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Steel Making

Instructions For Working High-speed Steel
Owing to the wide variations in the composition of high-speed...

The Leeds And Northrup Potentiometer System
The potentiometer pyrometer system is both flexible and subst...

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

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

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

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

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

Carbon In Tool Steel
Carbon tool steel, or tool steel as it is commonly called, us...

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

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

Crucible Steel
Crucible steel is still made by melting material in a clay or...

Drop Forging Dies
The kind of steel used in the die of course influences the he...

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

Composition Of Transmission-gear Steel
If the nickel content of this steel is eliminated, and the pe...

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

Making Steel Balls
Steel balls are made from rods or coils according to size, st...

Carbon-steel Forgings
Low-stressed, carbon-steel forgings include such parts as car...

Correction For Cold-junction Errors
The voltage generated by a thermo-couple of an electric pyrom...

Annealing Method
Forgings which are too hard to machine are put in pots with ...

Quenching The Work
In some operations case-hardened work is quenched from the bo...



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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