FLANGE SHIELDS FOR FURNACES.--Such porta_The Working of Steel Annealing, Heat Treating and Hardening of Carbon and Alloy Steel

one illustrated in Fig. 106 may prove serviceable before furnaces

required for plate work, where the doors are often only opened

for a moment at a time. This shield can be placed far enough in

front of the furnace, that it will be possible to work under it

or around it, in removing bulky work from the furnace, and yet

it will afford the furnace tender some relief from the excessive

glare that will come out the wide-opened door. To have this shield

of light weight so that it may be readily pushed aside when not

wanted, the frame may be made up of pipe and fittings, and a piece

of thin sheet steel fastened in the panel by rings about the frame.

About the most disagreeable task in a heat-treating shop is the

removal of the pots from the case-hardening furnaces; these must

be handled at a bright red heat in order that their contents may be

dumped into the quenching tank with a minimum-time contact with the

air, and before they have cooled sufficiently to require reheating.

Facing the heat before the large open doors of the majority of

these furnaces, in a man-killing task even when the weather is

moderately cool. The boxes soon become more or less distorted,

and then even the best of lifting devices will not remove a hot

pot without several minutes labor in front of the doors.

In Fig. 107 is shown a method of arranging a shield on one type of

charging and removing truck. This shield cannot afford more than

a partial protection to the body of the furnace tender, because

he must be able to see around it, and in some cases even push it

partly through the door of the furnace, but even small as it is it

may still afford some welcome protection. The great advantage in

this case of having the shield on the truck instead of stationary

in front of the furnace, is that it still affords protection as

long as the hot pot is being handled through the shop on its way

to the quenching tank.

It might be interesting to many engaged in the heat-treating or

case hardening of steel parts, to make a special note of the design

of the truck that is illustrated in connection with the shield;

the general form is shown although the actual details for the

construction of such a truck are lacking; these being simple, may be

readily worked out by anyone wishing to build one. This is considered

to be one of the quickest and easiest operated devices for the

removal of this class of work from the furnace. To be sure it may

only be used where the floor of the furnace has been built level

with the floor of the room, but many of the modern furnaces of

this class are so designed.

The pack-hardening pots are cast with legs, from two to three inches

high, to permit the circulation of the hot gases, and so heat more

quickly. Between these legs and under the body of the pot, the two

forward prongs of the truck are pushed, tilting the outer handle

to make these prongs as low as possible. The handle is then lowered

and, as it has a good leverage, the pot is easily raised from the

floor, and the truck and its load rolled out.

HEATING OF MANGANESE STEEL.--Another form of heat-treating furnace

is that which is used for the heating of manganese and other alloy

steels, which after having been brought to the proper heat are drawn

from the furnace into an immediate quenching tank. With manganese

steel in particular, the parts are so fragile and easily damaged

while hot that it is frequent practice to have a sloping platform

immediately in front of the furnace door down which the castings

may slide into a tank below the floor level. Such a furnace with

a quenching tank in front of its door is shown in Fig. 108.

These tanks are covered with plates while charging the furnace

and the cold castings are placed in a moderately cool furnace.

Since some of these steels must not be charged into a furnace where

the heat is extreme but should be brought up to their final heat

gradually, there is little discomfort during the charging process.

When quenching, however, from a temperature of 1,800° to 1,900°,

it is extremely unpleasant in front of the doors. The swinging

shield is here adapted to give protection for this work. As will

be noted it is hung a sufficient distance in front of the doors,

that it may not interfere with the castings as they come from the

furnace, and slide down into the tank.

To facilitate the work, and avoid the necessity of working with

the bars outside the edges of the shield, the slot-like hole is

cut in the center of the shield, and through this the bars or rakes

for dragging out the castings are easily inserted and manipulated.

The advantage of such a swinging shield is that it may be readily

moved from side to side, or forward and back as occasion requires.

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°F.

2. Carburizing furnaces 1,700 to 1,800°F.

3. Hardening furnaces 1,450 to 1,550°F.

4. Drawing furnaces 350 to 950°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°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°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

-------------------------------------------------------------------------------

-|------------|------------|----------|------------|----------|-------|--------

| 1 | 2 | 3 | 4 | 5 | 6 | 7

-|------------|------------|----------|------------|----------|-------|--------

Carburizing

-|------------|------------|----------|------------|----------|-------|--------

1|Oil | 52.0 gal. |$0.15 gal.| $2,400.00 | 12.6 | $.40 | $8.20

2|Natural gas | 4.4 M | 0.50 M | 2,400.00 | 18.8 | 0.40 | 2.60

3|City gas | 8.3 M | 0.80 M | 2,400.00 | 17.0 | 0.40 | 7.04

4|Water gas | 18.7 M | 0.40 | 2,400.00 | 16.4 | 0.40 | 7.88

5|Producer gas| 37.3 M | 0.10 M | 2,400.00 | 14.5 | 0.40 | 4.13

6|Coal |814.0 lb. | 6.00 ton | 3,600.00 | 9.4 | 0.60 | 3.98

7|Electricity |500.0 kw-hr.| 0.015 kw.| 9,000.00 | 53.0 | 1.50 | 9.00

-|------------|------------|----------|------------|----------|-------|--------

Heating

-|------------|------------|----------|------------|----------|-------|--------

1|Oil | 30.8 gal. | 0.15 gal.| 2,400.00 | 21.4 | 0.10 | 4.72

2|Natural gas | 2.61 M | 0.50 M | 2,400.00 | 32.0 | 0.10 | 1.40

3|City gas | 4.9 M | 0.80 M | 2,400.00 | 28.8 | 0.10 | 4.02

4|Water gas | 11.1 M | 0.40 M | 2,400.00 | 27.6 | 0.10 | 4.54

5|Producer gas| 22.1 M | 0.10 M | 2,400.00 | 24.6 | 0.10 | 2.31

6|Coal |348.0 lb. | 6.00 ton | 3,600.00 | 22.0 | 0.15 | 1.38

7|Electricity |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.

-----|------------|-------------|-------------|-------------|--------

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.

CHAPTER XII

PYROMETRY AND PYROMETERS

A knowledge of the fundamental principles of pyrometry, or the

measurement of temperatures, is quite necessary for one engaged

in the heat treatment of steel. It is only by careful measurement

and control of the heating of steel that the full benefit of a

heat-treating operation is secured.

Before the advent of the thermo-couple, methods of temperature

measurement were very crude. The blacksmith depended on his eyes

to tell him when the proper temperature was reached, and of course

the "color" appeared different on light or dark days. "Cherry"

to one man was "orange" to another, and it was therefore almost

impossible to formulate any treatment which could be applied by

several men to secure the same results.

One of the early methods of measuring temperatures was the "iron

ball" method. In this method, an iron ball, to which a wire was

attached, was placed in the furnace and when it had reached the

temperature of the furnace, it was quickly removed by means of

the wire, and suspended in a can containing a known quantity of

water; the volume of water being such that the heat would not cause

it to boil. The rise in temperature of the water was measured by a

thermometer, and, knowing the heat capacity of the iron ball and

that of the water, the temperature of the ball, and therefore the

furnace, could be calculated. Usually a set of tables was prepared

to simplify the calculations. The iron ball, however, scaled, and

changed in weight with repeated use, making the determinations

less and less accurate. A copper ball was often used to decrease

this change, but even that was subject to error. This method is

still sometimes used, but for uniform results, a platinum ball,

which will not scale or change in weight, is necessary, and the

cost of this ball, together with the slowness of the method, have

rendered the practice obsolete, especially in view of modern

developments in accurate pyrometry.

PYROMETERS

Armor plate makers sometimes use the copper ball or Siemens' water

pyrometer because they can place a number of the balls or weights on

the plate in locations where it is difficult to use other pyrometers.

One of these pyrometers is shown in section in Fig. 109.

SIEMENS' WATER PYROMETER.--It consists of a cylindrical copper vessel

provided with a handle and containing a second smaller copper vessel

with double walls. An air space _a_ separates the two vessels, and

a layer of felt the two walls of the inner one, in order to retard

the exchange of temperature with the surroundings. The capacity

of the inner vessel is a little more than one pint. A mercury

thermometer _b_ is fixed close to the wall of the inner vessel,

its lower part being protected by a perforated brass tube, whilst

the upper projects above the vessel and is divided as usual on the

stem into degrees, Fahrenheit or Centigrade, as desired. At the

side of the thermometer there is a small brass scale _c_, which

slides up and down, and on which the high temperatures are marked

in the same degrees as those in which the mercury thermometer is

divided; on a level with the zero division of the brass scale a

small pointer is fixed, which traverses the scale of the thermometer.

[Illustration: FIG. 109.--Siemens' copper-ball pyrometer.]

Short cylinders _d_, of either copper, iron or platinum, are supplied

with the pyrometer, which are so adjusted that their heat capacity at

ordinary temperature is equal to one-fiftieth of that of the copper

vessel filled with one pint of water. As, however, the specific heat

of metals increases with the temperature, allowance is made on the

brass sliding scales, which are divided according to the metal used

for the pyrometer cylinder _d_. It will therefore be understood that

a different sliding scale is required for the particular kind of

metal of which a cylinder is composed. In order to obtain accurate

measurements, each sliding scale must be used only in conjunction

with its own thermometer, and in case the latter breaks a new scale

must be made and graduated for the new thermometer.

The water pyrometer is used as follows:

Exactly one pint (0.568 liter) of clean water, perfectly distilled

or rain water, is poured into the copper vessel, and the pyrometer

is left for a few minutes to allow the thermometer to attain the

temperature of the water.

The brass scale _c_ is then set with its pointer opposite the

temperature of the water as shown by the thermometer. Meanwhile

one of the metal cylinders has been exposed to the high temperature

which is to be measured, and after allowing sufficient time for

it to acquire that temperature, it is rapidly removed and dropped

into the pyrometer vessel without splashing any of the water out.

The temperature of the water will rise until, after a little while,

the mercury of the thermometer has become stationary. When this

is observed the degrees of the thermometer are read off, as well

as those on the brass scale _c_ opposite the top of the mercury.

The sum of these two values together gives the temperature of the

flue, furnace or other heated space in which the metal cylinder

had been placed. With cylinders of copper and iron, temperatures up

to 1,800°F. (1,000°C.) can be measured, but with platinum cylinders

the limit is 2,700°F. (1,500°C.).

