GB2086774A

GB2086774A - Producing hollow metal profiled sections

Info

Publication number: GB2086774A
Application number: GB8132070A
Authority: GB
Original assignee: KM Kabelmetal AG
Current assignee: KM Kabelmetal AG
Priority date: 1980-10-24
Filing date: 1981-10-23
Publication date: 1982-05-19
Also published as: FI77794B; FR2492689A1; FI813307L; FR2492689B1; IT8124668A0; GB2086774B; FI77794C; CH660134A5; IT1139282B; JPS57100884A; JPH0350625B2

Abstract

Hollow profiled sections having at least one interrupted longitudinal bore therein, particularly such sections made of copper or a copper alloy for use in cooling rotating generator components, are made by extruding a profiled section (1) with an uninterrupted bore or bores (2, 3) therein, inserting a metal plug or plugs (5) of limited length into the bore, and reducing the section to its final dimensions by drawing, the or each plug (5) being connected to the section (1) by welding or soldering. In one embodiment, plugs (5) are inserted into the ends of the bores of two extruded sections, and the sections are resistance welded together at their end faces containing the plugs (5) either directly or indirectly through an intervening solid metal component (4). In another embodiment, plugs (5) covered with a solder layer are introduced into an extruded section (1) and soldered to the walls of the bore or bores by external heating, either before or after the final drawing. <IMAGE>

Description

SPECIFICATION Method of producing hollow metal profiled sections The present invention relates to a method of producing hollow metal profiled sections, particularly ones made of copper or a copper alloy, for example, for use as a cooling section for generators.

In a known process described in U.K. Patent Specification No. 1,099,850 copper profiled sections having a rectangular cross-section and at least two channels running in the longitudinal direction thereof, are produced by extrusion and are subsequently reduced to their final dimensions by drawing. It has for a long time been a desirable objective to use this known process to make available hollow profiled sections in which the channels are interrupted.

According to one earlier proposal the extruded hollow profiled section is first calibrated (i.e. given the required dimensions) externally and possibly also internally, a plug made of the same metal as the profiled section is then inserted into the bore or bores of the calibrated section, and the profiled section, together with the plug, is then reduced to its final dimensions by drawing, whereby the plug and inner walls of the hollow profile are joined together in sealed fashion. Since a high degree of dimensional accuracy is required in these hollow profiled sections, the use of a mandrel in the reducing drawing step is essential. The mandrels are in the form of rods carried either in a chain or on a mandrel bar in the vicinity of the drawing die.In this earlier process, it has been found to be disadvantageous that at least one half of the hollow profiled section must by drawn towards the mandrel, i.e. the mandrel bar must be subjected to pressure.

It is an object of the present invention to provide a method by the use of which hollowed profiled sections can be economically produced which have at least one interrupted cooling channel therein, i.e. having respective blind bores commencing from both ends.

According to the invention, there is provided a method of producing a hollow metal profiled section having at least one interrupted longitudinal bore therein, comprising the steps of producing a metal section of the required profile having a continuous bore or bores therein, inserting a metal plug or plugs of predetermined limited length into said bore or bores, and reducing said section to its final dimensions by drawing, wherein said plug or each of said plugs, is or are directly or indirectly connected to the section by welding or soldering. The metal used in usually copper or a copper alloy.

In a first way of carrying out the invention, two identical hollow profiled sections are produced by extrusion, plugs of predetermined length are inserted into the bores at one end of each section, so as to close the ends and the said ends of the two sections are then resistance welded to one another, and the combined section so formed reduced to its final dimensions by drawing.

In this first way of carrying out the invention, after having been inserted into the ends of the bores, the plugs may be joined to the walls of the bores so as to be leak-proof by drawing. However, it is equally possible to match the diameter of the plugs as far as possible to that of the bores and to drive the plugs into the bores by force. What is essential in the first way of carrying out he invention, is that the cross-sectional surfaces of the two profiled sections which are to be joined by resistance welding should be identical and in plane contact. If desired, the two profiled sections instead of being directly welded to one another are welded to opposite sides of an interposed solid component made of the metal used for the sections, e.g. copper or a copper alloy.This solid metal component has the same external cross-sectional dimensions as the profiled sections provided with the plugs.

The interrupted hollow profiled sections so produced is advantageously annealed after welding in order to recrystallise the weld structure. As already mentioned, this annealing process is followed by hollow drawing which serves to calibrate the profile as far as possible and to provide and to provide it with the requisite stability. It is also essential that the surfaces which are to be welded should be arranged plane parallel to one another. For this reason, in the region occupied by the plug, the profiled section to which the plug is joined in leak-proof fashion may be smoothed by sawing and possibly further treatment. The welding burr produced by resistance welding is chipped away prior to the hollow drawing, expediently in the same process stage as the welding.

