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

Sulphur
SULPHUR is another element (symbol S) which is always found i...

Molybdenum
Molybdenum steels have been made commercially for twenty-five...

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

Temperature Recording And Regulation
Each furnace is equipped with pyrometers, but the reading an...

Silicon
SILICON is a very widespread element (symbol Si), being an es...

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

Hardening
The forgings can be hardened by cooling in still air or quen...

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

Carbon Steels For Different Tools
All users of tool steels should carefully study the different...

Heat-treating Department
The heat-treating department occupies an L-shaped building. ...

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

Machineability
Reheating for machine ability was done at 100 deg. less than ...

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

Cyanide Bath For Tool Steels
All high-carbon tool steels are heated in a cyanide bath. Wi...

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

Annealing Of Rifle Components At Springfield Armory
In general, all forgings of the components of the arms manufa...

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

Heat-treating Equipment And Methods For Mass Production
The heat-treating department of the Brown-Lipe-Chapin Company...

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



Drop Forging Dies






Category: HEAT TREATMENT OF STEEL

The kind of steel used in the die of course influences the heat
treatment it is to receive, but this also depends on the kind of
work the die is to perform. If the die is for a forging which is
machined all over and does not have to be especially close to size,
where a variation of 1/16 in. is not considered excessive, a low
grade steel will be perfectly satisfactory.

In cases of fine work, however, where the variation cannot be over
0.005 to 0.01 in. we must use a fine steel and prevent its going
out of shape in the heating and quenching. A high quality crucible
steel is suggested with about the following analysis: Carbon 0.75
per cent, manganese 0.25 per cent, silicon 0.15 per cent, sulphur
0.015 per cent, and phosphorus 0.015 per cent. Such a steel will
have a decalescent point in the neighborhood of 1,355 deg.F. and for
the size used, probably in a die of approximately 8 in., it will
harden around 1,450 deg.F.

To secure best results care must be taken at every step. The block
should be heated slowly to about 1,400 deg.F., the furnace closed tight
and allowed to cool slowly in the furnace itself. It should not
soak at the high temperature.

After machining, and before it is put in the furnace for hardening,
it should be slowly preheated to 800 or 900 deg.F. This can be done in
several ways, some putting the die block in front of the open door
of a hardening furnace and keeping the furnace at about 1,000 deg.F.
The main thing is to heat the die block very slowly and evenly.

The hardening heat should be very slow, 7 hr. being none too long
for such a block, bringing the die up gradually to the quenching
temperature of 1,450 deg.. This should be held for 1/2 hr. or even a
little more, when the die can be taken out and quenched. There
should be no guess work about the heating, a good pyrometer being
the only safe way of knowing the correct temperature.

The quenching tank should be of good size and have a spray or stream
of water coming up near the surface. Dip the die block about 3 in.
deep and let the stream of water get at the face so as to play
on the forms. By leaving the rest of the die out of the water,
moving the die up and down a trifle to prevent a crack at the line
of immersion, the back of the block is left tough while the face
is very hard. To overcome the tendency to warp the face it is a
good plan to pour a little water on the back of the die as this
tends to even up the cooling. The depth to which the die is dipped
can be easily regulated by placing bars across the tank at the
proper depth.

After the scleroscope shows the die to be properly hardened, which
means from 98 to 101, the temper should be drawn as soon as convenient.
A lead pot in which the back of the die can be suspended so as
to heat the back side, makes a good method. Or the die block can
be placed back to the open door of a furnace. On a die of this
size it may take several hours to draw it to the desired temper.
This can be tested while warm by the scleroscope method, bearing
in mind that the reading will not be the same as when cold. If
the test shows from 76 to 78 while warm, the hardness when cold
will be about 83, which is about right for this work.





Next: S A E Heat Treatments

Previous: Cyanide Bath For Tool Steels



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