From the 1924 book, A Popular History of American Invention.
NEXT in importance to the air we breathe and the water we drink, comes iron, most indispensable of metals. Nothing can take the place of iron. Luckily, it is the most abundant and cheapest of the heavy metals, as well as the strongest and most magnetic of known substances. Iron and steel are the very foundation of the greatness of the United States of America, and the history of our country’s development to commercial ascendancy is linked with the history of these two metals. More iron and steel is produced and used by the United States than by any other country of the world.
There is a story that Sir Walter Raleigh, the great English explorer, brought the news of huge iron deposits in Virginia to England about the year 1685. True or not, certain it is that rich deposits of iron ore lay in the Alleghenies, and that iron mining was begun in Virginia about the year 1608, the first, by the way, in the New World. A quantity of it was shipped to England by the Virginia Company. Virginia colonists, iron-makers to the number of 150 from Warwickshire, Staffordshire, and Sussex, in England, established a colony and tried to smelt iron near Jamestown, on Falling Creek, a tributary of the James River, in 1619. Lack of money retarded their efforts, and in 1622 they were massacred to a man by the Indians. Twenty-five years later, the Massachusetts colonists tried smelting iron and were more successful.
In fact, iron ore was discovered in every one of the thirteen colonies by the middle of the eighteenth century, and iron furnaces were blazing in all directions. America even supplied a little iron to England. In those days, the metal was smelted with charcoal, which gave to the colonies an early advantage over the mother country because of their unlimited timber. In England, many people considered iron smelting almost a curse, since the demand for charcoal was rapidly destroying her forests.
|United States iron works, 1620 to 1675.|
After a hundred years of iron-making in the colonies, Parliament, in 1750, passed a law forbidding them to build any mill for rolling and splitting iron, or any furnace for making steel. This confined the colonists to pig and bar iron. They could not lawfully cast anchors and kettles, or make horseshoes, hammers, crowbars, and iron parts for farming tools, wagons, ships, and the like. Articles of steel, such as knives and scissors, and implements of rolled sheet-iron must all be imported from England. This was a costly proceeding; the colonists could have made them more cheaply themselves.
EARLY USES FOR IRON
For centuries man had used charcoal to make iron, as do savages in many parts of the world even now. But charcoal was expensive. Only two or three hundred pounds of iron could be made at a time, and the crude forges failed to melt the substance so that it might be poured to make castings.
It is supposed that man first learned to smelt iron with charcoal when he built a big fire upon red soil. The red soil contained iron, and the fire, fanned by a strong wind, burned fiercely, melting out little drops of a dark-colored metal, which were found to be extremely useful for the making of spearheads and hatchets. The dark metal was iron, and an iron spear-point or hatchet, hammered into shape, was more useful than one of stone.
Exactly when this early discovery was made is not known. The possibly oldest piece of iron known was found under the great Egyptian pyramid of Gizeh, and is at least 6,000 years old. Most of the primitive weapons that have come down to us are made either of copper or bronze. Although it is generally thought that copper and bronze were used before iron, authorities are by no means agreed on the point. Most of them are inclined to the belief that the use of iron was discovered later. This would follow from the fact that iron is much more difficult to melt than copper, and it is reasonable to assume that man first used the more easily meltable metal.
Bronze, being an alloy of copper and tin, it might be argued that its production is evidence of considerable technical ability. It must not be forgotten that copper is often found mixed with other metals, among them tin. It is probable that bronze implements found in very ancient ruins were made from some natural alloy of copper and tin. On the whole a metallurgist would be inclined to argue that copper and natural mixtures of copper and tin were used before iron. The early Egyptians, Assyrians, Chaldeans, Babylonians, and Hebrews most probably made iron, and ruins of large iron works have been found on the Sinai Peninsula, in Egypt. During the heyday of Rome, the ancient Britons and Scandinavians also practiced iron-making.
For centuries, iron was expensive because it could be made only in small quantities. Furnaces were little more than charcoal fires heaped up on hard stone. One kind of primitive furnace is still used in remote parts, even in our own South. It is called the “Catalan” furnace, because it was used in Catalonia, Spain. The Catalan furnace, similar to a country blacksmith’s forge, had a wall of stone or burnt clay in which a charcoal fire was built, more charcoal piled in gradually, and pieces of iron ore smelted.
A blast of air was blown into the burning mass with the aid of a bellows, and when the furnace cooled, a few pounds of iron would be found at the bottom. The heat secured in this way was not enough actually to melt iron, but the lump of metal could be heated again and hammered out until it became of fine quality. Some few improvements were made in furnaces, but present-day engineers have calculated that if modern smelting were conducted by the methods of the Romans, iron would cost about $1,000 a ton.
The Germans, in the Middle Ages, greatly improved iron-making. They raised the walls of the Catalan furnace, which had been about three or four feet high, and made it a chimney of ten to fifteen feet. That gave greater heat, and when the chimney was built still higher, iron was easily melted. The Belgians improved it a little more, and with a large bellows, worked by a water-wheel, to blow in greater quantities of air, they made the first blast furnace. The French imitated them, and, as already told, the English were soon making such a quantity of iron in their blast furnaces that, even before the death of Elizabeth, her forests were being razed to supply charcoal.
In 1619 an Englishman, named Dud Dudley (1599-1684), was the first man to melt iron in a blast furnace with charred coal (coke) instead of charcoal (charred wood.) His efforts were not commercially successful, and charcoal burners destroyed his furnace. But it was the beginning of the use of coke, which fuel is now indispensable in the making of steel and iron. Dud Dudley was the earliest of many British inventors who discovered better ways of making iron and steel, and his idea was made more practical by Abraham Darby, another Englishman, about 1713, nearly a century later.
|THE GERMAN STUCKOFEN. The German Stuckofen was an improvement on the Catalan furnace. To obtain greater heat the walls of the Catalan, which had been three or four feet high, were raised to form a chimney ten to fifteen feet in height. From Spring’s “Non-Technical Chats on Iron and Steel.” Courtesy of Frederick A. Stokes Company.|
HENRY CORT INVENTS THE “PUDDLING” FURNACE
Then came Henry Cort (1740—1800), who devised the “puddling” furnace and the rolling-mill. Cort built the first reverberatory furnace in 1784. This differed from the blast furnace. In the latter, charcoal and iron were mixed together. Cort’s furnace had two compartments; one contained the coal to be burned, the other the iron to be melted. Coal and iron should not be burned together, for coal contains sulphur, which makes iron and steel brittle.
Cort saw to it that the coal and iron were not in contact. A long flame passed from the coal burning on a grate, over a fire-wall, and melted the pig iron which was piled on a furnace bed or hearth. Upon stirring the melted mass it soon became stiff and pasty from loss of carbon, and was then taken out and hammered. This method of melting iron, known as “puddling,” is still in use.
Cort’s iron, made in this way, was cheap for those times, but after giving the world a better and speedier process for making wrought iron, he became impatient with the old slow method of hammering his iron into bars. The new process could supply iron much faster than it could be worked into bars, rods, and other shapes, ready for the blacksmith.
Cort went a step further and made the first iron rollers through which red-hot bars or balls of iron could be passed. For this he used two iron rolls, one underneath the other, in which were cut a series of grooves of different sizes. The rolls turned in opposite directions, like the rollers of a clothes-wringer. When a piece of red-hot iron was inserted in the largest groove, it was drawn in, squeezed down to the exact size of the groove, and thus shaped into a bar. Put through the next smaller groove, and so on, it was ultimately reduced to the thickness and width desired. Of course, as it was passed through the rolls, it grew longer and thinner.
