Puslapio vaizdai
PDF
„ePub“

the bottom of the crucible, from entering the mould, a plan which would at least surprise anyone seeing a thermit joint made for the first time. Having got everything ready for a run, Mr. Jurriaanse places a piece of -inch iron plate over the opening in the mould, and then, when he taps the crucible in the usual way, the first splashing of iron and sand is scattered, but the iron plate is no bar to the entry of the thermit iron that follows, and so the iron enters the mould, but the sand is kept out. Another point of importance, in which the beginner persists in going wrong, is to wait for a time-which in the excitement seems interminable-say half a minute or so after the reaction is complete, before tapping. This allows gas and particles of slag to get well separated from the metal, and a more clean and perfect run is to be expected, than any that can be obtained if the tapping of the crucible is effected with undue hurry. There is another point to which he attaches some importance; in order to ensure that the crystallisation of the metal shall be of fine grain, he gently and continuously taps with a hammer, the steel upon which a thermit weld is being made, from the time of the setting of the metal until the crystallisation may be considered complete, and finally he pays great attention to a careful preliminary heating and annealing, where that is possible.

As an example of an engineering repair which I fear it would be difficult to get accepted in this country, I am able to show slides of a repair made in Austria, for the Austrian State Railways, to a locomotive driving wheel, from which you will see that in three places, the spokes have had a break satisfactorily repaired.

A question that will very naturally be asked is: To what extent are welds made in this way?—really welds, and not mere patches and if welds, to what extent may the utility of an otherwise sound weld be destroyed by contraction strains? I think the best answer to this is found in the fact that not only have broken teeth been replaced in steel wheels, and stood up to their work, but a far more difficult operation, and one which involves the most severe stresses known in engineering, has been successfully accomplished. I refer to the casting of new steel journals on the ends of the broken rolls of a rolling mill. This is hardly so direct an operation as any that I am describing this evening, and would take too long to describe in detail; but the method was devised by Prof. Matthesius,

now appointed Professor of Metallurgy in the University of Berlin, and has been successfully accomplished. If a thermitwelded roll will stand to its work, it is hardly necessary to discuss the soundness and strength of the weld. I cannot give a better example of the British (it was in Scotland), mode of being interested in the progress of the arts than the answer of one of the engineers of a great steel works, to whom I was describing this process, as I saw a number of broken rolls. lying about. He showed his superiority over a mere outsider, and his just appreciation, in the following words: "The thing is ridiculous, the roll cost £300."

SHIP REPAIRS.

The success with which steel of moderatedimensions, such as has already been described, may be welded by the aid of thermit, naturally leads to the inquiry as to how far it would be applicable when the section of the metal, where a weld is desired, is very much greater say than 10 square inches. It is difficult, at first, to realise the possibiity of heating solid steel with a sectional area of say 50 or 100 square inches to the welding point, without at the same time, heating the metal through a considerable distance, which would inevitably be the case if the heating were performed by the use of an ordinary forge fire, which would require a greatly increased quantity of heat. The fact that thermit puts into our hands a temperature at least 1,000° Centigrade above that available in theforge, and the fact that the thermit iron carriesits heat at a rate enormously greater than that at which hot furnace gas can possibly carry it, simply on account of its far greater density and conductivity, completely alter the usual circumstances, and further, the relatively less. conductivity of the solid metal for heat when dimensions are great, as compared with that where the dimensions are small, makes it by no means so prohibitive a process to weld steel of the great dimensions of the propeller shafts. or the framings of ships, as at first one would be led to expect.

In the case of a repair to a ship, the stake is so great, that there must have been great anxiety when the first repair of the kind was effected. This has now become almost a common operation on the Continent. The importance of the subject is such that it will be worth while to spend a short time describing, by the aid of photographs kindly furnished by Dr. Goldschmidt and Mr. Jurriaanse, some

[merged small][merged small][graphic][ocr errors][merged small][merged small][merged small]

three sheet iron boxes, so as to allow of the entrance of the metal at the lower part of the desired cast, and of the overflow of so much metal as would ensure the passage of enough thermit iron through the gap as to bring the metal up to the welding point, and superficially melt it. In the case of the s.s. Sebenico, in order to avoid any contraction flaws, the stern post was forced outwards by means of a powerful screw jack before the metal was run, and then, as the cooling began, the jack was gradually released, so as to keep the joint in a state of compression, Of these ships, the Assyria and the Sevilla belong to the Hamburg-American line, and from the time of the weld to the present, i.e., about 14 months, they have experienced the usual Atlantic weather, and no trouble has resulted. The Sebenico repair was carried out in the floating dock at Trieste, and was also entirely successful.

