Once a Week (magazine)/Series 1/Volume 1/Bessemer and gun-metal
BESSEMER AND GUN-METAL.
Many of the readers of this periodical may not be familiar with the more prominent principles of iron and steel manufacture, and as they are an important part of great-gun manufacture, I will therefore name them as briefly as possible.
Pure iron like pure gold is homogeneous, but unlike gold it is rarely pure. If gold be kept in a melted condition a sufficiently long time, all extraneous matters may be burnt away, but if iron be kept in a hot state too long it will be burnt away itself. Pure iron appears to be ductile, but pure iron will not melt. To form cast-iron, a quantity of carbon must be mixed with the pure iron. If the quantity of carbon be less in amount, steel is the result.
The ancient method of making steel was to cover up bars of iron with charcoal powder and to keep them in a red-heated condition for a fortnight or so. When taken out the iron was found covered with blisters arising from gases constituting some of the impurities of the iron. Consequently, the purer the iron the less it would be blistered. To turn the blistered steel to use, it was shorn to pieces, and the pieces piled on each other, heated to a welding temperature—i.e., surface melted—and forged under the hammer. When drawn out into bars it was called “single shear steel.” To improve it, it was cut up again and repiled, welded, drawn into bars, and so called “double shear steel.” But these processes left the metal full of specks, flaws, and imperfect welds, with scaly particles, rendering it unfit for delicate cutting-tools.
In those days die-sinkers and others paid as much as three or four guineas per pound for a steel brought from India, called Wootz, which came in little half-round lumps, shaped as the bottom of a crucible, and weighing from two to three pounds. This was, in fact, the metal from which Indian sword-blades and other weapons were forged, and it was really natural steel cast by workmen sitting on their haunches and urging their fire by right and left-hand circular bellows.
In process of time it was discovered that, if instead of welding up the shorn blistered steel, it was put into the crucible, it could be melted into a homogeneous mass without flaw or speck, and then forged into a malleable bar. This was called cast steel, but it was a long time ere people would be persuaded that cast-steel would be other than brittle, like cast-iron. But as time went on die-sinkers found that what was called “Huntsman’s steel,” sold at about four guineas a hundred weight, was quite as good as Wootz at four guineas a pound, and Wootz was thenceforward kept at home in India for sword-blade making.
English steel was made from Swedish iron, simply because it was a purer iron than any other, and was manufactured by charcoal, and not by coke. But neither steel nor iron could be manufactured in large masses, save by the process of welding together smaller portions,—ever an imperfect process at best in the modes used; and so the prices ranged from eighty pounds per ton, for the highest qualities, to thirty pounds per ton for the lowest—carriage springs—till the advent of railways, when, with an enormously increased demand, the price went gradually down to twenty for manufactured springs, all specified to be of Swedish steel—all Sweden and Russia to boot not being competent to furnish the supply; English iron being in fact resorted to, to manufacture an inferior article.
One man finally solved for us the problem, how to produce both iron and steel in homogeneous masses of any required bulk. This man was Henry Bessemer, one of that not numerous inventive race by dint of whose brains England is not as China, but is ever progressive, a race ever seeking to develope the true meaning of what has been called the “primal curse,” not “sweat of the face” or “brow;” but rather sweat of the brain within the brow, wherein to seek redemption from all painful drudgery by converting it into healthy exercise. From sugar-refining to iron-making, yet with the bent of his mind—doubtless French Huguenot by derivation—ever leaning rather to chemistry than to mechanism, there are few things of the future that Henry Bessemer has not tried at, as witness the patent list, that record of pretended rewards for genius, wherein his name appears no less than sixty-seven times, beginning in March, 1838, and ending in December 1858, ranging over many subjects:
Printing, railway-breaks, glass, bronze powder, paints and colours, atmospheric propulsion, steam-vessels, locomotives, sugar, varnishes, kilns, furnaces, ornamenting surfaces, guns and projectiles, waterproof fabrics, screw propellers, iron and steel, railway wheels, beams and girders, treating coal, &c. Twenty-one patents were taken previous to the alteration of the law, for England only, exclusive of Irish and Scottish, and probably three thousand pounds were extracted from the inventor’s pockets in fees. The patents he has taken since the alteration of the law indicates the fact that the cost of patents is not less than before, but considerably greater, the restriction in title being so great that five patents for three years, at 30l. each, are required instead of one at 100l. for fourteen years; the five patents, if extended to fourteen years, costing about 160l. each, or 800l. instead of 350l., if English, Scotch, and Irish be included in both cases. Many of these latter patents probably did not go beyond “protection,” being, in truth, taken to prevent others from obtaining patents for every variety of article that could be made out of the improved iron and steel to the detriment of the real inventor.
Thus he went on, ever working through good report and ill report, falling often from a height where success seemed attained, not from false calculations, but from some adverse and before undiscovered fact in nature, most valuable to us to know, but not tending at the time to replenish the inventor’s purse.