For ordinary furnace work either copper or wrought-iron cylinders

may be used. Iron cylinders possess a higher melting point and have

less tendency to scale than those of copper, but the latter are

much less affected by the corrosive action of the furnace gases;

platinum is, of course, not subject to any of these disadvantages.

The weight to which the different metal cylinders are adjusted is

as follows:

Copper 137.0 grams

Wrought-iron 112.0 grams

Platinum 402.6 grams

In course of time the cylinders lose weight by scaling; but tables

are provided giving multipliers for the diminished weights, by

which the reading on the brass scale should be multiplied.

THE THERMO-COUPLE

With the application of the thermo-couple, the measurement of

temperatures, between, say, 700 and 2,500°F., was made more simple

and precise. The theory of the thermo-couple is simple; it is that

if two bars, rods, or wires of different metals are joined together

at their ends, when heated so that one junction is hotter than the

other, an electromotive force is set up through the metals, which

will increase with the increase of the _difference_ of temperature

between the two junctions. This electromotive force, or voltage, may

be measured, and, from a chart previously prepared, the temperature

determined. In most pyrometers, of course, the temperatures are

inscribed directly on the voltmeter, but the fact remains that

it is the voltage of a small electric current, and not heat, that

is actually measured.

There are two common types of thermo-couples, the first making use

of common, inexpensive metals, such as iron wire and nichrome wire.

This is the so-called "base metal" couple. The other is composed of

expensive metals such as platinum wire, and a wire of an alloy of

platinum with 10 per cent of rhodium or iridium. This is called

the "rare metal" couple, and because its component metals are less

affected by heat, it lasts longer, and varies less than the base

metal couple.

The cold junction of a thermo-couple may be connected by means

of copper wires to the voltmeter, although in some installations

of base metal couples, the wires forming the couple are themselves

extended to the voltmeter, making copper connections unnecessary.

From the foregoing, it may be seen that accurately to measure the

temperature of the hot end of a thermo-couple, we _must know the

temperature of the cold end_, as it is the _difference_ in the

temperatures that determines the voltmeter readings. This is absolutely

essential for precision, and its importance cannot be over-emphasized.

When pyrometers are used in daily operation, they should be checked

or calibrated two or three times a month, or even every week. Where

there are many in use, it is good practice to have a master pyrometer

of a rare metal couple, which is used only for checking up the

others. The master pyrometer, after calibrating against the melting

points of various substances, will have a calibration chart which

should be used in the checking operation.

It is customary now to send a rare metal couple to the Bureau of

Standards at Washington, where it is very carefully calibrated

for a nominal charge, and returned with the voltmeter readings

of a series of temperatures covering practically the whole range

of the couple. This couple is then used only for checking those

in daily use.

Pyrometer couples are more or less expensive, and should be cared

far when in use. The wires of the couple should be insulated from

each other by fireclay leads or tubes, and it is well to encase them

in a fireclay, porcelain, or quartz tube to keep out the furnace

gases, which in time destroy the hot junction. This tube of fireclay,

or porcelain, etc., should be protected against breakage by an

iron or nichrome tube, plugged or welded at the hot end. These

simple precautions will prolong the life of a couple and maintain

its precision longer.

Sometimes erroneous temperatures are recorded because the "cold

end" of the couple is too near the furnace and gets hot. This always

causes a temperature reading lower than the actual, and should be

guarded against. It is well to keep the cold end cool with water,

a wet cloth, or by placing it where coal air will circulate around

it. Best of all, is to have the cold junction in a box, together

with a thermometer, so that its temperature may definitely be known.

If this temperature should rise 20°F. on a hot day, a correction of

20°F. should be added to the pyrometer reading, and so on. In the

most up-to-date installations, this cold junction compensation is

taken care of automatically, a fact which indicates its importance.

Optical pyrometers are often used where it is impracticable to

use the thermo-couple, either because the temperature is so high

that it would destroy the couple, or the heat to be measured is

inaccessible to the couple of ordinary length. The temperatures of

slag or metal in furnaces or running through tap-holes or troughs

are often measured with optical pyrometers.

In one type of optical pyrometer, the observer focuses it on the

metal or slag and moves an adjustable dial or gage so as to get

an exact comparison between the color of the heat measured with

the calor of a lamp or screen in the pyrometer itself. This, of

course, requires practice, and judgment, and brings in the personal

equation. With care, however, very reliable temperature measurements

may be made. The temperatures of rails, as they leave the finishing

pass of a rolling mill, are measured in this way.

Another type of optical pyrometer is focused on the body, the

temperature of which is to be measured. The rays converge in the

telescope on metal cells, heating them, and thereby generating a

small electric current, the voltage of which is read an a calibrated

voltmeter similar to that used with the thermo-couple. The best

precision is obtained when an optical pyrometer is used each time

under similar conditions of light and the same observer.

Where it is impracticable to use either thermo-couples or optical

pyrometers, "sentinels" may be used. There are small cones or cylinders

made of salts or other substances of known melting points and covering

a wide range of temperatures.

If six of these "sentinels," melting respectively at 1,300°, 1,350°,

1,400°, 1,450°, 1,500°, and 1,550°F., were placed in a row in a

furnace, together with a piece of steel to be treated, and the

whole heated up uniformly, the sentinels would melt one by one and

the observer, by watching them through an opening in the furnace,

could tell when his furnace is at say 1,500° or between 1,500° and

1,550°, and regulate the heat accordingly.

A very accurate type of pyrometer, but one not so commonly used as

those previously described, is the resistance pyrometer. In this

type, the temperature is determined by measuring the resistance to an

electric current of a wire which is at the heat to be measured. This

wire is usually of platinum, wound around a quartz tube, the whole

being placed in the furnace. When the wire is at the temperature of

the furnace, it is connected by wires with a Wheatstone Bridge, a

delicate device for measuring electrical resistance, and an electric

current is passed through the wire. This current is balanced by

switching in resistances in the Wheatstone Bridge, until a delicate

electrical device shows that no current is flowing. The resistance

of the platinum wire at the heat to be measured is thus determined

on the "Bridge," and the temperature read off on a calibration

chart, which shows the resistance at various temperatures.

These are the common methods used to-day for measuring temperatures,

but whatever method is used, the observer should bear in mind that

the greatest precision is obtained, and hence the highest efficiency,

by keeping the apparatus in good working order, making sure that

conditions are the same each time, and calibrating or checking

against a standard at regular intervals.

THE PYROMETER AND ITS USE

In the heat treatment of steel, it has become absolutely necessary

that a measuring instrument be used which will give the operator an

exact reading of heat in furnace. There are a number of instruments

and devices manufactured for this purpose but any instrument that

will not give a direct reading without any guess work should have

no place in the heat-treating department.

A pyrometer installation is very simple and any of the leading

makers will furnish diagrams for the correct wiring and give detailed

information as to the proper care of, and how best to use their

particular instrument. There are certain general principles, however,

that must be observed by the operators and it cannot be too strongly

impressed upon them that the human factor involved is always the

deciding factor in the heat treatment of steel.

A pyrometer is merely an aid in the performance of doing good work,

and when carefully observed will help in giving a uniformity of

product and act as a check on careless operators. The operator

must bear in mind that although the reading on the pyrometer scale

gives a measure of the temperature where the junction of the two

metals is located, it will not give the temperature at the center

of work in the furnace, unless by previous tests, the heat for

penetrating a certain bulk of material has been decided on, and

the time necessary for such penetration is known.

Each analysis of plain carbon or alloy steel is a problem in itself.

Its critical temperatures will be located at slightly different

heats than for a steel which has a different proportion of alloying

elements. Furthermore, it takes time for metal to acquire the heat

of the furnace. Even the outer surface lags behind the temperature

of the furnace somewhat, and the center of the piece of steel lags

still further. It is apparent, therefore, that temperature, although

important, does not tell the whole story in heat treatment. _Time_

is also a factor.

Time at temperature is also of great importance because it takes

time, after the temperature has been reached, for the various internal

changes to take place. Hence the necessity for "soaking," when

annealing or normalizing. Therefore, a clock is as necessary to

the proper pyrometer equipment as the pyrometer itself.

For the purpose of general work where a wide range of steels or

a variable treatment is called for, it becomes necessary to have

the pyrometer calibrated constantly, and when no master instrument

is kept for this purpose the following method can be used to give

the desired results:

CALIBRATION OF PYROMETER WITH COMMON SALT

An easy and convenient method for standardization and one which

does not necessitate the use of an expensive laboratory equipment

is that based upon determining the melting point of common table

salt (sodium chloride). While theoretically salt that is chemically

pure should be used (and this is neither expensive nor difficult

to procure), commercial accuracy may be obtained by using common

table salt such as is sold by every grocer. The salt is melted in

a clean crucible of fireclay, iron or nickel, either in a furnace

or over a forge-fire, and then further heated until a temperature

of about 1,600 to 1,650°F. is attained. It is essential that this

crucible be clean because a slight admixture of a foreign substance

might noticeably change the melting point.

The thermo-couple to be calibrated is then removed from its protecting

tube and its hot end is immersed in the salt bath. When this end

has reached the temperature of the bath, the crucible is removed

from the source of heat and allowed to cool, and cooling readings

are then taken every 10 sec. on the milli-voltmeter or pyrometer. A

curve is then plotted by using time and temperature as coördinates,

and the temperature of the freezing point of salt, as indicated

by this particular thermocouple, is noted, _i.e._, at the point

where the temperature of the bath remains temporarily constant

while the salt is freezing. The length of time during which the

temperature is stationary depends on the size of the bath and the

rate of cooling, and is not a factor in the calibration. The melting

point of salt is 1,472°F., and the needed correction for the instrument

under observation can be readily applied.

It should not be understood from the above, however, that the salt-bath

calibration cannot be made without plotting a curve; in actual

practice at least a hundred tests are made without plotting any curve

to one in which it is done. The observer, if awake, may reasonably

be expected to have sufficient appreciation of the lapse of time

definitely to observe the temperature at which the falling pointer

of the instrument halts. The gradual dropping of the pointer before

freezing, unless there is a large mass of salt, takes place rapidly

enough for one to be sure that the temperature is constantly falling,

and the long period of rest during freezing is quite definite.

