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Title: Arc distribution during the vacuum arc remelting of Ti-6Al-4V

Abstract

Currently, the temporal distribution of electric arcs across the ingot during vacuum arc remelting (VAR) is not a known or monitored process parameter. Previous studies indicate that the distribution of arcs can be neither diffuse nor axisymmetric about the center of the furnace. Correct accounting for the heat flux, electric current flux, and mass flux into the ingot is critical to achieving realistic solidification models of the VAR process. The National Energy Technology Laboratory has developed an arc position measurement system capable of locating arcs and determining the arc distribution within an industrial VAR furnace. The system is based on noninvasive magnetic field measurements and a VAR specific form of the Biot–Savart law. The system was installed on a coaxial industrial VAR furnace at ATI Albany Operations in Albany, OR. This article reports on the different arc distributions observed during production of Ti-6Al-4V. It is shown that several characteristic arc distribution modes can develop. This behavior is not apparent in the existing signals used to control the furnace, indicating the measurement system is providing new information. It is also shown that the different arc distribution modes observed may impact local solidification times, particularly at the side wall.

Authors:
 [1];  [1];  [2]
  1. U.S. DOE
  2. ATI Albany Operations
Publication Date:
Research Org.:
National Energy Technology Lab. (NETL), Pittsburgh, PA, and Morgantown, WV (United States). In-house Research; National Energy Technology Lab. (NETL), Pittsburgh, PA, and Morgantown, WV (United States)
Sponsoring Org.:
USDOE Office of Fossil Energy (FE)
OSTI Identifier:
1129762
Report Number(s):
A-NETL-PUB-015
Journal ID: ISSN 1073--5615
Resource Type:
Journal Article
Resource Relation:
Journal Name: Metallurgical and Materials Transactions B - Processing Metallurgy and Materials Processing Science; Journal Volume: 44; Journal Issue: 1
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Woodside, Charles Rigel, King, Paul E., and Nordlund, Chris. Arc distribution during the vacuum arc remelting of Ti-6Al-4V. United States: N. p., 2013. Web. doi:10.1007/s11663-012-9760-1.
Woodside, Charles Rigel, King, Paul E., & Nordlund, Chris. Arc distribution during the vacuum arc remelting of Ti-6Al-4V. United States. doi:10.1007/s11663-012-9760-1.
Woodside, Charles Rigel, King, Paul E., and Nordlund, Chris. 2013. "Arc distribution during the vacuum arc remelting of Ti-6Al-4V". United States. doi:10.1007/s11663-012-9760-1.
@article{osti_1129762,
title = {Arc distribution during the vacuum arc remelting of Ti-6Al-4V},
author = {Woodside, Charles Rigel and King, Paul E. and Nordlund, Chris},
abstractNote = {Currently, the temporal distribution of electric arcs across the ingot during vacuum arc remelting (VAR) is not a known or monitored process parameter. Previous studies indicate that the distribution of arcs can be neither diffuse nor axisymmetric about the center of the furnace. Correct accounting for the heat flux, electric current flux, and mass flux into the ingot is critical to achieving realistic solidification models of the VAR process. The National Energy Technology Laboratory has developed an arc position measurement system capable of locating arcs and determining the arc distribution within an industrial VAR furnace. The system is based on noninvasive magnetic field measurements and a VAR specific form of the Biot–Savart law. The system was installed on a coaxial industrial VAR furnace at ATI Albany Operations in Albany, OR. This article reports on the different arc distributions observed during production of Ti-6Al-4V. It is shown that several characteristic arc distribution modes can develop. This behavior is not apparent in the existing signals used to control the furnace, indicating the measurement system is providing new information. It is also shown that the different arc distribution modes observed may impact local solidification times, particularly at the side wall.},
doi = {10.1007/s11663-012-9760-1},
journal = {Metallurgical and Materials Transactions B - Processing Metallurgy and Materials Processing Science},
number = 1,
volume = 44,
place = {United States},
year = 2013,
month = 1
}
  • An industrial vacuum arc remelting experiment was carried out at Cytemp Specialty Steel Corp. (Titusville, PA) during which a 0.432-m-diameter Alloy 718 electrode was remelted into a 0.508-m-diameter ingot. The purpose of the experiment was to investigate the response of the arc voltage distribution properties (mean, standard deviation, and skewness) and the drip-short frequency to melting current, electrode gap, and CO pressure. The responses were characterized by recording and analyzing changes in the temporally averaged properties. Each independent variable was systematically varied in accordance with a modified Yates order factor space experimental design within the following ranges: melting current, 5,000more » to 11,200 A; electrode gap, 0.004 to 0.056 m; and CO pressure, 0.40 to 14.7 Pa. Statistical models were developed describing the correlation between the averaged arc voltage distribution properties and the independent variables. The models demonstrate that all of the voltage distribution properties, as well as the drip-short frequency, are directly related to electrode gap. An arc column model is presented to account for the mean arc voltage properties and the model is used to estimate the arc column pressure. The potential usefulness of the distribution properties as process diagnostics and control responses is evaluated.« less
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