The electric furnace: its construction, operation and uses

The electric furnace; its construction, operation and usesEngineering Record Engineering News
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COLBY INDUCTION STEEL FURNACE. Frontispiece
THE ELECTRIC FURNACE
ITS CONSTRUCTION, OPERATION
BY
ALFRED STANSFIELD, D.Sc. ASSOCIATE OF THE ROYAL SCHOOL OF MINES; FELLOW OF
THE ROYAL SOCIETY OF CANADA; BIRKS PROFESSOR OF METALLURGY IN MCOILL UNIVERSITY
MONTREAL
LONDON: HILL PUBLISHING CO., LTD.
6 & 8 BOUVERIE ST., E.G.
1914
MCGRAW-HILL BOOK COMPANY, INC.
DEDICATED TO
DIRECTOR OF MINES, OTTAWA
TO ELECTRIC SMELTING THROUGHOUT THE WORLD
362500
PREFACE TO SECOND EDITION
Since the first appearance of this book, in 1907, the development of the electric furnace and its uses has been so rapid that this edition
has been increased to more than twice the size of the first, and the
whole has been reset.
Care has been taken to include, as far as possible, all recent devel-
opments of importance, but as the preparation of this edition has
occupied at least three years, it has been difficult to bring each part as closely up to date as is desirable in so up to the minute a subject
as electric smelting.
I wish to express my indebtedness to the following gentlemen and
others who have helped me with information, advice, or the use of
illustrations for the present edition: The Canadian Boving Com-
pany, The Carborundum Company, Electro Metals Company, Mr.
J. W. Evans, Mr. A. M. Fairlie, Dr. K. G. Frank, Mr. J. H. Gray, Dr. Eugene Haanel, Prof. L. A. Herdt, Dr. Carl Hering, Dr. R. S.
Hutton, Messrs. Harbison-Walker, Messrs. Leavitt and Company, Mr. F. Louvrier, Mr. Dorsey A. Lyon, The Norton Company, Dr.
H. N. Potter, Prof. J. W. Richards, Mr. T. D. Robertson, Mr. E. R.
Taylor, Titanium Alloy Manufacturing Company, Mr. F. J. Tone, Mr. R. Turnbull, Mr. W. R. Walker, Mr. T. L. Willson and Mr.
R. A. Witherspoon. I am very greatly indebted to my wife, who read the whole book
with me in proof, and to Mr. J. W. Hayward, who drew nearly all
the new illustrations for this edition, and read a large part of the
manuscript.
PREFACE TO FIRST EDITION
On my first visit to Canada, in 1897, I constructed an electric
furnace and showed it in operation at a lecture on Canada's metals,
which was delivered by the late Sir William Roberts-Austen. The
application of electrical heat to Metallurgy has always interested
me greatly and I hope that this little book may serve to instil this
interest in others, and to help forward the application of electric
smelting in a country which is so rich in water-powers and mineral
resources.
This book originated in a series of papers, written about a year
ago for the "Canadian Engineer," in which I endeavored to present,
as simply as possible, the principles on which the construction and
use of the electric furnace depend, and to give an account of its
history and present development. The original papers were written at a time when the experiments
of Dr. Haanel, at Sault Ste. Marie, were attracting public attention,
and a large section of the book has been devoted to the consideration
of these and other advances in the electrometallurgy of iron and
steel.
I wish to thank all who have helped me in the preparation of this
book, including Dr. Haanel, whose valuable monographs have
formed the basis of my chapter on iron and steel, and to whom I
am indebted for additional information on this branch of the sub-
ject: Prof. J. W. Richards, who has taken an interest in my work,
and whose book on "Metallurgical Calculations" has been of con-
siderable assistance in writing the chapter on furnace efficiencies;
Mr. E. A. Colby, who gave me information in regard to his induction
steel furnace and a sketch for Fig. 25; Mr. Francis A. J. Fitzgerald,
who supplied me with the data for Table X.; the editor of the
"Electrochemical and Metallurgical Industry," who loaned the
block for the frontispiece, and the International Acheson Graphite
Company, who gave me information about their furnaces and lent
the block for Fig. 40. I also wish to thank those of my personal
friends who assisted me in the tedious work of proof-reading.
