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.

scholarly journals Beta Fleck formation in Titanium Alloys

2020 ◽  
Vol 321 ◽  
pp. 10001
Author(s):  
K. Kelkar ◽  
A Mitchell
Keyword(s):  
Titanium Alloys ◽  
Formation Mechanism ◽  
Defect Formation ◽  
Melting Rate ◽  
Vacuum Arc ◽  
Formation Mechanisms ◽  
Alloy Development ◽  
Vacuum Arc Remelting ◽  
Freckle Formation ◽  
Nickel Base

Beta fleck is a troublesome segregation defect in many titanium alloys. It has previously been investigated by several authors and appears to have two formation mechanisms, one similar to that of “freckle” in steels and nickel-base alloys, the other arising in the “crystal rain” effect seen in conventional steel ingots. The freckle defect has been extensively studied and several theories developed to account for its formation in both remelted ingots and directional castings. In this work we compare the findings of investigations into the nickel-base freckle formation mechanism to similar conditions in the vacuum arc remelting of titanium alloys. We find that there are strong similarities between the beta fleck formation conditions and the parameters related to the Rayleigh Number criterion for freckle formation. In particular, the dendritic solidification parameters and the density dependence on segregation coefficients both fit well with the conditions proposed to characterise freckle formation. The second formation mechanism arises in the columnar to equiax transition in solidification. The condition for the avoidance of the defect in the two cases is the shown to be the same, namely the use of a very low VAR melting rate, but that it is unlikely to be 100% successful in preventing defect formation. We propose that the techniques presently in use for alloy development in the superalloy field through optimising the composition for minimum sensitivity to freckle formation should be applied to the formulation of future titanium alloys; also that attention should be paid to developing the PAM process to provide suitable solidification conditions for defect absence in a final ingot.

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.

Achieving the maximum melting rate for various vacuum arc remelting schemes

2010 ◽  
Vol 2010 (12) ◽  
pp. 1114-1116
Author(s):  
A. V. Filimonov ◽  
O. Kh. Fatkullin
Keyword(s):  
Melting Rate ◽  
Vacuum Arc ◽  
Vacuum Arc Remelting

scholarly journals Effect of Melting Interruption on Composition and Microstructure of BT22 Ingot in VAR

2020 ◽  
Vol 321 ◽  
pp. 10008
Author(s):  
Zhengli Hua ◽  
Wenzhong Luo ◽  
Tao He ◽  
Qiang Lei ◽  
Longzhou Wang ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Inductively Coupled Plasma ◽  
Melting Process ◽  
Melting Rate ◽  
Vacuum Arc ◽  
Vacuum Arc Remelting ◽  
Electron Probe Micro Analyzer ◽  
Normal Region ◽  
Distribution Of Elements ◽  
Equiaxed Grains

BT22 ingot was remelted by vacuum arc remelting (VAR) furnace with a melting rate of 20kg/min. The power of VA R was interrupted for five minutes when the weight of the remelted ingot is approximately 4000 kg. The melting process was then resumed at the same melting rate after the five minutes interruption. Optical microscopy (OM), inductively coupled plasma-mass spectrometry (ICP-MS) and electron probe micro analyzer (EPMA) were utilized to analyze the microstructure, composition and distribution of elements. No significant microstructural difference was oberved at the remelting interrupted region. The variation of Al, Mo, V, Cr, Fe contents between the melting interruption region and normal region is within 0.23 wt%. The distribution of elements in equiaxed grains of the melting interruption region and the normal regions were compared by EPMA analysis. The contents of Al, V, Fe and Cr increase from the center of equiaxed grains to their grain boundaries. The content of Mo decreases from the center of equiaxed grains to their grain boundaries. The trend of element content in the normal region is similar to that of the melting interrupted region. Key words: BT22; ingot; composition; microstructure

scholarly journals 3D Thermal Finite Element Analysis of the SLM 316L Parts with Microstructural Correlations

Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Ketai He ◽  
Xue Zhao
Keyword(s):  
Finite Element ◽  
Temperature Field ◽  
Molten Pool ◽  
Steel Powder ◽  
Element Model ◽  
Maximum Temperature ◽  
Element Analysis ◽  
Measurement Results ◽  
Scanning Strategies ◽  
Maximum Temperature Gradient

