Microwave heating device and material heating method

The invention discloses a microwave heating device and a material heating method, and belongs to the technical field of microwaves, the microwave heating device comprises a rectangular waveguide, a circular waveguide, a metal tube and a conversion part; the left end of the rectangular waveguide is provided with a microwave feed-in port, and the upper surface of the rectangular waveguide is provided with a circular waveguide. A metal tube is arranged in the circular waveguide; the metal tube and the circular waveguide are coaxially arranged; a material heating area is formed between the upper end of the metal tube and the upper end of the circular waveguide; the rectangular waveguide is internally provided with a conversion part, and the conversion part is located at the lower end of the metal tube; the conversion part is used for feeding the microwaves transmitted in the rectangular waveguide into the material heating area; a first material channel is arranged in the conversion part; a second material channel