The “Manufacture of Malleable Iron and Steel without Fuel” was the startling title of a scientific paper read in 1856 before the British Association for the Advancement of Science. This was the announcement to the world of Henry Bessemer’s invention of the process for making iron and steel which led to the greatest commercial development the world has seen.

To those of us who have had little or no experience along manufacturing lines the announcement seems strange enough, but metallurgists, engineers and manufacturers who know how serious is the matter of fuel bills realize at once how revolutionary the claim of Bessemer must have seemed to men of those days.

As occurs with so many new things the idea was scoffed at; Bessemer’s scheme was one purporting to give “something for nothing” and—well, it could not be.

It was ridiculous!

And why should it not have seemed strange when we consider that up to that time fuel had been required in all metallurgical processes. In the old Catalan furnace and the types that preceded it, in the Finery Fire, the Walloon and the several other refining furnaces fuel had to be provided without stint. The lowest proportion that seventy years of experiment and practice had brought about in Cort’s puddling process was one ton of coal per ton of iron, while the blast furnace required at the least four-fifths of a ton of coke for each ton of pig iron produced.

Whether Bessemer, an Englishman of French descent, or William Kelly, an American of Irish descent, of Eddyville, Ky., first conceived the idea of the “pneumatic” process is a moot question. Considerable evidence substantiates the claim that the latter first hit upon the scheme and during the ten years between 1846 and 1856 had considerable success with its development. Perhaps Bessemer had heard of Kelly’s experiments. There is no proof that he did. Whether he did or not, the fact remains that he quite independently and very fully developed the process in England, and with great business sagacity and energy made it the success that it is.

As fortune has withheld from Kelly and from this country credit which was deserved, it is desirable to tell briefly the part which he had in the development of this process that with a single furnace converts pig iron into steel at the rate of a thousand tons in 24 hours and first made mild steel available as a building material.

In 1846 Kelly, with a brother, bought the Suwanee Iron Works, near Eddyville, Ky. After about a year they encountered the same difficulty that charcoal iron manufacturers usually have encountered—the failure of the supply of fuel. This difficulty Kelly, a better inventor than business man, apparently had not foreseen. His business was threatened unless some other way of refining his iron was found.

One day while watching the operation of his Finery Fire he noticed that the blast of air from the tuyère made the molten iron where it impinged very much whiter and apparently hotter than the rest. Like other iron makers, he had always supposed that a blast of cold air chilled molten iron.

It appears that Kelly was not long in surmising the truth. In a few days he had rigged up a crude apparatus and made soft iron from which a horseshoe and a horseshoe nail were fashioned by a blacksmith.

Being conservatives, Kelly’s customers were not slow in informing him that they did not want iron made by anything other than the “good old process” and he was obliged to accede to their demands or lose their trade.

Like Galileo, however, he had not really surrendered. In the woods near by he built and experimented with seven successive “converters,” as the furnaces are called in which Bessemer steel is made.

Upon learning that Bessemer of England had been granted a United States patent (1856), Kelly came before the patent office and proved that he had several years before used the same process. The priority of his invention was acknowledged, and a patent was granted to him also (1857).

Financial troubles and finally bankruptcy handicapped him. However, the Cambria Steel Co., of Johnstown, Pa., became interested and let him experiment with his process at the company’s plant. Here in 1857 he built his first “tilting” converter. His first public demonstration resulted in failure and ridicule, but a few days later he was successful. Steel makers bought interests in his patent, which at its expiration in 1870 was renewed by the United States Patent Office, while renewal of Bessemer’s patent was refused.

The Kelly Pneumatic Process Company, which was organized to operate under Kelly’s patents, built a converter at an iron works at Wyandotte, Michigan. Here the first pneumatic process steel ever made in this country in other than an experimental way was “blown” in 1864.

Meanwhile Alexander L. Holley, an American engineer, had obtained for another American company the right to manufacture steel here under Bessemer’s patents. He built a plant at Troy, New York, which began making steel in 1865.

It was soon decided to merge the interests of the two companies and in 1866 this was done, the process thereafter being known as the Bessemer Process. During the early years of the process here Holley became very well known. As consulting engineer he designed practically all of the Bessemer plants which were built during the first ten or fifteen years.