In this study, a multitrack and multilayer finite element model was developed to simulate the temperature field and molten pool contours during selective laser melting (SLM) of 316L stainless steel powder under different scanning strategies. The simulated temperature field and its evolution over time were compared with experimental measurement results. Furthermore, a correlation was established by the presented results between the predicted thermal behavior and the microstructure of SLM specimens. It was found that the maximum temperature of the molten pool rose slightly with the increase of scanning tracks, but when laser scanned multilayer, the maximum temperature rose first and then decreased. There are large columnar crystals in molten pools, growing in the direction of the maximum temperature gradient. The microstructure defects are more likely to occur at the bonding regions between adjacent layers and islands, where the heat and stress are concentrated. Moreover, the results also showed that the scanning strategy affects the microstructure and microhardness. Also, the SLM 316L parts under the S-shaped strategy had finer grains and a higher Vicker hardness than that formed under the island strategy.

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

scholarly journals Thermal Behavior of Ti-64 Primary Material in Electron Beam Melting Process

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2853
Author(s):  
Jean-Pierre Bellot ◽  
Julien Jourdan ◽  
Jean-Sébastien Kroll-Rabotin ◽  
Thibault Quatravaux ◽  
Alain Jardy
Keyword(s):  
Electron Beam ◽  
Thermal Behavior ◽  
Electron Beam Melting ◽  
Continuous Process ◽  
Melting Process ◽  
Melting Rate ◽  
Vacuum Arc ◽  
Vacuum Arc Remelting ◽  
Primary Material ◽  
Set Up

The Electron Beam Melting (EBM) process has emerged as either an alternative or a complement to vacuum arc remelting of titanium alloys, since it is capable of enhancing the removal of exogenous inclusions by dissolution or sedimentation. The melting of the primary material is a first step of this continuous process, which has not been studied so far and is investigated experimentally and numerically in the present study. Experiments have been set up in a 100 kW laboratory furnace with the aim of analyzing the effect of melting rate on surface temperature of Ti-64 bars. It was found that melting rate is nearly proportional to the EB power while the overheating temperature remains roughly independent of the melting rate and equal to about 100 °C. The emissivity of molten Ti-64 was found to be 0.22 at an average temperature of about 1760 °C at the tip of the bar. In parallel, a mathematical model of the thermal behavior of the material during melting has been developed. The simulations revealed valuable results about the melting rate, global heat balance and thermal gradient throughout the bar, which agreed with the experimental values to a good extent. The modeling confirms that the overheating temperature of the tip of the material is nearly independent of the melting rate.

scholarly journals Analysis of an Approach for Detecting Arc Positions During Vacuum Arc Remelting Based on Magnetic Flux Density Measurements

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Miguel F. Soler ◽  
Kyle E. Niemeyer
Keyword(s):  
Magnetic Field ◽  
Finite Element ◽  
Large Scale ◽  
Element Model ◽  
Vacuum Arc ◽  
Magnetic Flux Density ◽  
Vertical Position ◽  
Element Analysis ◽  
Vacuum Arc Remelting ◽  
Position Sensing

Vacuum arc remelting (VAR) is a melting process for the production of homogeneous ingots, achieved by applying a direct current to create electrical arcs between the input electrode and the resultant ingot. Arc behavior drives quality of the end product, but no methodology is currently used in VAR furnaces at large scale to track arcs in real time. An arc position sensing (APS) technology was recently developed as a methodology to predict arc locations using magnetic field values measured by sensors. This system couples finite element analysis of VAR furnace magnetostatics with direct magnetic field measurements to predict arc locations. However, the published APS approach did not consider the effect of various practical issues that could affect the magnetic field distribution and thus arc location predictions. In this paper, we studied how altering assumptions made in the finite element model affect arc location predictions. These include the vertical position of the sensor relative to the electrode–ingot gap, a varying electrode–ingot gap size, ingot shrinkage, and the use of multiple sensors rather than a single sensor. Among the parameters studied, only vertical distance between arc and sensor locations causes large sources of error and should be considered further when applying an APS system. However, averaging the predicted locations from four evenly spaced sensors helps reduce this error to no more than 16% for a sensor position varying from 0.508 m below and above the electrode–ingot gap height.

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