The choice of gasket material mainly depends on the following three factors: temperature pressure medium
1. Metal gasket material
1. Carbon steel: Recommended maximum The working temperature does not exceed 538°C, especially when the medium is oxidizing. High-quality thin carbon steel plates are also not suitable for use in equipment that manufactures inorganic acids, neutral or acidic salt solutions. If carbon steel is subjected to excessive stress, the accident rate of equipment used in hot water conditions will be very high. Carbon steel gaskets are commonly used in high concentration acids and many alkaline solutions. Brinell hardness is about 120.
2. 304 stainless steel 18-8 (chromium 18-20%, nickel 8-10%), the recommended maximum working temperature does not exceed 760°C. In the temperature range of -196~538℃, stress corrosion and grain boundary corrosion are prone to occur. Brinell hardness 160.
3. The carbon content of 304L stainless steel does not exceed 0.03%. The 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 its grain boundary corrosion resistance is higher than that of 304 stainless steel. Brinell hardness is about 140.
4． 316 stainless steel 18-12 (18% chromium, 12% nickel), about 2% molybdenum is added to 304 stainless steel. When the temperature increases, its strength and corrosion resistance improve. When the temperature increases, it has higher creep resistance than other ordinary stainless steels. The recommended maximum operating temperature does not exceed 760°C. Brinell hardness is about 160.
5. The recommended maximum continuous working temperature of 316L stainless steel does not exceed 760℃~815℃. The carbon content does not exceed that of 316 stainless steel, which has better resistance to stress and grain boundary corrosion. Brinell hardness is about 140.
6. 20 alloy 45% iron, 24% nickel, 20% chromium and small amounts of molybdenum and copper. It is recommended that the maximum operating temperature does not exceed 760℃~815℃. Especially suitable for manufacturing equipment resistant to sulfuric acid corrosion, with a Brinell hardness of about 160.
7. Aluminum Aluminum (content is not less than 99%). Aluminum has excellent corrosion resistance and processability, making it suitable for manufacturing double-clamp gaskets. Brinell hardness is about 35. It is recommended that the maximum continuous operating temperature does not exceed 426°C.
8． Red copper The composition of red copper is close to pure copper, and it contains trace amounts of silver to increase its continuous operating temperature. It is recommended that the 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 is not suitable for acetic acid, ammonia, salt and acetylene. It is recommended that the 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). It is recommended that the maximum operating temperature does not exceed 1093°C. It has excellent resistance to corrosion by hot concentrated hydrochloric acid. It also has excellent resistance to corrosion by wet hydrogen chloride gas, sulfuric acid, phosphoric acid and reducing salt solutions. Has high strength under high temperature conditions. 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). It is recommended that the maximum operating temperature does not exceed 1093°C. Has excellent corrosion resistance. It has excellent corrosion resistance against various cold nitric acid or boiling nitric acid with a concentration of 70%, good hydrochloric acid and sulfuric acid corrosion resistance and excellent stress corrosion resistance. Brinell hardness is about 210.
12. Inconel 600 nickel-based alloy (77% nickel, 15% chromium and 7% iron). The recommended maximum operating temperature does not exceed 1093°C. It has high strength under high temperature conditions and is usually used in equipment that needs to solve stress corrosion problems. Under low temperature conditions, it has excellent processing properties. Brinell hardness is about 150.
13． Monel 400 (30% copper, nickel) recommended maximum continuous operating temperature not to exceed 815°C. Except for strong oxidizing acids, it has excellent corrosion resistance to most acids and alkali. It is easy to use in hydrofluoric acid, mercury chloride, and mercury media. Produces stress corrosion cracking and is therefore not suitable for use in equipment producing hydrofluoric acid.
Titanium
Recommended maximum working conditions. The temperature does not exceed 1093°C. It has excellent corrosion resistance under high temperature conditions and is well known to be resistant to chloride ion corrosion and has excellent resistance to nitric acid corrosion in a wide temperature and concentration range.
