Forming performance of valve castings: The pouring temperature is 1540, the casting formability is good, and the shrinkage rate of castings is generally 2.5%. It is necessary to consider the design of pressure, the arrangement of pouring riser and the selection of moulding materials. When the casting dimension is biased, it can be corrected after heat treatment, and the heat treatment should be carried out after rectification.
Compared with other gray iron castings, the manufacturing process of valve castings has the following characteristics:
Shan Valve Castings manufacturing process and inspection process is more complex.
The blank of the valve castings is a complex thin-walled shell. Its castings require a smooth surface, cast clarity, especially a tight defect. In order to meet the above requirements, casting should take a series of technological measures, such as the selection of high refractory molding materials and control of sand water, molding should be layered to ensure that the sand hardness, the use of a reasonable cap-and-mouth system and strict control of the pouring speed and temperature. Due to high technical requirements,
The casting process of valve castings is much more complicated than that of general castings.
In addition, the valve castings in addition to inspection size, location accuracy and appearance, and some also for metallographic structure, mechanical properties, corrosion resistance and nondestructive testing and other testing, so the valve castings inspection process is also more complex.
Shan valve castings are difficult to install on machine tools
The structure and shape of valve castings are complex, and some parts belong to thin wall, slender parts and poor rigidity. When machining on machine tools, locating and clamping are difficult, so complex special fixture is often needed.
Some valve parts, positioning base surface accuracy is lower, surface roughness is higher, and sometimes even the use of non machined surface positioning. and the processing of the cover and other parts of the precision and surface roughness requirements are very high, it is difficult to ensure the quality of processing. Therefore, in order to meet the needs of the process, it is often necessary to improve the precision of the positioning base surface and reduce surface roughness, or on the surface of the machining of the location of the base surface, which increases the complexity of the valve manufacturing process.
Shan machining is difficult.
As a result of various types of valve material castings, in addition to a variety of cast iron, carbon steel, the majority of its high-strength, corrosion-resistant and hard material cutting performance is very poor, it is difficult to achieve the required machining precision and surface roughness. The geometrical precision and surface roughness of the sealing surface of the valve castings are very high, so the machining difficulty of the valve castings is increased. At the same time, the cutting performance of the valve casting material is poor, and it brings many new problems to the processing method of the valve castings, the tool material, the cutting dosage, the process equipment and so on.