One of Mr. Jurriaanse's repairs to a dredger is interesting in that the heel just under the rudder frame had been broken away in running aground. In this case, a new piece over three feet long was forged to replace the missing corner, but it was purposely made too short, so as to leave a gap at each end. This was welded at both places as described already. The photographs will make the process more intelligible.

LUNKER AND TITAN THERMIT. Referring back to an early paragraph of this paper you will remember that I showed how, not only iron, but other metals may be reduced from their oxides by the aid of aluminium, In this way chromium, manganese, titanium, tungsten, and a number of metals may be obtained, free from carbon, and suitable for the purpose of making alloys, specially of copper or of steel. Specimens of several of these are upon the table. There is, however, a use for thermit containing some of these metals, to which I would refer, namely, the use of small tin boxes containing what Dr. Goldschmidt calls "lunker" thermit or "titan" thermit, which may be plunged, at the end of an iron bar, into ladles of cast steel or of cast iron, where the reaction sets up such a development of heat and such a churning and mixing of the metal as to make it possible to run thin and extensive castings in steel or in iron which, in the ordinary way, would be impracticable. The British Westinghouse Company have kindly given me permission to state that they are now using lunker thermit with this object,

and they have sent me some specimens of castings so made which they found impossible before, of which specimens are upon the table.

The production of heat has been ingeniously made use of to prevent the formation of cavities in steel ingots. A small box of thermit, prepared for the purpose, is pushed into the head of the ingot just as the crust is beginning to form. The heat set up there is so great that, as the metal below gradually solidifies, the cavity which ordinarily is formed, and which spoils the upper third of the ingot, is kept supplied with hot, finid metal, so that a very much smaller proportion of the ingot is wasted. The same purpose has been served where very extensive steel castings are made, by putting small boxes of special thermit in the risers at the distant parts of the mould. Where hitherto, the metal on reaching the riser has become too cool to be able to run back to supply the contracting metal during the process of feeding, the metal in the risers is made so hot, by the use of the thermit, as to get over this difficulty.

[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][ocr errors][ocr errors][merged small][ocr errors][ocr errors][ocr errors][ocr errors]
[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small]

COMPARATIVE RESISTANCE TESTS CARRIED OUT BY THE ELECTRICAL AND PERMANENT-WAY ENGINEERS TO THE LEEDS CITY COUNCIL. The following are the results of tests made of "Thermit" joints, a fish and sole plate joint, and the solid rail. The tests were made on the Headingly section, near Hyde-park-corner. The rail was disconnected at one end, so as to isolate the length containing the thermit and fish-plate joints, and the resistance was calculated from the voltage drop across each joint when a certain current was passing through it.

No. 1.-Rail with thermit welded joint with one bond 4/0 B. & S. Chicago type. This joint was made in February of this year, on a track that has been in operation since August 1898, and was not butt welded, there being an expansion space of 3-16 inch, and the rail packing underneath had given way, allowing the rail to vibrate as the cars passed over it.

No. 2 was the same joint, but with bond removed, and thermit joint only-not butt welded. No. 3.-Our ordinary fish-plate and sole-plate joint: fish-plates, 2 feet long, 46 lbs. per pair, secured by six inch bolts; sole-plate, 2 feet by 8 inch by

inch, and secured by twelve inch bolts and two 32 inch 4/0 B. & S. Chicago bonds. This joint was made in July, 1898.

No. 4.-Solid rail only on the same track. No. 5.-Thermit welded joint where clamps had been used, and a butt weld secured. No special care taken at the making of this weld, and it may be taken as a fair sample of an ordinary thermit welded rail joint.

[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small]

Colonel ALLAN CUNNINGHAM asked what was the longest length of continuous lines for trams in existence. There seemed to be a difficulty, owing to expansion, in the use of very long pieces. If one inspected the upright railings, such as those in Hydepark, it would be found that the rails were laid out straight on the top of stone foundations and were leaded down at intervals, whereby the expansion was resisted; and after a hot summer he had often noticed that the rails were curiously curved; the stresses set up were so great as frequently to break the railing away from the foot where it was leaded into the stone. The very same thing could be seen in the railings in the front of ordinary dwelling-houses, the straight railings being distorted into curves in a hot summer, and very frequently broken away from the foot.

