You must understand these manufacturing process characteristics of valves
At first glance, valves have few parts, simple structure, and average precision. They belong to simple components in the machinery manufacturing industry, but the key sealing parts of valves have particularly high requirements. The valve manufacturing process is complicated and the technical level is also high. What process characteristics should we pay attention to?
1. Manufacturing materials
Because there are many types and specifications of valves, such as general valves include stop valves, stop valves, check valves, gate valves, butterfly valves, hydraulic control valves; industrial valves include relays, regulating valves, pressure regulating valves, ultra-high pressure valves, ultra-low temperature valves and other special valves, all of which are used in various industries of the social economy. Their application fields are different, such as ultra-high pressure, ultra-low temperature hydrogen production, flammable and explosive materials, toxic, strong corrosive substances and other working conditions, which put forward strict requirements on the materials of valves.
In addition to cast iron, alloy steel, and alloy tool steel, CrNi stainless steel, CrMoAl high-frequency hardened steel, CrMoV wear-resistant steel, CrMnN acid-resistant steel, precipitation hardened steel, duplex steel, ultra-low temperature steel, aluminum alloy, Monel aluminum alloy, Inconel aluminum alloy, Hastelloy and G0CrW carbide tools are also widely used. The forging, welding and processing properties of these high-alloy products are very poor, which brings great difficulty to the manufacturing process. In addition, most of these raw materials are precious raw materials with high aluminum alloy, high toughness and high toughness. There are many difficulties in the selection, preparation and purchase of raw materials. Some raw materials cannot be purchased and supplied due to small demand.
2. Structure of forged blanks
Most valve blanks use thin-shell castings with complicated structures. They are not only required to have good appearance quality, but also have high-density intrinsic quality and good metallographic structure. There should be no defects such as vents, shrinkage, sand inclusions, and cracks. Therefore, its forging process is complicated and the heat treatment process technology level is high. In the machinery manufacturing industry, the forging difficulty of the pressure-resistant thin shell casting blank of the valve is much more complicated and difficult than the casting of other mechanical prefabricated components.
3. Machining process
Because the processing properties of most high-strength, high-hardness and high-corrosion-resistant materials are not good, such as high-aluminum alloy stainless steel and acid-resistant steel, which have defects such as high ductility, high compressive strength, poor heat dissipation, and strong tendency of diamond-grade cold hardening due to cutting viscosity, it is difficult to achieve the required size precision and smoothness, which brings certain difficulties to the machining of CNC blades, processes and equipment. In addition, the valve sealing surface has high requirements in processing accuracy, matching angle, smoothness and matching sealing pairs, which brings great difficulty to machining.
4. Process allocation of valve parts
The number of key parts of the valve is small, the structure is relatively simple, the processing accuracy of most sizes is not high, and the surface is relatively rough, which gives people an impression of belonging to simple machinery. In fact, the core sealing part of the valve is very important. The "three degrees" (flatness, smoothness, and strength) of the sealing surface are very demanding, and the compliance of the sealing pair formed by the two sealing surfaces must be zero-to-zero to achieve zero leakage in the airtightness test. This kind of zero-to-zero requirement of the core part with roughness is a major technological problem in valve production and processing.