Rolling improved the quality of iron in about the same way that hammering improved the crude iron melted in the Catalan furnace. Cort did not originate the idea of a rolling-mill, but he was the first to build one successfully. It was an extremely important invention, much the more important of the new methods Cort gave the iron industry, and rolling-mills of the same kind, though greatly improved, are now used the world over.
Iron made by Cort’s process was so good that the English navy soon required it in place of imported Swedish and Russian iron. Given large contracts, Cort and his partner decided to enlarge their ironworks. To do this, they borrowed money from a former government official, assigning Cort’s patent rights as security for the money advanced. It was found later that the official who loaned them the money had embezzled it from funds entrusted to him by the government for the payment of sailors’ wages. The direct result of this was a cruel blow to Cort.
Although his patents were earning enough to repay every cent that had been stolen, the government refused to listen to his pleas to allow him to make good the loss. Both the ironworks and his patent rights were seized without an effort to collect the royalties due him from those who were using his processes. As Cort had spent a great amount of money in experimental work, he and his family of twelve children were soon destitute. The government later granted him a small pension, but he died soon afterward, broken in health and spirit, in comparative poverty. In 1811, forty-one British iron-making firms raised a sum of money for his widow and children.
Thanks to Dudley and Cort, iron, once made by the pound, could now be made by the ton. During the next century inventors were to produce iron cheaply and in such quantity that it could be used by millions of tons. It was also to be as cheaply turned into steel, and iron and steel industries began to spring up in places that once had been wildernesses. To understand what these different inventors did, a little knowledge of the chemistry of iron and steel will be helpful.
CHEMISTRY AIDS STEEL-MAKING
Early iron-makers found that charcoal had a mysterious property that enabled it miraculously to change red stone or iron ore into iron. But they knew nothing about chemistry, and not until chemistry became a science was it possible to make iron and steel in almost unlimited quantities, and build with it railroads, bridges, skyscrapers, and all the machinery of modern life.
Iron is a metal, a chemical element, not quite so soft as copper, but when pure rather easily worked. It is the basis of all the irons and steels; for while we ordinarily speak merely “iron” or “steel” there are, in reality, many irons and steels, Just as there are many woods.
Now, there are two other chemical elements that iron particularly likes. One is oxygen, a gas contained in the air we breathe; the other is carbon, which we know best as charcoal, coal, coke, and the graphite in pencils. Iron and oxygen seize every opportunity to get at each other, for the liking is mutual. Unless the iron is constantly protected, the result is an iron-oxygen marriage, known as iron oxide, or rust. This union occurs under our very eyes, for all about us we see iron and steel rusting, and rusting particularly fast if the air is moist.
But, whatever has been done can usually be undone by some means or other. Iron and oxygen, after they are married, may be divorced. The divorce is effected by heat with the aid of the element carbon. It appears that carbon likes oxygen even better than iron does, so that when the iron-oxide combination (rust or iron ore) is mixed with carbon, and the mass heated, the carbon steals away the oxygen from the iron, and iron alone is left. It is this form of iron, somewhat modified, that we use in building machines and tall buildings and bridges. So that, when we make iron out of iron ore, we merely take vast quantities of rust from the earth and remove the oxygen. The process carried out is the second of iron’s two stages:
1. Iron rusts in oxygen to iron oxide, a red, yellow, or black powder. Iron ore is iron oxide, a form of rust.
2. Iron oxide or ore heated with charcoal or coke (carbon) gives up its oxygen and sets the iron in the ore free again.
It is, then, by the latter process that we get all our iron in the first place, for iron, as such, is not found free in nature, but in a state of rust. Man has had to “free” all the iron which we now have. The iron-ore rust comes from our mines, mostly by lake boats to Chicago, Gary, or Lake Erie ports, and from some of the latter to Pittsburgh, Youngstown, and so forth. It is put into big blast furnaces with coke, which burns and takes away the oxygen, whereupon the freed molten iron trickles to the bottom of the furnace and is drawn off—” tapped” as the iron-makers call it.
The other half of the chemical story is just as simple. Iron also likes carbon. But unless it is heated red hot, or hotter, or is in a molten condition, it has no appetite at all for the carbon. Iron is a comparatively slow “feeder,” but when molten it devours carbon with the voracity of a dragon.
Both “cast iron” and “pig iron” are iron which has wolfed a full meal of carbon, or the maximum. This is about four per cent—four pounds of carbon per hundred pounds of iron. Because of this carbon, cast iron and pig iron, after having cooled, melt more easily when heated again than does iron with less carbon, or iron with no carbon at all. So fluid do they become when molten that they will run into moulds like water. Such forms of iron are very brittle when cold, however. It is easy to break cast iron with a hammer.
Iron which has absorbed less than two percent of its own weight of carbon, when molten, does not “cast” into moulds so well, because it is less fluid. On the other hand, it does not become quite so brittle when cold; indeed, if it contains only a little carbon, the metal is very pliable. For this reason, it is the kind which is made into wire or other products which must bend easily if desired.
Such low-carbon, pliable irons are called “mild” steels. The high-carbon irons, i.e., those with from three-quarters to one and one-half per cent of carbon, are the harder steels from which most of our tools are made. Those with over two percent of carbon are not called steels, being altogether too brittle either to bend or forge. For the most part, iron without any carbon at all is called “wrought iron,” which we will describe later.
The following sketch of the iron and steel family tree shows very plainly the various combinations of iron and carbon.
|THE IRON AND STEEL FAMILY-TREE. Steels have generally less than 2 percent carbon. Cast irons have up to 5 percent carbon.|
The difference between pig iron and cast iron is this: Pig iron is the iron-carbon alloy, a combination, as it first comes from the blast or smelting furnace. Up to a few years ago the molten metal was run into long, narrow troughs of sand, which covered the floor of the furnace house. Here it was allowed to solidify and cool. The blocks of iron, called “pigs,” were then broken from the longer blocks, called “sows.”
To save heat, much of the molten iron as it comes from the furnace is now taken directly to the steel works as “hot metal” and used without being allowed to solidify. It does not get solid until after it has been converted, or made, into steel by the removal of most of its carbon.
Cast iron, on the other hand, is usually only a re-melt of pigs of iron, in a particular kind of furnace. While a few castings are made from iron taken directly from the blast furnace, practically all of our cast-iron articles are made from re-melted and blended iron, which, because of the re-melting, has a little less carbon, and is therefore a stronger, more uniform and refined metal.
This process of absorbing or taking up carbon can be reversed, so that the carbon, which was taken up by the iron in its change into pig iron, can also be taken away from it. As we have seen, carbon and oxygen have a great liking for each other; therefore oxygen can be made to take away the carbon which the iron has absorbed. We now have two more very important facts:
3. Iron heated to a red or white heat in powdered charcoal (carbon) for a considerable time, or melted iron plus carbon, gives what is called “mild” steel, harder steel, or cast iron, depending on how much carbon is taken up by the iron.
4. This iron-carbon combination can be broken up by heating with oxygen to steal the carbon away from the iron.
We now know more about the chemistry of iron, and about the reasons why there are different irons and steels, than was known up to the year 1855. In that year, Henry Bessemer made a great discovery, of which we shall have much to say later.
Although the alchemists of the Middle Ages had searched for the “Philosopher’s Stone” that would, so they thought, turn everything it touched into gold, real progress was not made in chemistry. Consequently the making of iron and steel was a crude performance until the few simple facts which have been explained became known. While the world at that time was several thousand years along in its knowledge of iron, in reality it had not yet begun to understand its most useful metal.
For many centuries men made small balls of soft iron in the Catalan kind of furnace. Only the chemical reaction No. 2 was possible, for their fires were never very big or hot, and their iron was fed little charcoal. All they got were little balls of soft iron without carbon.
