¿Cuáles son los materiales de válvula comúnmente utilizados

The material of the main parts of the valve should first consider the physical properties (temperature, pressure) and chemical properties (corrosion) of the working medium. At the same time, the cleanliness of the medium (with or without solid particles) should also be known.
 
Many kinds of materials can meet the requirements of the valve in many different working conditions.
 
There are many kinds of materials for valves, which 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 because of their low price and wide application range. They are usually used in the case of water, steam, oil and gas as the medium, and are widely used in chemical industry, printing and dyeing, oil chemical, textile and many other industrial products that have little or no influence on iron pollution.
 
It is suitable for low-pressure valves with working temperature between -15～200℃ and nominal pressure PN≤1.6MPa.
 
2. Black heart malleable cast iron is suitable for medium and low pressure valves with working temperature between –15～300℃ and nominal pressure PN≤2.5MPa.
 
The applicable medium is water, sea water, gas, ammonia, etc.
 
3. Ductile iron Ductile iron is a type of cast iron in which agglomerated or spherical graphite replaces flake graphite in gray cast iron. The change in the internal structure of this metal makes its mechanical properties better than ordinary gray cast iron, without compromising other properties. Therefore, valves made of ductile iron are used at higher pressures than those made of gray 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, sea water, steam, air, gas, oil, etc.
 
4. Carbon steel (WCA, WCB, WCC) initially developed cast steel to meet the production needs of those beyond the capacity of cast iron valves and bronze valves. However, due to the good overall performance of carbon steel valves and the high resistance to stress caused by thermal expansion, impact loads and pipeline deformation, its scope of use is expanded, usually including the working conditions of cast iron valves and bronze valves. .
 
It is suitable for medium and high pressure valves with working temperature between -29 and 425°C. Among them, 16Mn and 30Mn are used at temperatures between -40 and 400°C, and are often used to replace ASTMA105. The applicable medium is saturated steam and superheated steam. High and low temperature oil, 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 the temperature range below zero, but they cannot be extended to cryogenic regions. Valves made of these materials are suitable for media such as sea water, carbon dioxide, acetylene, propylene and ethylene.
 
It is suitable for cryogenic valves with working temperature between -46 and 345°C.
 
6. Valves made of low alloy steel (WC6, WC9) low alloy steel (such as carbon molybdenum steel and chrome molybdenum steel) can be used for many kinds of 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°C, and that of low alloy steel valves can be used above 600°C. At high temperatures, low alloy steels have higher mechanical properties than carbon steels.
 
It is suitable for high temperature and high pressure valves with non-corrosive medium with working temperature between -29 and 595°C; C5 and C12 are suitable for high temperature and high pressure valves with corrosive medium with working temperature between -29 and 650°C.
 
7. Austenitic stainless steel Austenitic stainless steel contains about 18% chromium and 8% nickel. 18-8 austenitic stainless steel is often used as valve body and bonnet material under high and low temperature and strong corrosion conditions. Adding molybdenum to 18-8 stainless steel and slightly increasing the nickel content substantially increases its corrosion resistance. Valves made of this steel can be widely used in chemical industry, such as conveying acetic acid, nitric acid, alkali, bleaching liquid, food, fruit juice, carbonic acid, tanning liquid and many other chemical products.
 
In order to apply to the high temperature range and further change the material composition, niobium is added to this stainless steel, which is known as 18-10-Nb, and the temperature can be used up to 800 °C.
 
Austenitic stainless steel usually does not become brittle at very low temperatures, so valves made of this material (such as 18-8 and 18-10-3Mo) are very suitable for working at low temperatures. For example, transport liquid gases, such as natural gas, biogas, oxygen and nitrogen.
 
Valves suitable for corrosive media with operating temperatures between –196 and 600 °C. Austenitic stainless steel is also an ideal low temperature valve material.
 
