Casting is a relatively early human mastery of a metal thermal manufacturing process, and has a history of about 6000 years. Casting is the liquid metal cast into the casting cavity with the shape of the part. To be cooled and solidified, And to obtain a certain shape, size and performance of the metal parts blank processing.
Casting is one of the primary process methods for producing metal parts blanks. Compared with other process methods, casting molding production costs, process flexibility, and adaptability are suitable for mass production of different materials, shapes, and weights of castings. However, it has the disadvantage of large tolerances, easy to produce internal defects.
According to the casting method used for casting, castings are divided into sand casting, investment casting, metal casting, pressure casting, and centrifugal casting. The most common application is sand casting, in addition to this, other castings are called special casting.
Silica sol stainless steel casting is a lost wax casting or precision casting, It is a casting process with less cutting or no cutting. It is an excellent process technology in the foundry industry.
Stainless steel casting is not only suitable for casting various types alloys, but also has higher dimensional accuracy, casting parts surface quality better than other casting methods. If other casting methods that are difficult to made, complex, high temperature resistant, and not easy to machining. It can be cast by investment casting.
The investment casting process uses a fusible material (such as wax or plastic) to make a fusible model (referred to as a investment mold or a model), which is coated with several layers of special refractory paint, dried and hardened to form a monolithic type. After the shell, the model is melted from the shell by steam or hot water, and then the shell is placed in a sand box, filled with dry sand shape around it, and finally the mold is placed in a roaster and subjected to high temperature roasting (if used) In the case of a high-strength type shell, the mold shell after demolding can be directly fired without styling. After the mold or the shell is fired, molten metal is poured therein to obtain a casting.
Investment castings have high dimensional accuracy, generally up to CT4-6 (sand casting is CT10~13, die casting is CT5~7). Of course, due to the complicated process of investment casting, there are many factors affecting the dimensional accuracy of castings, such as mold. The shrinkage of the material, the deformation of the investment mold, the change in the amount of the shell during heating and cooling, the shrinkage of the alloy, and the deformation of the casting during solidification, etc., so the dimensional accuracy of ordinary investment castings is high, but Consistency still needs to be improved (the dimensional uniformity of castings using medium and high temperature waxes is much higher).
When the investment mold is pressed, the molding having a high surface finish of the cavity is used, and therefore, the surface finish of the investment mold is also relatively high. In addition, the shell is made of a special high-temperature resistant binder and a refractory paint coated with a refractory material, and the inner surface of the cavity which is in direct contact with the molten metal has a high surface finish. Therefore, the surface finish of the investment casting is higher than that of the general casting, and generally reaches Ra.1.6~3.2μm.
The biggest advantage of investment casting is that because of the high dimensional accuracy and surface finish of the investment casting, the machining work can be reduced, but only a small amount of machining allowance is required on the parts, even some castings only The grinding and polishing allowance can be used without machining. It can be seen that the investment casting method can save a lot of machine tool equipment and processing man-hours, and greatly save metal raw materials.
Another advantage of the investment casting process is that it can cast complex castings of various alloys, particularly casting high temperature alloy castings. For example, the blade of a jet engine, the streamlined profile and the cooling cavity, can hardly be formed by a machining process. The production by the investment casting process can not only achieve mass production, but also ensure the consistency of the castings, and avoid the stress concentration of the residual knives after machining.