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Steel Making

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

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

MANGANESE is a metal much like iron. Its chemical symbol is M...

Rate Of Absorption
According to Guillet, the absorption of carbon is favored by ...

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

Hardening High-speed Steel
In forging use coke for fuel in the forge. Heat steel slowly ...

The Quenching Tank
The quenching tank is an important feature of apparatus in c...

Connecting Rods
The material used for all connecting rods on the Liberty engi...

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

Suggestions For Handling High-speed Steels
The following suggestions for handling high-speed steels are ...

Air-hardening Steels
These steels are recommended for boring, turning and planing...

Carburizing By Gas
The process of carburizing by gas, briefly mentioned on page ...

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

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

Cutting-off Steel From Bar
To cut a piece from an annealed bar, cut off with a hack saw,...

A Satisfactory Luting Mixture
A mixture of fireclay and sand will be found very satisfactor...

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

Steel is hardened by quenching from above the upper critical....

Short Method Of Treatment
In the new method, the packed pots are run into the case-har...

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

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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