The choice of gasket material mainly depends on the following three factors: Temperature and pressure medium
I. Metal gasket material
1. Carbon steel: Recommended maximum operating temperature does not exceed 538°C, especially when the media is oxidizing. High-quality thin carbon steel plates are also not suitable for use in equipment for the manufacture of inorganic acid, neutral or acidic salt solutions. If carbon steels are subjected to stress, the accident rate of equipment used in hot water conditions is very high. Carbon steel gaskets are often used for high concentrations of acids and many alkaline solutions. Brinell hardness is about 120.
2. 304 stainless steel 18-8 (chrome 18-20%, nickel 8-10%), recommended maximum operating temperature does not exceed 760 °C. In the temperature range of -196 to 538°C, stress corrosion and grain boundary corrosion occur easily. Brinell hardness 160.
3. The carbon content of 304L stainless steel does not exceed 0.33%. Recommended maximum operating temperature does not exceed 760°C. Corrosion resistance is similar to 304 stainless steel. The low carbon content reduces the precipitation of carbon from the crystal lattice and the resistance to grain boundary corrosion is higher than that of 304 stainless steel. Brinell hardness is about 140.
4. 316 stainless steel 18-12 (chrome 18%, nickel 12%) adds about 2% molybdenum in 304 stainless steel, its strength and corrosion resistance increase when the temperature is increased. When the temperature increases, it has higher creep resistance than other ordinary stainless steels. Recommended maximum operating temperature does not exceed 760°C. The Brinell hardness is about 160.
5. 316L stainless steel recommended maximum continuous operating temperature does not exceed 760 °C ~ 815 °C. The carbon content does not exceed that of 316 stainless steel with better stress resistance and grain boundary corrosion. Brinell hardness is about 140.
6. 20 alloy 45% iron, 24% nickel, 20% chromium and a small amount of molybdenum and copper. Recommended maximum operating temperature does not exceed 760°C~815°C. Particularly suitable for the manufacture of sulfuric acid corrosion resistant equipment, Brinell hardness of about 160.
7. Aluminum and aluminum (content not less than 99%). Aluminum has excellent corrosion resistance and processability and is suitable for the manufacture of double clamp gaskets. Brinell hardness is about 35. The recommended maximum continuous operating temperature does not exceed 426°C.
8. The composition of copper copper is close to that of pure copper, which contains a trace amount of silver to increase its continuous operating temperature. The recommended maximum continuous operating temperature does not exceed 260°C. Brinell hardness is about 80.
9. Brass (copper 66%, zinc 34%) has good corrosion resistance under most working conditions, but does not adapt to acetic acid, ammonia, salt and acetylene. The recommended maximum continuous operating temperature does not exceed 260°C. Brinell hardness is about 58.
10. Hastelloy B-2 (26-30% molybdenum, 62% nickel, and 4-6% iron). Recommended maximum operating temperature does not exceed 1093°C. Has excellent heat-resistant hydrochloric acid corrosion properties. It also has excellent corrosion resistance to wet hydrogen chloride gas corrosion, sulfuric acid, phosphoric acid, and reducing salt solutions. High strength at high temperatures. Brinell hardness is about 230.
11. Hastelloy C-276 16-18% molybdenum, 13-17.5% chromium, 3.7-5.3% tungsten, 4.5-7% iron, and the rest are nickel). Recommended maximum operating temperature does not exceed 1093°C. Has excellent corrosion resistance. For various attempts of cold nitric acid or boiling nitric acid with a concentration of 70%, it has excellent corrosion resistance, good resistance to hydrochloric acid and sulfuric acid corrosion, and excellent stress corrosion resistance. Brinell hardness is about 210.
12. Inconel 600 nickel-base alloy (77% nickel, 15% chromium and 7% iron). Recommended maximum operating temperature does not exceed 1093°C. High strength at high temperatures, commonly used in equipment that needs to address stress corrosion problems. In the low temperature conditions, with excellent processing performance. Brinell hardness is about 150.
13. Monel 400 (30% copper, nickel recommended maximum continuous operating temperature does not exceed 815 ° C. In addition to strong oxidizing acids, has excellent corrosion resistance for most acids and alkalis. Easy in the fluoride acid, mercury chloride, mercury medium Because of the stress corrosion cracking, it is not suitable for the above media and is widely used in equipment for the production of hydrofluoric acid, which has a Brinell hardness of about 120.
