scholarly journals A Parametric Study of the Vacuum Arc Remelting (VAR) Process: Effects of Arc Radius, Side-Arcing, and Gas Cooling

2019 ◽  
Vol 51 (1) ◽  
pp. 222-235 ◽  
Author(s):  
E. Karimi-Sibaki ◽  
A. Kharicha ◽  
M. Wu ◽  
A. Ludwig ◽  
J. Bohacek
Keyword(s):  
Molten Pool ◽  
Vacuum Arc ◽  
Internal Quality ◽  
Solidification Behavior ◽  
Vacuum Arc Remelting ◽  
Thermal Fields ◽  
Vacuum Plasma ◽  
Process Effects ◽  
Gas Cooling

Abstract Main modeling challenges for vacuum arc remelting (VAR) are briefly highlighted concerning various involving phenomena during the process such as formation and movement of cathode spots on the surface of electrode, the vacuum plasma, side-arcing, the thermal radiation in the vacuum region, magnetohydrodynamics (MHD) in the molten pool, melting of the electrode, and solidification of the ingot. A numerical model is proposed to investigate the influence of several decisive parameters such as arc mode (diffusive or constricted), amount of side-arcing, and gas cooling of shrinkage gap at mold–ingot interface on the solidification behavior of a Titanium-based (Ti-6Al-4V) VAR ingot. The electromagnetic and thermal fields are solved in the entire system including the electrode, vacuum plasma, ingot, and mold. The flow field in the molten pool and the solidification pool profile are computed. The depth of molten pool decreases as the radius of arc increases. With the decreasing amount of side-arcing, the depth of the molten pool increases. Furthermore, gas cooling fairly improves the internal quality of ingot (shallow pool depth) without affecting hydrodynamics in the molten pool. Modeling results are validated against an experiment.

Study on the Viability of the Recycling by Electric Arc Melting of Zirconium Alloys Scraps Aiming the Scalability of the Process

2018 ◽  
Vol 930 ◽  
pp. 495-500
Author(s):  
Cristiano Stefano Mucsi ◽  
L.A.M. dos Reis ◽  
Maurilio Pereira Gomes ◽  
L.A.T. Pereira ◽  
Jesualdo Luiz Rossi
Keyword(s):  
Nuclear Reactor ◽  
Zirconium Alloys ◽  
Vacuum Arc ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Vacuum Arc Remelting ◽  
Arc Melting ◽  
Vacuum Arc Furnace ◽  
Fuel Elements

Turning chips of zirconium alloys are produced in large quantities during the machining of alloy rods for the fabrication of the end plugs for the Pressurized Water Reactor (PWR) fuel elements parts of Angra II nuclear reactor (Brazil – Rio de Janeiro). This paper presents a study on the search for an efficient way for the cleaning, quality control and Vacuum Arc Remelting (VAR) of pressed zirconium alloys chips to produce a material viable to be used in the production of the fuel rod end plugs. The process starts with cutting oil clean out. The first step in this process consists in soaking a bunch of chips in clean water, to remove soluble cutting oils, followed by an alkaline degreasing bath and a wash with a high-pressure flow of water. Drying is performed by a flux of warm air. The oil free chips are then subjected to a magnet in order to detect and collect any magnetic material, essentially ferrous, that may be present in the original chips. Samples of the material are collected and then melted in a small non consumable electrode vacuum arc furnace for evaluation by Energy Dispersive X-ray Fluorescence Spectrometry (EDXRFS) in order to define the quality of the chips. The next step consists in the 15 ton hydraulic pressing the chips in a die with 40 mm square section and 500 mm long, producing an electrode with 20% of the Zircaloy bulk density. The electrode was finally melted in a laboratory scale modified VAR furnace located at the CCTM–IPEN, producing 0.8 kg ingots. The authors conclude that the samples obtained from the fuel element industry can be melting in a VAR furnace, modified to accommodate low density electrodes, allowing a reduction up to 40 times the original storage volume, however, it is necessary to remelt the ingots to correct their composition in order to recycle the original zirconium alloys chips. in a process to reduce volume and allow the reutilization of valuable Zircaloy scraps.

Production of Fe3Al-Based Intermetallic Alloys

1990 ◽  
Vol 213 ◽  
Author(s):  
Vinod K. Sikka
Keyword(s):  
Surface Finish ◽  
National Laboratory ◽  
Vacuum Arc ◽  
Vacuum Induction Melting ◽  
Induction Melting ◽  
Intermetallic Alloys ◽  
Vacuum Arc Remelting ◽  
Oak Ridge ◽  
Arc Melting

ABSTRACTThe melting of Fe3Al-based alloys at the Oak Ridge National Laboratory (ORNL) and commercial vendors is described. The melting processes evaluated include arc melting, air-induction melting (AIM), vacuum-induction melting (VIM), vacuum-arc remelting (VAR), and electroslag remelting (ESR). The quality of the ingots studied are based on internal soundness and the surface finish obtained. The ingots were analyzed for impurity levels observed in the alloys by various melting processes. Recommendations are made for viable processes for commercial melting of these alloys.

