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Heating Of Manganese Steel
Another form of heat-treating furnace is that which is used ...

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

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

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

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

Separating The Work From The Compound
During the pulling of the heat, the pots are dumped upon a ca...

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

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

Placing The Thermo-couples
The following illustrations from the Taylor Instrument Compan...

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

Ebbw Vale And The Bessemer Process
After his British Association address in August 1856, Besseme...

Restoring Overheated Steel
The effect of heat treatment on overheated steel is shown gra...

Application To The Automotive Industry
The information given on the various parts of the Liberty eng...

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

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

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

Carburizing By Gas
The process of carburizing by gas, briefly mentioned on page ...

Annealing In Bone
Steel and cast iron may both be annealed in granulated bone. ...

Plant For Forging Rifle Barrels
The forging of rifle barrels in large quantities and heat-tre...

Heat Treatment Of Milling Cutters Drills Reamers Etc
THE FIRE.--Gas and electric furnaces designed for high heats ...

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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