WO2000006317A2

WO2000006317A2 - A process for continuously working metal bars or rods, and a device for carrying out the process

Info

Publication number: WO2000006317A2
Application number: PCT/IT1999/000212
Authority: WO
Inventors: Pietro Bertolini
Original assignee: I.Fi.Co.M S.R.L.
Priority date: 1998-07-27
Filing date: 1999-07-09
Publication date: 2000-02-10
Also published as: IT1306341B1; WO2000006317A3; AU4648799A; ITMO980174A1

Abstract

The invention relates to a process and device for continuous processing of metal rods. The invention is applicable to rods transiting between a supply system (2) and a subsequent work station (3). During transit, the rod (1) is subjected to traction forces causing permanent deformations in an axial direction of the rod; the rod is also subjected to elastic deformation forces which cause only an inversion of direction of advancement of the rod; the device for actuating the process comprises an upstream rotor (4) and a downstream rotor (4a) rotating about fixed and parallel axes (5, 5a), each of which comprises coaxial gullets (6-7..n, 6a-7a..na), having increasing diameters with respect to the advancement direction of the rod, and in which the rod winds undraggingly and passing from one rotor to the other in its journey between the supply system (2) and the subsequent work station (3); means for drawing the rod.

Description

A Process for continuously working Metal Bars or Rods, and a Device for Carrying Out the Process-

Technical Field

The invention relates to a process for continuous working on metal bars or rods, and a device for carrying out the process. Background Art

The present invention proposes to obviate, in particular though not exclusively, the problems which arise at the moment in a process when the metal bars or rods are to be drawn into wires.

Following the heat or mechanical treatment a bar has undergone at high temperatures, especially a metal bar, the bar appears as a half-finished workpiece having a very hard layer of oxides which considerably complicates the following operations, especially drawing operations to reduce the bars into wires of various diameters. These oxides, which would quickly wear out the draw-plates, must therefore be removed before proceeding to the drawing operation. A first process used to carry out mis operation, commonly known as "peeling" is a chemical descaling method, using acid baths, for example chloride^' or sulphide baths in suitable solutions.

Apart from the problem of corrosion of the metal itself, which is prevented by the use of corrosion inhibitors or by anode-type descaling, these processes have two main drawbacks, i.e. high costs and difficulty both of use and of disposal of the acid solutions used. Any errors in the management of the process might create, given the extreme danger and toxicity of the substances, considerable damage to persons or the environment. For these reasons these methods tend to be used only when strictly necessary.

Another method used for this operation consists in bending the bar or rod about small-diameter rollers or pulleys so as to cause a plastic deformation in the metal. During the bending process, the oxides, which are much harder and more brittle than the metal, will not follow the bending process and will therefore break, crack and easily detach from the metal when brushed or removed by other mechanical methods. Figure 1 schematically illustrates a device which uses the above-described method, in which the rod is bent around a number of pulleys, at least three, during which the rod is necessarily bent, with plastic-type deformations, causing detachment of the "skin" of oxides. The pulleys are made of or plated with very hard materials, for example tempered steels or carbon steels, so that they will not wear rapidly. The rods usually have a diameter which exceeds 5mm., so the forces at work in bending them are of considerable entity, as are the reaction forces that develop between the rod and the pulleys. It is therefore inevitable mat some very small remains of oxides will enter the actual metal of the rod and be almost unremovable. This is the greatest drawback of the above-described process. The oxide splinters or remains constitute a serious problem for the rod, or more precisely for the wire which will be drawn from the rod. This problem, though, is not enormously relevant for large-diameter wires, inasmuch as the only drawback is greater wear on the draw-plates, or possible breakage thereof. For narrow-diameter wires, however, the splinter of oxide constitutes in effect a large part of the total thickness of the wire. The above-described process would only be practical, then, in an operation where a large number of draw-plate operations was envisaged, each one reducing the diameter of the wire until a final result of less than 1 mm. was reached, because otherwise the presence of the splinter would cause frequent breakage of the wire with a resultant breakdown in the continuous drawing process and a poor-quality final product. The aim of the present invention is to obviate the above drawbacks by providing a process and device for working, and in particular for peeling, a rod, wherein the peeling is perfectly executed and no use of chemical agents is required, and wherein there is practically no relevant intrusion of splinters of oxides into the metal of the rod. A further aim of the present invention is to provide a process and device for peeling the rod which are simple and economical to make and use.

