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Properties Of Steel
Steels are known by certain tests. Early tests were more or l...

Protectors For Thermo-couples
Thermo-couples must be protected from the danger of mechanica...

Hardening
Steel is hardened by quenching from above the upper critical....

Annealing
ANNEALING can be done by heating to temperatures ranging from...

Surface Carburizing
Carburizing, commonly called case-hardening, is the art of pr...

Pyrometers
Armor plate makers sometimes use the copper ball or Siemens' ...

Using Illuminating Gas
The choice of a carburizing furnace depends greatly on the fa...

Double Annealing
Water annealing consists in heating the piece, allowing it to...

Nickel-chromium
A combination of the characteristics of nickel and the charac...

Separating The Work From The Compound
During the pulling of the heat, the pots are dumped upon a ca...

Compensating Leads
By the use of compensating leads, formed of the same materia...

Brown Automatic Signaling Pyrometer
In large heat-treating plants it has been customary to mainta...

Mushet And Bessemer
That Mushet was "used" by Ebbw Vale against Bessemer is, perh...

Carburizing Low-carbon Sleeves
Low-carbon sleeves are carburized and pushed on malleable-ir...

Robert Mushet
Robert (Forester) Mushet (1811-1891), born in the Forest of D...

A Satisfactory Luting Mixture
A mixture of fireclay and sand will be found very satisfactor...

Hardening Operation
Hardening a gear is accomplished as follows: The gear is tak...

Leeds And Northrup Optical Pyrometer
The principles of this very popular method of measuring tempe...

Manganese
Manganese adds considerably to the tensile strength of steel,...

Blending The Compound
Essentially, this consists of the sturdy, power-driven separa...



For Milling Cutters And Formed Tools






Category: HIGH-SPEED STEEL

FORGING.--Forge as before.--ANNEALING.--Place the steel in a pipe,
box or muffle. Arrange the steel so as to allow at least 1 in.
of packing, consisting of dry powder ashes, powdered charcoal,
mica, etc., between the pieces and the walls of the box or pipe.
If using a pipe close the ends. Heat slowly and uniformly to a
cherry red, 1,375 to 1,450 deg.F. according to size. Hold the steel at
this temperature until the heat has thoroughly saturated through
the metal, then allow the muffle box and tools to cool very slowly
in a dying furnace or remove the muffle with its charge and bury
in hot ashes or lime. The slower the cooling the softer the steel.

The heating requires from 2 to 10 hr. depending upon the size of
the piece.

HARDENING AND TEMPERING.--It is preferable to use two furnaces
when hardening milling cutters and special shape tools. One furnace
should be maintained at a uniform temperature from 1,375 to 1,450 deg.F.
while the other should be maintained at about 2,250 deg.F. Keep the
tool to be hardened in the low temperature furnace until the tool
has attained the full heat of this furnace. A short time should be
allowed so as to be assured that the center of the tool is as hot
as the outside. Then quickly remove the tool from this preheating
furnace to the full heat furnace. Keep the tool in this furnace only
as long as is necessary for the tool to attain the full temperature
of this furnace. Then quickly remove and quench in oil or in a
dry air blast. Remove before the tool is entirely cold and draw
the temper in an oil bath by raising the temperature of the oil
to from 500 to 750 deg.F. and allow this tool to remain, at this
temperature, in the bath for at least 30 min., insuring uniformity
of temper; then cool in the bath, atmosphere or oil.

If higher drawing temperatures are desired than those possible
with oil, a salt bath can be used. A very excellent bath is made
by mixing two parts by weight of crude potassium nitrate and three
parts crude sodium nitrate. These will melt at about 450 deg.F. and
can be used up to 1,000 deg.F. Before heating the steel in the salt
bath, slowly preheat, preferably in oil. Reheating the hardened
high-speed steel to 1,000 deg.F. will materially increase the life
of lathe tools, but milling and form cutters, taps, dies, etc.,
should not be reheated higher than 500 to 650 deg.F., unless extreme
hardness is required, when 1,100 to 1,000 deg.F., will give the hardest
edge.





Next: Instructions For Working High-speed Steel

Previous: Lathe And Planer Tools



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