The origination of some defects in investment casting stainless steel parts was analyzed including pockmark

black point

indentation

shrinkage depression. The results show that pockmark defects are resulted from the non-quality of shell-mold materials for face layer

and black point is resulted from the existence of non-metal inclusion in liquid steel.Indentation is attributed to the deterioation of properties of Zr sand at high temperature due to the existence of trace Mg

Ca element

which leads to the expansion of shell mold.Shrinkage porosity is closely related to the high pouring temperature. Based on above analysis

some key factors of quality control in investment casting were proposed

including the control of raw materials

brushing

dewaxing

melting and pouring

and so on.