Sintered porous metal plate and its production

Claim 1

A process for producing a sintered porous metal plate comprising metal particles directly and integrally bonded together due to sintering, said plate being of porous structure and having a density gradient in the direction of thickness, characterized in that metal particles are charged into a mold having a pair of refractory side walls, refractory bottom wall and electrodes, pressed by a refractory press within the mold until the metal material attains a predetermined initial electric resistance value, an electric current is passed to the electrodes while controlling the current to uniformly heat the metal material approximately up to its transformation point, then the whole material is heated up to the sintering temperature to effect the sintering, the metal particles being charged in the mold in a plurality of layers respectively different in the metal particle size or a temperature difference being created layerwise in the direction of thickness of the metal material in the mold, wherein thermocouples are embedded in the press or bottom mold to measure the temperatures at various portions of the metal material in the mold, and in accordance with the temperatures so-measured, the electrical current to be passed to the electrodes is controlled in order to heat the whole metal material or particular layer of the material in the mold substantially uniformly.