The procedure of detecting the solidification point of the salt

by the hesitation of the pointer without plotting any curve is

suggested because of its simplicity.

COMPLETE CALIBRATION OF PYROMETERS.--For the complete calibration

of a thermo-couple of unknown electromotive force, the new couple

may be checked against a standard instrument, placing the two bare

couples side by side in a suitable tube and taking frequent readings

over the range of temperatures desired.

If only one instrument, such as a millivoltmeter, is available,

and there is no standard couple at hand, the new couple may be

calibrated over a wide range of temperatures by the use of the following

standards:

Water, boiling point 212°F.

Tin, under charcoal, freezing point 450°F.

Lead, under charcoal, freezing point 621°F.

Zinc, under charcoal, freezing point 786°F.

Sulphur, boiling point 832°F.

Aluminum, under charcoal, freezing point 1,216°F.

Sodium chloride (salt), freezing point 1,474°F.

Potassium sulphate, freezing point 1,958°F.

A good practice is to make one pyrometer a standard; calibrate it

frequently by the melting-point-of-salt method, and each morning

check up every pyrometer in the works with the standard, making the

necessary corrections to be used for the day's work. By pursuing

this course systematically, the improved quality of the product

will much more than compensate for the extra work.

The purity of the substance affects its freezing or melting point.

The melting point of common salt is given in one widely used handbook

at 1,421°F., although chemically pure sodium chloride melts at

1,474°F. as shown above. A sufficient quantity for an extended

period should be secured. Test the melting point with a pyrometer

of known accuracy. Knowing this temperature it will be easy to

calibrate other pyrometers.

PLACING OF PYROMETERS.--When installing a pyrometer, care should be

taken that it reaches directly to the point desired to be measured,

that the cold junction is kept cold, and that the wires leading to

the recording instrument are kept in good shape. The length of

these lead wires have an effect; the longer they are, the lower

the apparent temperature.

When pyrometers placed in a number of furnaces are connected up

in series, and a multiple switch is used for control, it becomes

apparent that pyrometers could not be interchanged between furnaces

near and far from the instrument without affecting the uniformity

of product from each furnace.

Calibration can best be done without disturbing the working pyrometer,

by inserting the master instrument into each furnace separately, place

it alongside the hot junction of the working pyrometer, and compare

the reading given on the indicator connected with the multiple

switch.

Protection tubes should be replaced when cracked, as it is important

that no foreign substance is allowed to freeze in the tube, so

that the enclosed junction becomes a part of a solid mass joined

in electrical contact with the outside protecting tube. Wires over

the furnaces must be carefully inspected from time to time, as no

true reading can be had on an instrument, if insulation is burned

off and short circuits result.

If the standard calibrating instrument used contains a dry battery,

it should be examined from time to time to be sure it is in good

condition.

THE LEEDS AND NORTHRUP POTENTIOMETER SYSTEM

The potentiometer pyrometer system is both flexible and substantial

in that it is not affected by the jar and vibration of the factory

or the forge shop. Large or small couples, long or short leads

can be used without adjustment. The recording instrument may be

placed where it is most convenient, without regard to the distance

from the furnace.

ITS FUNDAMENTAL PRINCIPLE.--The potentiometer is the electrical

equivalent of the chemical balance, or balance arm scales. Measurements

are made with balance scales by varying known weights until they

equal the unknown weight. When the two are equal the scales stand

at zero, that is, in the position which they occupy when there is

no weight on either pan; the scales are then said to be balanced.

Measurements are made with the potentiometer by varying a known

electromotive force until it equals the unknown; when the two are

equal the index of the potentiometer, the galvanometer needle,

stands motionless as it is alternately connected and disconnected.

The variable known weights are units separate from the scales, but

the potentiometer provides its own variable known electromotive

force.

The potentiometer provides, first, a means of securing a known

variable electromotive force and, second, suitable electrical

connections for bringing that electromotive force to a point where

it may be balanced against the unknown electromotive force of the

couple. The two are connected with opposite polarity, or so that

the two e.m.f.s oppose one another. So long as one is stronger

than the other a current will flow through the couple; when the

two are equal no current will flow.

Figure 107 shows the wiring of the potentiometer in its simplest

form. The thermo-couple is at _H_, with its polarity as shown by

the symbols + and -. It is connected with the main circuit of the

potentiometer at the fixed point _D_ and the point _G_.

[Illustration: FIG. 110.--Simple potentiometer.]

A current from the dry cell _Ba_ is constantly flowing through the

main, or so-called potentiometer circuit, _ABCDGEF_. The section

_DGE_ of this circuit is a slide wire, uniform in resistance throughout

its length. The scale is fixed on this slide wire. The current

from the cell _Ba_ as it flows through _DGE_, undergoes a fall

in potential, setting up a difference in voltage, that is, an

electromotive force, between _D_ and _E_. There will also be

electromotive force between _D_ and all other points on the slide

wire. The polarity of this is in opposition to the polarity of the

thermo-couple which connects into the potentiometer at _D_ and

at _G_. By moving _G_ along the slide wire a point is found where

the voltage between _D_ and _G_ in the slide wire is just equal to

the voltage between _D_ and _G_ generated by the thermo-couple. A

galvanometer in the thermo-couple circuit indicates when the balance

point is reached, since at this point the galvanometer needle will

stand motionless when its circuit is opened and closed.

[Illustration: FIG. 111.--Standard cell potentiometer.]

The voltage in the slide wire will vary with the current flowing

through it from the cell _Ba_ and a means of standardizing this is

provided. _SC_, Fig. 111, is a cadmium cell whose voltage is constant.

It is connected at two points _C_ and _D_ to the potentiometer

circuit whenever the potentiometer current is to be standardized.

At this time the galvanometer is thrown in series with _SC_. The

variable rheostat _R_ is then adjusted until the current flowing

is such that as it flows through the standard resistance _CD_,

the fall in potential between _C_ and _D_ is just equal to the

voltage of the standard cell _SC_. At this time the galvanometer

will indicate a balance in the same way as when it was used with

a thermo-couple. By this operation the current in the slide wire

_DGE_ has been standardized.

[Illustration: FIG. 112.--Hand adjusted cold-end compensator.]

DEVELOPMENT OF THE WIRING SCHEME OF THE COLD-END COMPENSATOR.--The

net voltage generated by a thermo-couple depends upon the temperature

of the hot end and the temperature of the cold end. Therefore, any

method adopted for reading temperature by means of thermo-couples

must in some way provide a means of correcting for the temperature of

the cold end. The potentiometer may have either of two very simple

devices for this purpose. In one form the operator is required

to set a small index to a point on a scale corresponding to the

known cold junction temperature. In the other form an even more

simple automatic compensator is employed. The principle of each is

described in the succeeding paragraphs, in which the assumption is

made that the reader already understands the potentiometer principle

as described above.

As previously explained the voltage of the thermo-couple is measured

by balancing it against the voltage drop _DG_ in the potentiometer.

As shown in Fig. 111, the magnitude of the balancing voltage is

controlled by the position of _G_. Make _D_ movable as shown in Fig.

112 and the magnitude of the voltage _DG_ may be varied either from

the point _D_ or the point _G_. This gives a means of compensating

for cold end changes by setting the slider _D_. As the cold end

temperature rises the net voltage generated by the couple decreases,

assuming the hot end temperature to be constant. To balance this

decreased voltage the slider _D_ is moved along its scale to a new

point nearer _G_. In other words, the slider _D_ is moved along

its scale until it corresponds to the known temperature of the cold

end and then the potentiometer is balanced by moving the slider

_G_. The readings of _G_ will then be direct.

[Illustration: FIG. 113.--Another type of compensator.]

The same results will be obtained if a slide wire upon which _D_

bears is in parallel with the slide wire of _G_, as shown in Fig.

113.

AUTOMATIC COMPENSATOR.--It should be noted that the effect of moving

the contact _D_, Fig. 113, is to vary the ratio of the resistances

on the two sides of the point _D_ in the secondary slide wire. In

the recording pyrometers, an automatic compensator is employed.

This automatic compensator varies the ratio on the two sides of

the point _D_ in the following manner:

The point _D_, Fig. 114, is mechanically fixed; on one side of

_D_ is the constant resistance coil _M_, on the other the nickel

coil _N_. _N_ is placed at or near the cold end of the thermo-couple

(or couples). Nickel has a high temperature coefficient and the

electrical proportions of _M_ and _N_ are such that the resistance

change of _N_, as it varies with the temperature of the cold end,

has the same effect upon the balancing voltage between _D_ and

_G_ that the movement of the point _D_, Fig. 114, has in the

hand-operated compensator.

Instruments embodying these principles are shown in Figs. 115 to

117. The captions making their uses clear.

[Illustration: FIG. 114.--Automatic cold-end compensator.]

PLACING THE THERMO-COUPLES

The following illustrations from the Taylor Instrument Company

show different applications of the thermo-couples to furnaces of

various kinds. Figure 118 shows an oil-fired furnace with a simple

vertical installation. Figure 119 shows a method of imbedding the

thermo-couple in the floor of a furnace so as to require no space

in the heating chamber.

[Illustration: FIG. 115.--Potentiometer ready for use.]

Various methods of applying a pyrometer to common heat-treatment

furnaces are shown in Figs. 120 to 122.

[Illustration: FIG. 116.--Eight-point recording pyrometer-Carpenter

Steel Co.]

LEEDS AND NORTHRUP OPTICAL PYROMETER

The principles of this very popular method of measuring temperature

are sketched in Fig. 123.

[Illustration: FIG. 117.--Multiple-point thermocouple

recorder--Bethlehem Steel Co.]

[Illustration: FIG. 118.--Tycos pyrometer in oil-fired furnace.]

The instrument is light and portable, and can be sighted as easily

as an opera glass. The telescope, which is held in the hand, weighs

only 25 oz.; and the case containing the battery, rheostat and

milliammeter, which is slung from the shoulder, only 10 lb.

[Illustration: FIG. 119.--Thermocouple in floor of furnace.]

[Illustration: FIG. 120.--Pyrometer in gas furnace.]

A large surface to sight at is not required. So long as the image

formed by the objective is broader than the lamp filament, the

temperature can be measured accurately.

[Illustration: FIG. 121.--Tycos multiple indicating pyrometer and

recorder.]

