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Hardening High-speed Steel
In forging use coke for fuel in the forge. Heat steel slowly ...

The Influence Of Size
The size of the piece influences the physical properties obta...

Tensile Properties
Strength of a metal is usually expressed in the number of pou...

Composition And Properties Of Steel
It is a remarkable fact that one can look through a dozen tex...

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

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

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

Judging The Heat Of Steel
While the use of a pyrometer is of course the only way to hav...

Knowing What Takes Place
How are we to know if we have given a piece of steel the ver...

Heat Treatment Of Axles
Parts of this general type should be heat-treated to show the...

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

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

Open Hearth Process
The open hearth furnace consists of a big brick room with a l...

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

Correction By Zero Adjustment
Many pyrometers are supplied with a zero adjuster, by means ...

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

Suggestions For Handling High-speed Steels
The following suggestions for handling high-speed steels are ...

The Penetration Of Carbon
Carburized mild steel is used to a great extent in the manufa...

Ebbw Vale And The Bessemer Process
After his British Association address in August 1856, Besseme...

Hardening High-speed Steels
We will now take up the matter of hardening high-speed steels...



The Modern Hardening Room






Category: HARDENING CARBON STEEL FOR TOOLS

A hardening room of today means a very
different place from the dirty, dark smithshop in the corner with
the open coal forge. There, when we wanted to be somewhat particular,
we sometimes shoveled the coal cinders to one side and piled a great
pile of charcoal on the forge. We now have a complete equipment;
a gas- or oil-heating furnace, good running water, several sizes
of lead pots, and an oil tank large enough to hold a barrel of
oil. By running water, we mean a large tank with overflow pipes
giving a constant supply. The ordinary hardening room equipment
should consist of:

Gas or oil muffle furnace for hardening.
Gas or oil forge furnace.
A good size gas or oil furnace for annealing and case-hardening.
A gas or oil furnace to hold lead pots.
Oil tempering tank, gas- or oil-heated.
Pressure blower.
Large oil tank to hold at least a barrel of oil.
Big water tank with screen trays connected with large pipe from bottom
with overflow.
Straightening press.
The furnace should be connected with pyrometers and tempering tank with
a thermometer.

Beside all this you need a good man. It does not make much difference
how completely the hardening department is fitted up, if you expect
good work, a small percentage of loss and to be able to tackle anything
that comes along, you must have a good man, one who understands
the difference between low- and high-carbon steel, who knows when
particular care must be exercised on particular work. In other
words, a man who knows how his work should be done, and has the
intelligence to follow directions on treatments of steel on which
he has had no experience.

Jewelers' tools, especially for silversmith's work, probably have
to stand the greatest punishment of any all-steel tools and to
make a spoon die so hard that it will not sink under a blow from
an 1,800-lb. hammer with a 4-ft. drop, and still not crack, demands
careful treatment.

To harden such dies, first cover the impression on the die with
paste made from bone dust or lampblack and oil. Place face down
in an iron box partly filled with crushed charcoal, leaving back
of die uncovered so that the heat can be seen at all times. Heat
slowly in furnace to a good cherry red. The heat depends on the
quality and the analysis of steel and the recommended actions of
the steel maker should be carefully followed. When withdrawn from
the fire the die should be quenched as shown in Fig. 80 with the
face of die down and the back a short distance out of the water.
When the back is black, immerse all over.



If such a tank is not at hand, it would pay to rig one up at once,
although a barrel of brine may be used, or the back of the die
may be first immersed to a depth of about 1/2 in. When the piece
is immersed, hold die on an angle as in Fig. 81.



This is for the purpose of expelling all steam bubbles as they
form in contact with hot steel. We are aware of the fact that a
great many toolmakers in jewelry shops still cling to the overhead
bath, as in Fig. 82, but more broken pieces and more dies with
soft spots are due to this method than to all the others combined,
as the water strikes one spot in force, contracting the surface
so much faster than the rest of the die that the results are the
same as if an uneven heating had been given the steel.





Next: Take Time For Hardening

Previous: Hardening Carbon Steel For Tools



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