ALFRED STANSFIELD.
viii
The electric arc Early electric furnaces W. Siemens' furnaces
Cowles Brothers' furnaces Aluminium furnaces Moissan's re-
searches Production of the Diamond Willson's carbide furnace
Carborundum Nitrates from the air Ferro-alloys Iron and steel Zinc.
CHAPTER II
electric furnace Classification Arc furnaces Resistance fur-
naces With special resistor Without special resistor Electro-
lytic furnaces Chart of classification.
CHAPTER III
EFFICIENCY OF ELECTRIC AND OTHER FURNACES AND RELATIVE COST OF ELECTRICAL AND FUEL HEAT 39~S4
Cost of electrical energy Efficiency of furnaces Calculation of
furnace efficiencies Heat units Rate of heating Temperature and heat of melting metals Calorific power of fuel Table of
calorific powers Calculation of efficiency of electric steel furnace
Cost of electrical energy.
Silica bricks Silica sand Lime Canister Magnesia Dolo-
mite Chromite Bauxite Alundum Carbon Carborundum
Crystolon Silundum Siloxicon Table of refractory materials
Thermal conductivity of furnace materials Table of thermal con-
ductivity and resistivity Radiation and convection of heat
Table of contact resistivity Furnace for testing heat losses Cal-
culation of heat losses Furnace with external gas-heating Fur-
nace walls without refractory materials Resistors Table of
electrical resistivity Electrical resistivity of heated fire-bricks
Electrodes Dimensions of electrodes Laws of electrode heat
losses Determination of electrode heat-losses Table of proper- ties of electrode materials Electrode holders.
ix
regulation Direct current Polyphase currents Electric power Electric measurements Rate of heat-production in electric
furnaces Voltage of electric furnaces Of arc furnaces Of
resistance furnaces Current density in furnaces Pinch effect
Regulation of electric furnaces Measurement of furnace tempera- tures Resistance pyrometer Thermo-electric pyrometers Op- tical pyrometers Scale of temperatures.
CHAPTER VI
sistance furnaces Furnaces with metallic heating-coils Howe's
crucible furnace Furnaces with carbon resistors Lampen's tube
furnace Crucible furnaces Arsem vacuum furnace Resistor tube
furnace Barker furnace Smelting furnaces Heroult steel furnace
McGill steel furnace Colby steel furnace Pig-iron furnace
Adjustable electrode holder Silicon furnace Power for electric
furnaces at McGill.
CHAPTER VII
THE PRODUCTION OF PIG IRON IN THE ELECTRIC FURNACE 173-211 Varieties of iron and steel Production of pig iron Electrical pro-
duction of pig iron Electric furnaces for iron smelting, Heroult
Keller HarmetHaanel-HerouU-^Turnbull-Heroult Possibilities
electric reduction furnaces Domnarfvet Frick Californian
Helfenstein Trollhattan Electric furnace design.
CHAPTER VIII
Introduction Electrical production of steel Series-arc furnaces
H&roult i$-ton Heroult Keller Single-arc furnaces Girod
Keller " Electro-metals
Gin Bering.
CHAPTER IX
THE PRODUCTION OF STEEL FROM IRON ORE 250-264 Electric steel smelting Stassano's furnace Experiments of Brown
and Lathe Evans' experiments Evans-Stansfield furnace
Keeney furnace Summary of electric steel smelting.
CONTENTS xi
Ferro alloys Analyses of ferro alloys Ferro silicon Silicon.
