Views: 8 Author: Site Editor Publish Time: 2018-05-19 Origin: Site
H2. So-called precision casting technology, simply be with fusible materials (such as wax material or plastic) into the meltability model (referred to as "investment pattern or model), on which the coated with several layers of tailor-made refractory coating, after drying and hardening type to form a whole shell, reoccupy steam or hot water from the melt in the shell model, and then put type shells in the sand, dry sand by filling in all round its modelling, finally will be cast into the furnace after high temperature roasting (such as high strength shell, can need not modelling and will release the shell directly after roasting), cast type or shell after roasting, and are casting in pouring molten metal.
H3. Size precision investment castings, general of CT4-6 (sand mold precision casting for CT10 ~ 13, die-casting is CT5 ~ 7), of course, due to the complexity of precision casting process, factors influencing the dimension accuracy of castings is more, such as mold material shrinkage and deformation of casting, shell in the process of heating and cooling line quantity change, alloy of shrinkage and deformation of the casting during solidification, etc., so ordinary size although higher precision investment castings, but still need to improve the consistency (in medium and high temperature of the wax casting size consistency to improve a lot).
H4. When pressing the mold, the surface finish of the cavity is high, so the surface finish of the mold is also high. In addition, the shell is made of a refractory coating made of high temperature resistant special binder and refractory material, which is made of the surface of the cavity with direct contact with molten metal. Therefore, the surface finish of the investment casting is higher than that of the general precision casting parts, which can generally reach Ra.1.6~3.2.
H5. Precision casting biggest advantage is due to the investment casting with high dimensional accuracy and surface finish, so can reduce machining work, only in parts a little higher requirements on the parts machining allowance, and even some castings only grinding, polishing allowance, don't need to machining can be used. It can be seen that the precision casting method can greatly save the machine tools and working hours, and greatly save metal raw materials.
H6. Another advantage of the precision casting method is that it can accurately cast complex castings of various alloys, especially precision casting of high-temperature alloy castings. If the blades of jet engines are streamlined and cooled, they are almost impossible to form with mechanical processing. The precision casting process can not only produce the batch production, ensure the consistency of the casting, but also avoid the stress concentration of the residual knife grain after machining.