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

Heat-treating Department
The heat-treating department occupies an L-shaped building. ...

The Theory Of Tempering
Steel that has been hardened is generally harder and more br...

Using Illuminating Gas
The choice of a carburizing furnace depends greatly on the fa...

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

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

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

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

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

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

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

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

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

Chrome-nickel Steel
Forging heat of chrome-nickel steel depends very largely on ...

Conclusions
Martien was probably never a serious contender for the honor ...

Fatigue Tests
It has been known for fifty years that a beam or rod would fa...

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

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

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

Pyrometers
Armor plate makers sometimes use the copper ball or Siemens' ...



Highly Stressed Parts






Category: APPLICATION OF LIBERTY ENGINE MATERIALS TO THE AUTOMOTIVE INDUSTRY

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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