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Brown Automatic Signaling Pyrometer
In large heat-treating plants it has been customary to mainta...

Restoring Overheated Steel
The effect of heat treatment on overheated steel is shown gra...

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

Classifications Of Steel
Among makers and sellers, carbon tool-steels are classed by g...

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

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

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

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

Hardening
Steel is hardened by quenching from above the upper critical....

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

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

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

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

Quality And Structure
The quality of high-speed steel is dependent to a very great ...

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

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

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

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

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

Forging High-speed Steel
Heat very slowly and carefully to from 1,800 to 2,000 deg.F....



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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