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Application To The Automotive Industry
The information given on the various parts of the Liberty eng...

Lathe And Planer Tools
TO FORGE.--Gently warm the steel to remove any chill is parti...

Annealing Alloy Steel
The term alloy steel, from the steel maker's point of view, r...

The Pyrometer And Its Use
In the heat treatment of steel, it has become absolutely nece...

Hardening
The forgings can be hardened by cooling in still air or quen...

Tempering Round Dies
A number of circular dies of carbon tool steel for use in too...

Annealing Of High-speed Steel
For annealing high-speed steel, some makers recommend using g...

Plant For Forging Rifle Barrels
The forging of rifle barrels in large quantities and heat-tre...

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

Process Of Carburizing
Carburizing imparts a shell of high-carbon content to a low-...

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

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

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

Detrimental Elements
Sulphur and phosphorus are two elements known to be detrimen...

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

Non-shrinking Oil-hardening Steels
Certain steels have a very low rate of expansion and contract...

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

Care In Annealing
Not only will benefits in machining be found by careful anne...

Effects Of Proper Annealing
Proper annealing of low-carbon steels causes a complete solu...

Lathe And Planer Tools
FORGING.--Gently warm the steel to remove any chill, is parti...



Quenching Tool Steel






Category: HARDENING CARBON STEEL FOR TOOLS

To secure proper hardness, the cooling of quenching of steel is
as important as its heating. Quenching baths vary in nature, there
being a large number of ways to cool a piece of steel in contrast
to the comparatively few ways of heating it.

Plain water, brine and oil are the three most common quenching
materials. Of these three the brine will give the most hardness,
and plain water and oil come next. The colder that any of these
baths is when the piece is put into it the harder will be the steel;
but this does not mean that it is a good plan to dip the heated
steel into a tank of ice water, for the shock would be so great
that the bar would probably fly to pieces. In fact, the quenching
bath must be sometimes heated a bit to take off the edge of the
shock.

Brine solutions will work uniformly, or give the same degree of
hardness, until they reach a temperature of 150 deg.F. above which
their grip relaxes and the metals quenched in them become softer.
Plain water holds its grip up to a temperature of approximately
100 deg.F.; but oil baths, which are used to secure a slower rate of
cooling, may be used up to 500 deg. or more. A compromise is sometimes
effected by using a bath consisting of an inch or two of oil floating
on the surface of water. As the hot steel passes through the oil,
the shock is not as severe as if it were to be thrust directly
into the water; and in addition, oil adheres to the tool and keeps
the water from direct contact with the metal.

The old idea that mercury will harden steel more than any other
quenching material has been exploded. A bath consisting of melted
cyanide of potassium is useful for heating fine engraved dies and
other articles that are required to come out free from scale. One
must always be careful to provide a hood or exhaust system to get
rid of the deadly fumes coming from the cyanide pot.

The one main thing to remember in hardening tool steel is to quench
on a rising heat. This does not mean a rapid heating as a slow
increase in temperature is much better in every way.





Next: The Theory Of Tempering

Previous: Double Annealing



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