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

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

Quenching The Work
In some operations case-hardened work is quenched from the bo...

Annealing Of High-speed Steel
For annealing high-speed steel, some makers recommend using g...

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

The Care Of Carburizing Compounds
Of all the opportunities for practicing economy in the heat-t...

Non-shrinking Oil-hardening Steels
Certain steels have a very low rate of expansion and contract...

Tungsten
Tungsten, as an alloy in steel, has been known and used for a...

Annealing
ANNEALING can be done by heating to temperatures ranging from...

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

Testing And Inspection Of Heat Treatment
The hard parts of the gear must be so hard that a new mill f...

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

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

A Chromium-cobalt Steel
The Latrobe Steel Company make a high-speed steel without tun...

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

Highly Stressed Parts
The highly stressed parts on the Liberty engine consisted of ...

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

The Thermo-couple
With the application of the thermo-couple, the measurement of...

Oil-hardening Steel
Heat slowly and uniformly to 1,450 deg.F. and forge thorough...

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



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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