronze is reduced, the secondary dendrite arm spacing is reduced, and the segregation is also improved. After aging treatment, nano-sized cellular Ni2Si and trace Ni5P4 phases are precipitated in the Ni-Si added phosphor bronze. With the formation of nanoprecipitates, Ni-Si added phosphor bronzes show excellent precipitation strengthening effect after aging treatment, and the electrical conductivity of Cu-8Sn-0.1P-0.5Ni-0.12Si and Cu-8Sn-0.1P-1Ni-0.24Si alloys is also slightly higher than that of Cu-8Sn-0.1P. This study provides a new solution for strengthening phosphor bronze, enabling phosphor bronze alloys to meet higher performance and broader applications.

Composition, Microstructure and Properties of Ultra-High-Strength Steel for Offshore Structural Application

In this paper, first, based on the employing environment and properties requirement of offshore platform, the influence of various alloying elements on the performance of steel was analyzed and chemical composition of a new ultra-high-strength alloy steel was designed. Then, the designed alloy steel specimen has been prepared using intermediate frequency induction furnace. Austenization temperature of the steel was determined through thermal dilatometer. The effects of quenching and tempering process on microstructure and mechanical properties of the steel were studied by means of optical microscopy (OM), scanning electron microscopy (SEM), durometer and universal material tensile tester. The research results indicated that the casting microstructure of the designed steel was a duplex structure of martensite and acicular bainite. The austenitizing onset temperature (Ac1) and termination temperature (Ac3) was 700°C and 790°C, respectively. With the increase of the austenitizing temperature, the hardness of the steel first increased until it reached the maximum value at 860°C and then decreased above 860°C. Meanwhile, the hardness of the steel decreased with the increasing of the tempering temperature in the range 150°C-500°C. The optimal heat-treatment processes were concluded as follows: heating up to 860°C, quenching by oil, and then tempering at 170°C. The superior mechanical properties of tensile strength of 1400MPa and elongation of 6.5% as well as the microstructure of tempered martensite were obtained after this heat treatment.

Effect of annealing treatment on the anti-pulverization and anti-corrosion properties of La0.67Mg0.33Ni2.5Co0.5 hydrogen storage alloy

The La0.67Mg0.33Ni2.5Co0.5 hydrogen storage alloy was prepared by the vacuum intermediate frequency induction furnace followed by annealing treatment. The pulverization degree of both the as-cast and annealed alloy powders after gaseous hydriding and dehydriding cycle was investigated and the discovery was that annealing treatment could hardly ameliorate their anti-pulverization ability. The element content of La, Mg, Ni and Co existing in electrolyte before and after the electrochemical cycles by using ICP-AES technology was also analyzed and it showed that a large amount of La and Mg were dissolved in the electrolyte, but the amount of dissolution for La and Mg significantly declined when the alloy was annealed. The XRD analysis revealed that all the alloys consisted of two main phases AB3 and AB2 and a residual phase AB5 while annealing treatment made the AB2 phase decrease slightly. Furthermore, the anti-corrosion abilities of various elements in different phases of the as-cast and annealed alloy samples were studied by analyzing the element (La, Mg, Ni, Co) change with the corrosion time in phases AB3 and AB2 by means of EDS. It turned out that the element of La was mainly corroded out from the phase AB2 while not easily from the phase AB3. However, the element of Mg was both easily corroded out from the phases AB2 and AB3, but the corrosion was more obvious in the phase AB3. Therefore, annealing improved the anti-corrosion performances of La and Mg in the phase AB2.

Composition Design, Microstructure and Properties of Ultra-High-Strength Steel Using for Energy Storage Flywheels

According to the properties request of energy storage flywheels running in high speed, chemical composition of a new ultra-high-strength steel has been designed. The designed steel specimen was prepared using intermediate frequency induction furnace and its transformation point, which had been simulated and calculated through J-Mat software in advance together with cooling curves, was investigated using by thermal dilatometer. Then the microstructure and mechanical properties of the designed steel have been evaluated by means of OM, SEM, durometer and universal material tensile tester. Simulation results showed that the pearlitic transformation of designed steel occurred at 687-453°C and bainite transformation at 453-340°C. Martensitic transformation started at 340°C and terminated at 220°C. The experimental results indicated that the casting microstructure of the designed steel was a duplex structure consisting of martensite and acicular bainite with a small amount of retained austenite. The austenization temperature ranged from 698°C to 790°C. The superior comprehensive mechanical properties of tensile strength of 1900MPa and elongation of 6.65% as well as the microstructure of tempered martensite was obtained after heat treatment.

Analysis of recoverable waste heat of circulating cooling water in hot-stamping power system

This article studies the possibility of using heat pump instead of cooling tower to decrease temperature and recover waste heat of circulating cooling water of power system. Making use of heat transfer theory the article carried on analysis and calculation about recoverable waste heat of circulating cooling water in hot-stamping power system which includes hot-stamping, closing-in and extrusion intermediate frequency induction furnace. The results show that the whole process can recover a calorie which is 2.642 × 106 kJ per hour. Using the recycled calories can make 15.82 tons hot water per hour which is 60 °C. So it can reduce burning capacity of coal 180.29 kg/h. The hot water can provide the needed water for production and workers bathing. This research shows that using heat pump to recover the waste heat of circulating cooling water is effectual. Realizing the use of waste heat, it can reduce pollution of condensing heat, reduce operating cost and noise of cooling tower, reduce site and the occupation of equipment, improve the production efficiency, and can also save the natural resources (fossil fuel-coal) and reduce the cost of needed hot water production.

