| 摘要 |
PURPOSE:To enable a welding with a high welding strength and a high reliability to be performed by welding an inner and an outer sleeve, which constitute an indirectly heated cathode structure, by use of laser light after the clearance formed between the inner and the outer sleeves is removed by making them in close contact with one another. CONSTITUTION:An inner sleeve 4 is subjected to oxidation treatment carried out at 900-1,100 deg.C in a furnace of wet hydrogen for 5-30 minutes so as to form an oxidized film 41 over the surface of the inner sleeve 4. On the other hand, after the circumference wall of a base metal 2 fitted into one end of an outer sleeve 3 is fixed to the sleeve 3 by a resistance welding, the inner sleeve 4 is inserted into the outer sleeve 3. Next, a core metal is inserted between the inner and the outer sleeves 4 and 3 so that the core metal touches the inner sleeve 4. Then, the outer sleeve 3 is deformed by applying external pressure so as to make the inner and the outer sleeves 4 and 3 to closely touch one another and to remove the clearance between the sleeves 4 and 3. After that, a laser light (L) is irradiated on a given part of the outer sleeve 4 from almost a perpendicular direction so as to make the inner and the outer sleeves 4 and 3 to be welded and fixed together and a welding point 3a. |
