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

Armor plate makers sometimes use the copper ball or Siemens' ...

Care In Annealing
Not only will benefits in machining be found by careful anne...

Affinity Of Nickel Steel For Carbon
The carbon- and nickel-steel gears are carburized separately...

The crankshaft was the most highly stressed part of the entir...

Plant For Forging Rifle Barrels
The forging of rifle barrels in large quantities and heat-tre...

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

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

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

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

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

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

An Automatic Temperature Control Pyrometer
Automatic temperature control instruments are similar to the ...

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

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

A combination of the characteristics of nickel and the charac...

Preventing Cracks In Hardening
The blacksmith in the small shop, where equipment is usually ...

Heat Treatment Of Gear Blanks
This section is based on a paper read before the American Gea...

Hardness Testing
The word hardness is used to express various properties of me...

For Milling Cutters And Formed Tools
FORGING.--Forge as before.--ANNEALING.--Place the steel in a ...

Liberty Motor Connecting Rods


The requirements for materials for the Liberty motor connecting rods
are so severe that the methods of securing the desired qualities
will be of value in other lines. The original specifications called
for chrome-nickel but the losses due to the difficulty of handling
caused the Lincoln Motor Company to suggest the substitution of
chrome-vanadium steel, and this was accepted by the Signal Corps. The
rods were accordingly made from chromium-vanadium steel, containing
carbon, 0.30 to 0.40 per cent; manganese, 0.50 to 0.80 per cent;
phosphorus, not over 0.04 per cent; sulphur, not over 0.04 per
cent; chromium, 0.80 to 1.10 per cent; vanadium, not less than 0.15
per cent. This steel is ordinarily known in the trade as 0.35 carbon
steel, S. A. E., specification 6,135, which provides a first-rate
quality steel for structural parts that are to be heat-treated.
The fatigue resisting or endurance qualities of this material are
excellent. It has a tensile strength of 150,000 lb. minimum per
square inch; elastic limit, 115,000 lb. minimum per square inch;
elongation, 5 per cent minimum in 2 in.; and minimum reduction
in area, 25 per cent.

The original production system as outlined for the manufacturers
had called for a heat treatment in the rough-forged state for the
connecting rods, and then semi-machining the rod forgings before
giving them the final treatment. The Lincoln Motor Company insisted
from the first that the proper method would be a complete heat
treatment of the forging in the rough state, and machining the
rod after the heat treatment. After a number of trial lots, the
Signal Corps acceded to the request and production was immediately
increased and quality benefited by the change. This method was
later included in a revised specification issued to all producers.

The original system was one that required a great deal of labor
per unit output. The Lincoln organization developed a method of
handling connecting rods whereby five workmen accomplished the
same result that would have required about 30 or 32 by the original
method. Even after revising the specification so as to allow complete
heat treatments in the rough-forged state, the ordinary methods
employed in heat-treating would have required 12 to 15 men. With
the fixtures employed, five men could handle 1,300 connecting rods,
half of which are plain and half, forked, in a working period of
little over 7 hr.

The increase in production was gained by devising fixtures which
enabled fewer men to handle a greater quantity of parts with less
effort and in less time.

In heat-treating the forgings were laid on a rack or loop A,
Fig. 14, made of 1-1/4-in. double extra-heavy pipe, bent up with
parallel sides about 9 in. apart, one end being bent straight across
and the other end being bent upward so as to afford an easy grasp
for the hook. Fifteen rods were laid on each loop, there being
four loops of rods charged into a furnace with a hearth area of 36
by 66 in. The rods were charged at a temperature of approximately
900 deg.F. They were heated for refining over a period of 3 hr. to
1,625 deg.F., soaked 15 min, at this degree of heat and quenched in
soluble quenching oil.

In pulling the heat to quench the rods, the furnace door was raised
and the operator pulls one of the loops A, Fig. 15 forward to
the shelf of the furnace, supporting the straight end of the loop
by means of the porter bar B. They swung the loop of rods around
from the furnace shelf and set the straight end of the loop on
the edge of the quenching tank, then raise the curved end C,
by means of their hook D so that all the rods on the loop slide
into the oil bath.

Before the rods cooled entirely, the baskets in the quenching tank
were raised and the oil allowed to partly drain off the forgings,
and they were stacked on curved-end loops or racks and charged into
the furnace for the second or hardening heat. The temperature of
the furnace was raised in 1-1/2 hr. to 1,550 deg.F., the rods soaked
for 15 min. at this degree of heat and quenched in the same manner
as above.

They were again drained while yet warm, placed on loops and charged
into the furnace for the third or tempering heat. The temperature of
the furnace was brought to 1,100 deg.F. in 1 hr., and the rods soaked at
this degree of heat for 1 hr. They were then removed from the furnace
the same as for quenching, but were dumped onto steel platforms
instead of into the quenching oil, and allowed to cool on these
steel platforms down to the room temperature.

Next: Pickling The Forgings

Previous: Corrosion

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