The effective control measures were adopted to improve the casting quality and to reduce or eliminate the slag inclusion defects through design of the process structure to the production process

thus improving the sealing performance of the valve and flange castings.The practical production verifies that:（1）the wax tree-assembling design of the process structure should avoid the sealing surface of the castings to be set in the slag surface of the process structure

or to set the scum riser on the casting scum surface

or to increase the processing allowance on the casting scum surface

which could reduce or avoid the slag inclusion to a certain extent.（2）during the production process

the wax impurity during wax reclamation should be reduced to avoid the inclusion falling into the shell mould cavity after dewaxing.At the same time

some measures should be paid attention

such as the selection of raw materials before casting

the deoxidization practice in the process of melting

the secondary oxidation of the molten steel and seting rational pouring temperature

to avoid or reduce effectively the defects in the castings.