At the British Association of 1857, Mr. Bessemer read a paper, wherein he described his process of iron making. The ordinary process is first, to run it from the ore into pigs by one heat. Secondly, to re-heat it and “puddle” it, i.e., stir it about in a melted condition with iron rods moved by men’s arms till it becomes stringy and tough, and gets rid of some extraneous matter. Thirdly, to beat it by hammer into a mass, called technically a bloom. Fourthly, to roll this bloom into a bar or bars, making the commonest iron. Fifthly, to cut the bar into short lengths, and pile them up. Sixthly, to reheat this pile and forge it into another bloom; and, seventhly, to re-roll it into a bar or bars. If, during the process of heating, the oxygen of the atmosphere gets access to the surfaces, scale is formed, which prevents perfect adhesion under the hammer, and the metal is not homogeneous.
Mr. Bessemer simplifies all this. When the metal is melted in the great furnace it is run out into a huge clay crucible, practically a colander, by reason of several openings in the bottom, through which the metal would run were it not impeded by a strong blast of air under great pressure, which is forced through all the interstices of the iron, and instead of cooling it, raises the heat to a greatly increased intensity. This burns away the carbon, which constitutes the chief difference between cast iron and malleable iron, and also some other matters; and when the metal is poured out, it is pure iron, if the process be carried on long enough, or if stopped at an earlier period so as to leave some carbon in it, it is pure steel: in both cases malleable. Thus one heat serves to make a malleable ingot, which is only limited in size by the size of the crucible, which may contain two tons; and, as many crucibles may be used and poured out together, there is no reason why a homogeneous lump of fifty or more tons should not be produced, either of iron or steel, which may be dealt with by the hammer, or by rolls, or both.
In rolling thin sheets of metal in the ordinary manner, the size is limited by the difficulty of retaining the heat. By another arrangement of Mr. Bessemer, this difficulty may be obviated. Hollow rolls are used, through which a stream of water pours, and on the surfaces of which jets of water play. Between these rolls, which are placed horizontally, and form a tank or channel when they approach each other, the molten metal is poured, and thus a sheet of any desired width or thickness may be formed, and only limited in length by the supply which the crucibles are capable of keeping up. The ore goes into the furnace a crude stone, and comes out of the rolls a sheet of tough metal. Iron-making is thus rendered as simple as the paper-making processes, where the rags go in at one end of the train of apparatus, and come out at the other perfect paper.
At Baxter House, St. Pancras, this new process of melting was first exhibited to the public, and excited an equal amount of wonder and incredulity. On one occasion, a sort of Welsh St. Thomas, iron-doubting, sneered as he saw the metal poured, and asked: “Do you call that malleable iron?” The inventor went into a shed, brought out a carpenter’s axe while the metal was still red, and cut three notches in the angle, just as might be done at the angle of a square foot of timber. The silent answer struck St. Thomas dumb.
Still the inventor had much to learn. The iron hissing, boiling, and bubbling in its clay colander, was poured out in its ebullient state, frothing like so much Champagne; and as it cooled was filled with innumerable air-cells; and the apparent want of success filled the mouths of fools and scoffers with matter for exultation. Far and wide the whole affair was considered a failure; natheless that men of logical mind knew to the contrary. But the resolute inventor stuck to his work, he had sounded the depth of his invention, but he had not explored many of its ramifications. Two years beheld him again before the world with the verification of his theories and of his earlier practice: the causes of failure unfolded. His next paper was read at the Institution of Civil Engineers; and those who know the critical acumen of that strong-brained body of men, and were present at the reception of Mr. Bessemer, and beheld the enthusiasm spontaneously kindled, as important truths were enunciated, and sample after sample was exhibited, opening new capabilities to these Anti-Chinese sons of eternal progress, are not likely to forget it. No actor at a successful début, no writer of a successful play, was ever more warmly greeted. A small cannon, a railway axle, a three-ply cable, twisted up of cold iron one-and-a-half inch diameter, steel bars and rods of all shapes, a large circular saw, boiler plates of perfect surface and great width, and, lastly, ribbons of iron as thin as paper, were exhibited. A small cylinder was shown of cast metal in a perfect condition, and another cylinder was also shown which had been doubled up flat under the hammer, without exhibiting the smallest crack at the sharp bends, but the tensile strength was shown to be nearly twenty-four per cent. greater than that of the most costly iron made in England.
A sheet of thin iron, reticulated and pierced with holes, almost like a lady’s veil, was produced, and stated to be a skin left on one of the crucibles after pouring out the metal. “Is that malleable iron?” asked one of the audience. The inventor simply folded it, and double folded it, and laid it again on the table in answer.
Representative men of the iron-master mould were present, some of whom denied that there was anything novel in the process, and others asserted that it was too costly to be of any use. Others inquired why it was that Mr. Bessemer chanced to be successful now, having failed of commercial success at the outset.
“I expended 7,000l.” said one, “and lost forty per cent. of iron in the process.”