In a second way of carrying out the invention, a plug of limited length and which has been provided with a layer of solder on at least a part of its peripheral surface is inserted into the or each bore and is soldered to the inner wall of the bore by supplying heat from the outside, either before or after after the final drawing step.

The basic advantage of this second procedure is that a hollow profiled section is obtained in which the plugs are fixed in the bores by the solder and that a reliable seal is thereof assured.

As regards the production of the soldered connection, it has been found to be advantageous to soft-anneal the profiled section prior to the final drawing. This step should be used when hard or semi-hard drawn profiled sections are required. The soft-annealing which serves to remove the hardening produced by preceding drawing may be carried out simultaneously with the soldering. The subsequent final drawing serves to reduce the profiled section to the required dimensions.

It is particularly advantageous if a solder foil made of hard solder containing phosphorus is wound around each plug. Expediently, the end regions of the plug are not covered by the solder foil in order to ensure that solder does not escape.

For this purpose, a plug may be used which has a cross-section which narrows between the end zones. Soldering then takes place only in the central region of the plug. This method of operation can be used with advantage when it is impossible to avoid the use of fluxes. The ends of the plug which are free of solder and of larger diameter prevent the flux from reaching the free channel cross-section of the bores.

As a variation of the soldering process, it is possible, prior to soldering, to form one or more bores in the hollow profiled section which open out into the region of reduced cross-section of the plug and to carry out the soldering step by supplying hard or soft solder through the bore or bores.

The soldering of the plugs can be carried out either before or after the final drawing step.

It can be effected simultaneously with soft annealing, or by the local supply of heat to the solder zone, for example, by means of a flame.

The method of the invention can be used with particular advantage for the production of square, or, in particular, rectangular profiled sections made of copper or a low-alloyed copper alloy and having at least two bores and a solid portion arranged between the ends of the sections; such profiled sections are used to cool the rotating components of generators.

The invention will now by further described with reference to the drawing, in which: Figure 1 is a schematic perspective view of a hollow profiled section which has been produced by a method in accordance with the invention; Figure 2 is a schematic side-sectional view of part of an arrangement of two profiled sections and an intervening block to illustrate an intermediate stage in the production of the finished section of Fig. 1; and Figures 3 and 4 are schematic side sections on an enlarged scale of a part of a hollow profiled section, to illustrate two further ways of carrying out the invention.

Fig. 1 shows a hollow profiled section which has been produced by a method in accordance with the invention. The hollow profile 1, which is made of oxygen4ree, copper, has a rectangular cross-section and is provided with two longitudinal channels 2 and 3. Approximately in its centre the section 1 has a solid portion 4 in the vicinity of which are located copper plugs 5 arranged in channels 2 and 3 on both sides of the portion 4, so that blind channels opening at the ends of the section are formed.

The method of producing the profile 1 is illustrated in Fig. 2. A hollow profiled section 1 a provided with the channels 2 and 3 is first produced by extrusion followed by cold drawing using a cotter or a mandrel. Copper plugs 5 are inserted into the ends of the channels 1 and 3 and are joined to the hollow profile so as to be leak-proof by subsequent cold drawing. Alternatively, it is possible to use copper plugs 5 having dimensions corresponding to those of the channels 2 and 3 and to drive the plugs into said channels by force. Those ends of the profiled sections which are provided with the plugs 5 are then smoothed by sawing, and, if necessary, ground, and the burr formed is removed.The ends of the profiled sections which have been treated in this way are then clamped in the welding jaws 6 and 7 of a resistance welding machine and welded to opposite sides of a copper block 4 of identical cross-sectional dimensions which is inserted between the ends of the sections.

During the welding process, a current of several kilo-amperes flows between the clamping jaws 6 and 7 and heats the boundary surfaces between the profiled sections and the solid copper block 4 to the welding temperature. A slight pressure is applied by the welding jaws 6 and 7. After completion of the welding process, the clamping jaws 6 and 7 are relaxed and the welding burr is chipped away.

The interrupted profile so produced is then subjected to a recrystalline annealing during which the welding seam structure is removed.

The next operation is a hollow drawing in which the outer dimensions of the hollow profile are reduced by at least 10%. This last cold drawing step provides the profiled section 1 with the requisite stability.

In the method illustrated in Figs. 3 and 4, a hollow profiled section having two or more cooling channels therein is first produced, up to the final drawing stage. Plugs around which solder foil is wound are inserted into the channels. In order to prevent the solder foil slipping during insertion of the plug, it is spot welded to the plug. The profiled section prepared in this way is now reduced by drawing, during which process the inner walls of the channels bear against the plugs. The profiled section is then soft annealed, whereby the plugs are soldered to the channel walls.

Finally the profile is calibrated by means of a die and mandrels or rods arranged in the channels.

