The main functions of lost foam casting with negative pressure casting are as follows:

(1) Compact the dry sand to prevent sand washing, mold collapse and mold wall movement (box expansion).

(2) The results show that the speed and quantity of exhaust gas are accelerated, the filling ability of liquid metal is improved, and the carbon defects on the surface of castings are reduced.

(3) Vacuum sealing casting is beneficial to the collection and treatment of smoke and dust, and improves the working environment.

For lost foam casting casting steel, the suitable negative pressure is 0.04MPa ~ 0.06mpa. Especially in the production of thick and large pieces, the lower negative pressure will easily lead to collapse of the box, but the higher the negative pressure is, the better it will be. If the negative pressure is too high, it will lead to instability of liquid metal filling, increase the wall attachment effect, and easily produce slag inclusion and carburization defects.