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Preventing Carburizing By Copper-plating
Copper-plating has been found effective and must have a thick...

Take Time For Hardening
Uneven heating and poor quenching has caused loss of many ve...

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

The Leeds And Northrup Potentiometer System
The potentiometer pyrometer system is both flexible and subst...

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

Heat Treatment Of Steel
Heat treatment consists in heating and cooling metal at defin...

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

Chromium
Chromium when alloyed with steel, has the characteristic func...

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

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

Steel Worked In Austenitic State
As a general rule steel should be worked when it is in the a...

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

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

Steel For Chisels And Punches
The highest grades of carbon or tempering steels are to be re...

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

Annealing
There is no mystery or secret about the proper annealing of d...

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

High-chromium Or Rust-proof Steel
High-chromium, or what is called stainless steel containing f...

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

Corrosion
This steel like any other steel when distorted by cold worki...



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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