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Steel Making

This steel like any other steel when distorted by cold worki...

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

Correction By Zero Adjustment
Many pyrometers are supplied with a zero adjuster, by means ...

Leeds And Northrup Optical Pyrometer
The principles of this very popular method of measuring tempe...

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

Pyrometers For Molten Metal
Pyrometers for molten metal are connected to portable thermoc...

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

Knowing What Takes Place
How are we to know if we have given a piece of steel the ver...

Application Of Liberty Engine Materials To The Automotive Industry
The success of the Liberty engine program was an engineer...

Making Steel Balls
Steel balls are made from rods or coils according to size, st...

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

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

Non-shrinking Oil-hardening Steels
Certain steels have a very low rate of expansion and contract...

For Milling Cutters And Formed Tools
FORGING.--Forge as before.--ANNEALING.--Place the steel in a ...

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

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

Instructions For Working High-speed Steel
Owing to the wide variations in the composition of high-speed...

Annealing To Relieve Internal Stresses
Work quenched from a high temperature and not afterward tempe...

Carbon Tool Steel
Heat to a bright red, about 1,500 to 1,550 deg.F. Do not ham...

Phosphorus is one of the impurities in steel, and it has been...

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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