In Figs. 3 and 4, a plug 5 is shown arranged in a channel 2 of the profiled section 1. Between its ends 14 and 1 5 is arranged a region 1 6 of reduced cross-section which in Fig. 4 is shown in the form of a grooving or knurling. Prior to the insertion of the plugs 5, the region 1 6 is coated with solder and flux.

The special shape of the plug 5 prevents the solder and the flux from coming into contact with the walls of the channel 2. In this embodiment, the profiled section must first be reduced by drawing and only then can it be soldered. After the drawing process, the ends 14 and 1 5 of the plug 5 seal off the solder zone. At the same time, the solder zone is compressed. As described above, the soldering is carried out either simultaneously with the soft annealing, or else by means of a flame.

The soldering can also be effected in a manner which has not been illustrated, by forming one or more bores into the profiled section 1 which open into the region 1 6 of reduced cross-section, whereupon solder and flux are introduced through the bore or bores.

If cooling profiled sections of this kind are used to cool rotating generator components, the solid section 4 of Figs. 1 and 2 and the region which is soldered to the plugs 5 (Figs.

3 and 4) basically serve to bring about a mass balancing, so as to improve the rotation.

Claims

1. A method of producing a hollow metal profiled section having at least one interrupted longitudinal bore therein, comprising the steps of producing a metal section of the required profile having a continuous bore or bores therein, inserting a metal plug or plugs of predetermined limited length into said bore or bores, and reducing said section to its final dimensions by drawing, wherein said plug or each of said plugs, is or are directly or indirectly connected to the section by welding or soldering.

2. A method as claimed in Claim 1, comprising the steps of producing two hollow metal profiled sections of identical cross-section by extrusion, inserting a plug or plugs into each of said bores in one end of each said section so as to close the bores at said one end in leak-proof fashion, directly or indirectly connecting said one ends of the two sections together by resistance welding, and reducing the profiled section so formed to its final dimensions by hollow drawing.

3. A method as claimed in Claim 2, wherein after insertion, the plugs are joined to the hollow profiled sections in leak-proof fashion by drawing.

4. A method as claimed in any one of Claims 1 to 3, wherein the end faces of said two profiled sections containing said plugs are directly welded to one another.

5. A method as claimed in any one of Claims 1 to 3, wherein the end faces of said sections containing said plugs are each welded to a respective opposite face of a solid metal component having the same external cross-sectional dimensions as said sections and located in register with and between said end faces.

6. A method as claimed in any one of the preceding Claims, wherein after the welding step, the profiled section formed is annealed in order to recrystallise the weld structure.

7. A method as claimed in any one of the preceding Claims, wherein, prior to the welding step, the end faces of said profiled sections containing said plugs are smoothed by sawing.

8. A method as claimed in Claim 1, comprising the steps of forming a hollow metal profiled section by extrusion, said section having at least one uninterrupted longitudinal bore therein; inserting into a central part of the or each said bore a plug or a respective plug of limited length and made of the same metal as the section; providing the or each said plug with a layer of solder on at least part of its peripheral surface before or after insertion into the bore; soldering said plug or plugs to the wall or walls of said bore or bores by the supply of heat from the outside; and reducing the interrupted profile section so formed to its final dimensions by drawing, the soldering step being carried out before or after said final drawing step.

9. A method as claimed in Claim 8, wherein the soldering step is carried out simultaneously with a soft annealing step.

10. A method as claimed in Claim 8, wherein said soldering step is effected by means of a flame.

11. A method as claimed in any one of Claims 8 to 10, wherein a solder foil, is wound around at least a part of the periphery of the or each plug.

1 2. A method as claimed in Claim 11, wherein said solder foil is made if hard solder containing phosphorus.

13. A method as claimed in any one of Claims 8 to 12, wherein the or each said plug has a central portion of reduced cross-sectional area, said solder layer being carried on the peripheral surface of said central portion.

14. A method claimed in Claim 13, as dependent on Claim 8, wherein prior to the soldering step, one or more further bores are formed in said profiled section which open into the region of the portion of the or each plug of reduced cross-section, and said soldering is carried out by the addition of hard or soft solder through said further bore or bores.

1 5. A method as claimed in any one of the preceding Claims, wherein said profiled section or sections, said plug or plugs, and said intermediate component when used, are made of copper, or a copper alloy.

1 6. A method of producing a hollow metal profiled section having at least one interrupted longitudinal bore therein, substantially as hereinbefore described with reference to Figs. 1 and 2, or Figs. 3 and 4, of the drawing.

1 7. A hollow metal profiled section having at least one interrupted longitudinal bore therein produced by a method as claimed in any one of Claims 1 to 1 6.

18. Rectangular or square-section hollow profiled sections as claimed in Claim 17, made of copper or a low-alloyed copper alloy, for use on cooling the rotating components of electric generators.