Vacuum Arc Remelting Research Articles

. Структура і властивості електрошлакових зварних з’єднань титанового сплаву ВТ6

Electrometallurgy Today, 2022, №02. SOVREMENNAYA ELEKTROMETALLURGIYA Quarterly scientific-technical and production journal. ISSN: 2415-8445, Since 1985. Text in Russian, contents and summaries in English. The journal presents the results of theoretical and experimental research carried out at the PWI in the field of electrometallurgy. Special attention is given to electroslag technology (electroslag melting, refining and casting). The journal is divided into the following main sections: electroslag technology; electron beam processes; plasma arc technology; vacuum arc remelting and vacuum induction melting; general problems of special electrometallurgy.

Математичне моделювання процесів випаровування при ЕПП сплавів на основі алюмініду титану системи легування Ti–Al–Nb–Cr–Mo

Electrometallurgy Today, 2022, №02. SOVREMENNAYA ELEKTROMETALLURGIYA Quarterly scientific-technical and production journal. ISSN: 2415-8445, Since 1985. Text in Russian, contents and summaries in English. The journal presents the results of theoretical and experimental research carried out at the PWI in the field of electrometallurgy. Special attention is given to electroslag technology (electroslag melting, refining and casting). The journal is divided into the following main sections: electroslag technology; electron beam processes; plasma arc technology; vacuum arc remelting and vacuum induction melting; general problems of special electrometallurgy.

Study on microsegregation and homogenization process of a novel nickel-based wrought superalloy

In this paper, the as-cast microstructure, microsegregation, precipitates and suitable homogenization process of a novel Ni-based wrought superalloy prepared by vacuum induction melting (VIM) + vacuum arc remelting (VAR) were investigated by optical microscope (OM), scanning electron microscope (SEM), electron probe microanalysis (EPMA), differential scanning calorimetry (DSC), high temperature confocal laser scanning microscope (HT-CLSM) and thermal simulation compression. The results show that severe element segregation exists in the ingot. Nb, Ti and Al are mainly segregated in the interdendritic region, while W is mainly segregated in the dendrite arm. The precipitates in the alloy mainly include non-uniform γ′ strengthening phase, coarse (γ + γ′) eutectic phase and MC carbide, among which, the redissolution temperature range of γ′ phase is 1060–1220 °C; the (γ + γ′) eutectic phase can be redissolved obviously above 1180 °C but melted into liquid at 1250 °C; the redissolution temperature range of MC carbide is 1349–1358 °C, exceeding the solidus temperature of the alloy. After homogenization at 1220 °C/10 h, all the γ′ phase and most of the (γ + γ′) eutectic phase can be redissolved, and the element segregation can be significantly alleviated, moreover, the hot deformation resistance of the alloy is lower and the dynamic recrystallization (DRX) degree is higher, indicating that 1220 °C/10 h is an ideal single-stage homogenization process.

Enhancement of mechanical properties of a novel single phase Ni1.5FeCrCu0.5 HEA through cold rolling and subsequent annealing

A novel single-phase Ni1.5FeCrCu0.5 High entropy alloy was fabricated by Vacuum Arc Remelting (VAR). The evolution of the alloy's microstructures, crystallographic texture, and mechanical behavior was investigated in as-cast, cold rolling (90% thickness reduction), and annealing (1000 °C for 1 h) conditions. Microstructural evolution demonstrated that the dendritic structure of the as-cast HEA was associated with a very small amount of Cu element segregation, which changed to tense elongated grains after cold rolling. Cold rolling resulted in development of Goss {110}<001>, Goss/Brass {110}<111> and Brass {110}<112> as the major texture components. After annealing, the complete recrystallization structure appeared in an average grain size of 3 μm, and deformation texture components remained. The results indicated the cold rolling led to a significant strengthening of the alloy; its yield strength and ultimate tensile strength of the alloy reached 1220 and 1574 MPa, which was 5 and 3.5 times the as-cast conditions (yield strength: 236 MPa and ultimate tensile strength: 454 MPa), respectively. However, the elongation was reduced to 5%. Eventually, the elongation in the recrystallization state increased approximately seven times.

