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Steel Making

Care In Annealing
Not only will benefits in machining be found by careful anne...

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

Tempering Colors On Carbon Steels
Opinions differ as to the temperature which is indicated by t...

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

SULPHUR is another element (symbol S) which is always found i...

The Leeds And Northrup Potentiometer System
The potentiometer pyrometer system is both flexible and subst...

Complete Calibration Of Pyrometers
For the complete calibration of a thermo-couple of unknown e...

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

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

Nickel may be considered as the toughest among the non-rare a...

Hardening High-speed Steels
We will now take up the matter of hardening high-speed steels...

Open Hearth Process
The open hearth furnace consists of a big brick room with a l...

Protective Screens For Furnaces
Workmen needlessly exposed to the flames, heat and glare from...

Properties Of Steel
Steels are known by certain tests. Early tests were more or l...

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

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

Rate Of Cooling
At the option of the manufacturer, the above treatment of gea...

Compensating Leads
By the use of compensating leads, formed of the same materia...

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

Preventing Decarbonization Of Tool Steel
It is especially important to prevent decarbonization in such...

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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