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Carburizing Low-carbon Sleeves
Low-carbon sleeves are carburized and pushed on malleable-ir...

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

The Penetration Of Carbon
Carburized mild steel is used to a great extent in the manufa...

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

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

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

Quenching The Work
In some operations case-hardened work is quenched from the bo...

The Electric Process
The fourth method of manufacturing steel is by the electric f...

Hardening
The forgings can be hardened by cooling in still air or quen...

Pickling The Forgings
The forgings were then pickled in a hot solution of either ni...

Uses Of The Various Tempers Of Carbon Tool Steel
DIE TEMPER.--No. 3: All kinds of dies for deep stamping, pres...

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

Complete Calibration Of Pyrometers
For the complete calibration of a thermo-couple of unknown e...

Heat Treatment Of Milling Cutters Drills Reamers Etc
THE FIRE.--Gas and electric furnaces designed for high heats ...

Annealing
ANNEALING can be done by heating to temperatures ranging from...

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

Highly Stressed Parts
The highly stressed parts on the Liberty engine consisted of ...

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

Connecting Rods
The material used for all connecting rods on the Liberty engi...

Heat Treatment Of Axles
Parts of this general type should be heat-treated to show the...



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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