Production Of Master Alloys Research Articles

ТЕХНОЛОГІЧНІ ОСОБЛИВОСТІ ОДЕРЖАННЯ СПЛАВІВ ТА ЛІГАТУР СИСТЕМИ TI–ZR–NB–SN В УМОВАХ ЕЛЕКТРОННО-ПРОМЕНЕВОЇ ЛИВАРНОЇ ТЕХНОЛОГІЇ

Electron beam casting technology is a unique method for obtaining cast products and semi-finished products from a wide range of titanium alloys. This technology can be very promissing in production of biocompatible titanium alloys for endoprosthesis. A particularly difficult and important task in this context is preparation of Ti-Zr-Nb-Sn system alloys with high strength and low modulus of elasticity. As a result of experimental development of specified alloys melt preparation technological modes, possibility of obtaining complex titanium alloys with a high content of zirconium and niobium was shown. It is also determined, that when the niobium content in the charge is more than 30 % wt. there is a decrease in the concentration of titanium and zirconium in the melt due to their freezing on the walls of the skull. As a result, there is a change in the chemical composition of the melt, the amount of niobium in which can exceed 50 % wt. Maximum amount of tin that can be assimilated in titanium-based melts under EBCT conditions is 5 % wt., and niobium-based melts are twice less. It has been proven that obtaining melts of Ti-Zr-Nb-Sn system with a precise chemical composition, using the chosen method, is a difficult and still unsolved problem, but due to the possibility of melting alloys with a high content of niobium and zirconium in its conditions, this method is effective in the production of master alloys and ingots for the production of powders used as raw materials for additive tmanufacturing. Keywords: titanium alloys for endoprosthesis, foundry production, Ti-Zr-Nb-Sn, electron-beam casting technology.

A Method of Producing Al–REE Master Alloys Using Exchange Reduction Reaction

Modern aerospace engineering relies on Al-based alloys with enhanced high-temperature strength properties and oxidation resistance. These requirements can be fulfilled by modifying alloys’ structure employing rare earths metal doping. Direct addition of metallic rare earths to aluminium is complicated due to high chemical activity of molten rare-earth metals and significant vapor pressure of aluminium at elevated temperatures. To overcome these drawbacks, lanthanide-containing master alloys with relatively low REE content can be employed instead of pure scandium.Currently there are three methods for preparing aluminium-based alloys containing rare earths, i.e. direct fusing, molten salt electrolysis and exchange or metallothermic reduction reactions. In the last case, Al–Gd and Al–Sc master alloy can be prepared by aluminothermic reduction of GdF3 or ScF3 in a molten binary NaF–KCl salt mixture at 800–1050 °С.In the present work we suggest the modification of the above mentioned method for aluminium–cerium and aluminium–neodymium master alloy production with a lanthanide concentration of 1 to 7 wt. %. Based on thermodynamic calculations we proposed that the high-temperature exchange reaction between metallic aluminum and corresponding fluoride containing salt electrolyte should be carried out at temperatures from 740 to 780 ° C to provide the higher recovery of REE. The influence of the time of the exchange reaction and «aluminium–salt» ratio on the process to obtain ligatures of various compositions is analyzed. The yield higher than 85 % is achieved.The microstructure of the alloys represents a metal matrix of aluminum in which intermetallic compounds of Ln3Al11 compositions are distributed In the case of an exchange reaction between aluminum and cerium fluoride, the formation of a new phase, presumably related to the Al4Ce intermetallic compound, is found.

World experience of aluminum master alloys application and advanced Ukrainian developments in this field

The work is devoted to the review of master alloys, used for the preparation of aluminum alloys. It is noted that the master alloys market in the world is represented by a small number of companies that specialize in their production. It is important that large aluminum casting manufacturers, such as the German company VAW, the French Pechiney, the Norwegian corporation Norsk Hydro and others also produce or have a production base and advanced technologies for the production of master alloys of their own production and are able to meet their own demand. The classification of master alloys for aluminum alloys according to their purpose is also considered. Depending on the master alloy type, the type in which it is supplied and the features of its introduction into the melt are determined. A comparison and assessment of the state of domestic production and the master alloy market is carried out, which shows that most companies in Ukraine do not enter the market with their proposals and mainly use foreign master alloys, or small volumes of their own production. The issue of attracting innovative experience and technologies for the production of aluminum master alloys at enterprises also remains unresolved. On the example of work carried out at the Physico-technological Institute of Metals and Alloys of the NAS of Ukraine, the existing scientific and technical potential to increase the competitiveness of Ukrainian ligatures is noted. Thanks to the unique technologies and approach implemented at the Institute, it is possible to obtain master alloys of Al-Zr and Al-V systems with quality and structure indicators better than foreign analogues. Especially important is the ability to create complex and unique ligatures with a high content of modifier components at the level of 5–20 %wt. These include Al-Mo, Al-Hf, Al-Ti-Zr, Al-Fe-Mn and some others. Existing technological solutions for obtaining these and many other master alloys have a huge potential and economic feasibility not only to meet the needs of domestic industries, but also to enter the international world market.

