Furnace Data





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.





Forging High-speed Steel Gas Consumption For Carburizing facebooktwittergoogle_plusredditpinterestlinkedinmail

Feedback