An advantage of the present invention is that the process and device can be used in existing drawing plants with no modifications thereto.

These aims and advantages and more besides are all attained by the present invention, as it is characterised in the appended claims.

Disclosure of Invention

Further characteristics and advantages of the present invention will better emerge from the detailed description mat follows, of the process and the device therefor for rod peeling, the device being illustrated purely by way of non-limiting example in the accompanying figures of the drawings, in which: figure 1 schematically illustrates a device of known type for continuous peeling of rods or metal bars; figure 2 is a schematic view from above of the device of the invention; figure 3 is a schematic lateral view of the device of the invention; figure 4 is a diagram of the path the rod takes internally of the device of the invention.

The process for continuously peeling rods or metal bars of the invention is applied to the rod as it transits between a supply system 2 of known type, which continuously feeds the rods to be peeled 1, and a further work station 3, also of known type, to which the peeled rod la is delivered. The process is particularly applicable to known-type wire drawing plants, where the supply system is generally constituted by large bobbins bearing the rod to be drawn, followed by the actual draw-plate station. The work stations might be of a different nature, however; for example they might be represented by the heat-treatment plant and a bobbin for winding the peeled rod before sending it on to further work stations. In any case, the supply system and the following work station obviously do not form a part of the process and device of the present invention.

During its transit from the supply system to the following work station, the rod is subjected to a sfretching tension which exceeds its permanent deformation threshold in an axial direction. To achieve this deformation, the rod, during its journey, is made to pass along straight paths and is stretched there, then to be made to follow curved trajectories where it is elastically deformed, not permanently, but turned to an angle of about 180°.

In a preferred process, the above-described straight and curved trajectories are obtained by winding the rod, with no dragging, about a pair of rotors, respectively an upstream rotor 4 arranged on the rod supply system 2 side, and a downstream rotor 4a arranged on the side where the next work station 3 is situated. The rotors 4 and 4a rotate about fixed axes 5 and 5a, which axes are parallel and distanced by a distance equal to the length of the straight trajectories. Each rotor comprises a plurality of axial gullets, respectively 6-7...n 6a-7a....«a, which have increasing diameters in relation to the direction the rod is travelling in.

The rod is advanced by either motorising one or other of the rotors, especially the downstream rotor, or by using the drawing system of the downstream work station. The first system, evidently more expensive, is preferable when it is desirable to render the peeling system independent of the subsequent work stations, for example to make plant start-up easier. The second system is more economical but requires that at plant start up a rod is already partially engaged in the following work station, so that the rod can in fact be drawn thereby.

The device for actuating the process of the invention comprises the pair of rotors, respectively the upstream rotor 4 and the downstream rotor 4a, which, as described above, rotate about fixed parallel axes 5 and 5a. Each rotor has coaxial gullets, respectively 6-7 ... n and 6a-7a .. na., which have an increasing diameter with respect to the advancement direction of the rod. In particular: the first gullet 6a of the downstream rotor 4a, around which the rod 1 coming from the supply system winds, has a smaller diameter than the first gullet 6 of the upstream rotor 4, in which the rod coming from the second gullet 6a winds; the first gullet 6 of the upstream rotor 4 has a smaller diameter with respect to the second gullet 7a of the downstream rotor 4a, in which the rod coming from the first gullet 6 winds; the nth gullet Na of the downstream rotor 4a has a smaller diameter than the nth gullet n of the upstream rotor 4 in which the rod coming from the Na-ma throat Na winds and from which the peeled rod 1 is sent on to the plant 3. Substantially, then, the rod, passing from one rotor to another, winds undraggingly on gullets having ever-decreasing diameters, arranged altematingly on the upstream and downstream rotors. To prevent dragging, which is improbable anyway, the throats could be coated with high friction coefficient materials; mis precaution is however almost always excessive as the friction developed between the rod and the gullet is usually sufficient to prevent any dragging.