8. Monel alloy 'Monel' is a high nickel-copper alloy with good corrosion resistance. This material is often used in valves conveying alkalis, saline solutions, food and many non-gas acids, especially sulfuric and hydrofluoric acids. 'Monel' alloy is well suited for steam, seawater and marine environments. It is mainly suitable for valves containing fluorine-chloric acid medium.
 
9. Hastelloy is mainly suitable for valves with strong corrosive media such as dilute sulfuric acid.
(1) 'Hastelloy' alloy B
This alloy contains 60% nickel, 30% molybdenum and 5% iron. It is especially resistant to the strong corrosion of inorganic acids. 'Hastelloy' alloy 'B' can be used for various concentrations of hydrochloric acid at the boiling point temperature, and for sulfuric acid, it can be used at the most corrosive concentration of 70 ℃. For phosphoric acid, it can be used in a variety of conditions, and 'Hastelloy' alloy 'B' is also good for ammonium chloride, zinc chloride, aluminum sulfate and ammonium sulfate.
 
In an oxidizing atmosphere, 'Hastelloy' alloy 'B' can be used at about 800°C, and in a reducing atmosphere, the service temperature can be higher.
 
(2) 'Hastelloy' alloy C
This alloy is a nickel-based alloy containing 15% chromium and 17% molybdenum. It can be used up to 1100°C under both oxidizing and reducing atmospheres. It has good corrosion resistance to hydrochloric, sulfuric and phosphoric acids. And in many cases, it can also be used for nitric acid.
 
'Hastelloy' Alloy 'C' is highly resistant to chlorides, hydrochlorides, sulphides, oxidizing salt solutions and many other aggressive media. It is also especially suitable for hydrohalic acid media, such as hydrofluoric acid.
 
10. Titanium alloy is mainly suitable for valves with various strong corrosive media.
 
11. Many valves used in the casting copper alloy industry are made of non-ferrous metal materials, mainly bronze and brass. The ratio of copper, tin, lead and zinc in the bronze alloy used to make valves is usually 85:5:5:5 or 87:7:3:3. If zinc-free bronze is desired, this must be stated. Bronze's physical strength, structural stability, and corrosion resistance make it particularly suitable for industrial production. The diameter of the bronze valve for industrial use can reach 100mm.
 
Bronze valves are often used in relatively medium temperature situations, and some grades of bronze can be used up to about 280 °C. In terms of low temperature, most copper alloys have the property of not being brittle at very low temperatures, which makes bronze widely used in low temperature conditions, such as liquid oxygen and liquid nitrogen, whose temperature is below -180°C.
 
Alloy No. 12 and No. 20 are high-alloy stainless steels that are most interesting to people under the very strict conditions that ordinary stainless steels cannot handle. Perhaps the most common one is 20 gauge alloy steel. It contains 29% nickel, 20% chromium, plus molybdenum and copper. This alloy has strong resistance to various temperatures and concentrations of sulfuric acid. In addition, it can also be used in phosphoric acid and acetic acid media in most cases, especially where chlorides and other impurities are present.
 
13. Two-way stainless steel The application and development trend of two-way stainless steel (ferrite structure or austenite structure). This kind of steel contains 20% or more chromium, about 5% nickel, and a certain amount of molybdenum. The ability to resist localized corrosion is very strong.
 
It is mainly suitable for valves used in oxygen pipelines and seawater pipelines with working temperatures between -273 and 200°C.
 
14. Plastic and ceramics are both non-metallic materials. The biggest feature of non-metal material valves is strong corrosion resistance, and even has advantages that metal material valves cannot possess. It is generally suitable for corrosive media with nominal pressure PN≤1.6MPa and working temperature not exceeding 60°C. Non-toxic plastic valves are also suitable for water supply industry. The material of the main parts of the valve should first consider the physical properties (temperature, pressure) and chemical properties (corrosion) of the working medium. At the same time, the cleanliness of the medium (with or without solid particles) should also be known.