With the popularization and promotion of continuous casting process, the importance of sealing pipe components is more and more recognized by the industry. Especially in the use of low pressure casting machine, the sealing pipe sealing requirements are very high. Silicon nitride ceramics because of its superior density, wear resistance, etc., it is also a more suitable material for sealing pipes and other related parts to maintain pressure during low pressure casting, and at the same time ensure high processing accuracy and high tightness.