The means for drawing, which cause the advancement of the rod in the device, can be constituted by a motor (not illustrated) driving the downstream rotor while the upstream rotor is idle about its own axis (or vice versa), or the downstream rotor could be drawn by the plant of the following work station in line. As one rotor is in any case idle, the only equilibrium position for rotor rotation, i.e. with no dragging of the rod on the gullets, is when the angular velocity of the two rotors is the same; in this way, as the gullet diameters are in increasing order, in the straight tracts of the rod as it passes from one rotor to another, the rod is subjected to traction, which lengthens it and consequently diminishes the diameter of the rod, which diameter is proportional to the ratio between the diameters of one gullet of a rotor and a next, i.e. the ratio between the circumferences of the rotors.

While in the straight sections the rod is deformed by lengthening, the layer of oxides constituting the peel, much harder and more fragile than the metal, does not deform plastically but cracks and detaches. To facilitate the detachment, which happens naturally anyway (the splinters of oxide can actually be seen to fly off the rod), mechanical devices can be provided, such as brushes or blowers or magnetic devices, which interfere to brush the rod as it passes and detach those splinters of oxides which are already detach but need removing completely. From a conceptual point of view, these results might also be obtained using a device having equal-diameter gullets but rotating at different angular speeds (a different peripheral speed would in any case obtain between one rotor and a next, which would stretch the rod). A device of this type would however not allow the rotors to be keyed on the two shafts alone; either each rotor would have to be provided with a separate motorisation or special mechanical transmissions would have to be provided between rotors and shafts. Constructing such an arrangement would also be complex and costly.

In order to have a large contact surface between the rod and the rotors, so as to obtain a distribution of the stresses developing between rod and gullet which would not create any single stresses exceeding the elastic limit of the material, and in order to avoid abrupt changes in the direction of the rod which might cause flexional stresses exceeding the elastic limit of the material, the ratios between the diameters of the throats and the rotors and the diameter of the rod being processed must be above 100: 1. Obviously the greater the gullet diameters, the better the device will function from the point of view of the stress the rod will be subjected to in the curved sections. It is also obvious that the diameters of the gullets must be compatible with an acceptable device mass. In the curved sections, the stresses the material of the rod is subjected to are not great enough to cause oxide detachment. In any case, given the ratio between the diameter of the rod and that of the gullets, the specific pressure between gullet and rod is not such as to cause any splinters of oxide to enter within the rod material. The total forces developing between the two rotors are of considerable entity. Thus in order to prevent possible deformations of the device, apart from a support frame 9 on which the rotor shafts are projectingly supported, a spacer 8 is provided to connect the free ends of the rotors, which spacer 8 keeps the positions of the axes constant. With regard to the reciprocal positions of the rotors, note that the downstream rotor is arranged slightly backward, in the direction of the support frame 9, with respect to the upstream rotor so that the rod, arriving from the supply system and going first to the downstream rotor, is not interfered with by the upstream rotor as it does so.

The rotors can have a variable number of gullets; furthermore, while when the rod enters, owing to problems of mass the rod passes first into the downstream rotor, when it exits from the device it can wind last about the final upstream rotor gullet or from an intermediate gullet thereof. This will obviously have an effect on the degree of oxide peeling achieved on the rod (which is remarkably good even after only a few passes around the rotors) but also the lengthening of the rod and its reduction in diameter. The process and the device described have also the advantage, therefore, of providing a worked rod of perfectly predetermined diameter as it depends precisely, as experiments have shown, on the dimensional ratios between the gullets and, in the final analysis, on the dimensional ratio between the input gullet and the output gullet. This enables any subsequent drawing operations to be reduced in number, which is useful, for example, when the rod is to be subjected to further drawing processes. A further considerable advantage that the process and the device exhibit with respect to known plastic-deformation peeling systems is that the exiting rod has a substantially circular section, with obvious advantages for subsequent processing operations; known processes produce an exiting rod which, apart from the previously-described drawbacks, has a deformed section, with some parts of the edge squashed and flat, all of which creates problems in particular of uneven wear on the draw-plates and in general on the tooling associated with subsequent work operations.