Titanium is rarely used in most alkaline solutions and is suitable for oxidation conditions. Brinell hardness is about 216.
2. Non-metallic gasket materials
1. Natural rubber NR has good corrosion resistance to weak acids and alkalis, salts and chloride solutions, but poor corrosion resistance to oil and solvents, and is not recommended for use in ozone media. Recommended operating temperature -57℃~93℃.
2． Neoprene CR Neoprene is a synthetic rubber that is suitable for corrosion resistance from moderately corrosive acid, alkali and salt solutions. Good corrosion resistance to commercial oils and fuels. However, its corrosion resistance is poor in strongly oxidizing acids, aromatic hydrocarbons and chlorinated hydrocarbons. Recommended operating temperature -51℃~121℃.
3. NBR is a synthetic rubber that has good corrosion resistance to oils, solvents, aromatic hydrocarbons, alkaline hydrocarbons, oil and natural gas over a wide temperature range. Good corrosion resistance to hydroxides, salts and nearly neutral acids. However, its corrosion resistance is poor in strongly oxidizing media, chlorinated hydrocarbons, ketones and lipids. The recommended working temperature is 51℃~121℃.
4. Fluorine rubber is compounded by mixing binary and ternary fluorine rubber with compounding agents and vulcanizing agents. In addition to excellent heat resistance, medium resistance, and good physical and mechanical properties, it also has low compression permanent deformation, good elasticity, and ultra-long service life. Fluorine rubber has outstanding heat resistance (200~250℃) and oil resistance. It can be used to manufacture cylinder liner seals, rubber bowls and rotating lip seals, which can significantly extend the service life. Recommended operating temperature -40℃~232℃.
5． Chlorosulfonyl polyethylene synthetic rubber has good corrosion resistance to acids, alkalis and salt solutions, and is not affected by climate, light, ozone, commercial fuels (such as diesel and kerosene, etc.). But it is not suitable for aromatic hydrocarbons, chlorinated hydrocarbons, chromic acid and nitric acid. Recommended operating temperature -45℃~135℃.
6． Silicone rubber Silicone rubber has outstanding high and low temperature resistance and can be used for a long time at 150°C without performance changes; it can be used continuously at 200°C for 10,000 hours and can maintain its unique properties within the operating temperature range of -70 to 260°C. With the advantages of elasticity, ozone resistance, and weather resistance, it is suitable for making sealing gaskets required in thermal mechanisms, such as sealing rings, valve gaskets, oil seals (suitable for water media), etc. Special silicone rubber can be used to make oil seals.
7. Ethylene propylene rubber has good corrosion resistance to strong acids, strong alkali, salt and chloride solutions. But it is not suitable for oils, solvents, aromatic hydrocarbons and hydrocarbons. Recommended operating temperature -57℃~176℃.
8. Graphite is an all-graphite material that does not contain resin or inorganic substances. It can be divided into graphite materials with or without metal elements. This material can be bonded to produce gaskets for pipes with diameters exceeding 600MM. It has excellent corrosion resistance to many acids, alkalis, salts, organic compounds and heat transfer solutions, even high temperature solutions. It cannot melt, but will sublimate when it exceeds 3316℃. Caution should be exercised when using this material in strongly oxidizing media under high temperature conditions. In addition to being used for gaskets, this material can also be used to make fillers and non-metallic spiral tape in spiral wound gaskets.
9. Ceramic fiber, ceramic fiber molded into tape, is an excellent gasket material suitable for high temperature and low pressure conditions and light flange conditions. The recommended operating temperature is 1093°C, and can be used to make non-metallic spiral tape in spiral wound gaskets.
10． PTFE combines the advantages of most plastic gasket materials, including temperature resistance from -95°C to 232°C. Except for free fluorine and alkali metals, it has excellent corrosion resistance to chemicals, solvents, hydroxides and acids. PTFE material can be filled with glass, the purpose of which is to reduce the cold flow and creep properties of PTFE.