Melting Stock Research Articles

Integrated processing of ferriferous materials in blank production for mechanical engineering facilities

The paper considers the possibility of reducing the use of crude ore for metal product by using aluminothermy, which facilitates effective integrated processing of metal waste generated by engineering and metallurgy facilities in the form of mill scale, ferrous and non-ferrous metal swarf with simultaneous castings production. The paper studies the impact patterns of thermite components ratios on the parameters of extracting chemical elements from the source components, metal phase output and its chemical composition. The possible applications for experimental alloys resulting from controlled exothermic reactions are determined for supplying castings and melting stock to blank production for mechanical engineering facilities.

USE OF OWN WASTE METAL IN THE PRODUCTION OF SINGLE-CRYSTAL PERMANENT MAGNETS

The applicability of waste metal formed in the manufacture of single-crystal permanent magnets of UNDKT5AA alloy is studied. Since this waste accumulates detrimental impurities, it cannot be re-used in the production. Additional cleaning of initial melting stock with solid oxidants was applied to prevent alloy contamination with impurities. An example was provided for calculating a required solid oxidant volume. The material of graphite intermediate ladle in contact with melt was replaced with pure alumina. Waste metal formed afterwards featured a reduced content of detrimental impurities. Such waste materials were used as a melting stock component in the production of single-crystal permanent magnets. All magnets met quality requirements, while the cost of production dropped by more than 30 %.

Aluminium Evaporation during Ceramic Crucible Induction Melting of Titanium Aluminides

Melting TiAl based alloys in ceramic crucibles often leads to chemical contamination, alloy heterogeneity and non-metallic inclusions. The severity of such phenomena usually depends on the nature of crucible materials, the melting stock composition and the melting parameters, namely superheating time and temperature and melting pressure. Among the referred drawbacks, Al loss during melting is a critical aspect, as its concentration in TiAl based alloys has a very strong effect in their mechanical properties. Although a few studies of critical factors affecting the evaporation behaviour of Al during electron beam and induction skull melting of Ti-Al alloys had been carried out, until now no information was released on this subject for the ceramic crucible induction melting process. In this work a Ti-48Al alloy was induction melted in a zircon crucible with Y2O3 inner layer, using 50 and 100 °C superheating temperatures and 0, 60 and 90 second holding times, and poured into a graphite mould. The effect of different temperature/time combinations in the alloy composition, Al loss by evaporation and extent of the metal/crucible interaction was studied for different melting pressures. Al loss was found to increase significantly for melting pressures below around 10-1 mbar, at a rate that increases as melting pressure decreases, until a maximum rate is reached, remaining constant for lower pressure levels. Metal/crucible interaction increased directly with the melting pressure and superheating time, leading to alloy contamination with yttrium and oxygen. For the experimental set-up and conditions used on this work, optimal superheating time/pressure combinations that lead to acceptable alloy composition and sanity have been identified.

Effect of melting pressure and superheating on chemical composition and contamination of yttria-coated ceramic crucible induction melted titanium alloys

When melting reactive alloys, chemical composition and alloy homogeneity strongly depend on processing conditions, especially if melting is performed in ceramic crucibles. In this case, the nature of crucible materials, the melting stock composition and the melting parameters (atmosphere, pressure, superheating time and temperature) are critical processing variables. In this work, a Ti–48Al alloy was induction melted in a ZrO2·SiO2-based crucible with Y2O3 inner layer using different superheating temperatures (1600 and 1650 °C) and times (0, 60 and 90 s) and poured into a graphite mould. The influence of different temperature/time combinations in the alloy composition, Al loss by evaporation and metal/crucible interaction was studied for different melting pressures. Al loss was found to increase significantly for melting pressures below 10−2 mbar and increases with increasing superheating time and temperature. The experimental results concerning to Al loss are in agreement with theoretical (and experimentally validated) models available for induction skull melting of TiAl. Metal/crucible interaction directly increased with melting pressure, superheating time and temperature, leading to alloy contamination with Y and O. For the experimental set-up used in this work, optimal temperature/superheating time/pressure combinations that lead to acceptable alloy composition have been identified.

