HB-9 updated text (PDF) - Corbin Bullet Swaging

There is no such thing as a single kind of die material called “carbide”,
except in the minds of ad writers. When you heat any tool steel to a high
enough temperature, some of the carbon in the material dissolves in the
nearby iron, and forms a ferric carbide material which can be captured in
the frozen matrix of the steel if the temperature is lowered quickly enough.
The ferric carbide trapped in the steel mixture is primarily what gives
the steel its hardness. The structure also has a matrix of iron and other
elements, which form complex compounds that give the steel ductility,
ability to remain hard at higher temperatures, and corrosion and shock
resistance. All hardened steels have “carbide” in them: that’s what makes
them hard.
If you systematically reduced the amount of iron and increased the
amount of carbon that dissolved in the iron that was left, you would wind
up with a very hard, but also very brittle material. It might be almost
“solid carbide” but it wouldn’t be very strong. By forming compounds of
tungsten and other metals with carbon, the General Electric company
(and others) developed commercially acceptable variations of “carbide”
in a wide variety of grades. General Electric’s trade name of “Carboloy”
was applied to some of these.
The important thing to note is that there are variations that are nearly
as soft as hardened tool steel, and others that are so brittle that they shatter
like glass if force is applied incorrectly. Some carbide materials can
handle high temperatures and some fracture when heated and cooled during
use. Some make good tool bits, and some are only good for a thin
coating on the surface of a hardened steel bit. Some are reasonable to
machine accurately, and some cost a fortune to machine compared to
making the same shape from a good tool steel.
If you were to be faced with the decision of a material from which to
build dies for a high speed punch press, working at 40 strokes per minute
or more, and making several million bullets, then one of these grades of
carbide material could give you higher temperature operation and thus
longer life than a tool steel die. Because the harder materials are more
abrasion resistant, you would be able to run the dies for a longer time
before replacing them.
They would still need to be lubricated: the idea that carbide dies need
no lubrication is foolish. It is like saying that because your car engine
might run 100,000 miles without changing the oil, you don’t need to
change the oil. It might run 250,000 miles if you did!
It is necessary to consider value to make a good decision about die
materials. Value is the cost of the die amortized over the number of bullets
you expect to make, considering the amount of wear which will take
place before the bullets are no longer acceptable quality. It is somewhat
29