14. titanium
Recommended maximum operating temperature does not exceed 1093°C. It has excellent corrosion resistance under high temperature conditions. It is well known that the erosion of chloride ions is excellent in resistance to nitric acid corrosion over a wide temperature and concentration range. Titanium is rarely used in most alkaline solutions and is adapted for oxidation conditions. Brinell hardness is about 216.
Non-metallic gasket material
1. Natural rubber NR has good corrosion resistance to weak acids and bases, salts and chloride solutions, and has poor corrosion resistance to oils and solvents and is not recommended for ozone media. Recommended operating temperature -57 °C ~ 93 °C.
2. Neoprene CR Neoprene is a synthetic rubber that is resistant to moderately corrosive acids, alkalis and salt solutions. It has good corrosion resistance to commercial oils and fuels. However, the corrosion resistance of strong oxidizing acids, aromatic hydrocarbons and chlorinated hydrocarbons is poor. Recommended operating temperature -51 °C ~ 121 °C.
3. NBR Cyanide rubber NBR is a synthetic rubber that is suitable for a wide range of oils, solvents, aromatic hydrocarbons, alkaline hydrocarbons, oil and gas corrosion resistance. Good corrosion resistance to hydroxides, salts, and near-neutral acids. However, in strong oxidizing media, chlorinated hydrocarbons, ketones and greases, their corrosion resistance is poor. The recommended working temperature is 51°C~121°C.
4. The fluororubber fluororubber compound is obtained by compounding a divalent and trivalent fluorocarbon compounding agent and a vulcanizing agent. In addition to excellent heat resistance, media resistance, and good physical and mechanical properties, it also has low compression set, good elasticity and long service life. Fluororubber has outstanding heat resistance (200-250°C), oil resistance, can be used to make cylinder liner seals, rubber bowls and rotating lip seals, which can significantly increase the use of time. Recommended operating temperature -40 °C ~ 232 °C.
5. Chlorosulphonated polyethylene synthetic rubber has good corrosion resistance to acid, alkali and salt solutions, and is not affected by climate, light, ozone, commercial fuels such as diesel and kerosene. However, it does not apply to aromatic hydrocarbons, chlorinated hydrocarbons, chromic acid, and nitric acid. Recommended operating temperature -45 °C ~ 135 °C.
6. Silicone rubber silicone rubber has outstanding high and low temperature resistance, can be used at 150 °C for long-term use without change in performance; can be used continuously at 200 °C for 10,000 hours, maintaining its unique characteristics within the operating temperature range of -70 to 260 °C. The use of elasticity and ozone resistance, weather resistance and other advantages, suitable for the production of thermal equipment required in the seal, such as the seal ring, valve pad, oil seal (applicable to water medium), special silicone rubber can be made of oil seals.
7. Ethylene propylene rubber has good corrosion resistance to strong acids, alkalis, salts and chloride solutions. However, it does not apply to oils, solvents, aromatic hydrocarbons and hydrocarbons. Recommended operating temperature -57°C~176.
8. Graphite This material does not contain a resin or inorganic all-graphite material and can be classified as a metal material with or without a metal element. The material can be bonded so that it can be manufactured more than 600MM diameter pipe gasket. For many acids, bases, salts and organic compounds and heat transfer solutions, even high temperature solutions have very good corrosion resistance. It cannot melt, but it sublimates when it exceeds 3316 °C. Use of this material in strong oxidizing media under high temperature conditions should be careful. In addition to the gaskets, this material can also be used to make non-metallic wraps in packing and wound gaskets.
9. The ceramic fiber and ceramic fiber formed on the strip are excellent gasket materials suitable for high temperature and low pressure working conditions and light flange conditions. The recommended working temperature is 1093°C, and the non-metal winding tape in the wound gasket can be produced.
10. PTFE concentrates the advantages of most plastic gasket materials, including temperature resistance from -95°C to 232°C. In addition to free fluorine and alkali metals, it has excellent corrosion resistance to chemicals, solvents, hydroxides and acids. PTFE material can fill glass, its purpose is to reduce the cold flow and creep of PTFE.
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