To the majority of the people of the United States to-day Kelly and his parallel part in the great invention are practically unknown, and thus not only he but the United States is without credit which should be ours.

Fortunately Kelly did not entirely fail to profit financially as so many times is the case with inventors. He received a total of about $500,000. Bessemer’s return from his process is said to have approximated $10,000,000 and he was knighted by the British sovereign.

More intimate details regarding Kelly and his work may be found in Munsey’s Magazine for April, 1906, where H. Casson gives information which he received direct from several of the men who knew and worked with Kelly.

While apparently not the originator of the process, Bessemer is without any doubt entitled to most of the credit he received. There is no proof that he had heard of Kelly’s experiments when he began his own or that he was aided by Kelly’s discoveries. He worked out the details of the process independently, as had Kelly, and it was Bessemer who put it on a commercial basis.

As has occurred with other new processes Bessemer’s first licensees were not particularly successful. When those who had bought the right to use his process had failed in their efforts to use it, and become discouraged as most of them did, he quietly bought back their rights and went ahead with his development of the process. Perhaps no man ever exhibited more perseverance in continuing experiments and development under very discouraging conditions than did Henry Bessemer. He had faith.

He had a genius for invention and was thorough in his experimental work. Practically no type of converter has since been brought out that he did not think of and try, and the process has been modified in but one or two important particulars in the years that have passed.

The essential part of the Bessemer process is the blowing of air through molten cast iron to remove the metalloids by which cast iron differs from steel and wrought iron, as has been explained before.

This being the essential point, and at first thought the lack of fuel seeming so peculiar, we must describe what happens during the Bessemer “blow.”

Technically speaking, the metalloids are “oxidized.” Oxidation is the chemical uniting of oxygen, generally from the air, which has 21 per cent of this element, with another element or material such as iron, silicon, carbon, wood, coal, etc. If the oxidation is slow as in the “rusting” of iron, the resulting heat dissipates as fast as it is generated and the change is hardly noticeable. If, however, the reaction occurs rapidly and with vigor enough, we say that the material “burns.” The latter sort of oxidation is what we call “combustion.”

The affinity between the metalloids and oxygen has been noted by us before, but in those cases most of the oxygen came from a different source.

In the wrought iron process most of it was furnished by the iron ore or scale which was stirred into the metal, or by the slag which covered the “bath.” In the Bessemer, or as it was first known in America, “Kelly’s air blowing process,” the oxygen of the air blown through the molten metal directly oxidizes or burns out the carbon, silicon, and manganese. The extremely rapid oxidation of these furnishes the heat.

The iron, then, furnishes its own fuel and no outside combustible is needed.

How can this be?

In every ton of molten cast iron there are approximately 70 pounds of carbon, 25 pounds of silicon, and 15 pounds of manganese or a total of about 2000 pounds of these metalloids in the fifteen-ton charge of molten metal which goes into the ordinary steel plant converter.

We know that if burned in a furnace this ton of high grade fuel would generate much heat. Burned inside of the mass of molten metal it generates exactly that same amount of heat and the heat is applied with such rapidity, directness and efficiency that the molten iron which had a temperature of 2300° F., say, when charged, in nine or ten minutes has become steel with a temperature of about 3000° F. simply through this rapid oxidation of its 4 to 6 per cent of metalloids.

How the blast under 15 to 30 pounds per square inch is applied through little nozzles in the bottom of the modern “converter” and the several types of vessels with which Bessemer experimented in the course of his investigations are shown in the illustrations.

Nor is it necessary that the air be blown through the metal. Air blown upon its surface accomplishes practically the same purpose, and in many of the steel foundries of to-day smaller converters of this “surface-blown” type are used for producing steel for castings. The large steel plants, however, use the larger “bottom-blown” converter. Two or three of these vessels, working with proper metal from the “mixer,” produce an immense tonnage of steel each 24 hours.

The “mixer” is quite necessary. It is a large vessel or furnace holding and keeping hot from 75 to 300 or more tons of metal from the blast furnace. It mixes and equalizes irons of various compositions, so that the converters have the advantage of uniform and hot metal with which to work.

In addition it is made to perform a “refining” service. By mixing into the metal a quantity of manganese, considerable of the sulphur present (a deleterious substance) is removed.

