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Judging The Heat Of Steel
While the use of a pyrometer is of course the only way to hav...

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

Tempering Round Dies
A number of circular dies of carbon tool steel for use in too...

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

Annealing In Bone
Steel and cast iron may both be annealed in granulated bone. ...

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

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

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

Open Hearth Process
The open hearth furnace consists of a big brick room with a l...

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

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

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

Carbon-steel Forgings
Low-stressed, carbon-steel forgings include such parts as car...

Carbon Tool Steel
Heat to a bright red, about 1,500 to 1,550 deg.F. Do not ham...

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

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

Shrinking And Enlarging Work
Steel can be shrunk or enlarged by proper heating and cooling...

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

Application Of Liberty Engine Materials To The Automotive Industry
The success of the Liberty engine program was an engineer...

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



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.





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Previous: Temperature Recording And Regulation



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