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ing plants. This cooling coil is shown in Fig. 5.
The quenching oil (27 barrels) is stored in a large
tank placed underground and in line with the quenching
tanks. The overflow from the quenching tanks
returns to the storage tank, and in turn is circulated
Forging- Stamping - Heat Treating
August, 1925
High Speed Steel Hardening.
The hardening of high speed steel tools is accomplished
by means of the well known type of preheating
oil-fired muffle furnace. The quenching of tools
made of high speed steel is usually done in a small
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FIG. 6—Sketch showing elevation of quenching tank system of air hoists and baskets.
through the water-cooled cooling coils. City water
flows through inner pipes which are surrounded by
larger pipes through which the quenching oil flows.
The temperature of the oil is regulated by the rapidity
of its flow through the system.
The fuel oil for the furnaces is pumped by means
of a rotary pump placed at a point near the oil storage
tank which is located adjacent to a railroad siding and
several hundred feet from the heat treatment department.
An ingenious device has been provided for the
automatic closing down of the pump in the case of
accident or unexpected interruption of the combustion
air. This device is a magnetically operated one which
has proven very efficient and was invented by the
electrical engineer of this company.
The combustion air is supplied by a large rotary
blower supplying air at 6 to 8 ounces of pressure. One
of these blowers is installed in the heat treating room
and a second auxiliary blower is installed in the power
plant which is located close by.
( )ne of the unique features of this plant is that
all of the wiring, pipe lines and drains, have been
placed in conduits under the floor. The conduits are
accessible, being simply covered by corrugated steel
flooring.
Tempering.
The tempering of hardened parts is accomplished
bv several methods. This plant is provided with oil
tempering baths, salt tempering baths, lead baths and
electric resistance oven furnaces as shown in Fig. 3.
A number of the parts, after tempering, are placed
in a bath of grease. This bath is maintained at about
250 deg. F.; and the parts are immersed for a few
minutes. When they are removed, a thin film of
grease solidifies which protects steel from corrosion.
tank of oil which is aranged in a similar manner to the
air hoist quenching tanks previously described, but
which is operated by hand.
Although this plant was designed a number of
years ago, it is doubtful whether many improvements
could be made in the layout or facilities for heat treating
parts for the master tools of industry.
Heat Treatment Changes Properties of Glass
Results of investigations which have been carried
on for the past two years by the Bureau of Standards,
Department of Commerce, show that by changing
the heat treatment of glass during the process of
manufacture, the density and refractivity may be materially
altered, and other properties can be greatly
changed.
Since the physical properties of glass are subject
to changes of considerable magnitude during the final
stages of production, even when the composition and
methods of melting are carefully controlled, these results
will prove valuable in many problems in the
manufacture of both optical and commercial glasses.
They should aid in preventing many losses heretofore
unavoidable, and make it possible to increase the
strength and durability of such articles as bottles, window
glass, and glazed and enameled wares.
Nickel coatings used on iron and steel parts of
automobiles should be at least 0.001 in. "thick, according
to findings of the Bureau of Standards, Washington.
A thinner film will make a finish which will not
be durable, because the thinner coating is almost invariably
porous. It was found that the protective
value of the coating can be materially increased by
adding thickness up to the figure recommended by the
bureau.