Re: [hobbicast] Re: Electric Melt, with fries please...
- Here's a helpful note describing resistance alloys from this URL:
Electric type resistance elements consist of a high temperature resistance
alloy either nickel-chrome alloy or iron chrome aluminum, usually formed in
sinuous, loops or coils. The elements may be supported from the furnace
sidewalls on refractory hooks or alloy hooks, suspended from the roof with
alloy hanger; hooks, or may be laid on the floor in comb type refractory
The type of alloy used depends on the furnace temperature rating and
the type of atmosphere used. The most common types are
Chromel "A" 80% nickel -20% chromium,
Chromel "D" 35% ,nickel -19% chromium -46% iron,
Hoskins "875" 22-1/2%-Chromium - 5-1/2%-Aluminum balance iron.
Elements are designed to deliver rated kilowatts at rated voltage only when
hot. If actual voltage differs from rated voltage, the power delivered will
vary as the square of the voltage. Remember a 1-% increase in voltage is
about a 2% increase in wattage, and vice-versa, a 1% reduction in voltage
is about a 2% reduction in wattage. The resistance of the heating elements
will be lower at room temperature than when hot. The resistance of the
elements will increase with age, due to the reduction in cross section by
oxidation, and also, due to elongation of the loops. This will result in
decreased power to the furnace and ultimate failure. Such failure
represents the normal life of the elements.
Certain impurities in the atmosphere will attack the alloy in the elements.
These impurities may be in the incoming gas, or may be given off by the
work entering the furnace. Cutting oils/fluids are major sources of
impurities, typically carbon and sulfur.
Sulfur even in small quantities; will cause rapid deterioration of heating
elements. Carburizing atmospheres tend to increase the carbon content of
the heating element causing it to become brittle and to develop a lower
melting point. Lead, tin, or zinc, and halides will attack the element.
These materials should not be put in a furnace.
At 10:50 PM 11/30/02, you wrote:...
>What exactly is a Kanthal element... aside from a brand name that doesn'tBrian Whatcott
>exist anymore... Am I right in assuming it is a "Kleenex" type deal.... a
>brand name used generically? Somehow, whenever I hear that word a picture of
>a shielded heating element comes to mind ....
> > > From: Jim Barnes <james.barnes@...>
> > >
> > SNIP
> > >
> > > Frankly, I've got Nichrome and Kanthal elements that will
> > > do the aluminum and brass melts and for enameling.
Altus OK Eureka!
- To quote an old TV commercial: Thanks, I needed that!
----- Original Message -----
From: "Brian Whatcott" <betwys@...>
> Here's a helpful note describing resistance alloys from this URL:
> <http://www.nationalelement.com/hottips.cfm?TipID=6 >