In the process of casting castings in Dalian, precision casting cracks may occur accidentally. Dongguan Daohui metal products Co., Ltd. reminds you that the following methods can be used to prevent them: by appropriately extending the heat preservation time of castings in the sand mold, the main thing is to control the unpacking temperature below 70 ℃, so as to ensure that the castings can fully complete the liquid and solid shrinkage in the sand mold and avoid the occurrence of precision casting due to stress concentration caused by external forces.
During casting, the factors affecting the liquid and solid shrinkage of castings, such as the structure, shape, large size, wall thickness and its transition, should be fully considered, and appropriate process parameters should be selected to prevent casting defects such as shrinkage cavity and porosity. The design of the gating and riser system of the casting shall be reasonable. If cold iron and other technological measures are adopted, the position of the pouring and riser system shall be reasonable, which shall not only ensure the compactness of the internal structure of the casting, but also try to avoid the occurrence of stress concentration.
According to statistics, in terms of weight, castings generally account for 30~85% of the total weight of machinery and equipment. For example, in metal cutting machine tools, the weight of castings accounts for 80%, the steel rolling mill accounts for 75~80%, the internal combustion engine accounts for 50%, the drilling equipment accounts for 40~50, and the automobile and tractor accounts for 30~40%. At the same time, due to the increasing development of casting metal materials, process methods and detection means, the internal quality of castings has been continuously improved, and the dimensional accuracy and surface finish have reached a higher level.
This makes some castings can be used instead of forgings and weldments; Some precision castings can also be directly assembled in machinery and equipment without machining. Whether the quality of raw materials for casting is excellent or not: if the quality of materials such as metal furnace charge, solvent, modifier or coating fails to meet the standard, the product will have problems such as porosity, slag inclusion and sand sticking, which will affect the internal and external quality of iron castings.
Then cast the wax by pouring to obtain the original wax mold. Glue the wax mold with high temperature resistant liquid sand layer by layer. After sufficient thickness is obtained, it is dried, and then heated to melt the internal wax mold to obtain a cavity consistent with the required blank.
