What Are The Commonly Used Valve Materials?

The material of the main parts of the valve should first consider the physical properties (temperature, pressure) and chemical properties (corrosiveness) of the working medium. At the same time, you should also know how clean the media is (whether there are solid particles). In addition, you must also refer to the relevant regulations and requirements of the country and the user department.

Many materials can meet the requirements of valves in various working conditions. However, correct and reasonable selection of valve materials can achieve the most economical service life and best performance of the valve.

Valves are made of a wide variety of materials and are suitable for various working conditions. The commonly used valve body materials, internal parts materials and sealing surface materials are introduced as follows.

Commonly used materials for valve bodies

1. Gray cast iron Gray cast iron valves are used in various fields of industry due to their low price and wide range of applications. They are usually used in the media of water, steam, oil and gas, and are widely used in chemical industry, printing and dyeing, oil chemical industry, textile and many other industrial products that have little or no impact on iron pollution.

It is suitable for low-pressure valves with operating temperatures between –15 and 200°C and nominal pressures PN≤1.6MPa.

2. Black-core malleable cast iron is suitable for medium and low-pressure valves with operating temperatures between –15 and 300°C and nominal pressures PN≤2.5MPa.

Applicable media are water, seawater, gas, ammonia, etc.

3. Ductile cast iron Ductile cast iron is a type of cast iron. In this cast iron, lump or spheroidal graphite replaces the flake graphite in gray cast iron. This change in the internal structure of the metal makes its mechanical properties better than ordinary gray cast iron without damaging other properties. Therefore, valves made of ductile iron will operate at higher pressures than those made of gray cast iron. It is suitable for medium and low pressure valves with working temperature between –30~350℃ and nominal pressure PN≤4.0MPa.

Applicable media are water, seawater, steam, air, gas, oil, etc.

4. Carbon steel (WCA, WCB, WCC) Cast steel was initially developed to meet production needs that exceeded the capabilities of cast iron valves and bronze valves. However, due to the overall good performance of carbon steel valves and their high resistance to stress caused by thermal expansion, impact loads and pipeline deformation, their use range has been expanded, usually including the working conditions of cast iron valves and bronze valves. .

Suitable for medium and high pressure valves with operating temperatures between –29 and 425°C. Among them, 16Mn and 30Mn have operating temperatures between –40 and 400°C, and are often used to replace ASTMA105. Applicable media are saturated steam and superheated steam. High and low temperature oil products, liquefied gas, compressed air, water, natural gas, etc.

5. Low-temperature carbon steel (LCB) Low-temperature carbon steel and low-nickel alloy steel can be used in sub-zero temperature ranges, but their use cannot be extended to cryogenic areas. Valves made of these materials are suitable for media such as seawater, carbon dioxide, acetylene, propylene and ethylene.

Suitable for low-temperature valves with operating temperatures between –46 and 345°C.

6. Low alloy steel (WC6, WC9) Valves made of low alloy steel (such as carbon-molybdenum steel and chromium-molybdenum steel) can be applied to many working media, including saturated and superheated steam, cold and hot oil, natural gas and air. The working temperature of carbon steel valves can be used up to 500℃, and the working temperature of low alloy steel valves can be used above 600℃. At high temperatures, the mechanical properties of low-alloy steel are higher than those of carbon steel.

It is suitable for high-temperature and high-pressure valves with non-corrosive media with working temperatures between –29 and 595°C; C5 and C12 are suitable for high-temperature and high-pressure valves with corrosive media with working temperatures between –29 and 650°C.