METHOD ANNEALING FLAT CERAMIC PARTS Russian patent published in 2017 - IPC C04B35/581 C04B35/64 

FIELD: metallurgy.

SUBSTANCE: initial annealing in a vacuum at a temperature of 1300-1400°C for 2 hours plates of porous graphite-like boron nitride used as a refractory tool for annealing aluminium nitride parts at a residual pressure of 10^-4mm Hg, the plates are heated in a furnace at a rate of 300°C/h, and cooling takes place with the furnace to room temperature. The annealing is performed in two stages: annealed plates made of porous graphite-like boron nitride are placed on flat parts on both sides, heat treatment in the first stage is carried out in air atmosphere at temperature 500-600°C, then the parts are placed in a high-temperature chamber, the volume of the chamber with the parts is vacuumed to a pressure of 0.002 mpa, after that heat treatment is carried out in flow of pure nitrogen under pressure 0.15-0.20 mpa at temperature 1650-1850°C for 2-3 hours followed by cooling. Heating and cooling rates in the high-temperature range 1500-1850°C should not exceed 30°C/h, and in the range of 500-1500°C is 300°C/h.

EFFECT: pre-annealing ofthe plates provides for their multiple use with no of defects of marbling structure non-uniformity on the parts surface, high level of physical and technical properties and high yield percentage of good parts.

22 cl, 2 tbl