Mr. F. W. FLETCHER asked if there was any firm in London which carried out repairs of machinery by the method described. He knew some firms in London, who had large rolling mills, where, if repairs could be done in the way mentioned, it would be a very valuable assistance.

Mr. A. P. TROTTER inquired what form of oxide of iron was used.

Mr. J. W. SUTTON asked whether the welding of rails had been applied to the main lines of railways as well as to tramways.

The CHAIRMAN thought that everyone who had heard the paper read, must have felt there were a number of applications for the beautiful system of welding described; but he was sorry to say he had observed the backwardness of Englishmen at present to adopt new inventions. It had lately been his duty to preside over a committee, the object of which was to inquire into the rules that should be made for the use of electricity in mines, a very big subject, because the mines of this country would soon be electrified, coal cut by electricity, and a great amount of money invested in apparatus, which would enormously increase the output. First of all English engineers gave evidence before the committee, and he was bound to say that, had the committee listened only to them, a set of rules might possibly be formulated that would not have answered at all. But the committee discovered that in the Düsseldorf district the Germans were entirely ahead of this country in the use of electricity in mines. Three-phase systems were being employed that were, he believed, partly invented by an Englishman, developed by a Swiss engineer, and worked out and practically applied by the Germans. For instance, men and coals were hoisted at a great rate from the pits with electrically driven hoists and winding gear, whereas there was not a single electrically driven winding gear in the whole of this country; although, he was bound to say, on the other hand, there was a three-phase coal-cutter in England which worked without any brushes, and consequently without sparking, but only one. That was due to the enterprise of Mr. Garforth, the well-known English mining engineer; but on the whole England was distinctly behind Germany in that respect. Two explanations occurred to him from his personal experience of factories. In the first place, there was too great a disposition among all classes simply to amuse themselves. The younger men, especially the sons of the owners, thought too much of golf and hunting and too little of the details of their business. If our great industries were to be conducted by captains of industry of that sort, the sooner some change took place the better it would be for the whole country. Again, there was too great a tendency, which was well known in engineering works, not to write off a sufficient amount against depreciation of capital. There was not half enough machinery scrapped, with the consequence that the machinery became antiquated. The second one was a deeper one still-viz., that our education had been distinctly defective. It had been run on clerical lines. He did not desire to say a word against clerical influence; it had made England a moral nation; but, unfortu

nately, there was another side. A clerical master, when he saw a boy at a lathe, said: "What a useless thing it is; it amuses him, I suppose, poor fellow." In many schools a boy who exhibited any mechanical ability was looked down upon. When the Board schools were founded an attempt was made to copy the public schools system, and, even in the manufacturing districts, masters were appointed not one single one of whom knew how to handle a machine, with the result that boys who exhibited a tendency for mechanics and industry were discouraged, and everybody thought that the only thing worth knowing was how to spell correctly, or some rubbish of that sort. When one saw the rapid way in which the Germans, the Italians, and the Japanese picked up science, it made one feel that England must seriously wake up. Our commercial supremacy was threatened, but if the people of the country would only seriously take the mattter to heart he thought we should retain it. It was the young that had to be trained. The boys must be taught that life was not all "beer and skittles," and golf and bridge, but that they must take an intelligent interest in the commerce of the country. In every school where boys were trained for industrial pursuits an endeavour should be made to destroy the philosophical system of Aristotle, and substitute in their place the modern methods of learning science.

Mr. Boys, in reply, said he was in perfect harmony with what the Chairman had said on the educational question. Mr. Inwards, who asked whether it was possible to use thermit without the crucible, had hit the nail upon the head, because in the most difficult operation to which he had referred, which was designed by Prof. Matthesius for welding new journals on rolls, the end of the roll was heated up by thermit ignited' not directly upon its end, but in a crater so as to produce its heat without any intermediate waste via the crucible. But that could not be done as Mr. Inwards wished to do it for the reason that, in the first place, the temperature was inconveniently high. Not only was damage done to metal in immediate contact with the ignited thermit, but worse than that, the slag formed in minute quantities throughout the mass, had no time to be separated and cleared free from the thermit iron, the result being what was so graphically described by Dr. Percy, the famous metallurgist, in relation to another operation, as "a nasty mess." It could not be done directly by burning the thermit upon the material to be welded. He would not go through the whole of the details of Matthesius' beautiful process, but he had designed a method whereby the slag was collected on a cold ring and removed, and when the end of the roll had been brought up to the welding point, then steel from the ladle was tipped into the empty space, and so was welded on to the end of the roller by the intervention of the heat of the thermit

« AnkstesnisTęsti »