[Illustration: FIG. 122.--Pyrometer in galvanizing tank.]

Distance does not matter, as the brightness of the image formed

by the lens is practically constant, regardless of the distance

of the instrument from the hot object.

[Illustration: FIG. 123.--Leeds & Northrup optical pyrometer.]

The manipulation is simple and rapid, consisting merely in the turning

of a knurled knob. The setting is made with great precision, due to

the rapid change in light intensity with change in temperature and

to the sensitiveness of the eye to differences of light intensity.

In the region of temperatures used for hardening steel, for example,

different observers using the instrument will agree within 3°C.

[Illustration: FIG. 124.--Too low.

FIG. 125.--Too high.

FIG. 126.--Correct.]

Only brightness, not color, of light is matched, as light of only

one color reaches the eye. Color blindness, therefore, is no hindrance

to the use of this method. The use of the instrument is shown in

Fig. 127.

OPTICAL SYSTEM AND ELECTRICAL CIRCUIT OF THE LEEDS & NORTHRUP OPTICAL

PYROMETER.--For extremely high temperature, the optical pyrometer is

largely used. This is a comparative method. By means of the rheostat

the current through the lamp is adjusted until the brightness of

the filament is just equal to the brightness of the image produced

by the lens _L_, Fig. 123, whereupon the filament blends with or

becomes indistinguishable in the background formed by the image

of the hot object. This adjustment can be made with great accuracy

and certainty, as the effect of radiation upon the eye varies some

twenty times faster than does the temperature at 1,600°F., and some

fourteen times faster at 3,400°F. When a balance has been obtained,

the observer notes the reading of the milliammeter. The temperature

corresponding to the current is then read from a calibration curve

supplied with the instrument.

[Illustration: FIG. 127.--Using the optical pyrometer.]

As the intensity of the light emitted at the higher temperatures

becomes dazzling, it is found desirable to introduce a piece of red

glass in the eye piece at _R_. This also eliminates any question

of matching colors, or of the observer's ability to distinguish

colors. It is further of value in dealing with bodies which do

not radiate light of the same composition as that emitted by a

black body, since nevertheless the intensity of radiation of any

one color from such bodies increases progressively in a definite

manner as the temperature rises. The intensity of this one color

can therefore be used as a measure of temperature for the body

in question. Figures 124 to 126 show the way it is read.

CORRECTION FOR COLD-JUNCTION ERRORS

The voltage generated by a thermo-couple of an electric pyrometer is

dependent on the difference in temperature between its hot junction,

inside the furnace, and the cold junction, or opposite end of the

thermo-couple to which the copper wires are connected. If the

temperature or this cold junction rises and falls, the indications

of the instrument will vary, although the hot junction in the furnace

may be at a constant temperature.

A cold-junction temperature of 75°F., or 25°C., is usually adopted

in commercial pyrometers, and the pointer on the pyrometer should

stand at this point on the scale when the hot junction is not heated.

If the cold-junction temperature rises about 75°F., where base metal

thermo-couples are used, the pyrometer will read approximately 1°

low for every 1° rise in temperature above 75°F. For example, if the

instrument is adjusted for a cold-junction temperature of 75°, and

the actual cold-junction temperature is 90°F., the pyrometer will

read 15° low. If, however, the cold-junction temperature falls below

75°F., the pyrometer will read high instead of low, approximately

1° for every 1° drop in temperature below 75°F.

With platinum thermo-couples, the error is approximately 1/2° for

1° change in temperature.

CORRECTION BY ZERO ADJUSTMENT.--Many pyrometers are supplied with

a zero adjuster, by means of which the pointer can be set to any

actual cold-junction temperature. If the cold junction of the

thermo-couple is in a temperature of 100°F., the pointer can be

set to this point on the scale, and the readings of the instrument

will be correct.

COMPENSATING LEADS.--By the use of compensating leads, formed of

the same material as the thermo-couple, the cold junction can be

removed from the head of the thermo-couple to a point 10, 20 or 50

ft. distant from the furnace, where the temperature is reasonably

constant. Where greater accuracy is desired, a common method is

to drive a 2-in. pipe, with a pointed closed end, some 10 to 20

ft. into the ground, as shown in Fig. 128. The compensating leads

are joined to the copper leads, and the junction forced down to

the bottom of the pipe. The cold junction is now in the ground,

beneath the building, at a depth at which the temperature is very

constant, about 70°F., throughout the year. This method will usually

control the cold-junction temperature within 5°F.

Where the greatest accuracy is desired a compensating box will

overcome cold-junction errors entirely. It consists of a case enclosing

a lamp and thermostat, which can be adjusted to maintain any desired

temperature, from 50 to 150°F. The compensating leads enter the box

and copper leads run from the compensating box to the instrument,

so that the cold junction is within the box. Figure 129 shows a

Brown compensating box.

[Illustration: FIG. 128.--Correcting cold-junction error.]

If it is desired to maintain the cold junction at 100°: the thermostat

is set at this point, and the lamp, being wired to the 110- or

220-volt lighting circuit, will light and heat the box until 100°

is reached, when the thermostat will open the circuit and the light

is extinguished. The box will now cool down to 98°, when the circuit

is again closed, the lamp lights, the box heats up, and the operation

is repeated.

[Illustration: FIG. 129.--Compensating box.]

BROWN AUTOMATIC SIGNALING PYROMETER

In large heat-treating plants it has been customary to maintain

an operator at a central pyrometer, and by colored electric lights

at the furnaces, signal whether the temperatures are correct or

not. It is common practice to locate three lights above each

furnace-red, white and green. The red light burns when the temperature

is too low, the white light when the temperature is within certain

limits--for example, 20°F. of the correct temperature--and the

green light when the temperature is too high.

[Illustration: FIG. 130.--Brown automatic signaling pyrometer.]

Instruments to operate the lights automatically have been devised and

one made by Brown is shown in Fig. 130. The same form of instrument is

used for this purpose to automatically control furnace temperatures,

and the pointer is depressed at intervals of every 10 sec. on contacts

corresponding to the red, white and green lights.

[Illustration: FIG. 131.--Automatic temperature control.]

AN AUTOMATIC TEMPERATURE CONTROL PYROMETER

Automatic temperature control instruments are similar to the Brown

indicating high resistance pyrometer with the exception that the

pointer is depressed at intervals of every 10 sec. upon contact-making

devices. No current passes through the pointer which simply depresses

the upper contact device tipped with platinum, which in turn comes

in contact with the lower contact device, platinum-tipped, and the

circuit is completed through these two contacts. The current is very

small, about 1/10 amp., as it is only necessary to operate the relay

which in turn operates the switch or valve. A small motor is used to

depress the pointer at regular intervals. The contact-making device

is adjustable throughout the scale range of the instrument, and an

index pointer indicates the point on the instrument at which the

temperature is being controlled. The space between the two contacts

on the high and low side, separated by insulating material, is

equivalent to 1 per cent of the scale range. A control of temperature

is therefore possible within 1 per cent of the total scale range.

Figure 131 shows this attached to a small furnace.

[Illustration: FIG. 132.--Portable thermocouple testing molten brass.]

PYROMETERS FOR MOLTEN METAL

Pyrometers for molten metal are connected to portable thermocouples

as in Fig. 132. Usually the pyrometer is portable, as shown in

this case, which is a Brown. Other methods of mounting for this

kind of work arc shown in Figs. 133 and 134. The bent mountings

are designed for molten metal, such as brass or copper and are

supplied with either clay, graphite or carborundum tubes. Fifteen

feet of connecting wire is usually supplied.

The angle mountings, Fig. 134, are recommended for baths such as

lead or cyanide. The horizontal arm is usually about 14 in. long,

and the whole mounting is easily taken apart making replacements

very easy. Details of the thermo-couple shown in Fig. 132 are given

in Fig. 135. This is a straight rod with a protector for the hand

of the operator. The lag in such couples is less than one minute.

These are Englehard mountings.

PROTECTORS FOR THERMO-COUPLES

Thermo-couples must be protected from the danger of mechanical

injury. For this purpose tubes of various refractory materials

are made to act as protectors. These in turn are usually protected

by outside metal tubes. Pure wrought iron is largely used for this

purpose as it scales and oxidizes very slowly. These tubes are

usually made from 2 to 4 in. shorter than the inner tubes. In lead

baths the iron tubes often have one end welded closed and are used

in connection with an angle form of mounting.

[Illustration: FIG. 133.--Bent handle thermocouple with protector.]

Where it is necessary for protecting tubes to project a considerable

distance into the furnace a tube made of nichrome is frequently used.

This is a comparatively new alloy which stands high temperatures

without bending. It is more costly than iron but also much more

durable.

When used in portable work and for high temperatures, pure nickel

tubes are sometimes used. There is also a special metal tube made

for use in cyanide. This metal withstands the intense penetrating

characteristics of cyanide. It lasts from six to ten months as

against a few days for the iron tube.

The inner tubes of refractory materials, also vary according to

the purposes for which they are to be used. They are as follows:

MARQUARDT MASS TUBES for temperatures up to 3,000°F., but they will

not stand sudden changes in temperature, such as in contact with

intermittent flames, without an extra outer covering of chamotte,

fireclay or carborundum.

[Illustration: FIG. 134.--Other styles of bent mounting.]

FUSED SILICA TUBES for continuous temperatures up to 1,800°F. and

intermittently up to 2,400°F. The expansion at various temperatures

is very small, which makes them of value for portable work. They

also resist most acids.

CHAMOTTE TUBES are useful up to 2,800°F. and are mechanically strong.

They have a small expansion and resist temperature changes well,

which makes them good as outside protectors for more fragile tubes.

They cannot be used in molten metals, or baths of any kind nor

in gases of an alkaline nature. They are used mainly to protect

a Marquardt mass or silica tube.

CARBORUNDUM TUBES are also used as outside protection to other

tubes. They stand sudden changes of temperature well and resist

all gases except chlorine, above 1,750°F. Especially useful in

protecting other tubes against molten aluminum, brass, copper and

similar metals.

CLAY TUBES are sometimes used in large annealing furnaces where they

are cemented into place, forming a sort of well for the insertion of

the thermo-couple. They are also used with portable thermo-couples

for obtaining the temperatures of molten iron and steel in ladles.

Used in this way they are naturally short-lived, but seem the best

for this purpose.