In time they progressed to reheating their swords, hammered from such iron, in powdered charcoal. In some places they seem to have made little pots of clay into which they put small pieces of iron, together with a few leaves or pieces of wood—carbon. In this manner, they made a steel which could be hardened, like our modern tool steels, by heating it red hot and plunging it in water to cool it suddenly. This gave them their keen, hard-edge swords and other implements of war.
In time, another and strange iron product arrived. Some unknown genius had used a large furnace, something like the German Stuckofen. In this, with more intimate mixing of charcoal and ore, and higher heat, the iron absorbed a great deal more carbon; instead of being the usual stiff, pasty mass while hot, it melted and became so liquid that it could run like water. The iron thus made could be melted at a much lower temperature than any other sort of iron then known, and was first made about the middle of the fifteenth century.
It had always been free-running when molten, but so brittle when cold that it could not be hammered into swords. It was that important product, “pig iron.” In 1918, the United States alone made about 40,000,000 tons of pig iron; probably more, in that one year, than the whole world had produced in all of the hundreds of thousands of years before 1800.
Since pig iron was a material readily produced in the larger furnaces, and since it could be melted easily for reworking, it came to be used as a sort of raw material or starting point from which all the other iron products were made.
Wrought iron was discovered by melting such pig iron in a charcoal fire, stirring and blowing air over it. Shortly after melting, the mass would become pasty and less fluid, even when white-hot. It was taken out as a white-hot pasty ball and hammered into bars. This was good wrought iron, similar to the celebrated Swedish or Norway iron of to-day, but it could be made only in small quantities, until Henry Cort invented the “puddling” process.
HOW CRUCIBLE STEEL IS MADE
Even as late as the year 1800, the world probably knew only the hard steels of which swords and tools were made. Up to the eighteenth century, the finest steel used in England came from India, at an estimated cost of $50,000 a ton! Such steel is still made in India, in native furnaces.
About one pound of metal is placed in a small clay crucible with finely chopped wood. The crucible is covered with leaves and damp clay, dried in the sun, and heated in a small furnace. The melted steel is found in the bottom of the clay pot.
In Europe, steel was produced slowly and tediously by packing pieces of carbonless iron, that is, wrought iron, with powdered charcoal in stone boxes, and keeping the boxes red hot in furnaces for upward of six weeks. When the bars were cold they were broken and sorted according to the hardness of the pieces, the hardness varying with the amount of carbon that had penetrated. This irregular steel, for such it was, was reheated, forged and hammered into swords, knives, etc., or made more uniform by melting it in a crucible. Such steel is called “crucible” steel, because it is melted in clay or graphite pots, called crucibles.
Before crucible steel came to be generally known, manufacturers guarded their methods with the utmost secrecy. One, a successful steel-maker named Benjamin Huntsman (1704-1776), of Sheffield, England, permitted nobody to enter his forge which, about 1740, he had erected in a forest. Huntsman, a skilful clockmaker, found the steel used in watch-springs of such poor quality that he experimented in the hope of finding a better steel. Succeeding, he kept his method to himself.
His competitors tried in every way to imitate his steel, and eventually they employed the services of a spy. During a severe storm the spy pretended he was lost in the forest and begged the shelter of Huntsman’s workshop. Moved by his wretched plight, the inventor unlocked his door and asked him in. Entering, the spy beheld a very simple apparatus: merely the melting of broken pieces of carbonized iron in a pot or crucible, a process which made steel more uniform. The secret was out! Since then most of our finest tool steels have been, and still are, produced in crucibles.
|PULLING A POT IN A CRUCIBLE STEEL PLANT. The crucible is a small pot formerly made of clay but now usually of graphite. This pot is filled with small pieces of steel and put in a furnace where it is entirely surrounded by coke or coal.|
The Crimean War of 1854-1856 made English army generals wish they had larger and better cannon. A young man named Henry Bessemer (1813-1898), determined to make them. He had invented a process for stamping deeds, records, and other important documents, and this the English Government found so good that it appropriated it for its own use without paying him a farthing, even though he protested.
Bessemer, the son of an inventor and owner of a print-type-foundry, had a considerable knowledge of metals. Through this knowledge he was able to invent an improved and marketable method of making bronze powder for gold paint. He kept the details of his discovery secret, and faring better than he had with his stamping invention, his bronze powder factory soon brought him in a steady profit.
Bessemer then set about studying the science of cannon and projectiles. He first devised a projectile which was not round, like the usual cannon-ball of his time, but long and pointed. He also caused it to spin as it left the gun. Instead of rifling the barrel of the cannon, as we now do, Bessemer put a rifling on the projectile. In either case, rifling makes the projectile spin so that it flies through the air without tumbling over and over, as does a stone.
But he soon found that little real progress could be made unless he could get a stronger metal for the gun-barrel, because heavier projectiles required much heavier and stronger guns to discharge them. It was first necessary to discover a method of producing iron in larger quantities.
Bessemer was a hard worker who never asked favors. Nevertheless, he was not bashful whenever opportunity came for making himself known, and the acquaintanceship his clever inventions had enabled him to make he later turned to good account.
Among others, Napoleon III was impressed by the young man. He introduced Bessemer to his army officers in charge of the manufacture of artillery, and directed that they assist and encourage him whenever possible. The young inventor soon produced a better cast iron; but while this helped, the metal problem was still unsolved.
Bessemer was not easily discouraged, however, and using the money which came from his bronze powder business, he devised, then experimented with a “hotter” furnace for the making of wrought iron. By blowing extra air into the flame he obtained more heat.
|Bessemer mortar and shell.|
HENRY BESSEMER’S GREAT DISCOVERY
One day, in the year 1856, he noticed that a pig of iron lying on the edge of the molten pool of metal in the furnace—the “bath” as it is called—did not melt as expected. He tried to push it in with a bar, but found that it was a mere shell of decarbonized iron; that is, iron with its carbon burned out, the inside metal having melted and drained away. Most people would pay slight attention to such a curious happening. Not so with Bessemer. It was a mystery he must solve.
“Why does the inner metal of the pig melt more easily than the outer?” he reasoned. “How can this be? I know that pig iron melts easily, while the wrought iron with little or no carbon does not. But this was not wrought iron. It was pig iron, and must have contained high carbon when I started. Yes, the inner portion melted as it should. If that happened because of lack of carbon in the outer part of the pig, when and where was the carbon in it lost? I must look into this!”
The more Bessemer thought about it, the more convinced he became that the outer part did not melt because it contained less carbon, and that the air and flame in his furnace must have burned some or all of the carbon from the outside of the pig. If carbon could be removed in that way it was surely possible that it could be done on a larger scale, and wrought iron made in vast quantities by blowing air into melted pig iron.
Bessemer could scarcely rest until he had fixed a crucible in a fire and tried blowing air into the bottom of the molten pig iron through a pipe made of clay. To his delight the iron was not made colder, and the carbon seemed to burn. The iron with which he had started to experiment could not be forged because it was too brittle. But now he found he had a material that was malleable! It could be easily shaped by hammering!
The iron in the crucible did not “freeze” when he blew air into it. This was fine. Now for the next step. Could it be possible that no outside heat at all was necessary, that is no fire around the crucible while he was blowing air into the inside metal? Bessemer hastened to find out.
He built a big steel pot, lined it with firebricks and clay, and left six openings near the bottom through which air could be blown up and into the molten metal. At last all was ready, and he started the air-blowing engine. The air bubbled very fast through the metal, a few sparks flew out from the top of the vessel. A little later a flame appeared. Bessemer was almost prostrated with joy! All that was needed to make iron into molten steel was a steady application of oxygen, the cheapest fuel in the world! Infinite quantities of it for nothing!
|BESSEMER CONVERTER BLOWING OFF. Bessemer steel is made by blowing air through molten un-malleable cast iron in a pear-shaped “converter.” First comes a brilliant shower of sparks, which finally subsides. When the metal is drawn off it is steel.|
Suddenly, the molten metal began to dance and jump about as though alive, and drop after drop spurted out and fell with a splash upon the roof. This was exceedingly dangerous, for molten steel is white-hot. Bessemer feared that he would set fire to his own and the neighboring buildings. Fortunately he did not stop his air-blowing engine.