Numerical modeling and experimental validation of the effect of arc distribution on the as-solidified Ti64 ingot in vacuum arc remelting (VAR) process

A numerical model coupling electromagnetic field and plasma arc impact with multiphase transport phenomena such as flow, heat transfer and solidification for the vacuum arc remelting (VAR) process is proposed. 3D simulations of the VAR process for refining a Titanium-based (Ti–6Al–4V) alloy are made. Different arc distributions (diffusive, constricted centric, constricted eccentric, and rotating arcs) under an axial magnetic field (AMF) are studied, focusing on their impact on the flow patterns and the resulting melt pool of the as-solidifying ingot. Simulation results show that diffusive arc leads to a shallow symmetrical melt pool; constricted centric and rotating arcs lead to electro-vortex flow and the symmetrical melt pool; constricted eccentric leads to electro-vortex flow as well, but the deepest non-symmetrical melt pool.

Microstructural Analysis and Mechanical Characterization of Shape Memory Alloy Ni-Ti-Ag Synthesized by Casting Route

The purpose of the current research is to study the microstructure and mechanical properties of Ni-Ti-Ag shape memory alloys prepared by the casting route. Ag (grain size at 1 mm) was incorporated into Ni-Ti alloys at varying percentages of weight (0, 1.5, 3 and 4.5 wt.% Ag) to produce shape memory alloys using a Vacuum Arc Re-melting (VAR) furnace. Microstructural analysis was defined by FESEM microscopy and XRD examinations, while the transformation temperatures of the Ni-Ti-Ag shape memory alloy were determined by DSC examination. On the other hand, determination of mechanical properties was carried out using micro-hardness and compressive tests. The results of this work show that Ag was dispersed homogeneously into the Ni-Ti alloy. Moreover, two primary phases (austenite phase and martensite phase) emerged with few impurities. The results of the XRD examination show that the number of Ag peaks increased with the increase in weight percentage of Ag. The transformation temperature of the austenitic phase was defined as −1.6 °C by DSC. The mechanical characterizations increased with the increase in weight percentages of Ag (1.5, 3 and 4.5 wt.%), and significantly affected the mechanical properties of the Ni-Ti alloy. An improvement in compressive strength (42.478%) was found for the alloy with 3 wt.% Ag, while the micro-hardness results show a slight decrease in micro-hardness (8.858%) for the alloy with 4.5 wt.% Ag.

Comparative investigation on ingot evolution and product quality under different arc distributions during vacuum arc remelting process

The arc characteristics especially the arc distribution of the vacuum arc remelting (VAR) process are closely related to the ingot evolution and consequently the final product quality. Taking segregation defects and solidification quality as the indexes to evaluate the final product quality under different arc distributions, a three-dimensional full-scale transient model for predicting segregation defects is developed in this paper. Local solidification time (LST) and secondary dendrite arm spacing (SDAS) are used to characterize the solidification quality. This model is adopted to predict channel segregation (freckle) and macrosegregation defects during VAR process of Ni-5.8 wt.%Al-15.2 wt.%Ta alloy under several typical arc distributions. The results show that the diffuse arc has the shallowest molten pool among several arc distributions. At the early stage of solidification, the solute enrichment channels formed under the Gaussian and diffuse arc are slender and concentrated, while they are relatively sparse and uneven in thickness under the rotating arc. The value of volume-averaged segregation extent is always the smallest under the diffuse arc and the largest under the Gaussian arc, with final values of 67.53% and 69.66%, respectively. The volume-averaged values of LST and SDAS are relatively the largest under the Gaussian arc, about 1599 s and 209 μm, respectively; and they are the smallest under the diffuse arc, about 1520 s and 206 μm, respectively. In the same process conditions, the product quality of VAR ingots prepared under the diffuse arc is the best, followed by the rotating arc, and the worst under the Gaussian arc.