[Illustration: FIG. 135.--Straight thermocouple and guard.]

CORUNDITE TUBES are used as an outer protection for both the Marquardt

mass and the silica tubes for kilns and for glass furnaces. Graphite

tubes are also used in some cases for outer protections.

CALORIZED TUBES are wrought-iron pipe treated with aluminum vapor

which often doubles or even triples the life of the tube at high

temperature.

These tubes come in different sizes and lengths depending on the

uses for which they are intended. Heavy protecting outer tubes

may be only 1 in. in inside diameter and as much as 3 in. outside

diameter, while the inner tubes, such as the Marquardt mass and

silica tubes are usually about 3/4 in. outside and 3/8 in. inside

diameter. The length varies from 12 to 48 in. in most cases.

Special terminal heads are provided, with brass binding posts for

electrical connections, and with provisions for water cooling when

necessary.

APPENDIX

TABLE 32.--Temperature Conversion Tables.

TABLE 33.--Comparison Between Degrees Centigrade and Degrees Fahrenheit.

TABLE 34.--Weight of Round, Octagon and Square Carbon Tool Steel

per Foot.

TABLE 35.--Weight of Round Carbon Tool Steel 12 In. in Diameter

and Larger, per Foot.

TABLE 36.--Decimal Equivalents of a foot.

