※Overview
→ One of the major issues that must be considered when designing and selecting valves is the operating temperature of the valve. In order to regulate the suitable working temperature of the valve body material, the suitable working temperature and relevant conditions for the valve body materials used in the petrochemical, chemical, fertilizer, electric power and metallurgy industries in China are related to the material properties of various types of valve steels and alloys. Requirements have been made clear for the valve product design, manufacture and inspection. In addition, from the aspects of technology management, production management and material procurement, for each type of steel, a combination of good steel grades and alloy grades should not be used to prevent confusion.
※Low temperature conditions
2.1 Ultra-low temperature valve material → ultra-low temperature valve (-254 (liquid hydrogen) ~ -101 °C (ethylene)) The body material must use face-centered cubic lattice austenitic stainless steel, copper alloy or aluminum alloy, its low-temperature mechanical properties after heat treatment In particular, low temperature impact toughness must meet the requirements of the standard.
→ The following austenitic stainless steels can be used to make cryogenic valves. ASTMA351 CF8M, CF3M, CF8, and CF3, ASTM A182F316, F316L, F304, and F304L, ASTM A433316, 316L, 304, 304L, and CF8D. The cryogenic valve body, bonnet, ram or flap must be cryogenically treated in liquid nitrogen (-196°C) before finishing.
2.2 Low-temperature valve materials → The main materials for low-temperature valves (-100～-30°C) include cryogenic austenitic stainless steel (low-temperature ball valve, low-temperature electric ball valve and low-temperature globe valve produced by Shanghai Yonglong Valve Factory) and low-temperature pressure-retaining parts. Ferritic and martensitic steels are used.
→ Austenitic stainless steels for low temperature use include ASTM A351CF8M, CF3M, CF8, and CF3, ASTM A182F316, F316L, F304, and F304L, ASTM A433316, 316L, 304, 304L, and CF8D.
→ Ferritic and martensitic steels for cryogenic pressure parts are available in ASTMA352 LCA (-32°C), LCB, LCC (-46°C), LC1 (-59°C), LC2, LC211 (-73°C) and LC3 (- 100 °C).
→ The primary price of the material in the ASTM A352 standard is low, but the chemical composition of the smelting must have reliable and demanding factory internal control standards. The heat treatment process is complex and requires multiple conditioning treatments to meet the requirements of the standard for low temperature impact toughness and long production cycle. When low-temperature impact toughness fails to meet the standard requirements, it is not allowed to use the material as cryogenic steel. Therefore, only in the production of large quantities, and can be used when the furnace smelting, and in general use of austenitic stainless steel.
※ Non-corrosive conditions
→ When the working medium of the valve is non-corrosive substances such as water, steam, air and oil, carbon steel is generally used. Carbon steel for valves refers to WCB, WCC cast steel and ASTMA 105 forged steel in the ASTM A216 standard. The suitable working temperature for carbon steel for valves is -29 to 425°C. However, for the sake of safety, considering that the operating temperature of the medium may fluctuate, the use temperature of carbon steel in general should not exceed 400°C.
※corrosion conditions
4.1 Chromium-molybdenum high temperature steel → Valves The Cr-Mo high temperature cast steels used in the valves are mainly WC6, WC9 and C5 (ZG1Cr5Mo) in the ASTM A217 standard. The corresponding rolling stocks are F11, F22 and F5 in ASTM A182 respectively.
(1) Low-chromium chromium-molybdenum steels → Low-chromium chromium-molybdenum steels have WC6, WC9, F11, and F22. Their applicable working media are water, steam, and hydrogen and should not be used for sulfur-containing oils. The suitable working temperature of WC6 and F11 is -29 ~ 540 °C, and the suitable working temperature of WC9 and F22 is -29 ~ 570 °C.
(2) Chromium five molybdenum high temperature steel → Chromium five molybdenum high temperature steel has C5 (ZG1Cr5Mo) and F5, the applicable working medium for water, steam, hydrogen and sulfur oil products.
→ C5 (ZG1Cr5Mo), if used in water vapor, has a maximum operating temperature of 600°C. When working media such as sulfur-containing oils, the maximum operating temperature is 550°C. Therefore, the working temperature of the specified C5 (ZG1Cr5Mo) is ≤550°C.
4.2 Stainless acid-resistant steel → Stainless acid-resistant steel is a chromium-nickel or chromium-nickel-molybdenum stainless acid-resistant steel that is used for corrosion resistance of nitric acid, sulfuric acid, acetic acid, and organic acids in petrochemical and chemical and fertilizer industries. The stainless acid-resistant steel cast steel mainly adopts CF8, CF8M, CF3, CF3M, CF8C, CD-4MCu and CN7M in the ASTM A743 or ASTM A744 standards, and the corresponding rolling materials are F304, F316, F304L, and F316L in the ASTM A182 standard. F347, F53 and United States UNSN08020.
(1) Cr-Ni stainless steel → Cr-Ni stainless steel acid-resistant steel CF8, CF3, F304, F304L, CF8C and F347, which applies to the working medium nitric acid and other oxidizing acids. Its maximum operating temperature is ≤200°C.
