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

Detrimental Elements
Sulphur and phosphorus are two elements known to be detrimen...

Standard Analysis
The selection of a standard analysis by the manufacturer is t...

Shrinking And Enlarging Work
Steel can be shrunk or enlarged by proper heating and cooling...

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

Carbon Steels For Different Tools
All users of tool steels should carefully study the different...

Blending The Compound
Essentially, this consists of the sturdy, power-driven separa...

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

Heating
Although it is possible to work steels cold, to an extent de...

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

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

Forging High-speed Steel
Heat very slowly and carefully to from 1,800 to 2,000 deg.F....

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

Heat Treatment Of Punches And Dies Shears Taps Etc
HEATING.--The degree to which tools of the above classes shou...

Sulphur
SULPHUR is another element (symbol S) which is always found i...

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

Carburizing Material
The simplest carburizing substance is charcoal. It is also th...

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

Nickel
Nickel may be considered as the toughest among the non-rare a...

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



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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