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The Pyrometer And Its Use
In the heat treatment of steel, it has become absolutely nece...

Connecting Rods
The material used for all connecting rods on the Liberty engi...

Manganese
Manganese adds considerably to the tensile strength of steel,...

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

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

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

The Modern Hardening Room
A hardening room of today means a very different place from ...

A Satisfactory Luting Mixture
A mixture of fireclay and sand will be found very satisfactor...

The Electric Process
The fourth method of manufacturing steel is by the electric f...

Protectors For Thermo-couples
Thermo-couples must be protected from the danger of mechanica...

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

Chrome-nickel Steel
Forging heat of chrome-nickel steel depends very largely on ...

Alloying Elements
Commercial steels of even the simplest types are therefore p...

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

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

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

The Effect
The heating at 1,600 deg.F. gives the first heat treatment w...

Liberty Motor Connecting Rods
The requirements for materials for the Liberty motor connecti...

Steel Can Be Worked Cold
As noted above, steel can be worked cold, as in the case of ...

A Chromium-cobalt Steel
The Latrobe Steel Company make a high-speed steel without tun...



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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