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

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

Hardening Operation
Hardening a gear is accomplished as follows: The gear is tak...

Heat Treatment Of Gear Blanks
This section is based on a paper read before the American Gea...

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

Steel Worked In Austenitic State
As a general rule steel should be worked when it is in the a...

Annealing
ANNEALING can be done by heating to temperatures ranging from...

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

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

Correction For Cold-junction Errors
The voltage generated by a thermo-couple of an electric pyrom...

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

Crucible Steel
Crucible steel is still made by melting material in a clay or...

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

Quenching The Work
In some operations case-hardened work is quenched from the bo...

Sulphur
Sulphur is another impurity and high sulphur is even a greate...

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

Introduction Of Carbon
The matter to which these notes are primarily directed is the...

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

Heavy Forging Practice
In heavy forging practice where the metal is being worked at...

Preventing Cracks In Hardening
The blacksmith in the small shop, where equipment is usually ...



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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