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Nickel-chromium
A combination of the characteristics of nickel and the charac...

Preventing Carburizing By Copper-plating
Copper-plating has been found effective and must have a thick...

Properties Of Alloy Steels
The following table shows the percentages of carbon, manganes...

Brown Automatic Signaling Pyrometer
In large heat-treating plants it has been customary to mainta...

Quenching
It is considered good practice to quench alloy steels from th...

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

Steel Before The 1850's
In spite of a rapid increase in the use of machines and the ...

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

Robert Mushet
Robert (Forester) Mushet (1811-1891), born in the Forest of D...

Hardness Testing
The word hardness is used to express various properties of me...

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

Composition And Properties Of Steel
It is a remarkable fact that one can look through a dozen tex...

Quenching Tool Steel
To secure proper hardness, the cooling of quenching of steel ...

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

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

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

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

Crankshaft
The crankshaft was the most highly stressed part of the entir...

William Kelly's Air-boiling Process
An account of Bessemer's address to the British Association w...

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



Rate Of Cooling






Category: APPLICATION OF LIBERTY ENGINE MATERIALS TO THE AUTOMOTIVE INDUSTRY

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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