CHAPTER XI
graphite furnace Electrode furnace Graphitized electrodes
Unctuous graphite Carborundum Improved carborundum fur-
nace Silundum Siloxicon Calcium carbide Ingot furnaces
Willson Improved WillsonBullier Horry Bradley Tapping furnaces Helfenstein Resistance furnaces Production of cal-
cium carbide Uses.
Salgues Stansfield Snyder Energy needed for zinc smelting
Zinc smelting at McGill Production of liquid zinc Recent zinc
processes and furnaces Cdte-Pierron Imbert Johnson Thierry
Louvrier-Louis Electric smelting of other metals Copper Nickel Tin Lead.
CHAPTER XIII
MISCELLANEOUS USES OF THE ELECTRIC FURNACE 346-365 Nitric acid and nitrates Processes and furnaces of Birkeland and
Eyde Pauling Schonherr Calcium cyanamide Fused quartz Glass Alundum Phosphorus Carbon bisulphide Monox.
CHAPTER XIV
processes Acker caustic soda process Sodium processes, Castner
A shcroft Carrier Virginia Company Potassium Magnesium Tucker furnace Muthmann crucible Barium Strontium
Zinc Swinburne and Ashcroft chlorine smelting process Alumin-
ium Electrolytic refining.
powers Achievements of the electric furnace Probable future
uses of electric furnace Other sources of electrical power.
INDEX 397
The rapid growth of the electric furnace makes it increasingly
difficult for the metallurgist to keep in touch with its recent devel-
opments. A few years ago it was a scientific curiosity; now it
threatens to rival the Bessemer converter, the open-hearth steel
furnace, and even the blast furnace itself.
The halo of romance, that has always surrounded electricity in
all its forms, has caused the wildest schemes to be originated, and
has given them a hearing; while, on the other hand, practicable
electric smelting processes have been considered visionary.
In this book, it has been the author's purpose to trace the evolu-
tion of the electric furnace from its simplest beginnings, and to set
forth, as briefly as is consistent with clearness, the more important facts relating to its theory and practice.
The scope and arrangement of the book can be gathered from the
titles of its fifteen chapters. The first is historical; four deal with
the classification, efficiency, construction and operation of electric
furnaces; nine chapters treat of the various uses of the electric fur-
nace, and the last is an attempt to look into the future of the electric
furnace.
Xlll
CHAPTER I
The electric furnace is of comparatively recent origin. The
first of any practical importance, was constructed by Sir W. Siemens
in 1878,* and in i882 2 he melted in an electric furnace some 20 Ib.
of steel and 8 Ib. of platinum. Since that time the development has
been rapid.
The beginning of the electric furnace may, however, be traced
much farther back than this. In 1800 only a few months after
Volta's discovery of the electric battery 'Sir Humphry Davy,
FIG. i. The electric arc.
experimenting with the new battery, produced the first arc light
between carbon points, 3 and, as the electric arc is the source of
heat in an important class of electric furnaces, its discovery was
the first step in their evolution.
1 Siemens' Electric Furnace, Journ. Soc. of Telegraph Engineers, June, 1880.
2 Siemens and Hunlington, British Assoc. for the Adv. of Science, 1882, p. 496. 3 Davy, S. P. Thompson's Electricity and Magnetism, Phil. Trans. Roy. Soc.,
vol. xcvii (1809), p. 71, and vol. cxi (1821), p. 427.
1
FURNACE
The electric arc, as shown in Fig. i, may be produced by passing
an electric current through two carbon rods which touch each other
and then drawing them apart. The arc consists of a flame of va-
porized carbon, extending from one carbon pole to the other. When an electric current meets with resistance, it is transformed into
heat, and, as the carbonaceous vapor offers a considerable resistance
to the electric current, a very high temperature is produced; high
enough to melt or vaporize any known substance.
