The Features of Valve Manufacturing Process
Compared with other manufacturing processes, the valve manufacturing process has the following characteristics:
1. The manufacturing process and inspection process of valve blank are rather complicated
The cast blank of valve is a structurally complex thin-walled shell part. The casting is required to have a smooth surface, a clear character casting, and in particular, a dense defect. In order to meet the above requirements, a series of processing measures should be taken during casting, such as the selection of high refractory molding material and the control of sand moisture, the layering during molding to ensure the hardness of the sand, the use of reasonable casting cap systems and strict control of pouring speed and temperature. Due to its high technical requirements, the casting process of the valve blank is far more complicated than that of general castings.
In addition to checking the size, position accuracy and appearance, sometimes, microstructure, mechanical properties, corrosion resistance and non-destructive probing are also tested. Therefore, the inspection process of the valve is also rather complicated.
2. The installation of valve part on machine tool is rather difficult
The structure and shape of the main parts of valve are very complex. Some parts are thin-walled and slender, with poor rigidity. When they are machined on machine tools, the positioning and clamping are very difficult, and complicated special fixtures are often needed.
For some sanitary valve parts, the positioning base has a low accuracy and a high surface roughness. Sometimes even non-machining surface positioning is used. But there are very high requirements for the accuracy and surface roughness of the processed sealing surface, so it’s very hard to ensure the processing quality. Therefore, to meet the processing needs, it is often necessary to increase the accuracy of the positioning base and reduce the surface roughness, or to produce a positioning surface on non-processing surface, which increases the complexity of the valve manufacturing process.
3. Difficult mechanical processing
Due to the wide variety of valve materials, except for various cast iron and carbon steel, the shearing performance of most high strength, corrosion-resistant and high-hardness materials is very poor, making it difficult for the parts to achieve the specified machining accuracy and surface roughness. And there are very high requirements for the geometrical precision and surface roughness of the sealing surface of the valve, so it’s even more difficult to perform mechanical processing on valves. Meanwhile, the poor shearing performance of valve materials causes quite a few new problems for the processing methods, cutting tool materials, shearing amount and processing equipment of the valve.