OPTIMIZATION OF PROCESS PARAMETERS IN MICROWAVE JOINING OF METALLIC MATERIALS IN A MULTIMODE MICROWAVE APPLICATOR

Abstract

Microwave energy has been in use for variety of applications for over 50 years. These applications include communication, food processing, wood drying, rubber vulcanization, medical therapy, polymers, etc. In the last two decades microwave heating has been also applied very effectively and efficiently to heat and sinter ceramic materials. Microwave heating is recognized for its various advantages, such as: time and energy saving, very rapid heating rates, considerably reduced processing cycle time and temperature, fine microstructures and improved mechanical properties, better product performance, etc. The most recent application of microwaves has been in the field of metallic materials for sintering, brazing/joining and melting, a surprising application, in view of the fact that bulk metals reflect microwaves. However, reflection by a metal occurs only if it is in a solid, nonporous form and is exposed to microwaves at room temperature. Metals in the form of powder absorb microwaves at room temperature and will be heated very effectively and rapidly. Several common steel compositions, pure metals and refractory metals have been sintered in microwaves to nearly full density with improved mechanical properties. Many commercial powder-metal components of various alloy compositions including iron and steel, copper, aluminum, nickel, Mo, Co, Ti, W, Sn, etc., and their alloys have also been sintered in microwaves producing better properties than their conventional counterparts by using a 2.45 GHz multimode microwave system. This work has been further extended to join and braze bulk metallic pieces in the same 2.45GHz multimode microwave cavity...