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

Preventing Cracks In Hardening
The blacksmith in the small shop, where equipment is usually ...

For Milling Cutters And Formed Tools
FORGING.--Forge as before.--ANNEALING.--Place the steel in a ...

Carbon Tool Steel
Heat to a bright red, about 1,500 to 1,550 deg.F. Do not ham...

Silicon
Silicon prevents, to a large extent, defects such as gas bubb...

Pyrometry And Pyrometers
A knowledge of the fundamental principles of pyrometry, or th...

Tempering Colors On Carbon Steels
Opinions differ as to the temperature which is indicated by t...

Tool Or Crucible Steel
Crucible steel can be annealed either in muffled furnace or b...

Hardening Carbon Steel For Tools
For years the toolmaker had full sway in regard to make of st...

High-carbon Machinery Steel
The carbon content of this steel is above 30 points and is ha...

Introduction Of Carbon
The matter to which these notes are primarily directed is the...

Take Time For Hardening
Uneven heating and poor quenching has caused loss of many ve...

Phosphorus
Phosphorus is one of the impurities in steel, and it has been...

Heating
Although it is possible to work steels cold, to an extent de...

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

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

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

Carburizing Material
The simplest carburizing substance is charcoal. It is also th...

Steel For Chisels And Punches
The highest grades of carbon or tempering steels are to be re...

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



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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