Kuninori Imai

A press-working technique for magnetron anodes with a magnetic path

Abstract Recently, increasingly compact and lighter magnetrons have been developed for household microwave ovens. These magnetrons feature a new-type anode composed of a circular steel cylinder for the magnetic path containing a copper resonator with twelve precise cavities. These two components, i.e. the copper resonator and the steel cylinder, are tightly bonded to maximize heat conduction from the copper resonator to the steel cylinder during operation of the magnetron. Present development, employing advanced warm forging and pressure welding, has focused on establishing an economical and reliable production technique for the new magnetron anodes. One of the most important objectives has been to define the working conditions and the material combinations necessary for the fabrication of satisfactorily shaped and bonded anodes. Experimental work has shown that: 1. (i) Bonding of the copper resonator to the cylinder is achievable whilst simultaneously warm forging the resonator within the steel cylinder. 2. (ii) Working temperatures of around 400°C are most suitable for prevention of the bursting of the steel cylinder. 3. (iii) Tapering on the inside of the steel cylinders improves both the bond strength and the shape of the anode. These newly-developed techniques facilitate the production of high-quality magnetrons at greatly reduced production costs.