PIPE AND TUBE MAKING 111[ACHINES. I. NEW PROCESSES OF MAKING SEAM LESS TUBES. —The manufacture of tubes without soldering has in recent years been the object of persistent research and important labors that have originated several new processes, among which those of Messrs. Flotow & Leidig, Robertson, and Mannesmann are especially worthy of notice.
The first of these processes. which is of limited application, employs a method of longi tudinal drawing upon a stationary mandrel. The two others have recourse to a helicoidaI or diagonal drawing. accompanied with a cooling of the metal, on a fixed or movable man drel, by the aid of revolving draw plates or rollers having a differential rotation. They constitute two of the most remarkable examples of the flow of solids through metals.
Up to the present, the Robertson process appears to have been applied with the most advantage to the working of plastic metals (copper, tin, bronze, etc.) in a cold state, while that of Mannesmann, which is of the most remarkable boldness and originality, is perfectly adapted to the manufacture of iron and steel tubes. This mode of manufacture, which is now worked in Germany on a large scale, produces, at a low price, absolutely homogeneous seamless tubes, whose metal, far from being weakened, is strengthened by the operations that it undergoes.
The Flotow & Leidig Proeess.-1 n the process of drawing employed by Messrs. Wilhelm von Flotow and Hermann Leidig, of the Dantzig Arms Manufactory, the mandrel, d (Figs. 1 and 2), is fixed, and the ingot is drawn between the head. v, of the mandrel and the draw plate, at, in such a way as to convert it into a tube of smaller diameter, To this effect, the ingot is held by its tenon and mortise extremity, e, in the head, s, which is movable under the action of the screws, o and p. Through successively reducing the diameter of the draw plate, this process permits of drawing out a tube conical externally, like a gun barrel.
The Robertson Process.—The mandrel, D (Figs. 3, 4, 5), of the apparatus of Mr. James Robertson, of Glasgow, revolves within the ingot. C, and is at the same time pushed forward by the hydraulic press, E. The rotary motion is given by a train, the pinion of which is fixed by tongue and groove to the shaft, L The draw-plate, A, which is firmly keyed between the jaws, B. is slightly conical, so that the ingot, C, fixes itself in the die by the very pressure of the mandrel. The form of the mandrels varies according to the metal and temperature of the ingot. The one shown in Fig. 5 serves to convert cold copper and soft steel ingots into thick sided tubes that are afterward drawn out. The point is provided with three longitudinal grooves, enlarged from the point to the base. and with rounded sides. so as to displace and face back the metal without cutting it, and designed likewise for the passage of the petroleum for lubricating the point when ingots of copper are thus treated in a cold state. The velocity of the tool at the circumference is then but about 3 in. per second, although it is very rapid (40 ft. per second) when hot steel ingots are being pierced, without a possibility of oiling the point. The advance of the tool in this case is about 5 ft. per second.
The Mannesmann Messrs. Reinhard & Max Mannesmann's process the seamless tubes are obtained by rolling solid bars. As shown in Fig. 6, at 1, the bar, 1, is held between two cones A a, revolving in the same direction, and the axes of which point in opposite directions in parallel planes. The converging sides of the cones, between which the bar is held, draw out the metal at its periphery in such a way as to gradually make it assume the form of a tube, the beginning of which is seen at b. When the finished tube comes from the roller, as shown at 2, there remains a blank. B, hollowed out at through the pressure of the cones. The cones are nearly always hollow helices with pitches increasing from the point to the base, so as to draw out the surface of the bar progressively in measure as it advances between the cones. If it is desired to avoid the black shown in 2, it will suffice
to push the tube submitted to drawing over a mandrel, D (3), which revolves in a bearing, E (4). For softer alloys, which may be rolled in a nearly cold state, a conical mandrel is em ployed (M. 5), and this, if need be, can be kept cool by a stream of water, and serve to increase the diameter of a tube already formed. This mandrel terminates in a grooved point, and can, as shown at 6 and 7, revolve in the same direction as the ingot. or the opposite, according as it is desired to retard or hasten the drawing around the point of the mandrel. The proc ess by means of which the tubes shown at 8 are obtained, is founded on the principle that an ingot rolled diagonally between two cones (A and a, 9), revolving in opposite directions, undergoes at the bearing point distortions that are distributed over the triangular wheels, e c, which cause within the ingot molecular stresses, whose resultant tends to distend its fibres all around its axis, in measure as it revolves between the cones. The tubes thus formed are smooth within. Their fibres are not broken, but lengthened out spirally around their axis. The apparatus represented at 10 serves for manufacturing copper tubes of uniform thickness, and of a diameter greater than that of the ingot. The point of the mandrel pene Crates the ingot very easily without heating it much. In a new variant of their process, Messrs. Mannesmann substitute mushroom-shaped rollers, a a (11), for the cones. The intersection of the vertical planes passing through the axis of rotation and through the apices of the rollers is situated in the vertical plane passing through the axis of the ingot, D, and man drel, E, Moreover, the angle, e, of the mandrel is a little more open than that of the roll ing generatrices of the Mushroom-shaped rollers, so that the lamination compresses and re duces the thickness of the sides of the tubes on the mandrel, while its diameter at the same time increases. From 12 will be seen how a tube may he made by means of two successive operations, one of them preparatory, and consisting in tubing the axis of the ingot by the diagonal rolling of the plates, F f, and the other a finishing operation, consisting in widen ing the tube on the mandrel, E. In this case the rollers, A a, may be given a velocity such as to make the mandrelled part of the tube rotate more rapidly than that part of the ingot submitted to the action of the plates, F Diagrams 13 to 18 show how it is possible to make a tube directly with but a single pair of rollers, G y. Before approaching the mandrel, E, as shown at 14, the ingot (13), held between the converging generatrices at G g, undergoes a preparation that reduces its dia meter and hollows its extremity at d (14), so that it can favorably meet the point of the mandrel in passing from the converging to the diverging generatrices of the rollers. Tho tubular part of the ingot is then, as shown at 15, pushed along and compressed on the man drel through the gradual action of G g, and converted into a thin-sided tube, until the pos terior end of the ingot leaves the rollers. When the entire manufacture of the tube is effected by means of a single pair of cones, it is necessary that the torsion given to the ingot by the converging generatrices during the first part of the operation (13 and 14) shall not be destroyed during the widening and calibrating (15, 16, 17), because such torsion, which winds the fibres spirally around its axis, considerably reduces its resistance to internal press ure. To this effect, the rollers are given a profile and inclination such that the vertical planes passing through their summits, situated (as shown at 18) at different levels. intersect each other in the vertical plane of the axis of the tube. The tube thus rolls without torsion between the divergent generatrices. Other descriptions of Mannesmann's tube process may be found in Trans. A. S. M. E., vol. viii,, p. 564, and Trans. Am, Inst. Mining Engrs., vol. xis., p. 384.