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

Judging The Heat Of Steel
While the use of a pyrometer is of course the only way to hav...

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

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

Gas Consumption For Carburizing
Although the advantages offered by the gas-fired furnace for ...

Refining The Grain
This is remedied by reheating the piece to a temperature slig...

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

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

Carbon In Tool Steel
Carbon tool steel, or tool steel as it is commonly called, us...

Classifications Of Steel
Among makers and sellers, carbon tool-steels are classed by g...

Sulphur
Sulphur is another impurity and high sulphur is even a greate...

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

Effect Of A Small Amount Of Copper In Medium-carbon Steel
This shows the result of tests by C. R. Hayward and A. B. Joh...

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

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

Heating
Although it is possible to work steels cold, to an extent de...

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

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

Complete Calibration Of Pyrometers
For the complete calibration of a thermo-couple of unknown e...

Bessemer Process
The bessemer process consists of charging molten pig iron int...



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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