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Steel Making

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

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

The Thermo-couple
With the application of the thermo-couple, the measurement of...

Optical System And Electrical Circuit Of The Leeds & Northrup Optical Pyrometer
For extremely high temperature, the optical pyrometer is lar...

Carbon Steels For Different Tools
All users of tool steels should carefully study the different...

Double Annealing
Water annealing consists in heating the piece, allowing it to...

Temperatures To Use
As soon as the temperature of the steel reaches 100 deg.C. (...

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

Flange Shields For Furnaces
Such portable flame shields as the one illustrated in Fig. 1...

Quenching
It is considered good practice to quench alloy steels from th...

Heat Treatment Of Steel
Heat treatment consists in heating and cooling metal at defin...

Protective Screens For Furnaces
Workmen needlessly exposed to the flames, heat and glare from...

Correction By Zero Adjustment
Many pyrometers are supplied with a zero adjuster, by means ...

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

The Care Of Carburizing Compounds
Of all the opportunities for practicing economy in the heat-t...

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

Making Steel Balls
Steel balls are made from rods or coils according to size, st...

Preventing Cracks In Hardening
The blacksmith in the small shop, where equipment is usually ...

Annealing To Relieve Internal Stresses
Work quenched from a high temperature and not afterward tempe...

Separating The Work From The Compound
During the pulling of the heat, the pots are dumped upon a ca...



Typical Oil-fired Furnaces






Category: FURNACES

Several types of standard oil-fired
furnaces are shown herewith. Figure 92 is a lead pot furnace, Fig.
93 is a vertical furnace with a center column. This column reduces
the cubical contents to be heated and also supports the cover.


A small tool furnace is shown in Fig. 94, which gives the construction
and heat circulation. A larger furnace for high-speed steel is
given in Fig. 95. The steel is supported above the heat, the lower
flame passing beneath the support.

For hardening broaches and long reamers and taps, the furnace shown
in Fig. 96 is used. Twelve jets are used, these coming in radially
to produce a whirling motion.


Oil and gas furnaces may be divided into three types: the open
heating chamber in which combustion takes place in the chamber
and directly over the stock; the semimuffle heating chamber in
which combustion takes place beneath the floor of the chamber from
which the hot gases pass into the chamber through suitable openings;
and the muffle heating chamber in which the heat entirely surrounds
the chamber but does not enter it. The open furnace is used for
forging, tool dressing and welding. The muffle furnace is used for
hardening dies, taps, cutters and similar tools of either carbon
or high-speed steel. The muffle furnace is for spring hardening,
enameling, assaying and work where the gases of combustion may
have an injurious effect on the material.



Furnaces of these types of oil-burning furnaces are shown in Figs.
97, 98, and 99; these being made by the Gilbert & Barker Manufacturing
Company. The first has an air curtain formed by jets from the large
pipe just below the opening, to protect the operator from heat.


Oil furnaces are also made for both high- and low-pressure air,
each having its advocates. The same people also make gas-fired
furnaces.

Several types of furnaces for various purposes are illustrated
in Fig. 100 and 101. The first is a gas-fired hardening furnace
of the surface-combustion type.

A large gas-fired annealing furnace of the Maxon system is shown
in Fig. 101. This is large enough for a flat car to be run into
as can be seen. It shows the arrangement of the burners, the track
for the car and the way in which it fits into the furnace. These
are from the designs of the Industrial Furnace Corporation.

Before deciding upon the use of gas or oil, all sides of the problem
should be considered. Gas is perhaps the nearest ideal but is as a
rule more expensive. The tables compiled by the Gilbert & Barker
Manufacturing Company and shown herewith, may help in deciding
the question.

TABLE 27.--SHOWING COMPARISON OF OIL FUEL WITH VARIOUS GASEOUS FUELS
Heat units
per thousand
cubic feet
Natural gas 1,000,000
Air gas (gas machine) 20 cp 815,500
Public illuminating gas, average 650,000
Water gas (from bituminous coal) 377,000
Water and producer gas, mixed 175,000
Producer gas 150,000

Since a gallon of fuel oil (7 lb.) contains 133,000 heat units, the
following comparisons may evidently be made. At 5 cts. a gallon,
the equivalent heat units in oil would equal:

Per thousand
cubic feet
Natural gas at $0.375
Air gas, 20 cp at 0.307
Public illuminating gas, average at 0.244
Water gas (from bituminous coal) at 0.142
Water and producer gas, mixed at 0.065
Producer gas at 0.057

Comparing oil and coal is not always simple as it depends on the
work to be done and the construction of the furnaces. The variation
rises from 75 to 200 gal. of oil to a ton of coal. For forging
and similar work it is probably safe to consider 100 gal. of oil
as equivalent to a ton of coal.

Then there is the saving of labor in handling both coal and ashes,
the waiting for fires to come up, the banking of fires and the dirt
and nuisance generally. The continuous operation possible with
oil adds to the output.

When comparing oil and gas it is generally considered that 4-1/2
gal. of fuel oil will give heat equivalent to 1,000 cu. ft. of
coal gas.

The pressure of oil and air used varies with the system installed.
The low-pressure system maintains a pressure of about 8 oz. on the
oil and draws in free air for combustion. Others use a pressure
of several pounds, while gas burners use an average of perhaps
1-1/2 lb. of air to give best results.

The weights and volumes of solid fuels are: Anthracite coal, 55 to
65 lb. per cubic foot or 34 to 41 cubic feet per ton; bituminous
coal, 50 to 55 lb. per cubic foot or 41 to 45 cubic feet per ton;
coke, 28 lb. per cubic foot or 80 cubic feet per ton--the ton being
calculated as 2,240 lb. in each case.

A novel carburizing furnace that is being used by a number of people,
is built after the plan of a fireless cooker. The walls of the
furnace are extra heavy, and the ports and flues are so arranged
that when the load in the furnace and the furnace is thoroughly
heated, the burners are shut off and all openings are tightly sealed.
The carburization then goes on for several hours before the furnace
is cooled below the effective carburizing range, securing an ideal
diffusion of carbon between the case and the core of the steel
being carburized. This is particularly adaptable where simple steel
is used.





Next: Protective Screens For Furnaces

Previous: Air-hardening Steels



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