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Steel Making

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

Suggestions For Handling High-speed Steels
The following suggestions for handling high-speed steels are ...

The Influence Of Size
The size of the piece influences the physical properties obta...

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

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

Oil-hardening Steel
Heat slowly and uniformly to 1,450 deg.F. and forge thorough...

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

The Quenching Tank
The quenching tank is an important feature of apparatus in c...

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

Placing Of Pyrometers
When installing a pyrometer, care should be taken that it re...

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

High Speed Steel
For centuries the secret art of making tool steel was handed ...

Tool Or Crucible Steel
Crucible steel can be annealed either in muffled furnace or b...

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

The Care Of Carburizing Compounds
Of all the opportunities for practicing economy in the heat-t...

Tensile Properties
Strength of a metal is usually expressed in the number of pou...

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

Heat Treatment Of Lathe Planer And Similar Tools
FIRE.--For these tools a good fire is one made of hard foundr...

Vanadium has a very marked effect upon alloy steels rich in c...

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

Rate Of Cooling


At the option of the manufacturer, the above treatment of gear
forgings could be substituted by normalizing the forgings at a
temperature of from 1,550 to 1,600 deg.F. The most important criterion
for proper normalizing, consisted in allowing the forgings to cool
through the critical temperature of the steel, at a rate not to exceed
50 deg.F. per hour. For the two standard steels used, this consisted in
cooling from the normalizing temperature down to a temperature
of 1,100 deg.F., at the rate indicated. Forgings normalized in this
manner will show a Brinell hardness of from 177 to 217. The question
has been repeatedly asked as to which treatment will produce the
higher quality finished part. In answer to this I will state that
on simple forgings of comparatively small section, the normalizing
treatment will produce a finished part which is of equal quality to
that of the quenched and annealed forgings. However, in the case of
complex forgings, or those of large section, more uniform physical
properties of the finished part will be obtained by quenching and
annealing the forgings in the place of normalizing.

The heat treatment of the finished gears consisted of quenching
in oil from a temperature of from 1,420 to 1,440 deg.F. for the No.
X-3,340 steel, or from a temperature of from 1,500 to 1,540 deg.F.
for No. 6,140 steel, followed by tempering in saltpeter or in an
electric furnace at a temperature of from 650 to 700 deg.F.

The question has been asked by many engineers, why is the comparatively
low scleroscope hardness specified for gears? The reason for this is
that at best the life of an aviation engine is short, as compared with
that of an automobile, truck or tractor, and that shock resistance
is of vital importance. A sclerescope hardness of from 55 to 65
will give sufficient resistance to wear to prevent replacements
during the life of an aviation engine, while at the same time this
hardness produces approximately 50 per cent greater shock-resisting
properties to the gear. In the case of the automobile, truck or
tractor, resistance to wear is the main criterion and for that
reason the higher hardness is specified.

Great care should be taken in the design of an aviation engine
gear to eliminate sharp corners at the bottom of teeth as well
as in keyways. Any change of section in any stressed part of an
aviation engine must have a radius of at least 1/32 in. to give
proper shock and fatigue resistance. This fact has been demonstrated
many times during the Liberty engine program.

Next: Connecting Rods

Previous: Gears

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