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Steel Making

Hardness Testing
The word hardness is used to express various properties of me...

Effect Of A Small Amount Of Copper In Medium-carbon Steel
This shows the result of tests by C. R. Hayward and A. B. Joh...

Preparing Parts For Local Case-hardening
At the works of the Dayton Engineering Laboratories Company, ...

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

Preventing Carburizing By Copper-plating
Copper-plating has been found effective and must have a thick...

Manganese
MANGANESE is a metal much like iron. Its chemical symbol is M...

Carburizing By Gas
The process of carburizing by gas, briefly mentioned on page ...

Flange Shields For Furnaces
Such portable flame shields as the one illustrated in Fig. 1...

Case-hardening Treatments For Various Steels
Plain water, salt water and linseed oil are the three most co...

Heavy Forging Practice
In heavy forging practice where the metal is being worked at...

Heating Of Manganese Steel
Another form of heat-treating furnace is that which is used ...

Protective Screens For Furnaces
Workmen needlessly exposed to the flames, heat and glare from...

Tungsten
Tungsten, as an alloy in steel, has been known and used for a...

Critical Points
One of the most important means of investigating the properti...

Classifications Of Steel
Among makers and sellers, carbon tool-steels are classed by g...

Annealing Work
With the exception of several of the higher types of alloy s...

Typical Oil-fired Furnaces
Several types of standard oil-fired furnaces are shown herew...

Knowing What Takes Place
How are we to know if we have given a piece of steel the ver...

The Effect
The heating at 1,600 deg.F. gives the first heat treatment w...

Hardening High-speed Steels
We will now take up the matter of hardening high-speed steels...



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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