METHOD FOR JOINING A JACKET PART TO A CORE PART

Abstract: A method for joining a highly electroconductive core part (2) to a jacket part of refined steel (1). In the method a highly electroconductive core part (2), such as a copper bar, and connection component (3) are placed inside a jacket (1) having poorer electroconductivity, and are heat treated at least where the join of the pieces to be connected is located, in such a way that a metallurgical bond is formed between the electroconductive core part (2) and the refined steel jacket.

Description: METHOD FOR JOINING A JACKET PART TO A CORE PART This invention concerns a method for connecting a pipe part to a core part, according to the preamble of patent claim 1. The method concerned in the invention is particularly suitable for the manufacture of suspension bars for electrodes, especially for permanent cathodes, used in metal electrolysis. The suspension bar structure of the permanent cathode and joining the plate part of the permanent cathode to the suspension bar become problematic in that, in order to conduct a large electric current to the plate part, the material on the suspension bar should have high electroconductivity, such as copper. Since acid-resistant steel has poor electroconductivity, it cannot be the sole material used in the bar. Patent publication WO 00/17419 describes alternative methods for manufacturing a permanent cathode suspension bar. These are typically complex and/or require special equipments. According to methods in the prior art, manufacturing solutions have not always been able to satisfactorily preserve the electroconductive properties of the joint, especially of the metals in predominantly corrosive conditions in metals electrolysis. The purpose of this invention is to achieve a completely new type of method for joining the pipe part and core part together. Another objective of the invention is to achieve a method for the manufacture of a suspension bar for an electrode, in particular for a permanent cathode, which is technically beneficial in manufacture and highly suitable as far as the application is concerned. The solution according to the present invention is characteristic of that mentioned in the patent claims. A number of notable advantages are to be gained by using the solution according to the present invention. Using the solution according to the invention will achieve a good, electroconductive contact between the jacket, having poorer electroconductivity, and the core part, which has good electroconductivity. The method can be easily adapted without the need for special equipment. The method is well suited for products of different sizing and secondly, can also be applied in connection with different manufacturing volumes. The solution according to the present invention is described in more detail with reference to the figures enclosed, as follows: Figure 1 shows a stage of the method according to the invention prior to the welding of pne of the end plates, and Figure 2 shows a bar according to the invention, prior to the heat treatment stage. The present invention relates to a method for joining a core part 2, having high electroconductivity, to a jacket 1 , being made of refined steel. In the method the electroconductive core part 2, such as a copper bar, and the connection component 3 are placed inside the jacket 1 , having poorer electroconductivity; heat treatment is applied, at least in the joint area, so that a metallurgical bond is formed between the electroconductive core part 2 and the refined steel jacket 1. The connection component 3 is substantially of the same length as the core part 2. As a rule, the connection component 3 is typically tin. The amount of the connection component 3 is dependent on the size of the gap between the jacket 1 and the core part 2, and on how large a part of the surface of the core part and the jacket is to be joined. The jacket is a pipe part, of which at least one end is at least partly closed at least during heat treatment. Typically, the first end opening of the jacket is closed, for example by welding an end plate 4 onto it before the core part 2 and the connection component 3 are placed inside the jacket 1. In the application form according to the figures, also the other end opening of the jacket is partly closed, for example by welding an end plate 5 onto it after the core part and connection component have been placed inside the pipe. An opening 7 is then left at the end of the jacket, at least during heat treatment. This can be achieved, for example, by leaving the upper edge of the welding seam 6 of the other end plate 5 unwelded. Typically, the parts to be joined together are kept substantially horizontal during heat treatment. Then, when smelting, the tin can penetrate the entire bond area. During heat treatment the tin melt dissolves the copper from the copper bar acting as the core part 2, forming tin bronze, which at the same time begins to dissolve the inner surface of the refined steel pipe acting as the cover part 1 , forming a metallic tin bronze connection between the core part 2 and the jacket 1.. On one typical occasion, the heat treatment was conducted in a furnace, of which the temperature was substantially raised to over about 900 °C. According to another application form, the heat treatment of the pieces to be joined is conducted in a position, which substantially differs from horizontal. Then the lower jacket end is typically closed, at least to the height of the desired joint surface. The method according to the invention is suitable for the manufacture of a suspension bar for an electrode, especially a permanent cathode. In the application, by refined steel is meant stainless or acid resistant steel. By copper is meant a material, which contains mostly copper or at least 50 per cent copper.

Claims: PATENT CLAIMS 1. A method for connecting a highly electroconductive core part (2) to a jacket part of refined steel (1), characterized in that the electroconductive core part (2), such as a copper bar, and the connection component (3) in the method are placed inside the jacket (1) and are heat treated, at least the joint area of the pieces to be joined, in such a way that a metallurgical bond is formed between the electroconductive core part (2) and the jacket of refined steel (1). 2. A method according to claim 1, characterized in that the core part (2) is mostly copper and the connection component (3) is mostly tin, whereupon in the method a mainly tin bronze join is formed between the jacket part (1) and the core part (2). 3. A method according to claim 1 or 2, characterized in that the connection component (3) is mainly tin. 4. A method according to any of claims 1 - 3, characterized in that the jacket (1) is a pipe part, of which at least one end is at least partly closed, at least during heat treatment. 5. A method according to any of claims 1 - 4, characterized in that the pieces to be joined together (1,2) are kept substantially horizontal during heat treatment. 6. A method according to any of claims 1 - 5, characterized in that at least when the pieces to be joined (1 ,2) are on a horizontal plane, the connection component (3) is placed on top of core part (2) inside jacket (1) before heat treatment. 7. A method according to any of claims 1 - 4, characterized in that the pieces to be joined together (1,2) are kept essentially in a position, which substantially differs from horizontal during heat treatment. 8. A method according to any of claims 1 - 7, characterized in that a suspension bar for an electrode, especially a permanent cathode, is manufactured in the method.

Inventors: HALMINEN VEIJO, KIVISTOE TUOMO, POLVI VEIKKO, HALMINEN, VEIJO, KIVISTOE, TUOMO, POLVI, VEIKKO
Applicants: HALMINEN VEIJO, KIVISTOE TUOMO, OUTOKUMPU OY, POLVI VEIKKO, HALMINEN, VEIJO, KIVISTOE, TUOMO, OUTOKUMPU OYJ, POLVI, VEIKKO
Application year: 2001
Main classification: C25C7
IPC codes: B23K20, B23K31, B23K103, C25C7