For release: November 12, 2002
Contacts:
Larry Jones, Materials Preparation
Center, (515) 294-5236
Kerry Gibson, Public Affairs, (515) 294-1405
AMES - Ames Laboratory's Materials Preparation Center has a new, powerful tool in its arsenal, one that even the toughest alloys can't stand up to. According to MPC Director Larry Jones, the Retech Model 150 Plasma Lab Furnace will melt just about anything.
"There's no limit to the metals or metal alloys it can melt," Jones
says. "The plasma torch generates temperatures estimated to be well in
excess of 10,000 degrees Celsius. We plan to use it primarily for melting
reactive metal alloys, but it gives us enhanced capabilities in other areas as
well."
One of the main advantages of the furnace is that reactive metal alloys can be
melted without the need for a crucible in which to contain them. "Some
materials can't be melted in a typical crucible furnace because they react with
the crucible material, thus contaminating the molten metal," Jones says.
"This new furnace doesn't require such crucibles so we eliminate that
problem. Instead, the metal alloy, such as bars of nickel-titanium, is
hydraulically pushed into the chamber by a bar feeder. The plasma torch moves
back and forth across the end of the bars as they stick out over a water-cooled,
thick copper mold."
Even though copper has a lower melting temperature than many metals, copper is
used for molds because it conducts heat so well. Heat is transferred so quickly
to the cooling water that the molten metal cools, solidifies and shrinks away
from the surface of the copper before the copper itself melts. The mold forms
the melted material into an ingot roughly four inches in diameter and up to a
foot long.
"We plan to add a granular feeder in the next six months so we can melt
materials that come in granule, flake, or shot form, such as titanium, iron or
nickel, just as easily as bar stock."
The heart of the furnace is a plasma torch that uses a helium and argon mixture
as the feed gas. The plasma torch works by injecting the feed gas into a hollow
electrode. The gas then carries an electrical arc from the electrode through a
nozzle and to the grounded workpiece. The electrical discharges add energy to
the gases in order to increase the gas temperature beyond that normally
attainable by chemical reaction.
To provide the electrical power necessary to run the 150 kilowatt torch, a new
350-amp electrical service panel had to be added to the first-floor lab area on
the east side of Metals Development. But that was only part of the utility
improvements needed for the equipment.
Cooling the torch requires deionized water, which is provided by the unit's own
closed-loop cooling system. Keeping this closed-loop system and other parts of
the furnace cool requires additional water supplied at the rate of 72 gallons
per minute. This meant connecting to the city water service in addition to the
Physical Plant loop and installing a large backflow preventer valve. A section
of the floor had to be jackhammered out to tie into the existing sewer lines to
handle the high-flow discharge. A new air- collection system vents exhaust air
from the furnace to a discharge stack on the roof.
Facilities staff did that prep work before the equipment arrived, and Jones
estimated it cost between $25,000 and $30,000 to complete the work. Occupying a
space roughly 30 feet by 50 feet, the bright blue furnace has a simple control
panel out front and a wraparound, elevated platform and observation ports on the
front and side. Dozens of hoses, valves and gauges connect various components,
and a row of helium-feed gas tanks lines the wall behind it.
Built by Retech, a company based in Ukiah, Calif., the furnace was tested prior
to being disassembled and shipped to Ames. Assistant scientist Paul Wheelock
went to California for training on operation of the furnace and has overseen the
on-site setup and testing. According to Jones, Retech makes primarily large,
industrial-scale furnaces with multiple torches, so the $500,000 model built for
Ames Lab is quite small by comparison.
"We've done some vacuum testing for leaks, and while they (Retech) think
those results are quite good, they aren't used to the tolerances used by a
research facility," Jones says. "Paul is being pretty thorough in
making sure we have things set up properly."
One of the initial tasks for the furnace will be to consolidate material,
turning multiple pieces of long metal bar stock or piles of granular material
into short, stout ingots. This dramatically reduces the overall surface area and
lessens the amount of surface oxidation that takes place while the metals are
being stored for future use.
"Beyond that, we can do any number of things when it comes to melting and
reforming materials," Jones says, "and it's just one more capability
we have to meet the research needs of our scientists." He adds that Los
Alamos may be the only other DOE research lab with such capabilities.
Ames Laboratory is operated for the DOE by Iowa State University. The Lab
conducts research into various areas of national concern, including energy
resources, high-speed computer design, environmental cleanup and restoration,
and the synthesis and study of new materials.
Last revision: 11/15/02 kbg