In the direct-current arc the positive carbon, which is marked
+ in the figure, is hollowed out by the current, and becomes intensely
white hot, presenting the dazzling bright light with which all are
acquainted. The arc light is, in fact, a miniature electric furnace
of the arc type; and produces a temperature not much inferior
to that in any modern electric furnace. It has been supposed that
the hollowing out of the positive carbon is due to an electrolytic
conveyance of carbon from the positive to the negative electrode;
but recent experiments show that any electrical transfer of carbon
is in the other direction, being a stream of electrons from the nega-
tive electrode, like the kathode discharge in a vacuum tube. The bombardment of the positive carbon by this stream of electrons,
generates so much heat that the electrode becomes white hot and
rapidly evaporates, thus producing the characteristic crater-like
form.
This explanation appears to fit in well with the appearance of
an arc that has been drawn out to a little more than its normal
length. The arc (which should only be observed through a dark-
colored glass screen) will be noticed to stream freely from the tip
of the negative electrode, and its starting-point on this electrode
is unaffected by drafts or magnetic influences. The current passes
with difficulty on to the positive electrode, and does not always select the point nearest to the negative electrode, but is blown
about and wanders over a considerable area of the electrode. The
temperature of the hottest part of the positive carbon in the electric
arc has been measured, and is considered to be about 3,600 C.
(6,500 F.), which is twice the temperature of melting platinum or
melting quartz, and more than twice the temperature of the open- hearth steel furnace. 1
In the use of a direct-current arc for lighting, it is usual to make
1 For additional information about electric arcs see W. S. Weedon, "A Contri-
bution to the Study of the Electric Arc," Trans. Am. Electrochem. Soc., v, 1904,
p. 171.
HISTORY OF THE ELECTRIC FURNACE 3
the upper carbon the positive electrode, in order to throw the great-
est illumination downward. In Fig. i this arrangement has been
reversed, and in this position the positive carbon serves as a minia-
ture cup in which any substance can be placed in order to study
its behavior at these high temperatures.
The writer has placed a small cylinder of refractory material
around the lower carbon of such an arc, and, with this simple
apparatus, was able to repeat some of Moissan's well-known experi-
ments on the production of the diamond.
In another form of electric furnace, the heat is produced by the passage of the electric current through a solid or liquid conduc-
tor. This method of producing electrical heat is typified in the
common incandescent lamp. The earliest use of this method
of heating was in 1815, when W. H. Pepys 1 solved an important
question in regard to the nature of steel by means of a miniature
resistance furnace operated by a battery. He placed some diamond
dust (a pure form of carbon) in a cut in a piece of wrought-iron wire,
and passed an electric current through the wire, thus heating it
to redness. The iron - absorbed the diamond dust and became
converted into steel.
Robert Hare2 described in 1839 an electric furnace which he had
constructed under the bell jar of an air pump. The furnace was
operated in a vacuum by means of an electric battery, and in spite
of the very small amount of power available, Hare succeeded
in forming calcium carbide and graphite, and in isolating phosphorus
and calcium.
Although the principle of electric heating had thus been discovered
early in the century, very little progress was made with the practical
application of this source of heat until the discovery of the dynamo.
Among those who attempted to utilize electrical heat in small
furnaces, with the aid only of powerful electric batteries, may be
mentioned Napier, who, in 1845, produced a small arc in a plum-
bago crucible, intending to reduce certain metals from their ores;
Despretz, 3 who, in 1849, made a small tube of charcoal, about an
inch long, and heated it by passing through it an electric current
1 Phil. Trans. Roy. Soc., 1815, vol. cv, p. 371. 2 Robert Hare's Electric Furnace. C. A. Doremus, Trans. Am. Electrochem.
Soc., xiii, 1908, p. 347. 3 Despretz, Comptes Rendus de 1'Acad. des Sciences, vol. xxviii, p. 755, and
vol. xxix, pp. 48, 545, 712 (1849).