Experimental growth and structural-morphological characteristics of co-tourmaline

Experiments aimed at investigating opportunities of Co-tourmaline growth onto a seed crystal in aqueous boron-chloride cobalt-containing solutions under temperatures of 400‐500 ° C and pressure up to 1000 bar were performed. Experiments were conducted under thermogradient conditions in titanium autoclaves, and in several cases with the help of a dividing diaphragm. Tourmaline growth onto a seed crystal occurs only with the use of separate tourmaline-forming components (monocrystal corundum and quartz rods) as the melting stock. The layer (up to 600 micron) of Co-tourmaline grown is intensively crimson-colored and occurs only at the face of positive monohedron {+0001}. Along with the monocrystal outgrowth, a great amount of very fine (30‐150 micron in size) tourmaline crystals of selfgeneration nucleation occurred on the seed crystals and in the melting stock. Their composition does not differ from the grown layer composition, and their unit cell parameters ( a = 15.82638 ± 0.00215 A, c = 7.09434 ± 0.00186 A) correspond to intermediate values of the tourmaline group minerals olenite and elbaite. Tourmaline is a complex borosilicate of the general crystal chemical formula XYZ , where X corresponds to large voids filled with Na, Ca, K, or a vacancy; Y corresponds to closely packed octahedrons of Mg, Fe 2+ , Li, Al, Mn, and Cr; and Z corresponds to deformed octahedrons of Al and Fe 3+ . In nature tourmaline rather often occurs in granite pegmatites and pneumatolyte‐hydrothermal and hydrothermal formations. Its presence is not unusual in such granites as well as in metasomatites and metamorphic rocks. This indicates the diversity of the tourmaline formation conditions. Interest in growing tourmaline monocrystals is connected with the task of obtaining new promising piezoelectric and pyroelectric materials possessing enhanced characteristics in comparison with those already known. Moreover, synthetic tourmaline can be used as a substitute for the natural form in the jewelry industry similar to other synthetic analogues of precious stones. There are many questions concerning the tourmaline formation conditions in nature that have remained unclear up until the present despite numerous geological, mineralogical, geochemical, and crystal chemical investigations. Safe and reproducible methods of growing its monocrystals have also not been developed. This situation is connected in general with the tourmaline complex chemical composition resulting in the existence of numerous varieties according to shades of color, which often change even within the single crystal. Obviously, this is a consequence of complex and changing physicochemical crystallization conditions of this mineral during its growth as well as special predisposition of its structure to a wide exhibition of iso- and heterovalent isomorphism. Investigations in the sphere of synthesis and growth

Wear of Direct-Bonded Magnesia-Chrome Ore Refractories in the RH-TOB Process

In order to elucidate the wear mechanism of direct-bonded magnesia-chrome ore refractories in RH-TOB (RH-Top Oxygen Blowing), crucibles were made from the MgO-Cr2O3 refractory, which are used as a side wall refractory material for the RH-TOB lower vessels. The crucibles were charged with melting stock to carry out the oxygen blowing experimental at 1650°C. Experiment was discriminated the wear by FeO permeation and the wear by Fe fume. The chromite in the MgO-Cr2O3 refractory creates a complex spinel of a high melting point with FeO, therefore chromite is stable and shows a high corrosion resistance on FeO. On the other hand, FeO that has a very low melting point permeates magnesia that are composed of fine particles combined by silicate bonds. Consequently, an eutectic reaction causes the bond melts and separating the particles. The wear during the RH-TOB process results from the oxidation heat that is produced when the Fe fumes react with oxygen and impact the refractory dissolve away both magnesia and chromite.

