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

The Effect Of Tempering On Water-quenched Gages
The following information has been supplied by Automatic and ...

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

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

The Influence Of Size
The size of the piece influences the physical properties obta...

Shrinking And Enlarging Work
Steel can be shrunk or enlarged by proper heating and cooling...

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

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

Temperature Recording And Regulation
Each furnace is equipped with pyrometers, but the reading an...

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

PHOSPHORUS is an element (symbol P) which enters the metal fr...

Lathe And Planer Tools
FORGING.--Gently warm the steel to remove any chill, is parti...

Hints For Tool Steel Users
Do not hesitate to ask for information from the maker as to t...

The Care Of Carburizing Compounds
Of all the opportunities for practicing economy in the heat-t...

Blending The Compound
Essentially, this consists of the sturdy, power-driven separa...

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

Process Of Carburizing
Carburizing imparts a shell of high-carbon content to a low-...

The Packing Department
In Fig. 56 is shown the packing pots where the work is packe...

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

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

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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