Utilization of Waste Heat of Circulating Cooling Water in Hot-Stamping Power System

This paper studies the possibility of using heat pump instead of cooling tower to decrease temperature and recover waste heat of circulating cooling water of power system. Making use of heat transfer theory the paper carried on analysis and calculation about recoverable waste heat of circulating cooling water in hot-stamping power system which includes hot-stamping, closing in and extrusion intermediate frequency induction furnace. The results show that the whole process can recover calories which is 2.642×106kJ per hour.Using the recycled calories can make 15.82 tons hot water per hour which is 60°C. This research shows that using heat pump to recover the waste heat of circulating cooling water is effectual.

Effects and mechanism of titanium modification on structures of cast steel ZG270-500

The influences of titanium modification on the solidification behavior, shrinkage characteristic and primary austenite refinement of cast steel ZG270-500 smelted in intermediate frequency induction furnace were studied. 0.15wt% titanium modification increased the fluidity of the steel liquid, enhanced the feeding capacity of cast steel, changed the dispersed shrinkage porosity to concentrated shrinkage cavity, turned the coarse dendrites into fine equiaxed grain structures and greatly reduced the primary austenite grain size. By scanning electron microscope (SEM) and energy disperse spectroscope (EDS) analysis, it was found that titanium combined with carbon to be solid phase particles TiC, with high melting point, to promote the primary austenite nucleation authentically by non-spontaneous nucleating. The crystal lattice match growing model between γ-Fe and TiC was established. The mechanism of TiC heterogeneous nucleating existed in that the primary austenite grew up by {111}γ-Fe parallel to the closest packed plane {111}TiC in the crystal orientation 〈110〉γ-Fe//〈211〉TiC. The crystal planes mismatch \( \delta _{\{ 111\} _{\gamma - Fe} }^{\{ 111\} _{TiC} } \) and the lowest orientation mismatch \( \delta _{\{ 110\} _{\gamma - Fe} }^{\{ 110\} _{TiC} } \) were 8.18%. and 2.25% respectively, almost achieving complete coherent lattice match growing of austenite on TiC.

Influence of Cr2O3-Al2O3 composite oxide scale on oxidation resistance of ZG40Cr24

Test alloys ZG40Cr24 with alloying of 3 wt% aluminium were cast by intermediate frequency induction furnace. The oxidation resistance of test alloys at 1 000 °C for 500 hours was examined according to oxidation weight gain method. The scale morphology and composition were studied using scanning electron microscope (SEM) and X-ray diffraction (XRD) respectively. By energy dispersive spectroscopy (EDS) studies, a kind of composite oxide scale compounded highly by Cr2O3, Al2O3 and spinel MCr2O4 in molecule scale came into being at high temperature. With flat and compact structure, fine and even grains, such composite scale granted complete oxidation resistance to alloy ZG40Cr24. The oxidation resistance mechanism was studied deeply in electrochemistry corrosion. The P+N semiconductor composite scale composed plenty of inner PN junctions, of which the unilateral conductive and the out-of-order arrangement endowed itself insulating in all directions. The positive and negative charges in scale could not move, and the mobile number and transferring rate of them both dropped enormously, as a result, the oxidation rate of the matrix metal was cut down greatly. So the composite scale presented excellent oxidation resistance.

Effects of Nickel on Structure and Properties of Ferro Superalloy

The affecting law of nickel on structure and properties of ferro superalloy, which was cast by intermediate frequency induction furnace, were studied by orthogonal experimental method. The tensile strength and oxidation weight gain rate at 1000°C were tested. The matrix microstructure and scale morphologies and composition were studied using scanning electron microscope (SEM) and X-ray diffraction (XRD) respectively. It was found that the high temperature tensile strength went up with the increase of nickel by the forming of high temperature strengthening phase of γ’. After 100 hours aging at 1000°C, γ’ phase separated in blocks. Certain content of nickel improved the high temperature oxidation resistance of test alloys, but excess of it caused the higher oxidation weight gain rate and loose structure oxide scales with holes and exfoliating. In considering of high temperature tensile strength and oxidation resistance, the ideal content of nickel in ferro superalloy should be 9wt.%, with which at 1000°C the tensile strength of test alloys mostly exceeded 70MPa, and the average oxidation weight gain rate was only 0.55g.m-2.h-1, reaching the strong oxidation resistance. Such scale was compounded by Cr2O3 and Fe(Ni)Cr2O4 with compact structure, fine and even oxide grains.

