The Steel of the Future (May, 1936)
The Steel of the Future
By H. W. Magee
FROM bronze to iron, from iron to steel, and now a new eraâ€”that of steel and its alloysâ€”such is the story of human progress.
Before the Napoleonic wars, this was a world of hard labor. Then came steam to lighten toil, and to lift loads off men’s backs.
Iron supplanted bronze. Steel displaced iron because it was stronger. Certain kinds of alloys today surpass ordinary steel in physical propertiesâ€” strength, toughness, hardness, resistance to oxidation, the action of chemicals, stability at high temperatures, electrical characteristics and luster.
The physical properties and characteristics of steel can be changed in an endless variety of ways not only by combining it with other metals but also by applying heat. Heat treatment gives almost as much promise for future growth in the uses of steel as do the developments of its alloys. Steel is alive. By heat alone, it is possible to change the two ends of a steel bar so that each has entirely different characteristics. The heat treatment of metals is still one of the great unexplored fields of science.
There are almost as many kinds of iron and its alloys today as there are uses for iron and steel products, and the number is constantly increasing. Your automobile, for instance, contains about forty different kinds of iron, steel and steel alloys, and those in your car may be entirely different from the metals with an iron base employed for thousands of other purposes ranging all the way from massive machinery to domestic cooking utensils.
To realize the possibilities of these new alloys, we must first know some of the properties of the mother metal, iron. While iron and iron products form the base upon which our civilization has been built, no one knows when or by whom iron was discovered. But it did have to be discovered because there are no nuggets of pure iron. Perhaps some early aborigines built a roaring fire against a bank of reddish earth consisting partly of iron ore. The prevailing wind served as a bellows to blast the hot flame against the bank. When the fire died out, they poked about among the embers and found a few pellets of malleable substance which made a very superior spearhead. Some such accident must have ushered in the iron age.
At any rate, the neolithic genius who “doped out” the secret seems to have spread the news, for the remnants of ancient furnaces are scattered all over the world, and a wedge of wrought iron was buried in the great pyramid of Cheops probably as early as 3,500 B.C. The real forerunner of our modern blast furnace, however, was the Catalan forge, a very crude furnace developed in Spain some 150 years before Columbus discovered America. It burned charcoal and used a blast of hot air to smelt a malleable iron.
Some of the troubles of these early metal workers are explained by the very nature of iron. Iron ore is a natural deposit consisting of the iron held in the chemical grip of oxygen. Under the influence of high heat, oxygen’s strangle hold on the metal can be broken by carbon. The first primitive furnaces produced a small ball of metal, soft and malleable, a variety of wrought iron.
Then a great discovery was madeâ€”a discovery which affected the future of civilization. It was found that when more charcoal was present in the furnace than was necessary to combine with the oxygen of the ore, the liberated iron absorbed enough of the excess carbon to change its own nature. The intense heat produced a fluid metal in the hearth of the furnace instead of the stiff, pasty ball of malleable iron. It also was found that this liquid iron could be “cast,” or poured into molds and made into shapes useful to man, so it became known as cast iron. That was a great stride forward in the iron ageâ€”the knowledge that a surcharge of three and one-half to five per cent of carbon gives iron a fluid quality while hot and an extreme brittleness when cold.
Next came steel, the master servant of mankind and the first alloy of iron. Steel has neither the softness of malleable iron, which is low in carbon content, nor the hard brittleness of cast iron which is high in carbon content. The early metal workers made very fine sword blades by heating rich ore in small closed crucibles, allowing the metal to absorb about two per cent of carbon instead of the three and one-half per cent or more of cast iron. The result was carbon steel. When hardened by cooling quickly in water, a forged-out blade of this material could cleave a piece of iron without dulling its edge or cut in half a piece of silk floss tossed into the air.
The triumvirate of wrought iron, cast iron and steel formed the basis of the iron and steel industry. As civilization advanced, the world needed more and more iron and from this need there the furnace, a casting device known as a pig machine forms it into “pigs” for use in foundry work, hence the name pig iron.
Cold pig iron is very brittle, high in carbon and other impurities and of low tensile strength but it can be converted into soft but tough wrought iron by “puddling.” The iron is heated, iron oxide and certain slag-forming materials are added and the molten mass is stirred, causing the iron oxide to react with the carbon to form iron while the slag removes other impurities. As the carbon is removed the melting point rises and the metal becomes a pasty mass like bread dough which is pressed between big rollers to squeeze out the slag.
Steel first was made commercially by the crucible process from wrought iron produced by “puddling.” The iron was packed in carbon and heated, causing it to absorb some of the carbon. The resulting product was melted in crucibles to obtain homogeneity, a slow and costly process.
The Bessemer converter ushered in the real age of steel and made possible our early railroads, battleships and skyscrapers. By this process, molten pig iron is placed in a giant egg-shaped vessel, the converter, and a blast of hot air is blown through it. The oxygen of the air burns up most of the carbon and non-ferrous impurities, the other impurities forming a slag. To keep the liquid steel from dissolving oxygen, a small amount of manganese is added.