Modern Control Theory Applied to Remelting of Superalloys

2012 ◽  
Vol 706-709 ◽  
pp. 2484-2489 ◽  
Author(s):  
Rodney L. Williamson ◽  
Joseph J. Beaman
Keyword(s):  
First Generation ◽  
Vacuum Arc ◽  
Alloy 718 ◽  
Remedial Action ◽  
Vacuum Arc Remelting ◽  
The Past ◽  
Model Based ◽  
Diameter Ingot ◽  
Ingot Solidification

Over the past several years we have worked to develop tools to improve the quality of superalloy ingots produced by vacuum arc remelting (VAR) and electroslag remelting (ESR). Part of this work has focused on developing model-based process controllers that employ predictive, dynamic, low-order electrode melting and ingot solidification models to estimate important process variables. These estimated variables (some of which are not subject to measurement) are used for feedback and to evaluate the health of the processes. Modern controllers are capable of detecting and flagging various process upsets and sensor failures, and can take remedial action under some circumstances. Model-based variable estimates are continuously compared with measurements when available, and the residuals are used to correct the next generation of estimates. This technology has led to improved VAR and ESR melt rate controllers and is currently being used to develop a VAR ingot solidification controller. A first generation ingot pool depth controller has been tested on a laboratory VAR furnace and the results are very encouraging. In this test, a 152 mm diameter Alloy 718 electrode was remelted into a 216 mm diameter ingot, but the technology is easily scaled to industrial sizes. Successful development of this technology could allow for melting at higher powers without the formation of channel segregates (freckles) by stabilizing the ingot solidification zone. It may also allow for the production of larger diameter VAR superalloy ingots than is possible to produce with the current generation of VAR controllers for the same reason.

Effect of remelting current on molten pool profile of titanium alloy ingot during vacuum arc remelting process

2011 ◽  
Vol 16 (2) ◽  
pp. 133-136 ◽  
Author(s):  
Zhi-jun Yang ◽  
Hong-chao Kou ◽  
Xiao-hua Zhao ◽  
Jin-shan Li ◽  
Rui Hu ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Molten Pool ◽  
Vacuum Arc ◽  
Vacuum Arc Remelting ◽  
Alloy Ingot ◽  
Pool Profile

Calculation of the molten pool depth in vacuum arc remelting of alloy Vt3-1

2007 ◽  
Vol 16 (1) ◽  
pp. 19-25 ◽  
Author(s):  
E. N. Kondrashov ◽  
M. I. Musatov ◽  
A. Yu. Maksimov ◽  
A. E. Goncharov ◽  
L. V. Konovalov
Keyword(s):  
Molten Pool ◽  
Vacuum Arc ◽  
Vacuum Arc Remelting ◽  
Pool Depth

Macroscale Modeling of Multi-Physics Fields during Vacuum Arc Remelting of Ti-6Al-4V

2014 ◽  
Vol 789 ◽  
pp. 603-607
Author(s):  
Bin Zhu ◽  
Xiang Yi Xue ◽  
Hong Chao Kou ◽  
Cong Xiao ◽  
Jin Shan Li
Keyword(s):  
Temperature Field ◽  
Molten Pool ◽  
Element Model ◽  
Melting Rate ◽  
Vacuum Arc ◽  
Physical Interaction ◽  
Water Cooling ◽  
Vacuum Arc Remelting ◽  
Cooling Conditions ◽  
Melting Current

A 3-D finite element model has been established using ANSYS12.0 software to simulate multi-physical interaction behavior during the Vacuum Arc Remelting (VAR) of 740-mm-diameter ingots of Ti-6Al-4V. The models of temperature field, electromagnetic and flow field were combined by progressive method. The effect of thermal contraction was considered in the simulation of temperature field and electromagnetic by setting a thin layer with different nature parameters at the ingot-crucible interface. The model results demonstrate the distributions of temperature, Lorenz force and flow velocity, and the influence of water cooling conditions, melting current and other process parameters. The molten pool behavior is mostly dominated by buoyancy force under circumstances in this case. The increase of the melting current results in an increase of the pool depth and melting rate, and causes great change of the molten pool profile, while the influence of the water cooling conditions is ignored.

Vacuum Arc Remelting Process of High-Alloy Bearing Steel and Multi-Scale Control of Solidification Structure

2015 ◽  
Vol 817 ◽  
pp. 826-836
Author(s):  
Yuan Sheng Huang ◽  
Mao Sheng Yang ◽  
Jing She Li ◽  
Li Guo Bai
Keyword(s):  
Molten Pool ◽  
Moving Boundary ◽  
Steel Ingot ◽  
Primary Dendrite ◽  
Bearing Steel ◽  
Solidification Structure ◽  
Vacuum Arc ◽  
High Alloy ◽  
Pool Shape ◽  
Vacuum Arc Remelting

Utilizing Pro-cast software, the whole vacuum arc remelting process of high-alloy bearing steel ingot (the diameter was 160 mm and the high was 600 mm) was simulated. And moving face quality and moving boundary conditions were added to the simulation. Purposes of the simulation were to explore the influence of smelting powers on the temperature field, pool shape and solidification microstructure in vacuum arc remelting process. The depth of molten bath gradually increased and stabilized finally and the pool shape transferred from flat to funnel. When smelting power increased, the depth of molten pool became deeper and the width of mushy zone slightly reduced; the size of primary dendrite and secondary dendrite spacing increased significantly; the percentage and size of columnar crystals also increased. A reasonable power-time cure was given to guide industrial melting after simulation, the size of molten pool morphology and microstructure were controlled in an ideal range under the reasonable cure. The simulated grain morphology agreed well with the experimental pickling result.

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