TEMPERATURE CONVERSION TABLES

By ALBERT SAUVEUR

--------------------------------------------------------------------------

-459.4 to 0 | 0 to 100 | 100 to 1000

-----------------|------------------------------|-------------------------

C. F. | C. F. | C. F. | C. F.| C. F.

-----------------|---------------|--------------|-----------|-------------

-273 -459.4 |-17.8 0 32 |10.0 50 122.0| 38 100 212|260 500 932

-268 -450 |-17.2 1 33.8|10.6 51 123.8| 43 110 230|266 510 950

-262 -440 |-16.7 2 35.6|11.1 52 125.6| 49 120 248|271 520 968

-257 -430 |-16.1 3 37.4|11.7 53 127.4| 54 130 266|277 530 986

-251 -420 |-15.6 4 39.2|12.2 54 129.2| 60 140 284|282 540 1004

-246 -410 |-15.0 5 41.0|12.8 55 131.0| 66 150 302|288 550 1022

-240 -400 |-14.4 6 42.8|13.3 56 132.8| 71 160 320|293 560 1040

-234 -390 |-13.9 7 44.6|13.9 57 134.6| 77 170 336|299 570 1058

-229 -380 |-13.3 8 46.4|14.4 58 136.4| 82 180 358|304 580 1076

-223 -370 |-12.8 9 48.2|15.0 59 138.2| 88 190 374|310 590 1094

-218 -360 |-12.2 10 50.0|15.6 60 140.0| 93 200 392|316 600 1112

-212 -350 |-11.7 11 51.8|16.1 61 141.8| 99 210 410|321 610 1130

-207 -340 |-11.1 12 53.6|16.7 62 143.6|100 212 413|327 620 1148

-201 -330 |-10.6 13 55.4|17.2 63 145.4|104 220 428|332 630 1166

-196 -320 |-10.0 14 57.2|17.8 64 147.2|110 230 446|338 640 1184

-190 -310 | -9.44 15 59.0|18.3 65 149.0|116 240 464|343 650 1202

-184 -300 | -8.89 16 61.8|18.9 66 150.8|121 250 482|349 660 1220

-179 -290 | -8.33 17 63.6|19.4 67 152.6|127 260 500|354 670 1238

-173 -280 | -7.78 18 65.4|20.0 68 154.4|132 270 518|360 680 1256

-169 -273 -459.4| -7.22 19 67.2|20.6 69 156.2|138 280 536|366 690 1274

-168 -270 -454 | -6.67 20 68.0|21.1 70 158.0|143 290 554|371 700 1292

-162 -260 -436 | -6.11 21 69.8|21.7 71 159.8|149 300 572|377 710 1310

-157 -250 -418 | -5.56 22 71.6|22.2 72 161.6|154 310 590|382 720 1328

-151 -240 -400 | -5.00 23 73.4|22.8 73 163.4|160 320 608|388 730 1346

-146 -230 -382 | -4.44 24 75.2|23.3 74 165.2|166 330 626|393 740 1364

-140 -220 -364 | -3.89 25 77.0|23.9 75 167.0|171 340 644|399 750 1382

-134 -210 -346 | -3.33 26 78.8|24.4 76 168.8|177 350 662|404 760 1400

-129 -200 -328 | -2.78 27 80.6|25.0 77 170.6|182 360 680|410 770 1418

-123 -190 -310 | -2.22 28 82.4|25.6 78 172.4|188 370 698|416 780 1436

-118 -180 -292 | -1.67 29 84.2|26.1 79 174.2|193 380 716|421 790 1454

-112 -170 -274 | -1.11 30 86.0|26.7 80 176.0|199 390 734|427 800 1472

-107 -160 -256 | -0.56 31 87.8|27.2 81 177.8|204 400 752|432 810 1490

-101 -150 -238 | 0 32 89.6|27.8 82 179.6|210 410 770|438 820 1508

-95.6 -140 -220 | 0.56 33 91.4|28.3 83 181.4|216 420 788|443 830 1526

-90.0 -130 -202 | 1.11 34 93.2|28.9 84 183.2|221 430 806|449 840 1544

-84.4 -120 -184 | 1.67 35 95.0|29.4 85 185.0|227 440 824|454 850 1562

-78.9 -110 -166 | 2.22 36 96.8|30.0 86 186.8|232 450 842|460 860 1580

-73.3 -100 -148 | 2.78 37 98.6|30.6 87 188.6|238 460 860|466 870 1598

-67.8 -90 -130 | 3.33 38 100.4|31.1 88 190.4|243 470 878|471 880 1616

-62.2 -80 -112 | 3.89 39 102.2|31.7 89 192.2|249 480 896|477 890 1634

-56.7 -70 -94 | 4.44 40 104.0|32.2 90 194.0|254 490 914|482 900 1652

-51.1 -60 -76 | 5.00 41 105.8|32.8 91 195.8| |488 910 1670

-45.6 -50 -58 | 5.56 42 107.6|33.3 92 197.6| |493 920 1688

-40.0 -40 -40 | 6.11 43 109.4|33.9 93 199.4| |499 930 1706

-34.4 -30 -22 | 6.67 44 111.2|34.4 94 201.2| |504 940 1724

-28.9 -20 4 | 7.22 45 113.0|35.0 95 203.0| |510 950 1742

-23.3 -10 14 | 7.78 46 114.8|35.6 96 204.8| |516 960 1760

-17.8 0 32 | 8.33 47 116.6|36.1 97 206.6| |521 970 1778

| 8.89 48 118.4|36.7 98 208.4| |527 980 1796

| 9.44 49 120.2|37.2 99 210.2| |532 990 1814

| |37.8 100 212.0| |538 1000 1832

--------------------------------------------------------------------------

----------------------------------------------------------------

1000 to 2000 | 2000 to 3000

-------------------------------|--------------------------------

C. F. | C. F. | C. F. | C. F.

--------------|----------------|----------------|---------------

538 1000 1832 | 816 1500 2732 | 1093 2000 3632 | 1371 2500 4534

543 1010 1850 | 821 1510 2750 | 1099 2010 3650 | 1377 2510 4552

549 1020 1868 | 827 1520 2768 | 1104 2020 3668 | 1382 2520 4560

554 1030 1886 | 832 1530 2786 | 1110 2030 3686 | 1388 2530 4588

560 1040 1904 | 838 1540 2804 | 1116 2040 3704 | 1393 2540 4606

566 1050 1922 | 843 1550 2822 | 1121 2050 3722 | 1399 2550 4622

571 1060 1940 | 849 1560 2840 | 1127 2060 3740 | 1404 2560 4640

577 1070 1958 | 854 1570 2858 | 1132 2070 3758 | 1410 2570 4658

582 1080 1976 | 860 1580 2876 | 1138 2080 3776 | 1416 2580 4676

588 1090 1994 | 866 1590 2894 | 1143 2090 3794 | 1421 2590 4694

593 1100 2012 | 871 1600 2912 | 1149 2100 3812 | 1427 2600 4712

599 1110 2030 | 877 1610 2930 | 1154 2110 3830 | 1432 2610 4730

604 1120 2048 | 882 1620 2948 | 1160 2120 3848 | 1438 2620 4748

610 1130 2066 | 888 1630 2966 | 1166 2130 3866 | 1443 2630 4766

616 1140 2084 | 893 1640 2984 | 1171 2140 3884 | 1449 2640 4784

621 1150 2102 | 899 1650 3002 | 1777 2150 3902 | 1454 2650 4802

627 1160 2120 | 904 1660 3020 | 1182 2160 3920 | 1460 2660 4820

632 1170 2138 | 910 1670 3038 | 1188 2170 3938 | 1466 2670 4838

638 1180 2156 | 916 1680 3056 | 1193 2180 3956 | 1471 2680 4854

643 1190 2174 | 921 1690 3074 | 1199 2190 3974 | 1477 2690 4876

649 1200 2192 | 927 1700 3092 | 1204 2200 3992 | 1482 2700 4892

654 1210 2210 | 932 1710 3110 | 1210 2210 4010 | 1488 2710 4910

660 1220 2228 | 938 1720 3128 | 1216 2220 4028 | 1493 2720 4928

666 1230 2246 | 943 1730 3146 | 1221 2230 4046 | 1499 2730 4946

671 1240 2264 | 949 1740 3164 | 1227 2240 4064 | 1504 2740 4964

677 1250 2282 | 954 1750 3182 | 1232 2250 4082 | 1510 2750 4982

682 1260 2300 | 960 1760 3200 | 1238 2260 4100 | 1516 2760 5000

688 1270 2318 | 966 1770 3218 | 1243 2270 4118 | 1521 2770 5018

693 1280 2336 | 971 1780 3236 | 1249 2280 4136 | 1527 2780 5036

699 1290 2354 | 977 1790 3254 | 1254 2290 4154 | 1532 2790 5054

704 1300 2372 | 982 1800 3272 | 1260 2300 4172 | 1538 2800 5072

710 1310 2390 | 988 1810 3290 | 1266 2310 4190 | 1543 2810 5090

716 1320 2408 | 993 1820 3308 | 1271 2320 4208 | 1549 2820 5108

721 1330 2426 | 999 1830 3326 | 1277 2330 4226 | 1554 2830 5126

727 1340 2444 | 1004 1840 3344 | 1282 2340 4244 | 1560 2840 5144

732 1350 2462 | 1010 1850 3362 | 1288 2350 4262 | 1566 2850 5162

738 1360 2480 | 1016 1860 3380 | 1293 2360 4280 | 1571 2860 5180

743 1370 2498 | 1021 1870 3398 | 1299 2370 4298 | 1577 2870 5198

749 1380 2516 | 1027 1880 3416 | 1304 2380 4316 | 1582 2880 5216

754 1390 2534 | 1032 1890 3434 | 1310 2390 4334 | 1588 2890 5234

760 1400 2552 | 1038 1900 3452 | 1316 2400 4352 | 1593 2900 5252

766 1410 2570 | 1043 1910 3470 | 1321 2410 4370 | 1599 2910 5270

771 1420 2588 | 1049 1920 3488 | 1327 2420 4388 | 1604 2920 5288

777 1430 2606 | 1054 1930 3506 | 1332 2430 4406 | 1610 2930 5306

782 1440 2624 | 1060 1940 3524 | 1338 2440 4424 | 1616 2940 5324

788 1450 2642 | 1066 1950 3542 | 1343 2450 4442 | 1621 2950 5342

793 1460 2660 | 1071 1960 3560 | 1349 2460 4460 | 1627 2960 5360

799 1470 2678 | 1077 1970 3578 | 1354 2470 4478 | 1632 2970 5378

804 1480 2696 | 1082 1980 3596 | 1360 2480 4496 | 1638 2980 5396

810 1490 2714 | 1088 1990 3614 | 1366 2490 4514 | 1643 2990 5414

| 1093 2000 3632 | | 1649 3000 5432

---------------------------------------------------------------

NOTE.--The numbers in bold face type refer to the temperature either

in degrees Centigrade or Fahrenheit which it is desired to convert

into the other scale. If converting from Fahrenheit degrees to

Centigrade degrees the equivalent temperature will be found in

the left column, while if converting from degrees Centigrade to

degrees Fahrenheit, the answer will be found in the column on the

right. These tables are a revision of those by Sauveur & Boylston,

metallurgical engineers, Cambridge, Mass. Copyright, 1920.

INTERPOLATION FACTORS

C. F. C. F.

0.56 1 1.8 | 3.33 6 10.8

1.11 2 3.6 | 3.89 7 12.6

1.67 3 5.4 | 4.44 8 14.4

2.22 4 7.2 | 5.00 9 16.2

2.78 5 9.0 | 5.56 10 18.0

Those using pyrometers will find this and the preceding conversion

table of great convenience:

TABLE 33.--COMPARISON BETWEEN DEGREES CENTIGRADE AND DEGREES FAHRENHEIT

-------------------------------------------------------------------------

---------|---------|---------|---------|---------|---------|-------------

F.| C. | F.| C. | F.| C. | F.| C. | F.| C. | F.| C. | F.| C.

---|-----|---|-----|---|-----|---|-----|---|-----|---|-----|-----|-------

-40|-40.0| 3|-16.1| 46| 7.7| 89| 31.6|132| 55.5|175| 79.4| 275| 135.0

-39|-39.4| 4|-15.5| 47| 8.3| 90| 32.2|133| 56.1|176| 80.0| 300| 148.8

-38|-38.8| 5|-15.0| 48| 8.8| 91| 32.7|134| 56.6|177| 80.5| 325| 162.7

-37|-38.3| 6|-14.4| 49| 9.3| 92| 33.3|135| 57.2|178| 81.1| 350| 176.6

-36|-37.7| 7|-13.8| 50| 10.0| 93| 33.9|136| 57.7|179| 81.6| 375| 190.5

-35|-37.2| 8|-13.3| 51| 10.5| 94| 34.4|137| 58.3|180| 82.2| 400| 204.4

-34|-36.6| 9|-12.7| 52| 11.1| 95| 35.0|138| 58.8|181| 82.7| 425| 218.3

-33|-36.1| 10|-12.2| 53| 11.6| 96| 35.5|139| 59.4|182| 83.3| 450| 232.2

-32|-35.5| 11|-11.6| 54| 12.2| 97| 36.1|140| 60.0|183| 83.8| 475| 246.1

-31|-35.0| 12|-11.1| 55| 12.7| 98| 36.6|141| 60.5|184| 84.4| 500| 260.0

-30|-34.4| 13|-10.5| 56| 13.3| 99| 37.2|142| 61.1|185| 85.0| 525| 273.8

-29|-33.9| 14|-10.0| 57| 13.8|100| 37.7|143| 61.6|186| 85.5| 550| 287.7

-28|-33.3| 15| -9.3| 58| 14.4|101| 38.3|144| 62.2|187| 86.1| 575| 301.6

-27|-32.7| 16| -8.8| 59| 15.0|102| 38.8|145| 62.7|188| 86.6| 600| 315.5

-26|-32.2| 17| -8.3| 60| 15.5|103| 39.4|146| 63.3|189| 87.2| 625| 329.4

-25|-31.6| 18| -7.7| 61| 16.1|104| 40.0|147| 63.8|190| 87.7| 650| 343.3

-24|-31.1| 19| -7.2| 62| 16.6|105| 40.5|148| 64.4|191| 88.3| 675| 357.2

-23|-30.5| 20| -6.6| 63| 17.2|106| 41.1|149| 65.0|192| 88.8| 700| 371.1

-22|-30.0| 21| -6.1| 64| 17.7|107| 41.6|150| 65.5|193| 89.4| 725| 385.0

-21|-29.4| 22| -5.5| 65| 18.3|108| 42.2|151| 66.1|194| 90.0| 750| 398.8

-20|-28.8| 23| -5.0| 66| 18.8|109| 42.7|152| 66.6|195| 90.5| 775| 412.7

-19|-28.3| 24| -4.4| 67| 19.4|110| 43.3|153| 67.2|196| 91.1| 800| 426.6

-18|-27.7| 25| -3.8| 68| 20.0|111| 43.8|154| 67.7|197| 91.6| 825| 440.5

-17|-27.2| 26| -3.3| 69| 20.5|112| 44.4|155| 68.3|198| 92.2| 850| 454.4

-16|-26.6| 27| -2.7| 70| 21.1|113| 45.0|156| 68.8|199| 92.7| 875| 468.3

-15|-26.1| 28| -2.2| 71| 21.6|114| 45.5|157| 69.4|200| 93.3| 900| 482.2

-14|-25.5| 29| -1.6| 72| 22.2|115| 46.1|158| 70.0|201| 93.8| 925| 496.1

-13|-25.0| 30| -1.1| 73| 22.7|116| 46.6|159| 70.5|202| 94.4| 950| 510.0

-12|-24.4| 31| -0.5| 74| 23.3|117| 47.2|160| 71.1|203| 95.0| 975| 523.8

-11|-23.8| 32| -0.0| 75| 23.8|118| 47.7|161| 71.6|204| 95.5|1,000| 537.7

-10|-23.3| 33| +0.5| 76| 24.4|119| 48.3|162| 72.2|205| 96.1|1,100| 593.3

-9|-22.7| 34| 1.1| 77| 25.0|120| 48.8|163| 72.7|206| 96.6|1,200| 648.8

-8|-22.2| 35| 1.6| 78| 25.5|121| 49.4|164| 73.3|207| 97.2|1,300| 704.4

-7|-21.6| 36| 2.2| 79| 26.1|122| 50.0|165| 73.8|208| 97.7|1,400| 760.0

-6|-21.1| 37| 2.7| 80| 26.6|123| 50.5|166| 74.4|209| 98.3|1,500| 815.5

-5|-20.5| 38| 3.3| 81| 27.2|124| 51.1|167| 75.0|210| 98.8|1,600| 871.1

-4|-20.0| 39| 3.8| 82| 27.7|125| 51.6|168| 75.5|211| 99.4|1,700| 926.6

-3|-19.4| 40| 4.4| 83| 28.3|126| 52.2|169| 76.1|212|100.0|1,800| 982.2

-2|-18.8| 41| 5.0| 84| 28.8|127| 52.7|170| 76.6|213|100.5|1,900|1,037.7

-1|-18.3| 42| 5.5| 85| 29.4|128| 53.3|171| 77.2|214|101.1|2,000|1,093.3

0|-17.7| 43| 6.1| 86| 30.0|129| 53.8|172| 77.7|215|101.6|2,100|1,148.8

+1|-17.2| 44| 6.6| 87| 30.5|130| 54.4|173| 78.3|225|107.2|2,200|1,204.4

2|-16.6| 45| 7.2| 88| 31.1|131| 55.0|174| 78.8|250|121.1|2,300|1,260.0

-------------------------------------------------------------------------

9 x degrees C.

Degrees Fahrenheit = -------------- + 32

5 x (degrees F. - 32)

Degrees Centigrade = ---------------------

Three other useful tables are also given on the following pages.