The Bessemer converter, whose spectacular blowing lights the country for miles, lowered the cost of steel through quantity production but Bessemers today have been replaced to a large extent by open hearth furnaces which produce a better and more uniform product. Open hearth furnaces provide the great dramatic spectacle today on the stage of steel. Into a battery of these brick-lined furnaces, each holding 100 tons or more, go molten iron from the blast furnace, limestone, metal scrap and any alloys needed to impart special properties. Here the metal seethes and bubbles for hours. Temperatures as high as 3,000 degrees are produced by burning intensely preheated gas and oil forced through checker cham- bers under pressure. Because of the terrific temperatures produced, furnaces must be entirely rebuilt at intervals.
When laboratory analysis of samples shows the metal has been refined and is of the required specifications, a big clay plug is rammed out and, with a mighty roar and a shower of sparks, the molten steel rushes into a great ladle which is lifted by a giant crane to pour the white-hot metal into molds, each holding 10,000 to 12,000 pounds. A mold train carries the steel into the yard to cool. Cranes release the red-hot metal ingots from the molds and carry them to huge gas-fired soaking pits where they are soaked with heat to bring them to uniform temperature. Then giant pincers lift them out and lay them on roll tables leading to the “blooming mill.”
No better illustration of the ability of the machine to shoulder the back-breaking tasks of man can be found than the modern process of rolling metal. Brawny steel workers wielding heavy tongs used to pass slabs of red-hot metal back and forth through the rolls of the mill, something like a huge clothes wringer, until a slab was reduced to a sheet of metal. Only the strongest men could stand the labor and the heat.
To the American Rolling Mill company at Middletown, Ohio, several years ago came a young paper-mill engineer, John B. Tytus. Tytus had an ideaâ€”a dream of straight-line production of steel, stand after stand of rolls, conveyors and reheating furnaces half a mile long with a three-foot slab of metal going in one end and coming out the other as a strip 200 feet long and as thin as a coin.
Iron and steel engineers ridiculed the plan as visionary and impracticable but the company was interested. For fourteen years Tytus labored with blueprints and designs under the supervision of Charles R. Hook, now president of the company. Thousands of dollars were spent on experimental work but the only way to find whether such a machine would work was to build one. So the company bet several million dollars that Tytus was right and ordered construction of a continuous rolling mill. And Tytus was right.
Today, starting in the blooming mill, ponderous 12,000-pound ingots are mauled through mighty rollers until they have been reduced into slabs eighteen or twenty feet long, five or six inches thick and three feet wide. Each is sheared into slabs ranging from 1,200 to 2,600 pounds, according to ordered size, and these are reduced to ribbons of metal 200 feet long at the rate of a ton every thirty-two seconds. All the labor required is the energy necessary to press push buttons. The continuous mill does the work.
During the journey through the rollers, the metal becomes strained, so annealing is necessary to allow rearrangement of the grains that make up its structure and control its temper. The sheets are allowed to soak up heat and “relax” for several days in great furnaces, then follow cleaning, cold-rolling, coating with lead or zinc, trimming, polishing and other operations, depending on the purpose for which the metal is intended.
Different processes are followed in the foundry and in the fabrication plant in order to shape the metal for its intended use, but the initial preparation is the same.
While man has used iron and steel for centuries, he is only now beginning to understand some of its hidden properties. The X-ray is helping to reveal this in metallurgical laboratories. Chemically pure iron has never been prepared in usable quantities and thus research to determine the actual properties of pure iron may disclose something entirely new about this age-old metal.
Nickel, chromium, manganese, cobalt, molybdenum, vanadium, titanium and tungsten are among the metals alloyed with steel today but it is likely we have hardly scratched the surface of the possibilities in alloy steel. Nickel makes steel hard without detracting from its toughness so we use it in gun barrels and armor plate. We know, too, that chromium has much the same effect as nickel and in addition those metals give steel a high resistance to corrosion, thus making possible our stainless steels. Manganese makes steel so tough it cannot be cut or bored, so we use it for vaults and safes.
The high-speed steels are alloyed with tungsten or molybdenum which enable the metal to hold its temper even when heated to incandescence, making such steel suitable for cutting very hard substances. And without iron we would be without electrical energy because the electrical industry is based on the magnetic properties of iron. Electrical steel has silicon added.
By proper treatment, iron and its alloys may be modified in an endless number of ways. For example, it may be prepared in such active form that it bursts into flame on contact with air, or it may be made resistant enough to withstand the action of boiling acids. This adaptability is constantly increasing the uses for the metal. The total ingot capacity of the American iron and steel industry is about 60,000,000 gross tons a year, or sixty per cent of world production. Who can predict the forms this material will take in a few years? Perhaps the best answer comes from George M. Verity, chairman of the board of the American Rolling Mill company. “Ninety per cent of Armco products today,” he said, “were not even produced twenty years ago. Two more decades may see an even greater change. The growth and expansion of iron and steel is an index to progress and as civilization advances, iron and steel must continue to perform greater and greater services.”
There are three pivots on which civilization turnsâ€”food, clothing and shelter. Once all three were scarce. Weapons and plowshares made of iron then made food abundant. The cotton gin, the loom and mechanical weaving have supplied us with plenty of clothing. But we still live in houses of wood and brick and stoneâ€” the identical materials which have been used for hundreds of years.
One of the next great tasks of iron and steel is to make shelter for mankind as easy to obtain as food and clothing. It should be as easy for an American family to own a home as to own a car. Iron and steel have made it possible for the average family to own a car and iron and its alloys can make it possible for the same family to possess a home with more comfort and conveniences than the modern home today, and at a fraction of the cost.