The fifteen or twenty minute blowing of 15 tons of metal in the big egg-shaped converters of a steel plant presents a spectacle which, when once observed, will never be forgotten.

One sees a little “dinky” engine come shooting into the converter building with its ladle of molten iron from the “mixer.” With America’s time saving routine not a single minute is lost while emptying the metal into the converter, now in a horizontal position. Almost before the ladle is out of the way, the converter swings to the upright position with the blast already on, for otherwise the metal would flow into the tuyère holes at the bottom.

Reddish-brown smoke and a shower of sparks come from the converter. These gradually develop into a flame.

The blast shows considerable partiality in selecting for its first attention the metalloids silicon and manganese, in preference to the iron itself or any other of the metalloids present. After from three to five minutes half of the silicon and manganese have been burned out. If the temperature of the metal and other conditions have become right the carbon then begins to burn. This gives a change in the nature of the flame which becomes large and of a dazzling whiteness.

The metal is hot—very hot—so much so that pieces of cold steel often must be dropped in to cool it somewhat. This is known as “scrapping” the charge.

An experienced blower can judge through every period of the operation of the condition of his metal and just how things are progressing.

After some minutes the flame begins to waver and later “drops”; i.e., there is scarcely a flame at all. This signal, which is very definite to an experienced man, cannot be lightly disregarded. Oxygen has affinity for iron as well as for the metalloids and it is only because of its greater love for silicon, manganese and carbon that it has thus far largely neglected the iron. With the metalloids mentioned out of the way, as they are when the drop occurs, the iron will begin to burn. Were the “blowing” continued we would shortly have no iron left, but in its place a mass of iron oxide and slag.

Thus we see that during the first minutes of the blow, more than one-half of the silicon and manganese are burned. The remainder of these and all of the carbon are removed in the subsequent five or six minutes. At the end of this short blowing period we have practically pure iron.

The metal is not yet in condition to pour well, however, largely because of the dissolved air and gases which it holds. Something akin to the “killing” of the steel which we observed in the crucible process must be accomplished or ingots from it will be spongy. And, having practically no carbon, it is not yet “steel.”

Bessemer, knowing that the finished steel should contain carbon, tried to stop the blow long enough before the drop of the flame to leave exactly the desired amount of this element. He found this difficult to do and therefore uncertain. It was found to be far better to blow until the drop of the flame and then put back sufficient carbon to give the proper composition.

An English metallurgist named Mushet discovered that addition of manganese ridded the metal of injurious gases and oxides and what is known as “red-shortness.” After a period of difficulty without it Bessemer acknowledged the necessity of manganese and adopted its use. It had before this been used in crucible steel.

Upon turning down the converter at the drop of the flame, the blast is turned off and a smaller ladle is run in on a track above. This brings a molten mixture of irons, usually known as “spiegel” or “spiegeleisen” which contains just enough carbon, manganese and silicon to give to the whole of the molten metal in the converter the metalloids needed to make of it steel of the composition desired. This addition also accomplishes the “deoxidation” of the metal. By deoxidation we mean that the iron is relieved of the oxygen and gases which have remained as a result of the blast. This is necessary in order to give proper fluidity for pouring and the best physical properties to the finished steel.

After “recarburization,” as this addition of manganese-silicon-carbon metal is called, the steel and slag are quickly poured out into a ladle waiting below from which the steel is “teemed” (i.e., poured), through a “nozzle” or hole in the bottom into ingot molds arranged on trucks on the railroad track which runs through the building.

When the molds have been filled and a strong crust develops on the steel the cars are pulled to the “stripper” where the molds are removed, leaving the white-hot ingots standing on the cars.

The ingots mentioned in the chapter on Cementation and Crucible Steel were usually small enough that one pot of 100 pounds of metal filled the mold. A four pot furnace therefore produced 400 pounds. Now for the first time, we are talking in tonnage figures. Instead of a batch of steel making four 3″ × 3″ × 36″ ingots of 100 pounds each, the ordinary “heat” of Bessemer steel from the 15–ton converter gives six or seven ingots about 18″ × 20″ × 60″ in size. Each of these weighs about two tons. The total is 30,000 pounds.