Effect of B, Zr, Ce and Nb addition on structure and mechanical properties of high carbon Fe-10.5 wt% Al alloy

Iron aluminides based on Fe3Al offer a combination of attractive properties such as excellent resistance to oxidation and sulfidation with lower density and material cost than austenitic and ferritic steels [1–3]. However poor room temperature ductility, poor toughness, poor machinability and low strength as well as poor creep resistance at temperature above 873 K have limited their acceptance for structural applications. Recent developments have indicated that the room temperature ductility to Fe3Al alloys can be improved by the addition of Cr, Ce and combined addition of Zr and C. [4–7]. The addition of Nb, Mo and W has significantly improved the high temperature strength and creep resistance [8– 10]. Recently, it has also been shown that, carbon may be an important alloying element to Fe–Al alloys containing 8–16 wt% (15–28 at.%) aluminum. The addition of carbon up to 1 wt% leads to improved strength, creep resistance and machinability and resistance to environmental embrittlement [11–14]. The addition of carbon also allowed the use of the low cost raw material such as steel scrap. The purpose of the present paper is to report the effect of B, Zr, Ce and Nb addition on microstructure and mechanical properties of ternary high carbon Fe-10.5 wt% Al-0.7 wt%C base alloy at ambient and high temperature of 873 K. Forty-kilogram melts of five alloys with nominal compositions listed in Table I were prepared in an Inductotherm medium frequency air induction-melting furnace (all compositions are in wt% unless otherwise specified). Induction melting was carried out under protective flux cover (AIMFC) in an alumina-lined crucible using proprietary charging schedule. The melt was top-poured in to 55-mm diameter spilt cast iron molds. Commercial purity aluminum, ferro-cerium, ferro-boron, Nb, zirconium sponge and steel scrap were used as raw materials. The total amount of impurities (Mn, Si, Cu, P etc.) present in melt stock was about 0.7 wt%. The 55-mm diameter AIMFC ingots were

Melting and casting of FeAl-based cast alloy

The FeAl-based intermetallic alloys are of great interest because of their low density, low raw material cost, and excellent resistance to high-temperature oxidation, sulfidation, carburization, and molten salts. The applications based on these unique properties of FeAl require methods to melt and cast these alloys into complex-shaped castings and centrifugal cast tubes. This paper addresses the melting-related issues and the effect of chemistry on the microstructure and hardness of castings. It is concluded that the use of the Exo-Melt™ process for melting and the proper selection of the aluminum melt stock can result in porosity-free castings. The FeAl alloys can be melted and cast from the virgin and revert stock. A large variation in carbon content of the alloys is possible before the precipitation of graphite flakes occurs. Titanium is a very potent addition to refine the grain size of castings. A range of complex sand castings and two different sizes of centrifugal cast tubes of the alloy have already been cast.

Reducing defects in remelting processes for high-performance alloys

Defect reduction is one of the most important goals in continuing research to improve remelting technologies, such as vacuum arc remelting, electroslag remelting, or hearth melting (plasma or electron beam), of specialty alloys. Ingot defects may originate from several sources in these processes, such as foreign materials in the melt stock or electrode, drop-in material from the furnace interior, and solidification defects. Laboratory-and industrial-scale melting experiments are used by Sandia National Laboratories and the Specialty Metals Processing Consortium to determine relationships between melt-processing conditions and defect formation. Examples described here include freckle formation, a solidification defect in large ingots of alloy 625 (electroslag remelting), and alloy 718 (vacuum arc remelting). These examples demonstrate how integrated melting experiments, process modeling, and ingot analysis can guide the control of melting conditions to reduce defects.

Exo-MeltTM process for melting and casting intermetallics

Abstract Melting of Ni 3 Al-based intermetallic alloys was successfully accomplished by the Exo-Melt TM process by modifying the furnace-loading sequence to initiate the highly exothermic NiAl reaction to form superheated NiAl liquid initially. Recorded images of the melting process showed the occurrence of exothermic diffusional reactions between liquid aluminum and solid nickel melt stock. Combustion synthesis of NiAl and Ni 3 Al is also described and compared with the Exo-Melt TM process. In contrast to the Exo-Melt TM process, the conventional melting practice of adding aluminum to molten nickel increased the temperature of the bath from 1600 to 2300 °C, and a vapor cloud formed due to the oxidation of alloying elements. The Exo-Melt TM process results in power savings of 47% over conventional melting practices, and the process has been used to melt and cast a total of 8000 kg of Ni 3 Al-based alloy. Reaction mechanisms involved in the Exo-Melt TM process and conventional melting processes are described and compared with the reaction mechanisms operating in combustion synthesis.