Soon the dangerous splashing was over, and the forced air bubbled quietly through the molten metal in the crucible. Upon removing the clay plug from the tap hole in the bottom, out flowed steel! It was a metal which, when cold, could be flattened under the hammer without cracking. Bessemer, in happy excitement, hacked with an axe the corner of a square block of it. Without doubt, it was a soft, malleable metal.
Here was an epoch-making discovery. Not only had he found a process by which he could make a malleable metal from un-malleable molten cast iron, but he could do it without the use of any further fuel whatsoever; something never dreamed of before.
The metal contained its own fuel: twenty-five pounds of silicon, fifteen pounds of manganese, and seventy pounds of carbon, a total of over one hundred pounds of fuel in every ton. These substances burned as fiercely as the wood and coal in our stoves, and being so intimately mixed, when air was blown upon or through the molten metal, their burning made the metal extremely hot. The steel, when finished, was at least 600 or 800 degrees Fahrenheit higher in temperature than the molten cast iron with which he started.
Satisfying himself by repeated trials that his results were similar, he called in an engineer acquaintance, George Rennie, in order to get his opinion on the matter. Bessemer had now become so enthusiastic about it and saw in it such great possibilities that he was afraid he might have made some miscalculation. A discovery of this momentous nature would, he realized, revolutionize the whole iron and steel industry.
After listening to his explanation and witnessing the making of steel in Bessemer’s furnace, Rennie exclaimed: “This is such an important discovery that you ought not to keep the secret another day. I am president of the Mechanical Section of the British Association, which meets next week. Why not present a paper describing your process at that meeting?”
Bessemer had never written a paper for an engineering society, and he suggested that his report might not be worth a hearing. Rennie replied: “Do not fear that. If you will only put on your paper just as clear and simple an account of your process as you have given to me, you will have nothing to fear. Though all the papers are now arranged for, your process is so important that I will take upon myself the responsibility of putting yours first on the list.”
|Early Henry Bessemer converter and ladle.|
With considerable misgiving, Bessemer wrote a simple account of his process, and in a few days he left London for Cheltenham, where the meeting was to be held. On the following morning, while finishing his breakfast at the hotel, he was talking to Mr. Clay, a Liverpool iron manufacturer, when a well-known Welsh iron-maker, Mr. Budd, came up and sat down opposite. Knowing Clay, but not Bessemer, Budd said:
“Clay, I want you to come with me into one of the sections this morning, for we shall have some fun. You must come, Clay! Do you know, there is actually a fellow come down from London to read a paper on the manufacture of malleable iron without fuel? Ha, ha, ha!”
“Oh,” said Mr. Clay, “that is just where this gentleman and I are going.”
“Come along, then,” said Mr. Budd.
The three arose from the table and went to the meeting. Imagine Mr. Budd’s feelings when Bessemer appeared on the platform, to be greeted by the president and introduced as the inventor of the new and very important process of iron-making. Bessemer then read his paper and showed samples of his steel.
Those present listened attentively. The very first person to rise after the reading of the paper was James Nasmyth, the famous inventor of the steam-hammer, that marvelous machine which is so delicately adjusted that at the will of the operator the blow can be terrific or so light that the hammer will actually touch the crystal of a watch lying on the anvil without breaking it. Nasmyth held up in his fingers a small piece of the metal which Bessemer had exhibited, and said:
“Gentlemen, this is a true British nugget. A while ago I took out a patent for making malleable metal in a manner somewhat like this, but Mr. Bessemer’s method goes so far beyond mine that I shall go home from this meeting and tear up my patent.”
Budd was the next to rise. He said he had listened with deep interest to the important details of the invention, and if Mr. Bessemer desired an opportunity of commercially testing it, he would be most happy to afford him every possible facility. His ironworks were entirely at Mr. Bessemer’s disposal, and if he wished to avail himself of the offer it should not cost him a penny.
A number of firms wished to use the new process, and to many of them Bessemer sold rights for which he received a great deal of money. It had taken hard work and much experimenting merely to discover the process, and he realized that much more work and experimentation would be necessary before the manufacture of his steel reached the stage of commercial perfection.
Like the majority of inventors, Henry Bessemer was threatened with failure. Disappointment and trouble soon made their appearance. The firms that had begun making steel under his patents did not succeed at all. The metal they produced was brittle! This amazing contradiction caused such dissatisfaction, and such was the amount of criticism and ridicule hurled at his head for his apparent failure to make good his promises, that Bessemer actually bought back all the rights he had sold.
Lucky it was for England that the young inventor, whom she was later to honor with a knighthood, did not lose heart. Bessemer knew he was right; he had made and always could make a wonderful steel. Something was amiss with either the methods or the materials used by the manufacturers, and whatever it was could be remedied. He was satisfied with his process.
He employed chemists to make a careful analysis of all the materials used before and after they had been subjected to his process. Week after week ran by without any report or analysis helping him to discover the error, but instead of being disheartened, Bessemer kept up his investigations, convinced that his process was perfectly correct.
Finally, after about two years of hard work, costly experimenting, and repeated disappointment, he found out that cast iron which had only a small amount of phosphorus—and this happened to be the kind he had used in his London experiments—made good steel, while iron which contained more than this small amount did not make satisfactory steel. Now he knew what was wrong. His licensees had used high phosphorus iron—and failed.
|Henry Bessemer also invented ways to transfer pig iron to his converter.|
Supplying this valuable information, he offered his licenses to the manufacturers. But no one would buy. Once bitten, twice shy, was their attitude. Bessemer had to build a plant of his own and go into the steel-making business simply to prove that he was right. A considerable time passed before the iron-makers would try again, but eventually the process came to be used extensively, not only in England, but also in this country. Here was the very steel for the heavier guns for England’s army and navy, and it furnished the material for plates for her ships, and tools for her machines.
Bessemer was richly rewarded. The royalties he received from licensees were so large that at the expiration of his patent, in 1890, he and his partners had received a total of £1,000,000 sterling (about $5,000,000), a return in fourteen years of eighty-one times their invested capital, or practically their entire money back every two months.
Henry Bessemer was the father of the steel age. Without him there might be no transcontinental railroads, no skyscrapers, no great bridges, ocean liners, or Panama Canals. In the development of the industrial world as we know it to-day, he stands next to Watt, the inventor of the steam-engine.
It is not commonly known, but right here in America this same process was worked out independently by an iron-maker named William Kelly. In his plant near Eddyville, Kentucky, about 1846, he invented a process for making large sugar-boiling kettles for the Southern planters, and in seeking to make better and cheaper wrought iron for his kettles, he discovered the same process as Bessemer—that a steady blast of air alone would refine iron and convert it into steel.
lronmakers laughed at the idea, Kelly’s father-in-law threatened to withdraw money from his ironworks, and his customers, hearing that he had a “new-fangled way of refining iron,” insisted that they wanted iron in the regular way or not at all. Then the ore supplies near his ironworks gave out. Despite these difficulties, he worked on his process in secret, built a converter in 1851 at the Cambria Iron Works, in Johnstown, Pennsylvania, and hearing of Bessemer’s process, patented his converter in 1857. Some authorities give Kelly credit for being the first inventor in this field.
