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Quenching
It is considered good practice to quench alloy steels from th...

The Thermo-couple
With the application of the thermo-couple, the measurement of...

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

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

Silicon
Silicon prevents, to a large extent, defects such as gas bubb...

Standard Analysis
The selection of a standard analysis by the manufacturer is t...

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

The Effect Of Tempering On Water-quenched Gages
The following information has been supplied by Automatic and ...

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

Annealing Of High-speed Steel
For annealing high-speed steel, some makers recommend using g...

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

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

Case-hardening Treatments For Various Steels
Plain water, salt water and linseed oil are the three most co...

Heating
Although it is possible to work steels cold, to an extent de...

Heat Treatment Of Punches And Dies Shears Taps Etc
HEATING.--The degree to which tools of the above classes shou...

Carbon-steel Forgings
Low-stressed, carbon-steel forgings include such parts as car...

Lathe And Planer Tools
FORGING.--Gently warm the steel to remove any chill, is parti...

Corrosion
This steel like any other steel when distorted by cold worki...

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

Effect Of A Small Amount Of Copper In Medium-carbon Steel
This shows the result of tests by C. R. Hayward and A. B. Joh...



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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