“I,” replied Mr. Bessemer, “sometimes lost a hundred per cent., but I persevered. I found that experimenting with heavier charges of metal, gave a decided improvement, and I found that all ores were not equally suited to my process. Blaenavon pig at 9l. 10s., was not so good as Swedish pig, nor as the red hematite of Cumberland, of which class of ores nearly a million tons are raised annually, yielding upwards of sixty per cent. of metal.”
“The process melted down the lining of our furnaces,” said another.
“So it did mine,” replied Bessemer, “till I established myself as a steel manufacturer at Sheffield, and got to use the Sheffield road-drift. In short, when I began my experiments, I was an amateur iron-master, and two years of consecutive work have converted me into a practical man.”
Most engineers present felt that they were in the presence of a benefactor, who had immeasurably enlarged the sphere of their operations, whether in bridges, rails, locomotives, or ships. It was the triumph of a simple-minded man, earnest of purpose, and frank of nature, with nothing to conceal, but with the instinct of unsealing every mystery of nature so far as he could, and giving it to man’s uses. And, verily, that man had toiled and ranged through matter for twenty years, and at last gave to the world a process of which the results are incalculable;—homogeneous iron and steel without limit as to size.
Upon projectiles and projectile weapons these results must have an enormous effect; the process of welding iron together for barrels of small arms and for great guns may now be dispensed with. A short, thick, hollow cylinder being cast, may be at once rolled out direct between rollers into a musket or rifle barrel of any desired form; and great guns may be cast hollow, and put under the operation of a tilt or steam hammer, if needed, to consolidate the metal. And these malleable iron guns can be procured at one-third the cost of the ordinary cast-iron guns; and, what is very important, the malleable steel is even cheaper in cost than the malleable iron. The class of guns described in the last number to be borne on wheels without horses, might be produced with little labour and cost, very rapidly to any amount.
With regard to monster guns, they may be regarded as useful only for two purposes—to mount on forts for defence, and to place in vessels. They are not otherwise transportable weapons of offence. This question is yet in embryo; but if armoured ships are to obtain, this question must obtain also. For shot that are to pierce armoured vessels, it is quite clear that the Bessemer malleable steel will prove a most important material, as it can easily be tempered to any required hardness to act as a punch, and can be more easily manufactured than the wrought-iron shot that have replaced fragile cast-iron.
Before constructing monster guns we have yet to settle the question of the form, proportion, and weight of the shot we are to use for given distances with a given destructive power. This ascertained, there will be no difficulty in the construction of the gun itself. But it should be a gun so proportionably heavy as to be absolutely without recoil; so long as to expend expansively the minimum amount of powder required to obtain the longest possible range; so dense in the material as not to fracture; and so solid as not to spring and temporarily enlarge its diameter with the explosion. A maximum-sized gun of this kind would probably weigh 100 tons, and if used for forts would require machinery to move it and aim it. If used in vessels it would be placed fore and aft with only a vertical movement, and the vessel itself would serve as a stock to it, lateral movement being given by the screw and rudder. Fitted to an armoured vessel, with the bows thoroughly protected, such a gun would be able to batter down everything in the shape of a stone wall at such a distance as to render being hit from the fort almost an infinitesimal chance. It would be like shooting at the edge of the east wind.
Long-range rifles, it may be remembered, were more than a match for the fort-mounted artillery at Bomarsund and in the Crimea, killing off the artillerymen. This will become more and more the rule as guns are improved. Monster guns are not calculated to pick off skirmishers, and it therefore becomes needful to protect their gunners. With the large embrasures of the ordinary kind which would be required for monster guns, the risk to the gunners would be much increased. It therefore is well to inquire whether there is any reason why the gun should not be closely covered in. With the ordinary mode of mounting on trunnions this seems scarcely practicable. But it would be very practicable to mount the gun on a sphere or ball working in a socket and capable of radiating in any direction. If the radius of the gun were only required to be small, as in a moving vessel, the ball might be placed at the muzzle, and in such case little sound or vibration, and no smoke whatever should come into the vessel, and no damage could be done to the gun save by shot striking exactly in the muzzle. This is so perfectly practical an arrangement, that nothing but the fact of a ship’s sides being too weak to sustain the recoil of guns so attached ought to keep it out of use. Our sailors are too precious a commodity to have them wasted in working muzzle-loading guns at open ports. The steam ram now constructing is perfectly adapted to this arrangement, and a properly constructed gun should be free from recoil. Even in our present state of knowledge, muzzle-loading guns must be regarded as things of the past, matching with “Brown Bess” and other Tower antiquities. Into the details of construction it is not desirable to enter; and although the improvements indicated give these advantages chiefly to nations with manufacturers widely spread and of a high order, still the State should ever have in reserve a stock of improvements to meet emergencies; not making them common till required by the presence of adverse circumstances. The State should “keep a hold of the actual, knit the new securely to it, and give to them both conjointly a fresh direction.” The astonishment created by the results of the Armstrong gun is simply a proof how much the progressive actual is overlooked by the many, while the special individual by time and thought turns it to account; and then it is assumed that we can go no further, not heeding the words of the philosopher poet—
Men my brothers! Men the workers! ever making something new;
That which they have done but earnest, of the things that they shall do.”