Optimization of Reduction Process of Egyptian Ilmenitevia Metallothermic reactions

It is important to develop technologies for the production of master alloys for industrial applications. Detailed research on reduction of titanium from Egyptian ilmenite by an aluminothermic process in a graphite Crucible was charged by the mixture of ilmenite, flux, aluminum was investigated. This paper study the effect of aluminum feed (10%- 35%), flux material (type, and amount), and temperature preheat from 50 o C to 400 o C and time of preheating from 0.5 hr. to 3 hrs. Then, the metallic samples formed by the reduction were analyzed using X-ray diffraction, scanning electron microscopy. The mixed fluxes were strongly and successfully reduced ilmenite to a high-purity master alloy with small amounts of detected impurities. Key words: Aluminothermic, Egyptian ilmenite, flux, ferrotitanium, master alloy DOI : 10.7176/CMR/11-7-04 Publication date :September 30 th 2019

OPTIMIZATION OF REDUCTION PROCESS OF EGYPTIAN ILMENITE VIA METALLOTHERMIC REACTIONS

It is important to develop technologies for the production of master alloys for industrial applications. Detailed research on reduction of titanium from Egyptian ilmenite by an aluminothermic process in a graphite Crucible was charged by the mixture of ilmenite, flux, aluminum was investigated. This paper study the effect of aluminum feed (10% - 35%), flux material (type, and amount), and temperature preheat from 50 oC to 400 oC and time of preheating from 0.5 hr. to 3 hrs. Then, the metallic samples formed by the reduction were analyzed using X-ray diffraction, scanning electron microscopy. The mixed fluxes were strongly and successfully reduced ilmenite to a high-purity master alloy with small amounts of detected impurities.

An integrated approach for production of stainless steel master alloy from a low grade chromite concentrate

As an alternative process, the production of stainless steel master alloys in blast furnace (BF) exhibits high economic efficiency and great potential to use low-grade chromite resources. To produce desirable sinter products required by the blast furnace smelting process, sintering tests of ore mixtures made from a low grade South African chromite concentrate (Cr2O3/FeO = 1.99) and Chinese magnetite concentrate were performed in a sinter pot in terms of various sintering parameters including coke dosage, mix moisture, sinter basicity and proportion of magnetite concentrate, etc. An integrated process comprising “high pressure grinding rollers (HPGR) pretreatment, pelletizing, coke coating, pre-drying and non-fluxed sintering” steps was proposed based on the pellet-sintering technique. The quality of Cr-bearing sinters was evaluated. The results show that high quality Cr-bearing sinters can be obtained through the proposed process. Addition of 40% or more magnetite concentrate in ore blends promises to yield desirable sinters of proper chemical composition and good metallurgical properties required by the blast furnace smelting process. The smelting performance of the Cr-bearing sinter made from the 40% chromite and 60% magnetite mixture was assessed under simulated blast furnace smelting conditions. It is feasible to use the Cr-bearing sinters in blast furnace for stainless steel master alloy production. A stainless steel master alloy containing 71.75% Fe, 19.52% Cr and 7.84% C with phosphorus and sulfur contents (<0.015%) is obtained at Fe and Cr recovery rates of 92.55% and 87.53%, respectively, when smelting at 1550 °C for 60 min with slag compositions (10% Al2O3, 10% MgO and R2 = 1.0). The bonding mechanism of Cr-bearing sinters and the formation mechanism of liquid phase were further revealed by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS). Both slag bonding (10 to 20% silicate) and solid bonding (recrystallization of spinel phase) contribute to the consolidation of the Cr-bearing sinters. Increasing the basicity of sinter made from 100% chromite concentrate or addition of magnetite concentrate in the ore blend at natural basicity lead to the formation of low-strength slag bonds, which generally reduces the sinter strength.

Preparation of Novel Al-Er Master Alloys in Chloride-Fluoride Melt

A novel Al-Er master alloy has been prepared through in situ metallothermic reactions of NaErF4 and aluminium melts. The compound NaErF4 is formed as a result of the interaction of NaF and ErF3 in the melt medium KCl. The metallothermic reactions produce erbium, which through low solubility in molten aluminium and forms intermetallic compound Al3Er. The microstructures of the Al-Er master alloy with different contents of the alloying metal has been investigated. The results showed that the Al-Er master alloy mainly consisted of phases of α-Al and Al3Er, that confirmed by the results of X-ray diffraction. Backscattered electron imaging of the Al-Er master alloy under a scanning electron microscope (SEM) revealed the presence of phase Al3Er, which crystallized in the eutectic composition [Al+Al3Er]. The observed microstructure is explained according to the eutectic reaction in an Al-Er phase diagram. The preparation of Al-Er master alloy by the metallothermic reduction method will allow to reduce energy consumption for master alloy production and to reduce the cost of aluminium alloys alloyed with Er through the novel master alloy.

