Investment casting
Release Time::2014-09-03
Lost wax casting now called precision casting, casting process of a less cutting or no cutting, is a superior technology and foundry industry, and its application is very extensive. Casting it not only applicable to all types,all kinds of alloy, and production of casting dimension precision, surface quality of casting method than other to high, and even other castingmethod to cast the complex, high temperature resistant, not easy machining castings, can use revestment precision casting cast.
Investment casting is developed based on the ancient wax casting. As acountry with an ancient civilization, China is using the technology of the earlier one country, far away in the centuries BC, ancient Chinese people to create this kind of lost wax casting technology for casting thetripod and vessels, with a variety of patterns and fine text and other products, such as the spring and Autumn Period had the tomb of Hou Yistatue etc.. The tomb of Ceng Houyi statue base for many mutual winding dragon, they end to end, staggered up and down, multilayermoire pattern forming a hollow in the middle, these designs with ordinarycasting process are hard to make out, but with the lost wax casting process, characters can use paraffin no strength, easy to carve, use common tools you can carve out and to get the tomb of Ceng Houyistatue as material handicraft of paraffin wax, and then additional gating system, coating, dewaxing, pouring, can get the tomb of Ceng Houyistatue exquisitely.
The modern investment casting method in industrial production in the practical application in the forty's of the twentieth Century. Thedevelopment of the aviation jet engine, to produce like blade, impeller,nozzle and other complex shape, heat-resistant alloy parts size precision and surface finish. Due to the heat resistant alloy material is difficult tomachining, complex shape parts, so that cannot or difficult to use other methods of manufacturing, therefore, need to look for a new precision molding process, then handed down from ancient times the lost wax casting, after the material and process improvement, the modern investment casting method to obtain important development based onthe ancient process. Theref. Therefore, the development of the aviation industry to promote the application of investment casting, and the castingof continuous improvement, but also for the aviation industry to furtherimprove the performance created favorable conditions.
Our country is in on century five, sixty time begin to melt casting applied to industrial production. Behind this advanced casting process get ahuge development, have been widely used in aerospace, automobile,machine tool manufacturing industry, ships, internal combustion engine,gas turbine, telecommunications equipment, weapons, medical equipment and tools, but also used in the manufacture of Arts and crafts.
The so-called investment casting process, simply with fusible materials(such as wax or plastic) made from fusible model (referred to as the moldor model) in refractory coating, special several layers of the coating,after drying and hardening to form a whole shell, and then steam or hot water from the shell in the melt model, and then the shell into the sandbox, dry sand filling in the round, finally will cast into the roasting furnaceafter high temperature calcination (such as the use of high-strength shell, need not other and direct baking shell after stripping), cast or shellafter roasting, in which pouring molten metal casting.
Investment casting dimension precision is high, can reach CT4 ~ 6(CT10 ~ 13 sand casting, die casting of CT5 ~ 7), of course, because the process of investment casting of complex, there are many factors influencing the dimensional accuracy of castings, such as mold material,mold shrinkage deformation, shell in the process of heating and coolingline change, alloy during solidification shrinkage and deformation of casting, so the size accuracy of common casting is higher, but still need to improve its consistency (the casting dimension consistency, high temperature wax to improve a lot).
Introduced.technology suppression, the pressure, cavity surface finish high therefore, casting surface finish is high. In addition, refractory coating shell by special binder and refractory material with high temperature resistance is formulated as a coating in the introduced.technology made, direct contact with the molten metal cavity surface finish high. Therefore, the investment casting surface finish than the general casting high, generally up to Ra.1.6~3.2 μ M
Investment casting the biggest advantage is due to the investment casting with high dimensional accuracy and surface finish, so can reduce mechanical processing work, just in the parts of the parts of the high demand for a little machining allowance can, even some casting only keep grinding, polishing allowance, need not mechanical processing can use. Therefore, the investment casting can save a large machine equipment and working hours casting method, greatly saving metal material.
Investment casting method another advantage is, it can be all kinds of alloy casting complex casting, special casting superalloy castings. Such as jet engine blades, the streamline the profile and cooling chamber, with the machining process can hardly formation. With investment castingtechnology not only can do production batch production, and ensure the consistency of the casting, but also avoid the stress concentration of the residual knife lines after machining.