The production process of stainless steel precision castings is the so-called investment casting process. Simply put, it uses fusible materials (such as wax or plastic) to make a fusible model (referred to as investment or model), and coat it with several layers of special After drying and hardening to form an integral shell, use steam or hot water to melt the model from the shell, then put the shell in the sand box, fill it with dry sand around it, and finally cast The mold is put into the baking furnace and baked at high temperature (if a high-strength mold is used, the mold shell after demolding can be directly baked without modeling). After the mold or mold is baked, molten metal is poured into it to obtain a casting .
The dimensional accuracy of investment castings is relatively high, generally up to CT4-6 (CT10~13 for sand casting and CT5~7 for die casting). Of course, due to the complex process of investment casting, there are many factors that affect the dimensional accuracy of castings, such as molds. The shrinkage of the material, the deformation of the investment mold, the linear change of the shell in the heating and cooling process, the shrinkage of the alloy and the deformation of the casting during the solidification process, etc., so the dimensional accuracy of ordinary investment castings is high, but its Consistency still needs to be improved (the size consistency of castings with medium and high temperature waxes should be improved a lot).
When pressing the investment mold, a pressure type with a high surface finish of the cavity is used, so the surface finish of the investment mold is also relatively high. In addition, the shell is made of a refractory coating made of a high-temperature-resistant special adhesive and refractory material, which is coated on the investment mold, and the inner surface of the cavity that is in direct contact with the molten metal has a high smoothness. Therefore, the surface finish of investment castings is higher than that of general castings, generally reaching Ra.1.6~3.2μm.
This type of product occupies an extremely important position in important engineering applications and is an important branch in the field of cast stainless steel.