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

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

Affinity Of Nickel Steel For Carbon
The carbon- and nickel-steel gears are carburized separately...

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

High-carbon Machinery Steel
The carbon content of this steel is above 30 points and is ha...

The material used for all gears on the Liberty engine was sel...

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

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

Reheating for machine ability was done at 100 deg. less than ...

MANGANESE is a metal much like iron. Its chemical symbol is M...

Carbon-steel Forgings
Low-stressed, carbon-steel forgings include such parts as car...

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

Effect Of Different Carburizing Material
[Illustrations: FIGS. 33 to 37.] Each of these different p...

Air-hardening Steels
These steels are recommended for boring, turning and planing...

Forging High-speed Steel
Heat very slowly and carefully to from 1,800 to 2,000 deg.F....

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

ANNEALING can be done by heating to temperatures ranging from...

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

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

Carburizing Material
The simplest carburizing substance is charcoal. It is also th...

Highly Stressed Parts


The highly stressed parts on the Liberty engine consisted of the
connecting-rod bolt, the main-bearing bolt, the propeller-hub key,
etc. The material used for parts of this type was selected at the
option of the manufacturer from standard S. A. E. steels, the
composition of which are given in Table 11.

TABLE 11.--COMPOSITION OF S. A. E. STEELS Nos. 2,330, 3,135 AND 6,130

Steel No 2,330 3,135 6,130
Carbon, minimum 0.250 0.300 0.250
Carbon, maximum 0.350 0.400 0.450
Manganese, minimum 0.500 0.500 0.500
Manganese, maximum 0.800 0.800 0.800
Phosphorus, maximum 0.045 0.040 0.040
Sulphur, maximum 0.045 0.045 0.045
Nickel, minimum 3.250 1.000
Nickel, maximum 3.750 1.500
Chromium, minimum 0.450 0.800
Chromium, maximum 0.750 1.100
Vanadium, minimum 0.150

All highly stressed parts on the Liberty engine must show, after
heat treatment, the following minimum physical properties: Elastic
limit, 100,000 lb. per square inch; elongation in 2 in., 16 per
cent; reduction of area, 45 per cent; scleroscope hardness, 40
to 50.

The heat treatment employed to obtain these physical properties
consisted in quenching from a temperature of 1,525 to 1,575 deg.F., in
oil, followed by tempering at a temperature of from 925 to 975 deg.F.

Due to the extremely fine limits used on all threaded parts for
the Liberty engine, a large percentage of rejection was due to
warpage and scaling of parts. To eliminate this objection, many
of the Liberty engine builders adopted the use of heat-treated
and cold-drawn alloy steel for their highly stressed parts. On
all sizes up to and including 3/8 in. in diameter, the physical
properties were secured by merely normalizing the hot-rolled bars
by heating to a temperature of from 1,525 to 1,575 deg.F., and cooling
in air, followed by the usual cold-drawing reductions. For parts
requiring stock over 3/8 in. in diameter, the physical properties
desired were obtained by quenching and tempering the hot-rolled bars
before cold-drawing. It is the opinion that the use of heat-treated
and cold-drawn bars is very good practice, provided proper inspection
is made to guarantee the uniformity of heat treatment and, therefore,
the uniformity of the physical properties of the finished parts.

The question has been asked many times by different manufacturers, as
to which alloy steel offers the best machineability when heat-treated
to a given Brinell hardness. The general consensus of opinion among
the screw-machine manufacturers is that S. A. E. No. 6,130 steel
gives the best machineability and that S. A. E. No. 2,330 steel
would receive second choice of the three specified.

In the finishing of highly stressed parts for aviation engines,
extreme care must be taken to see that all tool marks are eliminated,
unless they are parallel to the axis of strain, and that proper
radii are maintained at all changes of section. This is of the
utmost importance to give proper fatigue resistance to the part
in question.

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Previous: Carbon-steel Forgings

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