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Steel Making

Gas Consumption For Carburizing
Although the advantages offered by the gas-fired furnace for ...

Calibration Of Pyrometer With Common Salt
An easy and convenient method for standardization and one whi...

Heat Treatment Of Steel
Heat treatment consists in heating and cooling metal at defin...

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

The Forging Of Steel
So much depends upon the forging of steel that this operation...

Testing And Inspection Of Heat Treatment
The hard parts of the gear must be so hard that a new mill f...

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

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

Application Of Liberty Engine Materials To The Automotive Industry
The success of the Liberty engine program was an engineer...

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

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

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

Impact Tests
Impact tests are of considerable importance as an indication ...

Oil-hardening Steel
Heat slowly and uniformly to 1,450 deg.F. and forge thorough...

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

William Kelly's Air-boiling Process
An account of Bessemer's address to the British Association w...

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

Rate Of Cooling
At the option of the manufacturer, the above treatment of gea...

Temperatures To Use
As soon as the temperature of the steel reaches 100 deg.C. (...

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



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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