The invention relates to a method and equipment according to the independent claims for performing continuous extrusion of a metallic material, such as copper.
In continuous extrusion, the material to be extruded is conducted in a groove made on the outer circumference of a wheel-like element. As the element rotates around its axis, the material to be extruded gets into contact with an abutment that essentially fills the groove, so that the motion of the material to be extruded is changed with respect to the wheel-like member. Thus the material is arranged to be extruded in the proceeding direction of the material before the abutment, through a passageway arranged in the extrusion member. The method utilizes friction and thermal energy created in the working process. By means of the method, it is possible to advantageously extrude essentially long objects that are different in their transversal surfaces.
In the course of the process, it is possible that on the surface of objects made of copper or copper alloys, there are created oxide layers that are harmful in the further processing of said objects. In traditional extrusion, in the vicinity of the surface there may be created oxide layers that result in the tearing of the structure in hydrogen annealing. When welding thin strips into tubes, oxides may create leakages in the welding area. Surfaces must be cleaned several times of the oxide layers accumulated thereon. Oxide layers are difficult to detect or measure on the surface of copper, and they are not necessarily distinguished without special equipment. The removal of thick oxide layers from the surface of copper is fairly simple, but the removal of the last molecular layers has turned out to be more difficult.
In traditional continuous extrusion, oxides are removed as so-called extrusion scrap, the processing and recirculation of which bring forth disadvantageous extra expenses. In addition, the creation of hot extrusion scrap results in an intensive wearing of the extrusion tools. Even if oxides were removed from the surface of the feed material before the continuous extrusion, oxidation could also take place during the extrusion of the material. When manufacturing a copper product by extrusion, a completely oxygen-free process would ensure a better quality for the product. It is well-known that in order to solve said problem, the extrusion equipment is protected by surrounding the equipment by an atmosphere that prevents the passage of oxides and other impurities in the extruded product. However, it has been found out that even slight oxygen-contents in the protecting gas may cause oxidation that is harmful for the product. Also the groove lining may be oxidized owing to a too high oxygen level in the gas protection, which may cause occasional flaws in the products.
In the patent publication U.S. Pat. No. 5,782,120, there is described an equipment for continuous extrusion, where the feed member, i.e. a wheel, included in the extrusion equipment is protected by a hood containing non-oxidizing gas.
The object of the present invention is to introduce a novel solution for performing continuous extrusion of a material. A particular object of the invention is to introduce a solution where the product created in continuous extrusion is protected against oxidation.
The invention is characterized by what is set forth in the characterizing parts of the independent claims. Other preferred embodiments of the invention are characterized by what is set forth in the other claims.
Remarkable advantages are achieved by the arrangement according to the invention. The invention relates to a method for performing continuous extrusion of a metallic material, such as copper, so that the material to be extruded is fed in the extrusion member by means of a feed member provided with a groove on its peripheral wall and an abutment arranged in the groove; the groove is protected against oxidation by providing at least part of the peripheral wall of the feed member with a gas-protecting member. The gas-protecting member according to the invention advantageously enables the feeding of non-oxidizing gases in the groove area, which in turn prevents the passage of oxygen and oxides in the extrusion product. The gas-protecting member according to the invention is arranged at least on that part of the peripheral wall that does not contain material to be extruded, and the gas-protecting member covers at least part of the surface of the peripheral wall of the feed member in the width direction thereof. Thus the oxidation of the groove is particularly prevented at the hottest spot of the feed member, on the peripheral wall of the feed member after the abutment, where the material to be extruded is removed from the groove. The hot surface of the groove lining is a remarkable source of oxides and consequently enhances the oxidation of the product. According to the invention, the gas-protecting member is arranged on the peripheral wall of the feed member, so that it covers at least the groove, in which case the space left between the gas-protecting member and the feed member is arranged to be oxygen-free. In the space left between the gas-protecting member and the feed member, there is fed non-oxidizing gas, such as hydrogen or hydrogen and nitrogen, by means of the gas-protecting member. The gas can be preheated up to for example 400-800 degrees. According to a preferred embodiment of the invention, oxygen is removed from the gas to be fed in prior to feeding it in the space left between the gas-protecting member and the feed member. Oxygen can be removed by using prior art methods, such as filtering. Thus even extremely low oxygen contents can be eliminated. Hydrogen can advantageously be used for removing oxygen from neutral gases. Nitrogen is fed in for circulation-technical reasons. According to the invention, the extrusion process is surrounded by an inert gas protection, and the effects of the residual oxygen contained by said gas protection are eliminated by applying the solution of the invention. In the space left between the gas-protecting member and the feed member, i.e. in the vicinity of the groove, there prevails a higher pressure than in the inert gas protection, and the gas circulation is thus directed away from the groove.
The invention also relates to an equipment for performing continuous extrusion of metallic material, such as copper, so that the material to be extruded is fed in the extrusion member by means of a feed member provided with a groove on its peripheral wall and an abutment arranged in the groove, so that at least part of the peripheral wall of the feed member is provided with a gas-protecting member for protecting the groove against oxidation.
According to a preferred embodiment of the invention, the gas-protecting member comprises at least one protecting member provided with at least one gas channel for feeding gas into the space left between the gas-protecting member and the feed member. Thus the gas can be conducted, through the gas-protecting member, in a desired spot in the groove. According to an embodiment of the invention, the gas-protecting member comprises an inner protecting member and at least one outer protecting member. According to the invention, the gas fed in from the inner protecting member has a higher pressure than the gas fed in from the outer protecting member. There is thus created a circulation away from the groove through the gap left between the protection member and the feed member. On both sides of the groove, on the peripheral wall of the feed member, there is provided at least one lining element for sealing the gap between the gas-protecting member and the feed member. The lining element is made of the same material as the material to be extruded. Thus the residual oxygen from the gas protection surrounding the whole extrusion equipment is advantageously prevented from accessing the vicinity of the groove.
The solution according to the invention enables the creation of an oxygen-free space in the groove vicinity, which enhances the manufacturing of a flawless extrusion product. Consequently, the drawbacks caused by the processing and recirculation of extrusion scrap are avoided, because the creation of extrusion scrap is prevented.
The invention is described in more detail below with reference to the appended drawings.
The gas-protecting member 7 according to the example, illustrated in
For a man skilled in the art, it is obvious that the various preferred embodiments of the invention are not restricted to the examples described above, but may vary within the scope of the appended claims.
Number | Date | Country | Kind |
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20030956 | Jun 2003 | FI | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/FI04/00365 | 6/14/2004 | WO | 12/22/2005 |