From the stripper the ingots go to the gas-fired soaking pits where the molten interiors of the ingots gradually solidify by cooling while the outer crusts are reheated. After equalizing the temperatures of exteriors and interiors in this way, the ingots are white-hot again and ready for rolling.

The purpose for which the steel is intended, of course, determines the shapes and sizes into which the ingots are rolled. For rails they are rolled down directly, each ingot making about six rails, of thirty-three-foot length. For most other purposes the ingots are rolled in the slabbing mill into billets or slabs which are of intermediate shapes and sizes which are reheated and further rolled down into axles, bars, shapes, wire or other products.

Meanwhile the converter which we saw emptied has not been idle. The American steel engineer has genius for mechanical efficiency and all parts of a great steel plant are so co-ordinated that enormous quantities of material can be handled with not a moment lost between trips. Almost before the ladle of steel had swung away from the converter’s mouth, any remaining slag was dumped from the converter by further tipping, the vessel returned to receiving position and the ladle car, back again from the mixer, poured in the next charge.

Thus blow after blow is made without loss of time.

Repairs are allowed to take no longer than is absolutely necessary. When the lining around the tuyères gets too badly cut by the action of the air and metal the bottom is removed, another one is quickly substituted and the steel making goes on.

Blowers, ladlemen, cranemen, pourers, patchers, vesselmen, sample boys and the other workmen are relieved by their “partners” at the end of each shift, each man of necessity working until relieved—twelve, twenty-four, or even thirty-six hours, for there must be no delay. So day and night, through the entire week from Monday morning at six, when they begin, until the next Sunday morning at six, when the plant shuts down for a brief spell, the converters go on turning out three heats per hour or four to five hundred per week each.

It has been mentioned that most of Bessemer’s first licensees failed with the new process. The reasons for this were various, but one in particular was the attempt of many to use metal of high phosphorus content. Bessemer soon discovered that no phosphorus was removed during the “blow” and that, as phosphorus in quantity over one-tenth of one per cent was detrimental to steel, it was necessary to use raw material which had little of this element.

This could be done, but it barred many pig irons otherwise good. Fortunately Swedish and many English irons had low phosphorus. Germany’s vast beds of high phosphorus ores, however, were useless for the purpose.

For twenty years this situation existed, during which time many metallurgists endeavored to make the process applicable to irons which contained high phosphorus. After long study and many experiments the problem was solved by Sidney Thomas, an English metallurgist. With a cousin, Percy Gilchrist, he made hundreds of blows with a toy converter holding only eight pounds of iron.

Bessemer’s linings had been of sand, clay and other earths which are known chemically as “acid” materials. By using “basic” materials such as limestone, dolomite, etc., for the converter lining and additions of limestone or burnt lime to the charge before and during the blow to make and keep the slag “basic,” Thomas was able to make the phosphorus burn after the carbon had been removed. Therefore, a three or four minute “after blow” following the “drop” of the carbon flame took out the phosphorus,—again, with generation of heat.

So there are two varieties of the process—the acid Bessemer and the basic Bessemer, but the former, only, is used in this country as we have few high phosphorus ores. The analogous open-hearth processes, which are next to be described, are both used in this country with the basic open-hearth greatly in the lead.

However, the basic Bessemer process of Thomas and Gilchrist is credited with making Germany’s great industrial development possible.

The well-known “Thomas Slag” which is in demand as a fertilizer on account of its phosphorus content is the by-product of the basic-lined converter.

An idea of what the invention of the Bessemer process meant to railroad development alone may be gained by studying for a moment Table No. 1. Wrought iron was our first material for rails, but, being very soft, it did not give long service. But a short time was required for Bessemer steel to displace it for rails when steel became available. The greater uniformity, strength and hardness of the alloy gave such excellent wearing properties that few rails of iron were laid after the year 1880.

During recent years rails have been made of greater and greater strength and hardness to keep pace with the fast increasing weight, speed and frequency of railroad trains, steel being susceptible to much modification of properties.

Now it appears that Bessemer steel is giving way to other products which show even superior properties.

What happened in the railroad world to a great extent has happened elsewhere, as the figures of Table No. 2 show. They are a barometer which indicates what has been our industrial development and our advance in civilization.