Meanwhile Alexander Lyman Holley, an American engineer, had obtained a license to make steel in this country under Bessemer’s patents. Kelly, practically ruined in the panic of 1857, had sold his patent to his father for a thousand dollars. His father died, willing the patent rights to his daughters, and they in turn transferred them to Kelly’s children. For while their brother was clever at inventions, they had a poor opinion of his business ability. This brought him to a standstill, so he accepted an offer to merge his interests with those of Holley.
ALEXANDER HOLLEY AND THE AMERICAN STEEL INDUSTRY
Holley became an important figure in American steel-making. Being a man of intelligence and great personal magnetism, he quickly won the confidence of inventors and steel-makers. Taking discoveries like those of Bessemer and Kelly, he applied them on a large scale, and persuaded others to adopt them. With him began what has been called the “American plan of steel-making,” which is to make steel on an enormous scale.
Less than twenty-five years after Bessemer’s invention, the converter, backed by Holley’s ability, enthusiasm, and his belief that America must be first, had enabled the United States to rival England in steel production. For fifteen years, Holley was the leading steel plant engineer in this country, designing nearly all of the big works then building in the United States.
And now began what may be termed a great industrial procession. Up to this time there were only a few short railroad lines in this country. Following the great gold rush to California, in 1849, and the building up of the West, during the next thirty years the transcontinental railway lines were built which opened the entire western territory to immigration and trade. The earlier short railroad lines were largely absorbed and used as feeders to bring freight to the “through” lines. With the rapid settling and growth of population of the Western States, the demand for iron, steel, and other goods increased by leaps and bounds.
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The first railroads did not have the sort of rails we have to-day. As told in the chapter, “From Stephenson to the Twentieth Century Limited,” the early rails were only strips of wood. These were soon followed by strips of wrought iron, and then wrought-iron rails. But while wrought iron was good enough for the first engines, which were small and of light weight, they were too soft for service under the heavier engines and the denser railroad traffic which developed.
It almost seems as if the Bessemer process of steel-making had been devised at the right moment to furnish a proper material for rails, so that this wonderful railroad expansion might not be hindered. Wrought iron would not do. Steel was highly satisfactory. Bessemer steel could be readily made in large quantities and of any hardness desired. The old wrought-iron rails were torn up, and in their place were laid rails of Bessemer steel.
Where did the iron ore come from? The States of New York and Pennsylvania had considerable iron ore, and this was first smelted with charcoal and, later, with anthracite coal, which was mined locally. There were also iron ore deposits in Virginia, Tennessee, and Alabama. But the greatest source of iron ore was discovered on September 19, 1844, by William A. Burt, United States deputy surveyor, who was working with his men near what is now Negaunee, Michigan.
They found that the needle of a compass was behaving curiously. Burt, the inventor of the instrument, became worried. He knew that his compass was not at fault, so he cast about to find out the cause of the disturbance. One of his party discovered a deposit of iron ore just underneath the sod. That explained everything. Burt apparently was concerned only in devising a means of preventing a like interruption in the future. He paid no attention to the ore except to note in his book that it had been found there. Neither he nor any of his party ever profited, or attempted to profit, by their discovery.
THE MESABA IRON ORES AND THEIR EXPLOITATION
A few years before the Civil War there were rumors of gold in this northern wilderness, and among others who sought it was a woodsman, Lewis H. Merritt, who moved from New York State to Duluth, Minnesota, with a wife and four sons. It was only “fool’s gold,” glittering iron pyrites, but Merritt found some red iron ore. A few years later, when his boys had become lumbermen, they remembered the iron and explored the wilderness to locate it. Three nephews of the same name joined them, and they became known as the “seven Merritt brothers,” and also as fools, if not tricksters. For they insisted that there was boundless wealth in iron on the Mesaba range, first discovered by Surveyor Burt, and they wanted to raise capital to build a railroad and bring it out.
“Absurd !“ said wise folks, and warned their neighbors against buying the Merritts’ railroad shares. When they located their first iron mine, in 1885, and got money to start their railroad by pinching and borrowing, the people of Duluth would not permit them to use their city as a terminal. But they made connections with a railroad entering Duluth, and hauled their first train load of ore in 1892. Just as they had prospects of a rich reward for their long years of work and faith, they were ruined by the panic of 1893, and their railroad and mines passed into other hands.
This district has turned out to be the greatest ore producer in the world. At first a little iron was smelted near-by, but it was soon found advisable to carry the ore to the coke and the market, which was in the East. The first shipments were carried from the mine by mule. Later a plank railroad was built, with rails of strap iron, and grades so steep that the loaded cars sometimes ran over and killed the mules which drew them. Marquette, Michigan, was the shipping port; from there the ore coming around by water through the Sault Sainte Marie Canal.
When Congress was debating the question of building the Sault Sainte Marie Canal, Henry Clay spoke against it, saying that spending money in that distant, uncertain place was like investing in the moon. As against the $1,000,000 yearly value of the fisheries given as a chief reason for the building of the canal, over $100,000,000 worth of ore now passes through the canal each year. Other commodities have long been of secondary importance.
The hard or lump ores of northern Michigan and the soft or “Mesaba” ores of Minnesota are now shipped from the Lake Superior ports in specially built ore-carrying steamers. So rapidly did this enormous trade develop that, over a number of years, the tonnage of these boats was continually found to be inadequate. Ore-carrying steamers had to be either scrapped or sold, and new and larger ones built with greater carrying capacity. The locks of the Sault Sainte Marie Canal had to be built and rebuilt four different times, to pass larger and larger ore steamers.
|HOW ORE IS MINED BY STEAM-SHOVELS IN THE MESABA DISTRICT OF LAKE SUPERIOR.|
To get into the iron-ore mines in northern Michigan, the miners go down an elevator into a deep shaft. Here the ore is found in hard form, like rock. The miners drill holes into it, fill the holes with dynamite, and then scurry away so that flying particles of the ore, broken down by the explosion, shall not hit them. In Minnesota, where even larger deposits of iron ore exist, big steam-shovels are at work, shoveling off the shallow top soil to get at the ore; others are on terraces, shoveling the soft, red dirt (ore) into railroad cars. The filling of freight-cars by these remarkably efficient steam-shovels requires very little time.
Soon the train load of ore is hurrying to Two Harbors, Minnesota, or other ports. Here the bottoms of the “hopper” cars are dropped and the ore falls through the elevated tracks of a high trestle into large hoppers or ore bins underneath, which are themselves, built high up above the surface of the lake.
The hopper car is an American railroad device, developed for quickly dumping coal, gravel, and other bulky stuff by opening trap-doors in its bottom. At first it was made of wood, but about 1897 improved hopper cars were made of steel and used for hauling ore from the mine to the ship, and from the ship to the steel mill.
A later American invention, that of George H. Hulett, first built at Ashtabula, Ohio, in 1893, was the car-dumper, a device which picks up a whole car of ore or coal, tilts it, and dumps thirty, fifty, and sometimes a hundred or more tons as easily as though it were a pound box of candy.
Mammoth ore-carrying boats anchor alongside the huge ore bins, the hinged metal chutes lower, and the ore slides from the bin through them down into the boats. Loading requires but fifteen or twenty minutes. The top of an ore boat is built almost flat, with steel hatch covers, which are quickly slid into place, thus covering the ore inside. The boat now sinks low in the water because of its heavy load. It pulls away from the dock and steams down the lakes, bound for the port at which it is to deliver its cargo. During the shipping season it often occurs that the ore boats follow one another so closely that no boat of the string, from Two Harbors, Minnesota, to Buffalo, is out of sight of another.
Our ore boats contribute to the maintenance of American supremacy in steel. English steel manufacturers bring iron ore from Spanish mines by an ocean route of 750 miles, and about 20 miles at each end from mine to ship and ship to smelter. Fortunately for them, this Spanish route is in a mild climate, and can be travelled all year round. On our Great Lakes route, ore is hauled eighty miles from mine to ship, then 1,000 miles by water, and often 150 miles more to the smelter.
