Sintering furnace and silicon nitride powder sintering method

The sintering furnace comprises a furnace shell, a heat preservation cylinder arranged in the furnace shell and a temperature equalizing cylinder arranged in the heat preservation cylinder, a gas flowing cavity is formed between the temperature equalizing cylinder and the heat preservation cylinder, and an induction heating piece which is controlled by an external controller and has heating and temperature sensing functions is arranged in the gas flowing cavity. The furnace is characterized in that an internal circulation assembly for pumping gas in the temperature equalizing cylinder to circularly flow between the temperature equalizing cylinder and the gas flowing cavity is arranged in the furnace shell, and the internal circulation assembly is controlled by an external controller to operate. High heat is prevented from being focused in the uniform-temperature cylinder, the sintering reliability is improved, and the sintering activity of powder is improved; the influence of over-limit temperature in the tem