Microstructural refinement of a superalloy by progressive induction melting

The microstructure of a nickel-based superalloy has been refined by a progressive induction melting technique. The control on heating rate was achieved by manipulating the melt stock position with respect to the induction furnace coils and by regulating the power supply to the furnace. The melt stock was suspended to obtain molten metal droplets with minimum superheat. These droplets were collected in a rotating watercooled copper mould to obtain an ingot with fine microstructure. Measurements of secondary dendrite arm spacing show reduction of one order of magnitude in the refined ingot. Increase in hardness was also registered and is considered to be a result of grain refinement.

超清浄メルティング・ストックの製造技術について

Production of super clean Ni base melting stocks were fundamentally investigated by using two vacuum induction furnaces having capacities of 50kg and 1ton.Under an usual MgO lining, it was possible to obtain about 10ppm of oxygen content, by limiting each titanium addition less than 2% of the melt and by lowering the bath temperature after the addition of active elements.Application of CaO lining enabled more effective deoxidation to attain oxygen levels less than 10ppm.Nitrogen content in the stocks can be removed to about 10ppm, by strict selection of charged materials, high temperature vacuum refining, reduction of air leakage and shortening interrupted time of vacuum evacuation.A thin wall mold and strong heat insulating hot top provided the melting stock with much better surface properties and decreased shrinkage cavities. As the result of these technical improvements, the overall quality of stocks are remarkably elevated.

Atmospheric corrosion of steels prepared from the magnetic fraction of urban refuse

The magnetic fraction of urban refuse was used as melting stock in the preparation of a high-strength, low-alloy (HSLA) steel and a carbon steel. Product steels were made from incinerated steel can scrap, nonincinerated-nondetinned steel can scrap, nonincinerated-detinned steel can scrap, and dilutions of these scraps with No. 1 heavy melting scrap. In continuing tests, 101.6 x 152.4 x 3.2 mm panels of the product steels were exposed to industrial, rural, and marine environments to determine their atmospheric corrosion properties. Panels of the respective commercial steels were exposed at the same time to establish baseline data for the test sites. Weight-loss data are reported for atmospheric exposures of 0.5, 1.0, 1.5, and 3.8 years. The marine environment was the most corrosive; the industrial environment was the least corrosive. The atmospheric corrosion resistance of the carbon steel was improved 25% by using incinerated scrap and nonincinerated-nondetinned scrap in the steelmaking process. In no case was the atmospheric corrosion resistance of the carbon steel degraded by using the magnetic fraction of urban refuse as melting stock. The residual elements responsible for improving the corrosion resistance of the carbon steel were identified as tin and copper. At the levels present in the product steels, chromium, nickel, and lead had no observable effect on the corrosion resistance of either the HSLA steel or the carbon steel.

Use of urban refuse magnetic fractions for steelmaking

A study was conducted by the Bureau of Mines to determine problems associated with the use of magnetic fractions from urban refuse as melting stock for steelmaking and to evaluate the resulting steel products. The study involved 50-pound (22.7 kg) ingots from laboratory melts and 50-pound ingots from 1-ton (907 kg) electric-arc-furnace melts. The 50-pound ingots from the laboratory melts and the arc-furnace melts were hot-rolled to provide material for mechanical and corrosion testing. Results obtained in the study include the following: Most steels rolled successfully and exhibited acceptable surface and edge conditions. Tensile strengths of the plain carbon steels were not significantly affected by copper up to concentrations of 0.65 percent and were not affected by tin content up to 0.16 percent. Yield strength increased with increasing copper and tin contents and impact strength decreased with increasing tin content. Hardness increased slightly with increasing copper content. In general, properties of the steel produced were not measurably affected by charge composition (that is, melting stock), melting practice, or method of scrap preparation.