Effects of Vanadium Microalloying on Hardness of Alloy ZG270-500

The effects of vanadium microalloying on the hardness and its distribution of alloy ZG270-500 smelted in intermediate frequency induction furnace were studied. Vanadium microalloying increased the hardness of test alloys effectively. By scanning electron microscope (SEM) and energy disperse spectroscope (EDS) analysis, it was found that VC was the powerful heterogeneous nuclei, which prompted numerous nucleating, refined the structure grains and caused the serious crystallographic lattice distortion, so the hardness increased. Proper content of vanadium prompted more even hardness distribution across the whole temperature front section. However, overdoes vanadium microalloying easily caused mass oxides of V2O3, which kept solid phases with high meting point in metal liquid to increase the viscosity and decrease the fluidity of metal liquid, resulting in inadequate metal liquid feeding, serious structure shrinkage porosity in center and worse hardness distribution along the different isotherm fields. 0.16wt.% vanadium microalloying brought the optimal hardness uniformity among test alloys with the approximate 1 hardness ratio R between the center and the margin.

Study of Titanium Modification on Hardness of Cast Steel

The effects of titanium modification, which was added along with the pouring liquid in ladles, on the hardness and its distribution of cast steel ZG45 smelted in intermediate frequency induction furnace were studied. Titanium modification increased the hardness of cast steel effectively. By scanning electron microscope (SEM) and energy disperse spectroscope (EDS) analysis, it was found that TiC, acting as heterogeneous nuclei, could refine the structure grains, causing the serious crystallographic lattice distortion. So the hardness increased. Proper content of titanium prompted more even hardness distribution across the whole temperature front section. However, overdoes titanium modification easily caused mass nitrides or oxides, which kept solid phases with high meting point in metal liquid to cause difficulties in metal liquid filling and shrinkage, resulting in less concentrated shrinkage cavity and serious structure rarefaction. The hardness ratio between that of internal and external with overdose titanium modification decreased instead compared to that of none modification.

Effects of Titanium Microalloying on Steel Feeding and Contraction

Proper content of titanium, microalloying in steel ZG200-400 smelted in intermediate frequency induction furnace, could effectively increase the volume of concentrated shrinkage cavity, and restrain the forming of shrinkage porosity. The concentrated shrinkage cavity was analyzed quantitatively by stuffing wet gluten and draining water method. The maximal cavity arrived at 0.18wt.% titanium microalloying. By scanning electron microscope (SEM) and energy disperse spectroscope (EDS) analysis, it was found that TiC, acting as heterogeneous nuclei, could refine the structure grains, diminish the strong dendrites, and increase the fluidity and feeding capacity of steel liquid. However, overdoes titanium microalloying easily caused mass nitrides or oxides, which kept solid phases with high meting point in metal liquid to increase its viscosity, decrease the fluidity and enlarged the composition supercooling. So the metal liquid, with poor feeding, left more shrinkage porosity, less concentrated shrinkage cavity in solidification.

Effects and Mechanism of Titanium on Cast Fluidity of ZG45

The effects of titanium modification, which was added along with the pouring liquid in ladles, on the shrinkage porosity and cavity of cast steel ZG45 smelted in intermediate frequency induction furnace were studied. The metal liquid fluidity was measured by casting spiral samples. 0.2 wt.% titanium modification achieved the highest fluidity for steel liquid. Proper content of titanium could effectively increase the volume of concentrated shrinkage cavity, and restrain the forming of shrinkage porosity. By scanning electron microscope (SEM) and energy disperse spectroscope (EDS) analysis, it was found that TiC, acting as heterogeneous nuclei, could refine the structure grains, diminish the strong dendrite, and increase the fluidity and feeding capacity of steel liquid. However, overdoes titanium modification easily caused mass oxide TiO2, which kept solid phases with high meting point in metal liquid to increase its viscosity and decrease the fluidity. Meanwhile, these solid state titanium compounds enlarged the composition supercooling, so the metal liquid changed from sequential solidification to simultaneous solidification, resulting in inadequate metal liquid feeding, less oncentrated shrinkage cavity and serious shrinkage porosity.

Effects and Mechanism of Titanium Modification on Shrinkage Cavity and Porosity of Cast Steel

The effects of titanium modification, which was added along with the pouring liquid in ladles, on the shrinkage porosity and cavity of cast steel ZG35 smelted in intermediate frequency induction furnace were studied. Proper content of titanium could effectively increase the volume of concentrated shrinkage cavity, and restrain the forming of shrinkage porosity. The concentrated shrinkage cavity was analyzed quantitatively by stuffing wet gluten and draining water method. The maximal cavity arrived at 0.15wt.% titanium modification. By scanning electron microscope (SEM) and energy disperse spectroscope (EDS) analysis, it was found that TiC, acting as heterogeneous nuclei, could refine the structure grains, diminish the strong dendrites, and increase the fluidity and feeding capacity of steel liquid. However, overdoes titanium modification easily caused mass nitrides or oxides, which kept solid phases with high meting point in metal liquid to increase its viscosity and decrease the fluidity. On the other hand, these solid state titanium compounds enlarged the composition supercooling, so the metal liquid changed from sequential solidification to simultaneous solidification, resulting in inadequate metal liquid feeding, less oncentrated shrinkage cavity and serious shrinkage porosity.