. Аналіз металургійних і зварювальних флюсів, шлаків, аерозолей на вміст гідрогену, нітрогену, оксигену

Electrometallurgy Today, 2022, №01. SOVREMENNAYA ELEKTROMETALLURGIYA Quarterly scientific-technical and production journal. ISSN: 2415-8445, Since 1985. Text in Russian, contents and summaries in English. The journal presents the results of theoretical and experimental research carried out at the PWI in the field of electrometallurgy. Special attention is given to electroslag technology (electroslag melting, refining and casting). The journal is divided into the following main sections: electroslag technology; electron beam processes; plasma arc technology; vacuum arc remelting and vacuum induction melting; general problems of special electrometallurgy.

. Структура і властивості зварних зʼєднань сталі 20, модифікованої наночастинками на основі карбіду вольфраму

Electrometallurgy Today, 2022, №01. SOVREMENNAYA ELEKTROMETALLURGIYA Quarterly scientific-technical and production journal. ISSN: 2415-8445, Since 1985. Text in Russian, contents and summaries in English. The journal presents the results of theoretical and experimental research carried out at the PWI in the field of electrometallurgy. Special attention is given to electroslag technology (electroslag melting, refining and casting). The journal is divided into the following main sections: electroslag technology; electron beam processes; plasma arc technology; vacuum arc remelting and vacuum induction melting; general problems of special electrometallurgy.

. Технологія виплавки зливків цирконієвого сплаву способом вакуумно-дугового переплаву з витратним електродом

Electrometallurgy Today, 2022, №01. SOVREMENNAYA ELEKTROMETALLURGIYA Quarterly scientific-technical and production journal. ISSN: 2415-8445, Since 1985. Text in Russian, contents and summaries in English. The journal presents the results of theoretical and experimental research carried out at the PWI in the field of electrometallurgy. Special attention is given to electroslag technology (electroslag melting, refining and casting). The journal is divided into the following main sections: electroslag technology; electron beam processes; plasma arc technology; vacuum arc remelting and vacuum induction melting; general problems of special electrometallurgy.

. Електрошлакова виплавка у відкритому кристалізаторі зливків з відходів листових обрізків титану ВТ1-0

Electrometallurgy Today, 2022, №01. SOVREMENNAYA ELEKTROMETALLURGIYA Quarterly scientific-technical and production journal. ISSN: 2415-8445, Since 1985. Text in Russian, contents and summaries in English. The journal presents the results of theoretical and experimental research carried out at the PWI in the field of electrometallurgy. Special attention is given to electroslag technology (electroslag melting, refining and casting). The journal is divided into the following main sections: electroslag technology; electron beam processes; plasma arc technology; vacuum arc remelting and vacuum induction melting; general problems of special electrometallurgy.

. Вплив мікроструктури багатошарових фольг Al/Ni на фазові перетворення, ініційовані нагріванням

Electrometallurgy Today, 2022, №01. SOVREMENNAYA ELEKTROMETALLURGIYA Quarterly scientific-technical and production journal. ISSN: 2415-8445, Since 1985. Text in Russian, contents and summaries in English. The journal presents the results of theoretical and experimental research carried out at the PWI in the field of electrometallurgy. Special attention is given to electroslag technology (electroslag melting, refining and casting). The journal is divided into the following main sections: electroslag technology; electron beam processes; plasma arc technology; vacuum arc remelting and vacuum induction melting; general problems of special electrometallurgy.

. Отримання зливків алюмініду титану Ti–28Al–7Nb–2Mo–2Cr способом електронно-променевої плавки

Electrometallurgy Today, 2022, №01. SOVREMENNAYA ELEKTROMETALLURGIYA Quarterly scientific-technical and production journal. ISSN: 2415-8445, Since 1985. Text in Russian, contents and summaries in English. The journal presents the results of theoretical and experimental research carried out at the PWI in the field of electrometallurgy. Special attention is given to electroslag technology (electroslag melting, refining and casting). The journal is divided into the following main sections: electroslag technology; electron beam processes; plasma arc technology; vacuum arc remelting and vacuum induction melting; general problems of special electrometallurgy.