Thus, therefore, the present process and device enable operations such as oxide- peeling, the principal operation, but also enable the rod to be reduced in diameter while at the same time producing a circular section thereof.

Claims

Oaims.

1). A process for continuous working of metal rods or bars, of a type which can be applied on unprocessed rods (1) as they pass from a rod supply station (2) to a next work station (3), wherein during a transit from the supply station (2) to the next work station (3), the rod (1) is subjected to a traction force which is greater than a force needed to permanently deform a material of which the rod (1) is made, said traction force being exerted only in an axial direction of the rod (1). 2). The process of claim 1, wherein: during the transit the rod is made to follow a straight path, during which it is subjected to traction forces exceeding a permanent deformation stress limit of the material the rod is made of; between each straight path and a next straight path the rod is made to bend, and is therefore subjected to elastic deformations, which cause an inversion of a direction travelled by the rod, by about 180°.

3). The process of claim 2, wherein the straight pathways and the curves are obtained by causing the rod to wind undraggingly about a pair of rotors (4) and (4a), which rotate about fixed, parallel suitably axes (5, 5a), spaced from one another by a distance equal to a length of the straight pathways, each of which rotors (4, 4a) comprises a plurality of coaxial gullets (6,-7.. n, 6a-7a..wa) having increasing diameters with respect to an advancement direction of the rod. 4). The process of claim 3, wherein an advancement of the rod is obtained by motorizing one of the rotors (4, 4a).

5). The process of claim 3, wherein an advancement of the rod is obtained using a known-type system for drawing belonging to the subsequent work station. 6). A device for continuous processing of metal rods (1), arranged between a supply system (2) of known type for continuously feeding rods still to be processed, and a subsequent work station (3), also of known type, which the processed rods (la) will be passed on to, wherein: the device comprises a pair of rotors, respectively an upstream rotor (4) arranged at a same side as the supply system (2) and a downstream rotor (4a), arranged at a same side as the subsequent work station (3); said rotors (4 and 4a) being able to rotate about fixed and parallel axes (5, 5a), each of which rotors (4, 4a) is provided with a plurality of coaxial gullets (6-7.. n, 6a-7a..«a) having, for each rotor, a diameter which increases in step with an advancement direction of the rod; a first gullet (6a) of the downstream rotor (4a), in which the rod (1) corning from the supply system (2) is introduced, has a smaller diameter man a first gullet (6) of the upstream rotor (4) about which the rod (1) winds in sequence after coming from the first gullet (6a) of the downstream rotor (4a); the first gullet (6) of the upstream rotor (4) having a smaller diameter than the second gullet (7a) of the downstream rotor (4a), about which the rod (1) coming from the first gullet (6) winds; an «th gullet (Na) of the downstream rotor (4a) having a smaller diameter than an τ?th gullet (N) of the upstream rotor (4) about which the rod corning from the nth gullet (Na) winds and from which the processed rod (la) is sent to the subsequent work station (3); means are provided for causing an advancement of the rod (1) in the device.

7). The device of claim 6, wherein: either the upstream or downstream rotor is idle about an axis thereof; said means for drawing the rod comprise a motor which sets the upstream or downstream rotor in rotation. 8). The device of claim 6, wherein each rotor is idle about an axis thereof; the means for drawing the rod (1) are constituted by a drawing system of known type, which also drive the subsequent work station. 9). The device of claim 6, wherein ratios between diameters of gullets of rotors and a diameter of the rod being processed are greater than 100:1. 10). The device of claim 6, wherein it comprises at least one spacer (8) to which the axes of the rotors are connected, which spacer (8) maintains unaltered positions of the axes.