TWI Industrial Member Report Summary 640/1998
W Lucas and G Verhaeghe
Microwave power has been largely applied in telecommunication technology (eg radar) and as a relatively low cost method of generating heat (eg for industrial and household ovens). Microwaves are electromagnetic radiation which is in the form of very short wavelength/high frequency oscillations. Typical microwave frequencies are between 1 and 1000GHz, ie wavelengths of 300 and 0.3mm respectively. This form of electromagnetic radiation has the potential of generating a concentrated beam of energy and could be considered as an alternative to laser energy which has a much higher frequency, ie typically 30,000GHz. The power source itself, called the magnetron, is fairly small and capable of generating power from several hundred of watts up to 100kW. Magnetrons at low frequencies, like the commercially available 2.45GHz magnetron, are very efficient in terms of energy conversion, but at higher frequencies, eg 1000GHz, the efficiency falls at approximately 1%.
TWI has carried out a unique work programme to determine the feasibility of using microwave energy to produce a stable plasma discharge and to use it for welding and cutting of thin materials. This report details the basics of microwave technology when applied for plasma generation, a concept which is radically different from the electric arc commonly used for welding and cutting. Thus, the main purpose of the project was to establish the feasibility of generating a controllable plasma discharge using microwave energy. The initial phase of the research was principally concerned with the design and construction of a system, based on a conventional magnetron, for generating a reliable plasma discharge. Emphasis in the torch design was placed on producing a focused beam which could be emitted from the torch as a stable heat source. Cutting and welding trials were then carried out on thin C-Mn steel and aluminium to demonstrate the potential of the system.
- To establish the feasibility of generating a stable plasma using microwave energy.
- To establish the feasibility of cutting and welding thin materials using a microwave powered plasma.