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

Knowing What Takes Place
How are we to know if we have given a piece of steel the ver...

Placing Of Pyrometers
When installing a pyrometer, care should be taken that it re...

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

Application To The Automotive Industry
The information given on the various parts of the Liberty eng...

Alloying Elements
Commercial steels of even the simplest types are therefore p...

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

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

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

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

The Effect
The heating at 1,600 deg.F. gives the first heat treatment w...

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

The Packing Department
In Fig. 56 is shown the packing pots where the work is packe...

Cyanide Bath For Tool Steels
All high-carbon tool steels are heated in a cyanide bath. Wi...

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

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

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

Double Annealing
Water annealing consists in heating the piece, allowing it to...

Ebbw Vale And The Bessemer Process
After his British Association address in August 1856, Besseme...

Chrome-nickel Steel
Forging heat of chrome-nickel steel depends very largely on ...



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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