The Great Lakes are frozen over four months each year. But British ore ships make only ten or twelve trips a year between Spain and England, while our Great Lakes ore-carriers make just twice as many. The value of time is shown in the story of one ore boat which still had a thousand tons of ore in her hold when a holiday interrupted the unloading. Instead of waiting over the holiday, she steamed back for another cargo, carrying that thousand tons which had not been unloaded.
UNLOADING THE ORE
Unloading the ore is a harder job than loading. The ore simply falls into the boat when it is loaded; but it cannot fall out, it must be lifted. No sooner does the American boat touch the unloading dock than huge machines roll down to it, and the mammoth steel arm of each, with its huge bucket, swings around and down into the hold of the boat, the covers of which have been removed.
The bucket opens on the way down, dropping into the ore with a thud, and there burying it-self. As it starts upward, its jaws close. Rising, it swings away from the boat, carrying not less than five tons of ore. It is as though a huge giant dipped his hand into a pile of dirt, closed his steel fingers, lifted his arm, and deposited the material in whichever place he desired.
All along the wharf these machines work in the same way. The ore which was put into the boat so quickly by means of the ore chutes, now goes out almost as quickly, as these steel grab buckets continue their work. Not so many years ago, such unloading required days. Now an ore boat may be unloaded in about four hours.
|DETAIL OF ORE-UNLOADING GRAB-BUCKET WHICH DIPS INTO THE HOLD OF A SHIP AND LIFTS TONS OF ORE AT A TIME.|
|DUMPING A WHOLE CAR-LOAD OF ORE OR COAL. The car is pushed upon the machine by a “ground-hog” which operates in the centre of the track. When the car is empty and lowered to car level again, it is run off on the other side, whereupon the machine is ready for another car. Car-dumpers of this type were invented by George H. Hulett in 1893.|
The first iron ore shipped from the Lake Superior ranges was in barrels. It had to be unloaded and hauled around rapids in wagons. In 1855, the opening up of the Sault Sainte Marie Canal made it possible to load ore loose for the whole voyage. But for the next ten years the work of unloading was all done by muscle and wheelbarrow. Then somebody ran a rope through a pulley on the ship’s rigging, hoisting ore out of the ship with a tub raised by a horse, and in 1867 Robert Wallace used a steam-engine to hoist several tubs. A boat could be unloaded in a single day, and that was thought wonderful.
|BEFORE THE MECHANICAL ORE UNLOADER WAS INVENTED. How ore was unloaded from boats before Alexander E. Brown invented his hoisting apparatus. The ore was loaded by hand into wheelbarrows, which were then hoisted to the ship’s deck by horse or steam windlasses and then wheeled on gang-planks to the docks.|
But men had to shovel the ore into the tubs, and this cost forty or fifty cents a ton. It was an expense which inventors tried to do away with, and the result was the development of the huge unloading devices used to-day. A young man named Alexander E. Brown was first. In 1880, he invented and built a mechanical ore unloader with two towers supporting a cableway. One tower was placed at the edge of the dock where the ore ships were moored, the other some distance from it. A trolley travelled over this cable carrying buckets of ore to the second tower, where it was dumped in a pile. This was the Brownhoist.
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|UNLOADING ORE SHIPS WITH BROWN MACHINES. Each machine is equipped with a man-riding trolley from which is suspended a round bucket. The trolley with bucket travels from the extreme end of the front cantilever to the extreme end of the rear cantilever. Each machine is a separate operating unit that travels along the face of the dock. The operator on the trolley controls the trolley travel, operation of the bucket, and the movement of the machine along the docks.|
Several years later, another young man, George H. Hulett, saw ore being unloaded with buckets, and decided the method was too slow. Although born a farm boy, he had become interested in machinery, and in 1884, turning his attention to ore unloading, he made some improvements in an unloading derrick used at South Chicago. In 1891, he built an unloading device in Cleveland, calling it the “Little Giant,” but could not get people interested.
In 1896, he invented and patented something entirely new. Iron ore was loaded into cars at the mine with steam-shovels. Hulett saw no reason why steam-shovel buckets should not lift it out of the ships, and he made drawings and models to illustrate his invention. It was so big and costly a machine that even the largest shippers were afraid to build one. Eventually, in 1898, he found a company willing to pay $48,000 for a Hulett unloader—provided it would work; otherwise he was to get nothing for his machine and tear it down at his own expense.
The following year, 1899, after many trials and mechanical changes had been made, Hulett’s unloading machine proved successful. It was received with opposition by the workmen, who thought it would rob them of their employment. In reality, it helped them; for the machine unloader did away with the hardest drudgery in the whole process of manufacturing and delivering steel.
|THE HULETT ORE UNLOADER. In 1896 George H. Hulett devised a machine for unloading ore from ships by means of grab-buckets which were dipped into the hold and lifted by a huge working-beam. The machine was successfully introduced before 1900. Courtesy of Wellman-Seaver-Morgan Company.|
The iron and steel industry has largely centred around Pittsburgh, because near by are the coal-fields of the Connelsville district, from which come exceedingly good coking coals. As the ore must go through the blast furnace before it comes into the pig-iron form, coke and limestone will probably always be used for fuel and flux. The coke is made by “baking” certain grades of soft coal; the gas which the coal contains is driven off, and coke is the part which remains.
Much ore also goes to Chicago, Milwaukee, Gary, Cleveland, Youngstown, Buffalo, and other well-known iron and steel-making cities. At the furnaces, the ore and coke meet. These materials are weighed into proper “charges,” hoisted by machinery to the tops of the furnaces and dumped in with some limestone. This gives alternate layers of fuel, iron ore, and limestone. The fuel burns, part of the carbon of the coke takes away the oxygen of the ore as has been described, and the melted pig iron, containing between four and five per cent of carbon, is “tapped” or drawn out at the bottom of the blast-furnace as often as sufficient metal collects there.
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|BROWN POWER SCRAPER AT WORK IN A HOLD. In unloading boats of ore there is always a certain amount of material that lies between the hatches and cannot be reached by the unloading grasps. In this picture a Brown power scraper-shovel is shown placing this material beneath the hatch openings, thereby doing away with hand-shovelling. This power scraper-shovel has reduced the time of unloading boats of ore or coal five to twenty-five per cent.|
INSIDE OF A STEEL PLANT
In the old days there was nothing more fascinating than the sight of molten, smoking-hot metal gurgling out of the tap-hole, running down the centre channel of the sand floor of the “cast house” until, at the farthest end, it ran into side channels cut in the sand, thence into the smaller channels where it lay until it solidified into “pigs.” These were shortly broken off by men with sledge hammers, and eventually carried into the yard to be shipped.
American efficiency did not like to lose the heat which evaporated when the metal was allowed to cool, so steel-making plants were built close to the blast furnace. In this way, without having cooled off much the molten metal arrived at the Bessemer converters, which “converted” it into steel. Now only the excess metal and that produced on Sunday morning—for steel plants work continuously night and day, from Monday morning until the next Sunday morning, when the Bessemer plant shuts down—goes into the old-time pig form.
|EXTERIOR OF BLAST-FURNACES. Coke, ore, and limestone are weighed into proper “charges” and hoisted to the top of a furnace and dumped in the coke-burner; part of the carbon of the coke takes away the oxygen of the ore; and molten pig iron is tapped from the bottom of the furnace.|
Bessemer steel, which in this country is usually “blown” fifteen tons at a time in brick-lined, egg-shaped, steel vessels or converters, goes into tall, square, iron moulds, which stand on little cars on a narrow railroad track. The steel soon solidifies, the moulds are pulled off, and reveal “ingots,” or red-hot blocks of steel, standing on the cars. In order to lose no more of the heat than is necessary, these ingots are rushed by small screechy engines, called “dinky” or donkey-engines, into the rail or blooming-mill.