F. A. J. FitzGerald, Electrochem. and Met. Ind., iii, 1905, p. 215.
THE ELECTRIC FURNACE
from a battery of 600 Bunsen cells; and Pichou, 1 who described,
in 1853, a furnace, heated by a series of electric arcs. The furnace,
which was probably never constructed, was intended for the reduc-
tion of metallic ores. Joule and Thomson also attempted to util-
ize the high temperature of the electric arc.
Until the invention of the dynamo, in 1867, experiments requiring
any considerable amount of electrical power could only be conducted
at great trouble and expense by means of electric batteries. Sir
W. Siemens, with the aid of the dynamo, began, in 1878, to experi-
FIG. 2. Siemens' vertical arc furnace.
ment on the electric furnace, which he used mainly for melting metals.
The form of furnace usually associated with his name2 is shown
in Fig. 2, and consists of a crucible A of graphite or similar refrac-
tory material, and of two rods, B and C, for leading in the current.
The lower rod was made of metal, and fitted into the base of the
crucible, while the upper was of carbon, or a water-cooled metal
tube, and was actuated by an automatic regulating device to main-
tain the arc of a constant length. The metal to be melted was
placed in the crucible, making electrical contact with the lower
1 Mentioned by Andreoli, Industries, 1893, see Borchers' Electric Smelting. 2 W. Siemens' English patent, 2,110, 1879, see Borchers' Electric Smelting.
HISTORY OF THE ELECTRIC FURNACE 5
pole C; then the rod B was lowered until an arc was started between
this rod and the metal in the crucible. In the illustration the metal
is shown melted, at D, as it would be at the end of the operation.
The positive pole is always hotter than the negative pole, and
for this reason the metal to be melted is made the positive pole of
the arc. A lid, F, was provided with a hole for observing the opera-
tion, or making additions to the charge, and a protecting covering
G, was arranged to reduce as far as possible the radiation of heat
from the crucible.
FIG. 3. Siemens' horizontal arc furnace.
In this furnace he was not only able to melt several pounds of steel
and platinum, but even to vaporize copper which had been packed with carbon in the crucible. 1
Siemens also invented a furnace having horizontal electrodes, as
shown in Fig. 3. 2 In this furnace the arc passes between the two
electrodes B and C, and heats, by radiation, the material contained
in the crucible. In both furnaces he provided water-cooled copper electrodes for the negative pole of the arc, to avoid the wasting that
takes place when carbon electrodes are used. In Fig. 3, the negative
electrode, C, consists of .a copper tube, closed at one end, and cooled
by water, which is introduced by a smaller pipe inside it. The posi-
tive electrode, B, is a hollow carbon rod, and through it a neutral or
reducing gas, can be introduced into the furnace.
In 1883, Faure patented an electric furnace of the resistance type, the heat being generated by the passage of the current through
1 Siemens and Huntington, British Assoc. for the Adv. of Science, 1882, pp.
496-98. 2 W. Siemens' English patent, 4,208, 1878, see Borchers' Electric Smelting.
6 THE ELECTRIC FURNACE
solid conducting rods imbedded in the hearth of the furnace, on the
same principle as the electric cooking stove.
The resistance type of electric furnace was made a commercial
success by the brothers, E. H. and A. H. Cowles, whose inventions
were described in I885- 1 Their furnace was heated by passing an
electric current through coarsely powdered charcoal or gas carbon.
This new method was used for a variety of purposes, one of these
being the production of aluminium alloys by heating a mixture of
alumina and carbon with copper or some other alloying metal.
Fig. 4 represents the Cowles furnace for aluminium alloys. It
consists of a rectangular brick chamber fitted with inclined carbon
electrodes, A and B, and filled with the mixture of alumina, carbon
FIG. 4. Cowles' furnace for aluminium alloys.
and copper. The electric current flows between the electrodes
through some pieces of retort carbon, C, and thus heats the charge,
which, when heated, carries part of the current. The gases resulting
from the chemical reaction escape and burn at D, and the molten
alloy collects at the bottom of the…