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Steel Making

S A E Heat Treatments
The Society of Automotive Engineers have adopted certain heat...

Shrinking And Enlarging Work
Steel can be shrunk or enlarged by proper heating and cooling...

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

Fatigue Tests
It has been known for fifty years that a beam or rod would fa...

Rate Of Absorption
According to Guillet, the absorption of carbon is favored by ...

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

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

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

Properties Of Alloy Steels
The following table shows the percentages of carbon, manganes...

A Satisfactory Luting Mixture
A mixture of fireclay and sand will be found very satisfactor...

The Theory Of Tempering
Steel that has been hardened is generally harder and more br...

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

Nickel
Nickel may be considered as the toughest among the non-rare a...

Heat Treatment Of Milling Cutters Drills Reamers Etc
THE FIRE.--Gas and electric furnaces designed for high heats ...

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

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

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

Separating The Work From The Compound
During the pulling of the heat, the pots are dumped upon a ca...

Phosphorus
PHOSPHORUS is an element (symbol P) which enters the metal fr...

Cutting-off Steel From Bar
To cut a piece from an annealed bar, cut off with a hack saw,...



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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