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Steel Making

High Speed Steel
For centuries the secret art of making tool steel was handed ...

Annealing Of High-speed Steel
For annealing high-speed steel, some makers recommend using g...

Pyrometers For Molten Metal
Pyrometers for molten metal are connected to portable thermoc...

Surface Carburizing
Carburizing, commonly called case-hardening, is the art of pr...

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

Gas Consumption For Carburizing
Although the advantages offered by the gas-fired furnace for ...

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

Leeds And Northrup Optical Pyrometer
The principles of this very popular method of measuring tempe...

Protectors For Thermo-couples
Thermo-couples must be protected from the danger of mechanica...

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

Preparing Parts For Local Case-hardening
At the works of the Dayton Engineering Laboratories Company, ...

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

William Kelly's Air-boiling Process
An account of Bessemer's address to the British Association w...

Impact Tests
Impact tests are of considerable importance as an indication ...

The Theory Of Tempering
Steel that has been hardened is generally harder and more br...

Molybdenum
Molybdenum steels have been made commercially for twenty-five...

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

Manganese
Manganese adds considerably to the tensile strength of steel,...

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

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



Hardening Operation






Category: HEAT TREATMENT OF STEEL

Hardening a gear is accomplished as follows:
The gear is taken from the furnace by the furnaceman and placed in
the lower die, surrounding the centering jaws, as shown at H in
Fig. 62 and C in Fig. 63. Air is then turned into the cylinder
D, and the piston rod E, the die carrier B, the top die F
and the expander G descend. The pilot H enters a hole in the
center of the lower die, and the expander G enters the centering
jaws I, causing them to expand and center the gear C in the
lower die. On further advance of the piston rod E, the expander
G is forced upward against the pressure of the springs J and
the upper die F comes in contact with the upper surface of the
gear. Further downward movement of the dies, which now clamp the
work securely, overcomes the resistance of the pressure weight
K (which normally keeps up the plunger A), and the gear is
submerged in the oil. The quenching oil is circulated through a
cooling system outside the building and enters the tempering machine
through the inlet pipe L. When the machine is in the position
shown, the oil passes out through the ports M in the lower plunger
to the outer reservoir N, passing to the cooling system by way of
the overflow O. When the lower plunger A is forced downward,
the ports M are automatically closed and the cool quenching oil
from the inlet pipe L, having no other means of escape, passes
through the holes in the lower die and the grooves in the upper,
circulating in contact with the surfaces of the gear and passes to
the overflow. When the air pressure is released, the counterweights
return the parts to the positions shown in Fig. 63, and the operator
removes the gear.

The gear comes out uniformly hard all over and of the same degree of
hardness as when tempered in an open tank. The output of the machine
depends on the amount of metal to be cooled, but will average from
8 to 16 per hour. Each machine is served by one man, two furnaces
being required to heat the work. A slight excess of oil is used
in the firing of the furnaces to give a reducing atmosphere and
to avoid scale.





Next: Carburizing Low-carbon Sleeves

Previous: Temperature Recording And Regulation



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