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Steel Making

Carburizing Low-carbon Sleeves
Low-carbon sleeves are carburized and pushed on malleable-ir...

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

Tempering Round Dies
A number of circular dies of carbon tool steel for use in too...

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

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

Piston Pin
The piston pin on an aviation engine must possess maximum res...

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

Calibration Of Pyrometer With Common Salt
An easy and convenient method for standardization and one whi...

Plant For Forging Rifle Barrels
The forging of rifle barrels in large quantities and heat-tre...

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

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

Effects Of Proper Annealing
Proper annealing of low-carbon steels causes a complete solu...

Rate Of Cooling
At the option of the manufacturer, the above treatment of gea...

Hardening High-speed Steels
We will now take up the matter of hardening high-speed steels...

Typical Oil-fired Furnaces
Several types of standard oil-fired furnaces are shown herew...

Steel Worked In Austenitic State
As a general rule steel should be worked when it is in the a...

Surface Carburizing
Carburizing, commonly called case-hardening, is the art of pr...

Correction For Cold-junction Errors
The voltage generated by a thermo-couple of an electric pyrom...

Steel For Chisels And Punches
The highest grades of carbon or tempering steels are to be re...

For Milling Cutters And Formed Tools
FORGING.--Forge as before.--ANNEALING.--Place the steel in a ...



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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