China Traditional Investment Casting Process

Now known as lost wax casting precision investment casting is a little cutting or no cutting of the casting process, is the casting industry a superior technology, its application is widely used. It is not only applicable to all types, all kinds of alloy casting, and the production of casting dimensional accuracy, surface quality is higher than other casting methods, and even other casting methods were difficult to cast complex, high temperature and difficult in the processing of castings, can be cast using investment casting too.

Casting is the ancient wax casting based on the developed. As ancient civilization, China is using this technology, the earlier one of the countries as far away as several hundred years before Christ, ancient working people of our country has created such a lost-wax casting technique is used with a variety of fine casting patterns and words tripods and housewares products, such as the Spring and Autumn when the tomb statue drives. The base plate tomb statue more than the dragon intertwined, they are connected end to end, alternating from top to bottom to form a hollow center of the multi-moire-like patterns, these patterns difficult to manufacture with ordinary casting process out, but with the lost wax casting process, can make use of paraffin is not strength, easy-to-carved features, with ordinary tools can be carved out with the tomb of the statue to get the same paraffin plate arts and crafts materials, and then additional gating system, paint, wax, casting, you can get exquisite tomb statue plate.

Modern investment casting method in practical application of industrial production in the twentieth century forties. At that time the development of aviation jet engines, require manufacturers such as blades, impellers, nozzles and other complex shape, size, precision, and smooth surface of the heat-resistant alloy parts. As the heat-resistant alloy material difficult machining, parts complex shape, which is not possible or difficult to manufacture using other methods, therefore, needs to find a new precision molding process, so learn from the ancient lost wax casting handed down through the materials and processes improvements, the modern investment casting method is based on the ancient craft was an important development. Therefore, the aviation industry¡¯s development has contributed to the application of investment casting and investment casting of continuous improvement and perfection for the aviation industry to further improve performance and create favorable conditions.

Our country is in the last century, the fifties and sixties began to Casting applied to industrial production. This advanced casting process was a tremendous development, and have in the aviation, automobile, machine tools, ships, internal combustion engines, gas turbine, telecommunications equipment, weapons, medical equipment and cutting tools in the manufacturing industry has been widely used, but also for process the manufacture of artworks.

The so-called investment casting process, it simply is to use fusible materials (such as wax or plastic material) may be made of melting models (melting mold or model), in its several layers coated with a special fire-resistant coating, after drying and hardening After the formation of a whole shell, and then steam or hot water from the melting off shell model, and then placed in sand box in the Shell, in its four weeks filled with dry sand molding, and finally into the roaster in the mold at high temperatures Roasting (such as the use of high-strength shell, it can not form but will shell ejection after direct calcination), the mold or mold shell after roasting, after which pouring molten metal casting obtained.

Investment Casting a higher dimensional accuracy, generally up to CT4-6 (sand casting for the CT10 ~ 13, die-casting for the CT5 ~ 7), of course, investment casting process due to a complicated process, affecting the accuracy of casting size more factors, such as the Wax contraction, melting mold deformation, Shell in the heating and cooling process in the line of the amount of change in the alloy solidification shrinkage and deformation during the casting, so the size of ordinary Investment Casting precision while high, but still need to improve their consistency (using the high-temperature wax casting material to improve the lot size consistency).

Suppression of melting mode, the use of cavity surface finish of high pressure type, therefore, melting mold surface finish is also relatively high. In addition, Shell by a special high temperature binder and refractory coated preparation of the fire-resistant paint hanging in the melting mode rather made direct contact with the molten metal cavity surface finish higher. Therefore, the Investment Casting surface finish higher than the general castings, usually ranging from Ra.1.6 ~ 3.2¦̀m.

Casting of the biggest advantages is that because of Castings has a very high dimensional accuracy and surface finish, it can reduce the machining work, only in part on the demand for a higher position you can stay a little machining allowance, and even some casting only stay grinding, polishing margin, without mechanical processing can be used. This shows that the use of investment casting method can save a lot of machine tools and processing man-hours, substantial savings of metal raw materials.

Investment Casting Method Another advantage is that it can be made into a variety of alloys of complex castings, in particular, can be made into high-temperature alloy castings. Such as jet engine blades, its streamlined profile and the cooling outside the cavity, using machining process is almost impossible to form. With the Investment Casting Process production is not only mass production can be done to ensure consistency in casting, but also avoids the machining profile of the knife after the residual stress concentration.