By Paul Miller, Editor
— Reprinted with permission from MetalFax, July 1995.
Brian Ritter verifies the dimension on a picture-tube support frame die.
The TD Process is a surface-modification technique that works by diffusion. Parts to be treated are immersed in a fused borax salt bath at temperatures from 1700°F to 1900°F. Atoms of vanadium dispersed in the salt bath combine with carbon atoms in the substrate of the tooling to form a 0.0001" to 0.0008" thick vanadium-carbide layer. The extremely hard, dense layer of vanadium carbide ranges from 3200 to 3800 on the Vickers scale of hardness (theoretically 90 Rc). Metallurgically bonded to the tooling, the layer is extremely peel resistant.
TD achieves good results on air-hardening cold steels and hot-working die steels such as AISI-A2, AISI-D2, and AISI-H13; high-speed steels; powdered-particle high-performance steels; and cemented carbides. Cemented carbide, although very hard (1200 to 1800 Vickers), is still subject to galling and can benefit from TD.
Sandra LaShure, press operator, forms picture-tube frames on TD treated tooling.
Tough dies use less lubricant
Kauffman Products, Carmel, IN, a 27-yr-old company that is registered to ISO 9002 quality standards, cuts tooling expenditures and lubrication use by 50% with the TD Center Thermal Diffusion Process (TD). The TD Process is a surface-modification process that extends tooling life 5 to 50 times.
Kauffman is a major manufacturer of metal stampings, specializing in seating components for the automotive industry—as well as the appliance industry—producing picture-tube support frames. The company is committed to 100% on-time delivery and as low a ratio of scrap-rework and returns as possible. It demands the best its suppliers can provide so that it can meet its commitment.
Because TD is a high-temperature process, and the vanadium atoms in the salt bath combine with the carbon in the steel substrate, tooling considered for treatment must have a 0.3% or greater carbon content. Even though TD is effective, the treatment is not a substitute for good-quality design, proper heat treatment, and correct tool-steel selection.
According to David Jarboe, Kauffman tooling and skilled trades manager, TD has been a real problem solver. Jarboe says, “The materials we use, such as cold rolled and stainless steel, are hard on the dies because of the way the material flows and is drawn into shape.”
Getting the picture
The company was having galling problems with dies used to produce picture-tube frames. Manufacturing the frames is a major portion of Kauffman's output. In 1992, of the 21,056,255 television sets produced in the US, Kauffman provided just over 15% or nearly 3.2 million support frames.
Tooling used to produce the picture-tube frames was good for only a few hundred hits before gall appeared, even when it had a good polish job. After being TD treated, with proper die clearances, the tooling lasts a few hundred thousand hits. Kauffman has since TD treated all of the dies used to manufacture picture tube frames.
Also at Kauffman, a die that produces automobile struts was pulled for polishing after every 5000 pieces. After TD, 150,000 to 200,000 parts can now be run before the die has to be pulled for maintenance. A die used to produce baffles for exhaust systems was being pulled after every 1000 pieces for polishing. With TD, the die produces 25,000 parts.
In addition to using TD, the company has used Ferrotic and carbide tooling. In the same applications where all variables were equal, TD improved the results.
Jarboe says, “Using TD-treated dies has cut our tooling expenditures and lubricant usage 50% and has reduced downtime by up to 90%. We no longer have to stop production in the middle of a run to polish die sections, and cosmetics are greatly improved.”
Convinced that TD works, Kauffman does not wait until it has problems with a die to have it TD treated. Jarboe says, “If die sections need to be TD treated, we do it before a die is put into production.”
For more information contact the TD Center, Columbus, IN.