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- Information about technological processes
and working systems . Everybody can contribute with documentation,
that must be sended to info@rioweb.it
accompanied with the name of the source, and if possible the link
of the site one where there is the possibility of a deepening.
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Heat Treating
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- The use of fire to heat and thermally alter
a stone preform in an attempt to improve its working characteristics
and flaking qualities prior to knapping and flaking. Typical result
of heat treating is a color change of the stone as well as the
molecular structure. Heat treating occurs at temperatures that
approximate or exceed 350 degrees Centigrade.
• There are a number of ways to bring the steel to temperature
for heat treating. Expensive industrial or commercial heat treating
equipment will not be discussed, but rather we will cover what
is within the means of a small shop.
- Perhaps the oldest method for heating
and heat treating metals has been the charcoal fire. Charcoal
is an excellent fuel because you can make an even heat over a
long bed, it is a non oxidizing environment and is easily controlled.
Charcoal cut to the right size chunks makes a soft bed and is
not likely to bend or deform the blade as it is move in the fire.
On the negative side however, charcoal is a fire hazard. It throws
sparks, gives off intense radiant heat and is sometimes hard to
put out, reigniting itself long after it has been doused. It is
also a nuisance to make, expensive to buy and very messy.
- Tempering
After the steel has been quenched and hardened to martensite,
it will be hard, but also quite brittle. By reheating the steel
toughness is added and also the hardness can be controlled. Tempering
is a function of time and temperature and is greatly affected
by the various alloys in the steel. A polished piece of steel
will oxidize as it is reheated and begin to show colors, the higher
the temperature the thicker the oxide layer and the darker the
color. These have been used to judge the "temper" of
the steel, but the color is also affected by the surface polish,
the alloy elements in the steel and the duration of the tempering
cycle and are not reliable indicators of the tempered condition
of within the structure of the steel.
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