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Steel Making

It is considered good practice to quench alloy steels from th...

Hardness Testing
The word hardness is used to express various properties of me...

Protective Screens For Furnaces
Workmen needlessly exposed to the flames, heat and glare from...

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

Hardening Carbon Steel For Tools
For years the toolmaker had full sway in regard to make of st...

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

The Modern Hardening Room
A hardening room of today means a very different place from ...

SILICON is a very widespread element (symbol Si), being an es...

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

Manganese adds considerably to the tensile strength of steel,...

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

Introduction Of Carbon
The matter to which these notes are primarily directed is the...

Properties Of Alloy Steels
The following table shows the percentages of carbon, manganes...

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

Annealing Work
With the exception of several of the higher types of alloy s...

Temperatures To Use
As soon as the temperature of the steel reaches 100 deg.C. (...

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

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

Annealing Method
Forgings which are too hard to machine are put in pots with ...

Heat Treatment Of Gear Blanks
This section is based on a paper read before the American Gea...

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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