. Формування зони з’єднання шарів в композитному зливку, наплавленому електрошлаковим процесом з рідким металом, для роторів енергетичних турбін

Electrometallurgy Today, 2022, №01. SOVREMENNAYA ELEKTROMETALLURGIYA Quarterly scientific-technical and production journal. ISSN: 2415-8445, Since 1985. Text in Russian, contents and summaries in English. The journal presents the results of theoretical and experimental research carried out at the PWI in the field of electrometallurgy. Special attention is given to electroslag technology (electroslag melting, refining and casting). The journal is divided into the following main sections: electroslag technology; electron beam processes; plasma arc technology; vacuum arc remelting and vacuum induction melting; general problems of special electrometallurgy.

Design characteristics of the strength of VKS-9M and 300M steels

The mechanical properties of square section (up to 350 mm) forgings made of domestic steel VKS-9M (obtained by the duplex process of vacuum induction melting plus vacuum arc remelting) are studied. The mechanical properties of steel VKS-9M and American high-strength structural steel 300M are compared in terms of the calculated characteristics of materials. We extend the concept of «design characteristics of materials» to all the mechanical properties of materials used in determination of the strength and durability of structures. The design characteristics of materials include the strength characteristics under quasi-static tension, compression, crushing and shearing, as well as the strength under variable loads and the crack resistance of the material. The correctness of comparing the calculated values of the static strength of steels VKS-9M and 300M is based on the identity of test methods and the equivalence of processing and presentation of test results. The determination of the strength characteristics was carried out according to domestic standards, which are basically harmonized with the American standards. A difficult situation arises when determining the strength indicators of a newly developed material. Nowel material, as a rule, is developed in laboratory conditions, produced on experimental equipment in small volumes, and, therefore, the statistical assessment of the general population at the development stage is unreliable. In conditions of the full-scale manufacture of industrial semi-finished products, a statistical assessment of their strength characteristics becomes necessary. In the aviation industry, a statistical assessment of the calculated values of the strength characteristics of the material is prescribed by the law. The airworthiness standards set the levels of the calculated values of strength characteristics with a certain probability of non-destruction. For parts, the destruction of which can lead to an accident, the calculated values of the strength characteristics of materials should be selected in such a way that the strength of the material is to be ensured with a probability of 99% — with a 95% confidence interval (basis «A»). Statistical evaluation of the static strength characteristics of two heats of VKS-9M steel on the basis of «A» revealed their insignificant excess in comparison with steel 300M. The data obtained allow us to believe that the calculated values of the static strength characteristics of VKS-9M steel will not be lower than the calculated values for 300M steel. Large-scale fatigue tests of VKS-9M steel were carried out, which proved that the fatigue characteristics of VKS-9M and 300M steels practically coincide, as well as the arrays of their determinations. The equivalence of the strength characteristics of the VKS-9M and 300M steels allows replacement of the American 300M steel by the domestic VKS-9M steel.

Impact of a Transient and Asymmetrical Distribution of the Electric Arc on the Solidification Conditions of the Ingot in the VAR Process

Vacuum Arc Remelting is an important method of processing reactive and refractory liquid metal alloys, including titanium and zirconium alloys. Recent measurements of the electric arc dynamics under the presence of a time-varying magnetic field during an industrial melt of a Ti64 alloy provided evidence of the existence of an ensemble arc motion. Such motion is responsible for transient and non-axisymmetric inputs of electric current and energy at the top surface of the remelted ingot. The present work is an attempt to evaluate, using a simplified numerical simulation approach, to what extent the solidification conditions of the VAR ingot and, consequently, the quality of the final product, may be affected by this phenomenon. The reported results indicate that, under the worst case conditions, the relative vanadium segregation in the solidified ingot can reach values as high as 12.5%.