Huge travelling cranes lift them from the cars and lower them into furnaces, or “soaking pits,” built in the floor, to reheat them. When the ingots are again at white heat, they are one by one pulled out and taken to the rolling-mill, through which they are passed backward and forward, and squeezed smaller and smaller, and longer and longer, until they have been reduced to the required size.
They are then cut into lengths, “blooms,” which go to the rail-mill or to the rod and wire mill, as the case may be, where the rail or rod rolls quickly reduce them in size. For instance, in the rail-mill, after being rolled back and forth many times, each “bloom” becomes a rail, accurately shaped to size, and is then cut into proper lengths. If intended for rods and wire, the ingots are cast smaller, and the blooms cut are smaller than are those for rails. These are usually called “billets.” Being small, they lose their heat faster than the larger ones, and must be reheated before going to the rolls.
|ROLLING AN INGOT IN A BLOOMING-MILL. All of the steel is rolled in a continuous operation so that it does not cool very much from the time it is measured until it is in the shape of blooms, of which one is shown in the foreground emerging from the rolls.|
The men engaged in this exciting work go about their duty with matter-of-fact unconcern. Practice has not only made them perfect, but also indifferent to ever-present dangers. The “roller” operator, standing in front of the many-grooved “three-high,” or three-roll mill, catches the on-coming end of the fast travelling white-hot steel rod as it darts at him from the first groove in the rolls. Coolly and unerringly, he seizes it with his tongs, whirls it around, and inserts the end of it in the next smaller groove of the rolls turning in the opposite direction. The white-hot snake keeps on coming out of the larger groove, runs around him in a loop on the steel floor, and speeds into the next smaller groove into which he has just thrust it.
This work the “roller” continues hour after hour. In the midst of such danger his only weapon is a hatchet, with which he can defend himself by cutting the fiery rod should it fail to go as intended and start on a rampage, as occasionally occurs. Not only one loop, but two or three he has almost constantly circling around him; for the rolls run very fast, and with two or three loops running at once, he gets greater “tonnage,” and consequently more pay, than if he should roll only one at a time.
Undoubtedly Bessemer steel made possible the great railroad expansion of the years 1870 to 1905, and started the great industrial growth. But Bessemer steel did not accomplish it all. Within ten years after the discovery of the Bessemer process, William and Frederick Siemens invented a system of chambers lined with brick-work, which treasured up the heat by taking it from the flame and hot gases as they passed through on their way to the chimney.
|PIG-CASTING MACHINE IN ONE OF THE BETHLEHEM STEEL COMPANY’S FOUNDRIES. The moulds travel on an endless chain up an incline, and the metal is cast at the lower end. By the time the metal reaches the upper end of the incline, the pigs are solid and fall into the car.|
|POURING A HEAT OF SPECIAL STEEL INTO INGOT MOULDS. The ingots are taken by the cars to the rail or blooming-mill.|
|RAIL-MILL, FINISHING END.|
THE DEVELOPMENT OF THE SIEMENS-MARTIN FURNACE
This “regenerative” furnace was chiefly the invention of William Siemens, a German, who was born in 1823, and was five years younger than his brother. He was a scientist as well as an inventor, developing the process for electroplating, helping in the construction of telegraphs, designing a cable-laying ship, and he lived to promote the electric light and trolley car.
The Siemens furnace grew out of scientific studies made by William Siemens to prevent the waste of heat in steam-engines, and he invented a “regenerative engine” which was not commercially successful. But this same idea of saving heat, when applied to steel-making, brought about far-reaching changes.
His furnace, proposed in 1861, had two chambers, one for air and one for gas, oil or other volatile fuel. These connected with the furnace and chimney—by means of a reversing valve. The gas and flame is shot through the furnace in one direction, and then alternately through the other by directing the flow of incoming gas and air through the hottest chambers. In burning this preheated gas in the furnace, intense heat is produced sufficient to melt even the carbonless wrought iron, which, as we have read, was an unmeltable, pasty, white-hot ball in Cort’s puddling process. The valve is reversed every little while, thus alternately utilizing the hottest chambers for heating the gas and air, and reheating the other ones after they have become somewhat cool from like service.
This furnace is often called the Siemens-Martin furnace, because two Frenchmen, the brothers Pierre and Emil Martin, licensed by the Siemens under their patent, were active in developing the invention commercially, near Paris, in 1864. In connection with this there is a dispute, as often happens with great inventions. Some maintain that the Martin brothers deserve credit for improving the Siemens brothers’ idea, while others credit the latter, saying that the Frenchmen were the first to carry out the idea in a practical way.
Be this as it may, the regenerative furnace quickly transformed the steel industry, making possible what is known as the open-hearth process. In the long brick-lined shallow furnace above described, either cold pig iron or pig iron and scraps of steel are melted and made into new steel by expert furnacemen. The making of steel by this process is considerably slower than is steel-making in the Bessemer converter, and the process is far less spectacular. But the steel is generally considered to be somewhat better in quality.
|THE OPEN-HEARTH METHOD OF STEEL-MAKING. Early type of gas-producer, regenerators, and open-hearth furnace, showing the course taken by air, gas, and products of combustion, and also the valves that change the direction of flow. From Spring’s “Non-Technical Chats on Iron and Steel.” Courtesy of Frederick A. Stokes Company.|
In 1868, the first small furnace was erected at Trenton, New jersey, by Cooper, Hewitt & Company, after their engineer, Fred J. Slade, had visited France to study the Martins’ furnaces. It was not successful, because steel workers had to be taught new methods. An American engineer, Samuel T. Wellman, has been called the “father of the open hearth in America,” because he spent many years installing and improving furnaces of this kind.
With the first appreciation of the high quality of open-hearth steel, fifty years ago, the prophecy was made many times that the Bessemer process must soon be a thing of the past. However, much Bessemer steel is still made. An enormous tonnage of open-hearth steel now goes into rails, plate, wire and structural steel for buildings, bridges, and so forth. Steel is measured by the “long ton” of 2,240 pounds, and a few figures of production may be interesting.
In 1869 the making of open-hearth steel first recorded in the United States was 893 tons; against this there was manufactured 10,714 tons of Bessemer. By 1880 the figures were 1,074,000 tons of Bessemer, and 110,850 of open-hearth. In 1900 it was 6,685,000 tons of Bessemer, and 3,398,000 tons of open-hearth; in 1910, 10,328,000 Bessemer, 20,780,000 open-hearth. In 1920 the open-hearth steel had increased to 32,672,000 tons, while the Bessemer had decreased to 8,883,000 tons.
Perhaps we may be able to realize the immensity of the iron and steel industry in the United States, by noting that the 1920 production of over 40,000,000 tons is nearly one-half ton per year for every man, woman and child in the country, or over two pounds per day.
MAKING STEEL IN THE ELECTRIC FURNACE
But ever finer grades of steel than that produced in the open-hearth are needed for automobiles, machines, and many other purposes. These steels are made in electric furnaces, the most modern method, and one that is apparently very near perfection.
It was this same William Siemens, afterward Sir William, who, about 1870, designed many small experimental furnaces for melting iron and steel by aid of the electric arc. The electric arc is produced by forcing electric current to jump a gap like that between two carbons of the arc lamps used to light our streets. In jumping, the current is bent, forming an “arc,” and it also develops a terrific heat—the greatest heat that man has yet been able to produce, upwards of 5,000 degrees Fahrenheit.
