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

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

Machineability
Reheating for machine ability was done at 100 deg. less than ...

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

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

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

Crankshaft
The crankshaft was the most highly stressed part of the entir...

Oil-hardening Steel
Heat slowly and uniformly to 1,450 deg.F. and forge thorough...

S A E Heat Treatments
The Society of Automotive Engineers have adopted certain heat...

The Quenching Tank
The quenching tank is an important feature of apparatus in c...

Knowing What Takes Place
How are we to know if we have given a piece of steel the ver...

Mushet And Bessemer
That Mushet was "used" by Ebbw Vale against Bessemer is, perh...

Introduction Of Carbon
The matter to which these notes are primarily directed is the...

Steel Worked In Austenitic State
As a general rule steel should be worked when it is in the a...

Detrimental Elements
Sulphur and phosphorus are two elements known to be detrimen...

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

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

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

Care In Annealing
Not only will benefits in machining be found by careful anne...

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



Furnace Data






Category: PYROMETRY AND PYROMETERS

In order to give definite information concerning furnaces, fuels
etc., the following data is quoted from a paper by Seth A. Moulton
and W. H. Lyman before the Steel Heat Treaters Society in September,
1920.

This considers a factory producing 30,000 lb. of automobile gears
per 24 hr. The transmission gears will be of high-carbon steel and
the differential of low-carbon steel, carburized. The heat-treating
equipment required is:

1. Annealing furnaces 1,400 to 1,600 deg.F.
2. Carburizing furnaces 1,700 to 1,800 deg.F.
3. Hardening furnaces 1,450 to 1,550 deg.F.
4. Drawing furnaces 350 to 950 deg.F.

All of the forging blanks are annealed before machining, about
three-quarters of the machined gears and parts are carburized,
all the carburized gears are given a double treatment for core and
case, all gears and parts are hardened and all parts are drawn.

The possible sources of heat supply and their values are as follows:--

1. Oil 140,000 B.t.u. per gallon
2. Natural gas 1,100 B.t.u. per cubic foot
3. City gas 650 B.t.u. per cubic foot
4. Water gas 300 B.t.u. per cubic foot
5. Producer gas 170 B.t.u. per cubic foot
6. Coal 12,000 B.t.u. per pound
7. Electric current 3,412 B.t.u. per kilowatt-hour

For the heat treatment specified only comparatively low temperatures
are required. No difficulty will be experienced in attaining the
desired maximum temperature of 1,800 deg.F. with any of the heating
medium above enumerated; but it should be noted that the producer
gas with a B.t.u. content of 170 per cubic foot and the electric
current would require specially designed furnaces to obtain higher
temperatures than 1800 deg.F.

TABLE 28.--COMPARATTVE OPERATING COSTS

Assuming
Cost of oil- and gas-fired furnaces
installed as $100.00 per square foot of hearth
Cost of coal-fired furnace installed as 150.00 per square foot of hearth
Cost of electric furnace 100 kw.
capacity installed as 90.00 per kilowatt
Cost of electric furnace 150 kw.
capacity installed as 70.00 per kilowatt

Output 3,000 lb. charge, 8 hr. heat carburizing, 2 hr. heating
only. Annual service 7,200 hr. Fixed charges including interest,
depreciation, taxes, insurance and maintenance 15 per cent. Extra
operating labor for coal-fired furnace 60 cts. per hour, one man
four furnaces.

COST OF VARIOUS TYPES OF FURNACES
-------------------------------------------------------------------------------
Class fuel Fuel per Unit fuelInstallationEfficiency Fixed Cost per
charge cost cost per cent charges charge
------------------------------------------------------------------------
1 2 3 4 5 6 7
------------------------------------------------------------------------
Carburizing
------------------------------------------------------------------------
1Oil 52.0 gal. $0.15 gal. $2,400.00 12.6 $.40 $8.20
2Natural gas 4.4 M 0.50 M 2,400.00 18.8 0.40 2.60
3City gas 8.3 M 0.80 M 2,400.00 17.0 0.40 7.04
4Water gas 18.7 M 0.40 2,400.00 16.4 0.40 7.88
5Producer gas 37.3 M 0.10 M 2,400.00 14.5 0.40 4.13
6Coal 814.0 lb. 6.00 ton 3,600.00 9.4 0.60 3.98
7Electricity 500.0 kw-hr. 0.015 kw. 9,000.00 53.0 1.50 9.00
------------------------------------------------------------------------
Heating
------------------------------------------------------------------------
1Oil 30.8 gal. 0.15 gal. 2,400.00 21.4 0.10 4.72
2Natural gas 2.61 M 0.50 M 2,400.00 32.0 0.10 1.40
3City gas 4.9 M 0.80 M 2,400.00 28.8 0.10 4.02
4Water gas 11.1 M 0.40 M 2,400.00 27.6 0.10 4.54
5Producer gas 22.1 M 0.10 M 2,400.00 24.6 0.10 2.31
6Coal 348.0 lb. 6.00 ton 3,600.00 22.0 0.15 1.38
7Electricity 329.0 kw-hr. 0.015 kw. 10,500.00 81.75 0.44 5.38
-------------------------------------------------------------------------------

This shows but two of the operations and for a single furnace.
The total costs for all operations on the 30,000 lb. of gears per
24 hr. is shown in Table 29.

TABLE 29.--COMPARATIVE ANNUAL PRODUCTION COSTS FOR 30,000 POUNDS
OUTPUT IN 24 HOURS

----------------------------------------------------------
No. Equipment Installation
cost
--------------------------------------------------------
1 2 3

I Oil $179,000.00
II Oil and electric 213,000.00
III Natural gas 117,000.00
IV (A) Natural gas containing furnaces 120,000.00
V Natural gas and electric 181,000.00
VI City gas 122,000.00
VII City gas and electric 182,000.00
VIII Water gas 214,000.00
IX Water gas and electric 238,000.00
X Producer gas 246,000.00
XI Producer gas and electric 255,000.00
XII Coal and electric 194,000.00
XIII Electric 257,000.00
----------------------------------------------------------

---------------------------------------------------------------------
Annual operating expenses Cost
No. ---------------------------------------- Total per lb.
Fixed Heat Labor metal,
charges cents
----------------------------------------------------------------
1 4 5 6 7 8

I $26,850.00 $156,000.00 $105,000.00 $287,850.00 $3.19
II 31,950.00 142,770.00 97,000.00 271,720.00 3.02
III 17,550.00 44,250.00 97,000.00 158,800.00 1.78
IV 18,000.00 41,000.00 94,000.00 153,000.00 1.70
V 27,150.00 73,820.00 90,000.00 190,970.00 2.13
VI 18,300.00 123,200.00 94,000.00 235,500.00 2.62
VII 27,300.00 128,820.00 90,000.00 246,020.00 2.74
VIII 18,600.00 104,000.00 94,000.00 216,600.00 2.41
IX 27,450.00 117,420.00 90,000.00 234,870.00 2.62
X 18,900.00 69,300.00 90,000.00 178,200.00 1.98
XI 27,750.00 92,520.00 90,000.00 210,270.00 2.34
XII 29,100.00 87,220.00 90,000.00 206,320.00 2.30
XIII 38,550.00 135,000.00 84,000.00 257,550.00 2.86
---------------------------------------------------------------------

NOTE.--Producer plant fixed charges are included in the cost of
gas and are charged as heat in column 5, so they are omitted
from column 4.





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Previous: Heating Of Manganese Steel



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