Evolution of texture in Alloy 80A during initial ingot breakdown

Abstract This paper presents details on the evolution of texture in Alloy 80A during the initial ingot break-down process by means of repeated hot-working (cogging). The ingot was produced by vacuum arc re-melting showing equiaxed and columnar grains. Compression tests were performed with a Gleeble system covering the range of temperatures, strains, and strain rates experienced during processing on an industrial scale. Texture analysis (neutron and electron backscatter diffraction) was applied to all specimens before and after hot deformation to reflect the thermo-mechanical history. The ingot exhibited a well pronounced &lt;100&gt;-fiber texture of the initial microstructure. Low deformation ratios did not change the type of texture, but the degree of the preferred orientation. High strains partially result in the destruction of the fiber texture and lead to the appearance of additional texture components, such as cube- and Goss-components. With continued deformation, recovery and recrystallization become predominant.

Effect of nitrogen addition and aging treatment on microstructure and high temperature mechanical properties of Ti‐48Al‐2Cr‐2Nb (at%) intermetallic alloy

Effects of nitrogen (N) addition (0.5, 1, and 2 at%) on microstructure formation and high temperature mechanical properties of the age-hardened Ti‐48Al‐2Cr‐2Nb (4822, at%) intermetallic alloy were investigated. Alloys were fabricated by vacuum arc re-melting followed by hot isostatic pressing, solution annealing, and finally aging at two different conditions of 700 °C/10 h or 900 °C/1 h. Mechanical properties of the age-hardened samples were investigated via small punch testing at 800 °C. Results showed that N addition resulted in microstructure refinement and increased uniformity of microstructures and mechanical properties. Lamella coarsening and fragmentation was occurred during both aging conditions; however, a more stable lamellar microstructure was achieved by N addition. Colonies with various lamellar orientation showed different fragmentation behavior. Better mechanical properties was achieved in the alloy containing 1 at%N after aging at 900 °C/1 h. Inter-lamellar fracture was the predominant fracture mechanism in all intermetallic alloys.

POWDER CHARACTERISTICS BLENDING AND MICROSTRUCTURAL ANALYSIS OF A HOT-PACK ROLLED VACUUM ARC-MELTED gamma-TIAL-BASED SHEET

In the quest for cost-effective fabrication processes capable of producing sound gamma-TiAl products, the microstructure and mechanical properties of a modified second-generation hot-rolled gamma-TiAl-based alloy with nominal composition Ti-48Al-2Nb-0.7Cr-0.3Si were investigated in this work. The alloy was fabricated using a processing route that involved uniaxial cold-pressing of powders and vacuum arc re-melting. Prior to the cold pressing, the elemental powder characteristics, such as particle sizes and morphologies, were blended to minimise porosity in the compact that might be inherited by the final ingot. A hot-pack rolling process was carried out directly from the melted button-ingot using a conventional two-high rolling mill to produce a 4 mm-thick sheet. The relative density results of both as-compacted and as-melted alloy parts showed a significant reduction of porosity in the alloy. In addition, both the optical and the scanning electron microscopy micrographs of the rolled sheet revealed a typical ‘duplex’ microstructure with a mean grain size of about 9 µm. Moreover, the results from a room-temperature indentation plastometry test of the hot-rolled sheet indicated good mechanical properties with recorded yield strength of about 600 MPa, an ultimate tensile strength of about 850 MPa, and a true plastic strain of about 3%.

Порівняльні показники різних способів переробки стружки високолегованих сталей і сплавів

Electrometallurgy Today, 2021, №04. SOVREMENNAYA ELEKTROMETALLURGIYA Quarterly scientific-technical and production journal. ISSN: 2415-8445, Since 1985. Text in Russian, contents and summaries in English. The journal presents the results of theoretical and experimental research carried out at the PWI in the field of electrometallurgy. Special attention is given to electroslag technology (electroslag melting, refining and casting). The journal is divided into the following main sections: electroslag technology; electron beam processes; plasma arc technology; vacuum arc remelting and vacuum induction melting; general problems of special electrometallurgy.