The gap in an arc light is only the fraction of an inch, but in electric furnaces it may be several feet. Siemens succeeded in melting iron and steel in his electric furnaces, but as electric current was then very costly, he was unable to make the process pay. It was not until 1895 that an Italian army officer, Major Ernesto Stassano, designed a furnace that profitably melted steel. By that time electric current was cheaper. Stassano overcame many difficulties. Having no skilled helpers, he had to be his own machinist, electrician, chemist, laborer, and furnace-tender. More than $200,000 was sunk in his experiments before he succeeded in making steel on a large scale.
|TAPPING AN OPEN-HEARTH FURNACE. The large ladle contains steel and the small one slag.|
The electric furnace had already been applied to melting and making things of greater value than steel. An American, Robert Hare, a Philadelphia chemist, born in 1781, is given credit for constructing the first electric furnace. With only a battery current he converted charcoal into graphite, and performed other scientific feats. In 1886, another American, Charles M. Hall, invented a process for making aluminum, passing an electric current through a heated mass of aluminum oxide and a Greenland mineral known as cryolite, which fused the metal.
Up to that time, aluminum had been as costly as silver, but Halls’s process made it cheap enough for everyday use. Hall was a clergyman’s son, and developed his process at Oberlin College in Ohio, to which institution he left his large fortune. It is said that, as a boy, he took a fancy to chemistry through happening upon an old text-book in his father’s library. The cover and title-page of this book had been torn off, so he never knew who was the author.
Two brothers, Alfred and Eugene Cowles, who had worked with Hall, applied the process of the electric furnace to the making of aluminum bronze. In 1891, Edward G. Acheson, an American who had been in the employ of Edison, used the electric furnace to convert coke, sawdust, sand, and salt into a new substance, carborundum, now in everyday use for grinding. Acheson also made by far the purest graphite obtainable, in the electric furnace.
In 1886, the year Hall took out his patent, a French inventor, Paul T. L. Héroult, patented a similar process for making aluminum in an electric furnace, and established the first aluminum works in Europe, at Neuhausen, Germany. Three years later, he turned his attention to making ferro-chrome, ferro-silicon, ferro-tungsten, and other iron alloys.
The alloy steels are ordinary steel containing other metals, such as chromium, silicon, tungsten, manganese, vanadium, molybdenum, and the like, metals that make steel harder, tougher, and stronger. Realizing that such steels sold for higher prices than ordinary steel, Héroult found that it was possible to make a handsome profit by means of the electric-furnace process. He, Stassano and others also used the high temperature of the electric furnace to purify steel, taking out of it the two dreaded impurities, sulphur and phosphorus.
|ELECTRIC STEEL-FURNACE. In this form it is the development of Paul Héroult, a French engineer. His original furnace was a brick-lined pot heated by an electric arc.|
Héroult’s furnace was a brick-lined pot heated by the electric arc passed to and from the metal being melted by means of long rods of carbon or graphite, called electrodes. It is because of the great quantity of air blown through the metal in the Bessemer process that Bessemer steel suffers in quality. Air, though in a lesser amount, is used in the open-hearth process to make the gas, or fuel, burn. In both these processes the presence of air in the furnace is unavoidable.
In the electric furnace no air is necessary. This, with a closer control of composition of the metal and various other advantages, gives to electric steel a quality that is near absolute perfection.
In 1900, a Swedish engineer, F. A. Kjellin, patented another electric furnace along different lines. Up to that time inventors had used the arc, melting steel in its intense heat, or taking steel already melted in an ordinary furnace and refining it in the higher heat of the electric arc. Kjellin’s furnace utilized the principle of “induction.” Instead of an arc in which electricity jumped a gap, he ran his current through the steel itself, and the resistance of the steel to electric current melted it. As the arc type of electric furnace works like the arc lamp, so the induction furnace works like an incandescent lamp, with its filament heated white hot because it resists the current.
The electric furnace makes better steel than either the Bessemer or open-hearth processes, and makes it cheaper than the crucible process. Crucible steel began with Huntsman, in 1740, and is made by pretty much the same process to-day. The crucible is a small pot, formerly made of clay but now usually of graphite. This pot is filled with small pieces of steel and put into a furnace where it is entirely surrounded by coke or coal, the fire being so regulated that the steel is not too quickly melted. Fresh coal or coke must be put around the crucibles two or even three times, and they must be tended by an expert workman, called the “melter.” This attention, together with the cost of crucibles and the small quantities of steel melted in that way, compared with the large charges of the Bessemer and open-hearth processes, make crucible steel expensive.
Our automobiles have frames of vanadium steel, forgings of nickel or chrome nickel steel, roller and ball-bearings of chrome steel, all made in the electric furnace. Even the tools which so swiftly and accurately shape the automobile parts are now, to a considerable extent, made from steel produced in the electric furnace, though many tool steel manufacturers still hold to the crucible process.
|1,400-TON HYDRAULIC FORGING-PRESS.|
When our railroads demand still better rails than even the open-hearth can produce, the electric furnace must make them. Steel containing fourteen percent of manganese is known as manganese steel. This cannot be drilled or cut by ordinary machine tools, and its hardness makes it a wonderful material for “frogs” and rails which are to resist wear as on track curves, etc. Manganese steel is used for burglar-proof safes, crusher-rolls, gears, etc., which must resist excessive wear, although chrome steel is used for some such parts.
There is a wonderful future for these alloy steels. Some are so strong that they will not break under a pull of 350,000 pounds per square inch; some are hardened and used for armor plates for battleships; some, because they do not change much in length upon heating and cooling, as do most other metals, are used for parts of scientific instruments; and some are rustless, and therefore are used for cutlery, surgeons’ instruments, and the like.
Another most important series of steels are the “high-speed steels.” They are tool steels which will keep their hardness even when working red-hot. The old carbon tool steels, though apparently just as hard, very soon lose their hardness and cutting power when worked hot. The heat-withstanding properties of the high-speed steels are imparted by tungsten, chromium, and carbon.
When the first of these steels appeared, their valuable properties could not be fully utilized because our lathes, shapers, and other machines, though strong enough for the old carbon steel tools, were neither strong nor powerful enough to push the tool for the deeper and faster cut which the high-speed steel tool was capable of taking. With the powerful machines and tools of to-day, so much metal can be cut away by one tool that it is sometimes difficult to carry away the chips as fast as the machine cuts them.
This is the Age of Steel. Why? Firstly, because more and more steel was required. America’s output, in the eighteen-sixties, was less than 15,000 long tons a year, that is, under ten pounds a year per capita. We are now approaching the day when every man, woman, and child in this broad nation of ours will need a ton of steel every year.
The yearly gain since 1900 has averaged 1,500,000 tons, as much increase each year as our total annual output in 1880. This means that the man of the eighteen-sixties who had only a few tools, who had to walk to his work, and who took an occasional railroad trip, has, to-day, an automobile, uses the trolley and railroad regularly, works in a steel-frame building, and is able to perform his tasks not by hand but with steel machines. Such was the answer to the demand for more steel.
Secondly, the cry was for cheaper steel. When Bessemer and Kelly patented their converter process, English manufacturers were selling steel at $300 a ton. During the past twenty years the price of steel “billets” has averaged only twenty-five to thirty-five dollars a ton.
Thirdly, there was the desire for better steel, new steel, with which it would be possible to do more work and make things stronger and lighter while they were also being made cheaper. The electric-furnace steel, and the wonderful alloy steels were the answer. With the latter steel, it is possible to take a thousand pounds weight out of a high-powered automobile.
This, then, is the meaning of the Age of Steel. Those who make iron and steel, from the workers in the mine to the experts in the finishing laboratories, serve us every moment of our lives. Steel, each year, becomes more and more indispensable to us.