Effect of cooling rates of production process of Al-3%B-3%Sr master alloy on grain refinement and eutectic modification efficiency in cast A356 alloy

In this paper, size and morphology of the grain refiner and modifier particles in the Al-3%B-3%Sr master alloy production by using different cooling rates were investigated. Two Al-3%B-3%Sr master alloys were produced with 0.2 and 10°C/s, respectively. The grain refinement and eutectic modification efficiency of the Al-3%B-3%Sr master alloy were tested in casting process of A356 alloy by addition of 4wt.% and holding times for 10-120 min. The experimental result showed that microstructure of the M1 alloy (Slow cooling) consisted of larger solidified particles of AlB2, SrB6and Al4Sr in the matrix of α-Al compared to the M2 alloy (Rapid cooling). The addition of the M1 alloy in cast A356 alloy, it was found that small grain size and fully modify eutectic silicon were obtained from the holding time in a range of 10-60 min. While the addition of M2 alloy, a small grain size was achieved in shorter holding time in a range of 10-30 min but the eutectic silicon was partly modify. From the thermal analyzed result, solidification of un-modified A356 alloy was changed after addition of Al-3%B-3%Sr master alloy. It was clearly observed that both the undercooling of nucleation and eutectic reaction was reduced and the solidification time was shifted to longer.

Concentration of Scandium during Processing the Distillate of Production of the Aluminum–Scandium Foundry Alloy

The composition and characteristics of the sublimate of the aluminum–scandium Al–2%Sc master-alloy production are investigated using electron microscopy, electron probe microanalysis, X-ray phase analysis, and inductively coupled plasma emission spectroscopy. It is established that the sublimate consists of particles 1–5 μm in size by 60 %; the coarser of them have a shell, inside which, inclusions (segments, particles, pieces) of various phases are present. The sublimate consists of metal aluminum (~35 %), two modifications of aluminum fluoride (~57 % total), and the rest is corundum. The scandium content is 0,5–0,6 wt %. It is shown that the use of hydrometallurgic methods is reasonable for its processing. The method of preparing «rich» concentrate with 3–11 wt % Sc from this type of waste by the treatment of the sublimate with the 10-% caustic soda solution at 80 °C is proposed.

Concentration of scandium during processing the sublimate of production of the aluminum-scandium master alloy

The composition and characteristics of the sublimate of the aluminum-scandium Al-2%Sc master alloy production are investigated using electron microscopy, microprobe analysis, derivatography, X-ray analysis, and emisionno-spectral method with inductively coupled plasma. It is established that 98% of the sublimate consists of particles 1–2 μm in size; the coarser ones have a shell in which inclusions (segments, particles, and pieces) of various phases are present. The sublimate consists of metal aluminum (∼35%), two polymorphs of aluminum fluoride (∼57% total), and the rest is corundum. The scandium content is 0.5–0.6 wt %. It is shown that the use of hydrometallurgic methods is reasonable for its processing. The method of preparing a “rich” concentrate with 3–11 wt % Sc from this type of waste by treating the sublimate with a 10% caustic soda solution at 80°C is proposed.

Production of in situ aluminum–titanium diboride master alloy formed by slag–metal reaction

Al–TiB 2 master alloys have received much attention in recent years owing to their potential as efficient grain refiners for aluminum foundry alloys. In this study, the process of production of master alloys was investigated to develop a low cost method, namely, slag–metal reaction. This method can be used to fabricate Al–TiB 2 master alloy in situ from the TiO 2–H 3BO 3–Na 3AlF 6 and Al system. Since the price of the raw materials is low and the technology is simple, the processing technique appears to reduce the cost of the master alloy. Because of exothermic reactions, not much energy is needed to melt materials. In this process, Titanium diboride particles were formed in situ through the reactions of TiO 2, H 3BO 3 and Na 3AlF 6. Results showed that when the aluminum melted, the condensed TiB 2 particles that formed in situ were spherical with an average diameter of 1 μm. Furthermore, these TiB 2 particles were distributed uniformly through the master alloy.

Reduction of tantalum pentoxide with aluminium and calcium: thermodynamic modelling and scale skilled tests

High reactivity of powdered aluminium together with its relatively low price are the main reasons for the application of this metal as a reducing agent for the reduction of oxides and fluorides of rare and rare earth metals by the aluminothermal method. This technology is widely used in the production of master alloys for ferrous metallurgy. The ”out-of-furnace” process (i.e. without external heat access) is the prevailing technology for metallic niobium production worldwide. However, aluminothermal reduction for industrial production of metallic tantalum has been limited because of the high required temperature, over 2800℃. In this paper the results of simultaneous reduction of tantalum (V) and iron (Ⅲ) oxides by calcium-aluminothermal ”out-of-furnace” process are presented. Powdered aluminium and metallic calcium were used as reductants. The pickup of tantalum at smeltings with the mass of raw materials over 1 kg reached 94%. The metal was obtained in the form of compact ingot; separation of metallic and slag phases was excellent. Crushed melt underwent refining remelting in an electron beam furnace. For thermodynamic studies and optimization of the aluminothermal reduction processes of Ta2O5 and Fe2O3 in the temperature range of 1000-3000℃ a licensed computer simulation program ”HSC Chemistry 6.1, 2007”, elaborated by the company Outotec Oy, was applied.