TABLE 34.--WEIGHT OF ROUND, OCTAGON AND SQUARE CARBON TOOL STEEL PER FOOT

------------------------------------------------------------------------

--------|--------|--------|--------|--------|--------|---------|--------

1/16 | 0.010 | 0.011 | 0.013 | 2-1/2 | 16.79 | 17.71 | 21.37

1/8 | 0.042 | 0.044 | 0.053 | 2-5/8 | 18.51 | 19.52 | 23.56

3/16 | 0.094 | 0.099 | 0.120 | 2-3/4 | 20.31 | 21.42 | 25.86

1/4 | 0.168 | 0.177 | 0.214 | 2-7/8 | 22.20 | 23.41 | 28.27

5/16 | 0.262 | 0.277 | 0.334 | 3 | 24.17 | 25.50 | 30.78

3/8 | 0.378 | 0.398 | 0.481 | 3-1/8 | 26.23 | 27.66 | 33.40

7/16 | 0.514 | 0.542 | 0.655 | 3-1/4 | 28.37 | 29.92 | 36.12

1/2 | 0.671 | 0.708 | 0.855 | 3-3/8 | 30.59 | 32.27 | 38.95

9/16 | 0.850 | 0.896 | 1.082 | 3-1/2 | 32.90 | 34.70 | 41.89

5/8 | 1.049 | 1.107 | 1.336 | 3-5/8 | 35.29 | 37.23 | 44.94

11/16 | 1.270 | 1.339 | 1.616 | 3-3/4 | 37.77 | 39.84 | 48.09

3/4 | 1.511 | 1.594 | 1.924 | 3-7/8 | 40.33 | 42.54 | 51.35

13/16 | 1.773 | 1.870 | 2.258 | 4 | 42.97 | 45.34 | 54.72

7/8 | 2.056 | 2.169 | 2.618 | 4-1/4 | 48.51 | 51.17 | 61.77

15/16 | 2.361 | 2.490 | 3.006 | 4-1/2 | 54.39 | 57.37 | 69.25

1 | 2.686 | 2.833 | 3.420 | 4-3/4 | 60.60 | 63.92 | 77.16

1-1/8 | 3.399 | 3.585 | 4.328 | 5 | 67.15 | 70.83 | 85.50

1-1/4 | 4.197 | 4.427 | 5.344 | 5-1/4 | 74.03 | 78.08 | 94.26

1-3/8 | 5.078 | 5.356 | 6.646 | 5-1/2 | 81.25 | 85.70 | 103.45

1-1/2 | 6.044 | 6.374 | 7.695 | 5-3/4 | 88.80 | 93.67 | 113.07

1-5/8 | 7.093 | 7.481 | 9.031 | 6 | 96.69 | 101.99 | 123.12

1-3/4 | 8.226 | 8.674 | 10.474 | 7 | 131.61 | 138.82 | 167.58

1-7/8 | 9.443 | 9.960 | 12.023 | 8 | 171.90 | 181.32 | 218.88

2 | 10.744 | 11.332 | 13.680 | 9 | 217.57 | 229.48 | 277.02

2-1/8 | 12.129 | 12.793 | 15.443 | 10 | 268.60 | 283.31 | 342.00

2-1/4 | 13.598 | 14.343 | 17.314 | 11 | 325.01 | 342.80 | 413.82

2-3/8 | 15.151 | 15.981 | 19.291 | 12 | 386.79 | 407.97 | 492.48

------------------------------------------------------------------------

High-speed steel, being more dense than carbon steel, weighs from

10 to 11 per cent more than carbon steel. This should be added

to figures given in the table.

TABLE 35.--WEIGHT OF ROUND, CARBON TOOL STEEL 12 IN. IN DIAMETER

AND LARGER, PER FOOT

--------------------------------------------------------------------

-----------|----------|-----------|----------|-----------|----------

12 | 386.790 | 15-7/8 | 677.527 | 19-3/4 | 1,049.010

12-1/8 | 395.518 | 16 | 687.600 | 19-7/8 | 1,061.705

12-1/4 | 404.246 | 16-1/8 | 699.017 | 20 | 1,074.400

12-3/8 | 412.974 | 16-1/4 | 710.435 | 20-1/8 | 1,088.502

12-1/2 | 421.702 | 16-3/8 | 721.852 | 20-1/4 | 1,102.605

12-5/8 | 430.430 | 16-1/2 | 733.270 | 20-3/8 | 1,116.707

12-3/4 | 439.158 | 16-5/8 | 744.687 | 20-1/2 | 1,130.810

12-7/8 | 447.886 | 16-3/4 | 756.105 | 20-5/8 | 1,144.912

13 | 456.615 | 16-7/8 | 767.522 | 20-3/4 | 1,159.015

13-1/8 | 465.343 | 17 | 778.940 | 20-7/8 | 1,173.118

13-1/4 | 474.071 | 17-1/8 | 790.358 | 21 | 1,187.220

13-3/8 | 482.799 | 17-1/4 | 801.777 | 21-1/8 | 1,201.322

13-1/2 | 491.527 | 17-3/8 | 813.195 | 21-1/4 | 1,215.425

13-5/8 | 500.255 | 17-1/2 | 824.614 | 21-3/8 | 1,229.527

13-3/4 | 508.983 | 17-5/8 | 836.030 | 21-1/2 | 1,243.630

13-7/8 | 517.711 | 17-3/4 | 847.447 | 21-5/8 | 1,257.732

14 | 526.440 | 17-7/8 | 858.863 | 21-3/4 | 1,271.835

14-1/8 | 536.512 | 18 | 870.280 | 21-7/8 | 1,285.937

14-1/4 | 546.585 | 18-1/8 | 883.105 | 22 | 1,300.040

14-3/8 | 556.657 | 18-1/4 | 895.920 | 22-1/8 | 1,315.485

14-1/2 | 566.730 | 18-3/8 | 908.740 | 22-1/4 | 1,330.930

14-5/8 | 576.802 | 18-1/2 | 921.560 | 22-3/8 | 1,346.375

14-3/4 | 586.875 | 18-5/8 | 934.380 | 22-1/2 | 1,361.820

14-7/8 | 596.947 | 18-3/4 | 947.200 | 22-5/8 | 1,377.265

15 | 607.020 | 18-7/8 | 960.020 | 22-3/4 | 1,392.710

15-1/8 | 617.092 | 19 | 972.840 | 22-7/8 | 1,408.155

15-1/4 | 627.165 | 19-1/8 | 985.035 | 23 | 1,423.600

15-3/8 | 637.237 | 19-1/4 | 998.230 | 23-1/8 | 1,454.490

15-1/2 | 647.310 | 19-3/8 |1,010.925 | 23-1/4 | 1,485.380

15-5/8 | 657.382 | 19-1/2 |1,023.620 | 23-3/8 | 1,516.270

15-3/4 | 667.455 | 19-5/8 |1,036.315 | 24 | 1,547.160

--------------------------------------------------------------------

To find the weight of discs made of carbon steel, in diameters

up to and including 12 in., without any allowance for finishing

multiply the per foot weight of round bar steel, shown herewith

by the decimal equivalent of a foot given in the following table:

TABLE 36.--DECIMAL EQUIVALENTS OF A FOOT

---------------------------------------------------------------------

In. | 0 | 1/8 | 1/4 | 3/8 | 1/2 | 5/8 | 3/4 | 7/8

-----|-------|-------|-------|-------|-------|-------|-------|-------

0 | 0.000 | 0.010 | 0.021 | 0.031 | 0.042 | 0.052 | 0.063 | 0.073

1 | 0.083 | 0.094 | 0.104 | 0.115 | 0.125 | 0.135 | 0.146 | 0.156

2 | 0.167 | 0.177 | 0.188 | 0.198 | 0.208 | 0.219 | 0.229 | 0.240

3 | 0.250 | 0.260 | 0.270 | 0.281 | 0.292 | 0.302 | 0.313 | 0.323

4 | 0.333 | 0.344 | 0.354 | 0.364 | 0.375 | 0.385 | 0.396 | 0.406

5 | 0.416 | 0.427 | 0.437 | 0.448 | 0.458 | 0.469 | 0.479 | 0.480

6 | 0.500 | 0.510 | 0.520 | 0.531 | 0.542 | 0.552 | 0.563 | 0.573

7 | 0.583 | 0.594 | 0.604 | 0.615 | 0.625 | 0.635 | 0.646 | 0.656

8 | 0.666 | 0.677 | 0.687 | 0.698 | 0.708 | 0.719 | 0.729 | 0.740

9 | 0.750 | 0.760 | 0.770 | 0.781 | 0.792 | 0.802 | 0.813 | 0.823

10 | 0.833 | 0.844 | 0.854 | 0.865 | 0.875 | 0.885 | 0.896 | 0.906

11 | 0.916 | 0.927 | 0.937 | 0.948 | 0.953 | 0.969 | 0.979 | 0.990

---------------------------------------------------------------------

EXAMPLE.--If the weight of a carbon steel disc 7 in. diameter,

1-5/8 in. thick is desired, turn to page 233, where the per foot

weight of 7 in. round is given as 131.6 lb. Multiply this by the

decimal equivalent of 1-5/8 in., or 0.135, as shown in the above

table, and the product will be the net weight of the disc.

131.61 lb. = the weight of 1 ft. of 7 in. round.

0.135 = the per foot decimal equivalent of 1-5/8 in:

------------

65805

39483

13161

------------

17.76735 lb. = weight of disc 7 in. diam. 1-5/8 in. thick without any

allowance for finishing.

AUTHORITES QUOTED

ADDIS, W H.

AMERICAN MACHINISTS' HANDBOOK

AMERICAN STEEL TREARERS' SOCIETY

AMERICAN GEAR MFRS. ASSO.

AUTOMATIC AND ELECTRIC FURNACES LTD.

ARNOLD, PROF. J. O.

BURLEIGH, R. W.

BORDEN, B.

BOKER, HERMAN & Co.

BROWN INSTRUMENT Co.

BROWN-LIPE-CHAPLIN Co.

CAMPBELL, H. H.

CARHART, H. A.

CLAYTON, C. Y.

CURTIS AIRPLANE Co.

ENGLEHARD, CHARLES

ENSAW, HOWARD

FIRTH-STERLING STEEL Co.

FIRTH, THOMAS & SONS

FOWLER, HENRY

GILBERT & BARKER

HAYWAHD, C. R.

HOWE, DR. H. M.

HOOVER STEEL BALL CO.

HEATHCOTE, H. L.

HARRIS, MATTHEW

HUNTER, J. V.

JANITZKY, E. J.

JOHNSTON, A. B.

JUTHE, K. A.

LATROBE STEEL CO.

LUDLUM STEEL CO.

LEEDS & NORTHRUP CO.

LYMAN, W. H.

MANSFIELD, C. A.

MIDVALE STEEL Co.

McKENNA, ROY C.

MOULTON, SETH A.

NILES, BEMENT, POND

PARKER, S. W.

POOLE, C. R.

RAWDON, H. S.

S. A. E. (SOCIETY AUTOMOTIVE ENGINEERS)

SAUVEUR, ALBERT

SPRINGFIELD ARMORY

SELLACK, T. G.

SMITH, A. J.

SHIRLEY, ALFRED J.

TAYLOR INSTRUMENT Co.

THUM, E. E.

TIEMANN, H. P.

U. S. BALL BEARING Co.

UNITED STEEL Co.

UNDERWOOD, CHARLES N.

