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

Phosphorus
PHOSPHORUS is an element (symbol P) which enters the metal fr...

Steel Can Be Worked Cold
As noted above, steel can be worked cold, as in the case of ...

Placing The Thermo-couples
The following illustrations from the Taylor Instrument Compan...

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

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

Quality And Structure
The quality of high-speed steel is dependent to a very great ...

Properties Of Steel
Steels are known by certain tests. Early tests were more or l...

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

Annealing Method
Forgings which are too hard to machine are put in pots with ...

Piston Pin
The piston pin on an aviation engine must possess maximum res...

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

The Effect Of Tempering On Water-quenched Gages
The following information has been supplied by Automatic and ...

Carbon In Tool Steel
Carbon tool steel, or tool steel as it is commonly called, us...

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

Phosphorus
Phosphorus is one of the impurities in steel, and it has been...

Annealing Alloy Steel
The term alloy steel, from the steel maker's point of view, r...

Silicon
Silicon prevents, to a large extent, defects such as gas bubb...

Heavy Forging Practice
In heavy forging practice where the metal is being worked at...

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



Composition Of Transmission-gear Steel






Category: APPLICATION OF LIBERTY ENGINE MATERIALS TO THE AUTOMOTIVE INDUSTRY

If the nickel content of this steel is eliminated, and the percentage
of chromium raised slightly, an ideal transmission-gear material is
obtained. This would, therefore, be of the following composition:
Carbon, 0.470 to 0.520 per cent; manganese, 0.500 to 0.800 per
cent; phosphorus, 0.040 maximum per cent; sulphur, 0.045 maximum
per cent; chromium, 0.800 to 1.100 per cent.

The important criterion in connection with the use of this material
is that the steel be properly deoxidized, either through the use
of ferrovanadium or its equivalent. Approximately 2,500 sets of
transmission gears are being made daily from material of this analysis
and are giving entirely satisfactory results in service. The heat
treatment of the above material for transmission gears is as follows:
Normalize forgings at a temperature of from 1,5.50 to 1,600 deg.F.
Cool from this temperature to a temperature of 1,100 deg.F. at the
rate of 50 deg. per hour. Cool from 1,100 deg.F., either in air or quench
in water.

Forgings so treated will show a Brinell hardness of from 177 to
217, which is the proper range for the best machineability. The
heat treatment of the finished gears consists of quenching in oil
from a temperature of 1,500 to 1,540 deg.F., followed by tempering
in oil at a temperature of from 375 to 425 deg.F. Gears so treated
will show a Brinell hardness of from 512 to 560, or a scleroscope
hardness of from 72 to 80. One tractor builder has placed in service
20,000 sets of gears of this type of material and has never had to
replace a gear. Taking into consideration the fact that a tractor
transmission is subjected to the worst possible service conditions,
and that it is under high stress 90 per cent of the time, it seems
inconceivable that any appreciable transmission trouble would be
experienced when material of this type is used on an automobile,
where the full load is applied not over 1 per cent of the time,
or on trucks where the full load is applied not over 50 per cent
of the time.

The gear hardness specified is necessary to reduce to a minimum
the pitting or surface fatigue of the teeth. If gears having a
Brinell hardness of over 560 are used, danger is encountered, due
to low shock-resisting properties. If the Brinell hardness is under
512, trouble is experienced due to wear and surface fatigue of
the teeth.

For ring gears and pinions material of the following chemical
composition is recommended: Carbon, 0.100 to 0.200 per cent; manganese,
0.350 to 0.650 per cent; phosphorus, 0.040 maximum per cent; sulphur,
0.045 maximum per cent; chromium, 0.550 to 0.750 per cent; nickel,
0.400 to 0.600 per cent.

Care should be taken to see that this material is properly deoxidized
either by the use of ferrovanadium or its equivalent. The advantage
of using a material of the above type lies in the fact that it will
produce a satisfactory finished part with a very simple treatment.
The heat treatment of ring gears and pinions is as follows: Carburize
at a temperature of from 1,650 to 1,700 deg.F. for a sufficient length
of time to secure a depth of case of from 1/32 to 3/64 in., and
quench directly from carburizing heat in oil. Reheat to a temperature
of from 1,430 to 1,460 deg.F. and quench in oil. Temper in oil at a
temperature of from 375 to 425 deg.F. The final quenching operation
on a ring gear should be made on a fixture similar to the Gleason
press to reduce distortion to a minimum.

One of the largest producers of ring gears and pinions in the automotive
industry has been using this material and treatment for the last 2
years, and is of the opinion that he is now producing the highest
quality product ever turned out by that plant.

On some designs of automobiles a large amount of trouble is experienced
with the driving pinion. If the material and heat treatment specified
will not give satisfaction, rather than to change the design it is
possible to use the following analysis material, which will raise
the cost of the finished part but will give excellent service:
Carbon, 0.100 to 0.200 per cent; manganese, 0.350 to 0.650 per
cent; phosphorus, 0.040 maximum per cent; sulphur, 0.045 maximum
per cent; nickel, 4.750 to 5.250 per cent.

The heat treatment of pinions produced from this material consists
in carburizing at a temperature of from 1,600 to 1,650 deg.F. for a
sufficient length of time to secure a depth of case from 1/32 to
3/64 in. The pinions are then quenched in oil from a temperature
of 1,500 to 1,525 deg.F. to refine the grain of the core and quenched
in oil from a temperature of from 1,340 to 1,360 deg.F. To refine and
harden the case. The use of this material however, is recommended
only in an emergency, as high-nickel steel is very susceptible
to seams, secondary pipe and laminations.

The main criterion on rear-axle and pinion shafts, steering knuckles
and arms and parts of this general type is resistance to fatigue and
torsion. The material recommended for parts of this character is
either S. A. E. No. 6135 or No. 3135 steel, which have the chemical
composition given in Tables 9 and 7.





Next: Heat Treatment Of Axles

Previous: Application To The Automotive Industry



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