Abstract: In a pump for use in a hot chamber type die casting machine wherein corrosive molten metal particularly aluminum or alloys thereof is injected into a metal mould through a goose neck shaped passage, a porous ceramic tube having a porosity of 10 to 40% and acting as the goose neck shaped passage is cast in the main body of the pump. The porous ceramic tube comprises sintered zircon or porous graphite.

Abstract: A microwave heating oven has a seal located in the path formed by a gap between the oven body and the oven door for preventing microwave leakage. The seal may comprise several seals, and includes a microwave absorber as one of the seals. The microwave absorber consists of a mixture of a powder of magnetic material and an organic high molecular weight compound. The length of the microwave absorber in the direction of propagation of microwave in the path of microwave leakage is an integral multiple of about 1/2.lambda., wherein .lambda. is a wavelength of the microwave in the microwave absorber. Absorption is improved by setting the absorber in a recess in the wall or door of the oven, or by surrounding the absorber by a metal layer except on the surface thereof parallel to the direction of propagation and facing the gap.