VAN DE VENTER, JOHN H.

WALP, H. O.

WOOD, HAROLD F.

WHEELOCK, LOVEJOY & Co.

INDEX

ABC of iron and steel

Absorption of carbon, rate of

Air hardening steels

Analysis of high speed steel

Allotropic modifications

Alloy steel, annealing

properties of

Alloys and their effect

in high speed steel

in steel, value of

upon steel

Alpha iron

Annealing

care in

furnace

high-chromium steel

high speed tools

in bone

methods

proper

rifle components

rust-proof steel

steels

temperature

Arrests

Austentite

Automotive industry, application of Liberty engine materials to

temperature control

Axles, heat treatment of

Balls, making steel

Barium chloride process

Baths for tempering

Bessemer converter

Beta iron

Blending compounds

Blister steel

Blue brittleness

Bone, annealing in

Boxes for case hardening or carburizing

Breaking test gears

Brinell hardness

Broach hardening furnace

Brown automatic pyrometer

Burning

Calorized tubes

Carbon

content at various temperatures

content of case hardened work

in cast iron, ix

in tool steel

introduction of

penetration of

steel

steel forgings, Liberty engine

steel tools

steels, S. A. E.

steels, temper colors

strengthens iron

tool steel, forging

Carbonizing, _see_ Carburizing

Carborundum tubes

Carburization, preventing

Carburizing by gas

boxes

compounds

gas consumption by

local

material

nickel steel

or case hardening

pots for

Carburizing, process of

short method

sleeves

with charcoal

_See_ Case hardening

Car door type of furnace

Case, depth of

Case hardening boxes

cast iron

local

or surface carburizing

treatments for various steels

_see_ Carburizing

Cast iron, carbon in

case hardening

Cementite

Center column furnace

Centigrade table

Chamotte tubes

Chart of carbon penetration

heat treatment

shape

Chrome steel

Chrome-nickel steel

steel, forging

Chrome-vanadium steel

Chromium

steels, S. A. E.

Chromium-cobalt steel

Chromium-vanadium steel, S. A. E.

Classification of steel

Clay tubes

Cold end compensator

junction errors

shortness

worked steel

Color in tempering

Colors on carbon steels

Combination tank

Comparison of fuels

Compensating leads

Compensator for cold ends

automatic

Composition of steel

Compound, blending

separating from work

Compounds for carburizing

Connecting rods, Liberty motor

Continuous heating furnace

Converter, Bessemer

Cooling curves

Cooling quenching oil, roof system

rate of, for gear-forgings

Copper, effect of, in medium carbon steel

Copper-plating to prevent carburizing

Corrosion of high-chromium steel

of rust-proof steel

Corundite tubes

Cost of operating furnaces

Cracks in hardening, preventing

Crankshaft, Liberty motor

Critical point

Crucible or tool steel

Cutting off high speed steel

Cyanide bath for tool steel

Decarbonizing of outer surface

preventing

Depth of case

Detrimental elements in steel

Dies, drop forging

quenching

soft spots in

tempering round

Drawing

ends of gear teeth

Drop forging dies

Ductility

Effect of alloys

of different carburizing material

of size of piece

of copper in medium carbon steel

Elastic limit

Electric process of steel making

Electrode

Elements, chemical

Elongation

Endurance limit

Energizer, 81

Enlarging steel

Equipment for heat treating

Eutectoid

Fahrenheit temperature table

Fatigue test

Ferrite

File test

Flame shields

Flange shields for furnaces

Forging furnace

high speed tools

improper

of steel

practice, heavy

rifle barrels

Forgings, carbon steel Liberty engine

Formed tools, high speed

Fractures, examining by

Furnace, continuous heating

crucible

data

electric

Heroult

open hearth

records

Furnaces

annealing

broach hardening

car door type

center column

cost of operating

data on

forging, heavy

fuels for

gas fired

high speed steel

lead pot

manganese steel

muffle

oil fired

operating costs

screens for

tool

Furnaces, water cooled fronts

Fuels, comparison of

for furnaces

Gages, changes due to quenching

tempering

Gamma iron

Gas, carburizing by

consumption for carburizing

fired furnace

illuminating, for carburizing

Gear blanks, heat treatment of

forgings, rate of cooling for Liberty engine

hardening machine

steel, transmission

teeth, drawing ends of

Gears, Liberty engine

Gleason tempering machine

Grade of steel

Grain, refining

size

Graphitic carbon

Grinding high speed steel

Hair lines in forgings

Hardening

carbon steel for tools

cracks, preventing

dies

gears

high speed steel

high speed tools

of high-chromium steel

of rust-proof steel

room, modern

Hardness tests

Heating, effect of size

for forging

Heat, judging by color

treating departments

equipment

forgings

inspection of

Liberty motor

Heat treating, of axles

of chisels

of gears

of high speed steel

of steel

S. A. E.

Heat treatment

Heroult furnace

High-chromium steel

annealing of

corrosion of

hardening of

Highly stressed parts of Liberty engine

High speed steel, analysis of

annealing

cutting off

forging

furnace

hardening

heat treatment of

instructions for

manufacture

pack hardening

structure of

Hints for steel users

Illuminating gas for carburizing

Impact test

Improper forging

Influence of size on heating

Inspection of heat treatment

Internal stresses, relieving

Introduction of carbon

Jewelers' tools

Judging heat of steel by color

Latent heat

Lathe and planer tools

tools, high speed

Latrobe temper list

Lead bath

pot furnace

Leeds & Northrup potentiometer

optical pyrometer

Liberty engine, highly stressed parts of

Liberty engine materials, application to automotive industry

motor connecting rods

motor, crankshaft

motor piston pin

Local case hardening

Luting mixture

Machineability of steel

Machinery steel, annealing

Magnet test

Making steel in electric furnace

Manganese

steel

furnace

Manufacture of high speed steel

Marquardt mass tubes

Martensite

Medium carbon steel, effect of copper on

Metallography

Microphotographs

Microscopic examination

Milling cutters, high speed

Mixture for luting

Modern hardening room

Molten metal pyrometers

Molybdenum

Muffle furnace

Nickel

Nickel-chromium steel

steels, S. A. E.

Nickel, influence of, on steel

steel

affinity for carbon

steels, S. A. E.

Non-homogeneous melting

Non-shrinking steels

Normalizing

Oil bath for tempering

cooling on roof

fired furnace

hardening steel, forging

steels

temperature of quenching

Open hearth furnace

Operating costs of furnaces

Outer surface decarbonizer

Over-heated steel, restoring

Overheating

dies

Pack-hardening

high speed steel

Packing work for carburizing

Paste for hardening dies

Pearlite

Penetration of carbon

carbon, chart of

in case hardening

Phosphorus

Pickling Liberty motor forgings

Pig iron

Piston pin, Liberty motor

Placing pyrometers

Planer tools, high speed

"Points" of carbon in steel

Potentiometer, Leeds & Northrup

Pots for carburizing

Press for testing gears

Preventing carburization

cracks in hardening

Properties of alloy steels

of alloy steels, table

of steel

Protective screens for furnaces

Puddled iron

Punches and chisels, steels for

Pyrometers

calibration

copper ball

indicating

inspection

iron ball

molten metal

optical

placing

recording

Siemens

testing

water

Quality and structure of high speed steel

of steel

Quenching,

after carburizing

dies in tank

obsolete method

oil, temperature of

tank

tool steel

Rate of absorption of carbon

Recording temperatures

Red shortness

Refining the grain

Regenerative open hearth furnace

Restoring overheated steel

Rifle barrels, forging

components, annealing

Roof system of cooling oil

Rust-proof steel

annealing of

corrosion of

hardening of

S. A. E. carbon steels

chromium steels

chromium-vanadium

heat treatments

nickel-chromium steels

nickel steels

screw stock

silico-manganese steel

standard steels

Salt bath for tempering

Scleroscope test

Scratch hardness

Screens for furnaces

Screw stock, S. A. E.

Sensible heat

Sentinels, melting of

Separating work from compound

Shields for furnace doors

Shore Scleroscope

Short method of carburizing

Shrinking steel

Silica tubes

Silico-manganese steels, S. A. E.

Silicon

Silversmiths' tools

Size of piece, effect of

Slags

Sleeves, carburizing

hardening and shrinking

shrinking

Solid solution

Sorbite

Specimens, test

Standard S. A. E. steels

Steel,

balls, stock for

bolts, making

composition of

deoxidation

for chisels and punches

forging of

give it a chance

heat treatment of

high speed

making

Bessemer process

crucible process

electric furnace process

open hearth

tools, carbon, in

users' hints

Structure of high speed steel

Sulphur

Tables, air, oil and water hardened steel

alloy steels, properties of

carbon content

carbon steels

case hardening

changes due to quenching

chromium steels

chromium-vanadium steels

colors and temperature

composition of steels

cost of furnaces

effect of size

fuels, comparison of

high-chromium steel

nickel-chromium steels

nickel steels

operating cost of furnaces

production cost of furnaces

S. A. E. steels

screw stock

silico-manganese steels

stock for balls

temperature conversion

tempering temperatures

weight of steel

Tank for quenching

dies

Taylor instruments

Temper, colors of

list, Latrobe

of steel

Temperature recorders

tables

Temperatures for tempering

Tempering colors on carbon steels

gages

high speed tools

machine, Gleason

round dies

temperatures

theory of

Tempers of carbon steel

Tensile test

Testing heat treatment

Tests of steel

Test specimens

Theory of tempering

Thermocouple

base metal

cold end

placing

protectors

rare metal

Time for hardening

Tool furnace, small

Tool or crucible steel, annealing

Tool steel, cyanide bath for

quenching

Tools, carbon in different

carbon steel

of high speed steel

sulphur in

tempers of various

transformation points

Transmission gear steel

Treatments for various steels

Troosite

Tubes, calorized

carborundum

Chamotte

clay

Marquardt mass

silica

Tungsten steel

Ultimate strength

Users of steel, hints for

Vanadium steel

Water annealing

cooled furnace fronts

Weight of steel bars

Working instructions for high speed steel

Wrought iron, ix

Yield Point

The Working of Steel Annealing, Heat Treating and Hardening of Carbon and Alloy Steel · 第 9 / 9 章

FLANGE SHIELDS FOR FURNACES.--Such portable flame shields as the