The re-solution of inclusions in remelted stainless steels

As a follow-up to work done on the remelting of three grades of 300 series stainless steels on a small scale electroslag remelting unit, adjunct studies were made on the kinetics of inclusion re-solution during the “electrode stage” of remelting. The objective of this study was to attempt to quantify the metallographic observations of many investigators that vary-ing degrees of inclusion re-solution do take place during the consumable remelting of numer-ous grades of metals and alloys. In specific, the rate(s)of re-solution of the large stringer inclusions found in the 300 series air melt stock was investigated. A known and controlled temperature gradient was imposed on long cylindrical specimens for varying times and, by a metallographic inclusion sizing and counting technique described in this paper, a series of isochronal and isothermal data was generated. Plots of rates of re-solutionvs time indi-cated a zero-order reaction mechanism and the activation energy calculated from the mea-sured reaction rate constants was found to be 36,000 J/mole.

The effect of trace impurities on the stress-corrosion cracking susceptibility and fracture toughness of 18Ni maraging steel

A series of 18Ni maraging steels of overall commercial purity but containing also deliberate impurity additions of S, P, C, Cr and Si + Mn has been studied. The fracture toughness and stress-corrosion resistance (determined using plane-strain fatigue-precracked specimens tested in 35x NaCl solution) of these steels have been compared to the fracture toughness and stress—corrosion resistance of a commercial-purity 18Ni maraging steel with no deliberate impurity additions, and to a similar steel prepared from special high-purity melting stock. The most important conclusions reached are that: (I) Ultra-high purity steels do not have significantly improved stress—corrosion resistance but show useful increases in fracture toughness when the C content is less than 0005 per cent; (II) Simultaneous additions of Mn + Si result in extremely low fracture toughness values; (III) High C contents (greater than 003 per cent) result in marginally improved stress—corrosion resistance; (IV) High Cr contents result in rather poor stress—corrosion properties. The fracture toughness results have been correlated with the electron transmission microstructure of the steels and the results of a fractographic analysis of the fracture surfaces.

Sponge Iron and H-lron For Electric Furnace Charging

Economics of the use of virgin melting stock in electric furnace steelmoking is not only a matter of the relative cost of melting stock as charged. Possible savings also result from Sower furnace operating costs. Sower rolling, forging, and annealing costs, and improved customer rehtions resulting from a known and uniform quality steel. Producers know that a large portion of their problems would be solved by reducing residual content of their steel ingots to half the present levels and ma’mtoinmg it at a known level. This desirohSe end can be achieved by use of virgin melting stocks.

Effect of Certain Elements on the Graphitization of Steel

Abstract An investigation was undertaken to obtain information on (a) the relationship, if any, between the aluminum and nitrogen contents of a steel and the susceptibility of the steel to graphitization, (b) the manner in which chromium influences the process, and (c) the effect of normal amounts of Mn, Si, S, and P in the graphitization of steel. Toward these objectives, twelve laboratory heats of iron-carbon alloy were made from specially prepared melting stock. Various amounts of Al, N, Cr, Mn, Si, S, and P were added to these heats. They were forged to ⅝-in-square bars, variously heat-treated, bead-welded, and tested for graphitization at 1025 F for periods of time extending to 8000 hr. Information on the progress of graphitization in the specimens was obtained by metallographic examination. The data obtained included the number of graphite nodules per unit area (as a measure of nucleation), the average nodule diameter, and the per cent conversion of carbide to graphite—all as functions of time. The evidence generally indicated that the graphitization process, whether occurring in the weld-heat-affected zone or in unaffected parent metal, took place by means of a nucleation and growth mechanism, which envisages a time rate of nucleation.