(2) Cr-Ni-Mo stainless steel → Cr-Ni-Mo stainless steel acid-resistant CF8M, CF3M, F316 and F316L, which applies to the working medium is acetic acid and other reducing acids.
→ CF8M, CF3M, etc. can replace CF8 and CF3, but CF8, CF3 cannot replace CF8M and CF3M. Therefore, stainless acid-resistant steel valves used in the United States and other countries mainly use CF8M and CF3M, and their maximum operating temperature is ≤200°C.
(3) CN7M alloy → CN7M alloy has a good overall corrosion resistance, and it is widely used in harsh corrosion conditions, including sulfuric acid, nitric acid, hydrofluoric acid and dilute hydrochloric acid, caustic alkali, seawater and hot chloride salt solutions, etc. In particular, it can be used in sulfuric acid in various concentrations and temperatures in the range of ≤70°C. The use temperature of CN7M and UNSN08020 alloys is -29 to 450°C.
(4) Duplex stainless steel → two-phase stainless corrosion-resistant steel (Table 1) is precipitation hardening stainless steel, which contains 35% to 40% of austenite in the ferrite matrix, and its yield strength is about 19Cr-9Ni. 2 times that of stainless steel, with high hardness and good plasticity and impact toughness. It is especially suitable for use in corrosion and erosive corrosive working conditions, so it is widely used in the oxidation and reduction of strong acid conditions, and has special stress corrosion cracking resistance in the presence of chlorine. The use temperature of CD-4MCu, CD3MN, CE3MN, and F53 duplex stainless steels is -29 to 316°C.
4.3 Corrosion-resistant nickel-base alloy → Corrosion-resistant nickel-base alloy valves are mainly made of cast Monel (M35-1), cast nickel (CZ-100), Inconel (CY-40), Hastelloy (ASTA494), and Hastelloy. Alloy B (N-12MV, N-7M) and Hastelloy C (CW-12MW, CW-7M, CW-6MC, CW-2M).
→ Monel alloys for corrosion-resistant Monel valves are mainly UNSN 04400 (Monel 400) and UNSN 05500 (MonelK 500). Cast nickel alloys have no corresponding rolling stock, and Inconel 600 and Inconel 625 are used for the British Cornell alloys.
(1) Monel → Monel (Monel) has high strength and toughness, in particular, it has excellent resistance to reducing acids and alkalis and seawater and other corrosive properties. Therefore, equipment and valves commonly used in the manufacture of media for the transport of hydrofluoric acid, brine, neutral media, alkali salts, and reducing acids are also suitable for drying chlorine, chlorinated hydrogen, high temperature chlorine at 425°C, and high temperature chlorinated gas at 450°C. Medium, but not corrosion of sulfur-containing media and oxidizing media (such as nitric acid and highly oxygenated media). The overall Monel alloy valve material code is MM, the internals are Monel alloy valves, the valve material code is C/M when the shell is carbon steel, and the valve material code is P/M when the shell is CF8. When the body is CF8M valve material code R/M. Suitable operating temperatures for Monel alloys M35-1, Monel 400 and MonelK 500 alloys are -29 to 480°C.
(2) The chemical composition of cast nickel alloy → cast nickel alloy (CZ-100) is 95% Ni and 1.00% C, and there is no corresponding rolled material. When CZ-100 is used in high temperature and high concentration or anhydrous alkali solution, it has excellent corrosion resistance. CZ-100 is commonly used in the production of chlor-alkali at high corrosion concentrations (including molten anhydrous sodium hydroxide) and in applications where metals such as copper and iron cannot be used to contaminate the product. The material code for cast nickel alloy CZ-100 valves is Ni. Suitable working temperature of CZ-100 alloy is -29 ~ 316 °C.
(3) Inconel-Inconel CY-40 and Inconel 600 (ASTMB 564 N 06600) are mainly used for stress corrosion resistance, especially for high-concentration chloride media. When the Ni content is ≥45%, Chloride stress corrosion has an "immune" effect. In addition, it is also resistant to corrosion of high boiling gases such as concentrated nitric acid, fuming nitric acid, sulfur and vanadium, and combustibles.
→ Inconel alloys have been widely used in the manufacture of boiler feed water system components in nuclear power plants because of its higher safety than stainless steel. At the same time, it is also suitable for high-resistance, high-pressure seals that require high-strength seals, and industrial production that resists mechanical wear and oxidation at high temperatures. For example, large chemical fertilizer plants use Inconel 600 or Inconel 625 alloys (which are Hastelloy CW-6MC grades) to produce high pressures (600 to 1500)
→ LB) High concentration oxygen valve. The material code for the CY-40 and Inconel 600 alloy valves is In. Suitable working temperature is -29~650°C.
(4) Hastelloy → Hastelloy is a trade name, which includes a series of alloy grades, mainly for Hastelloy B on corrosion resistant valves.
→ (Hastelloy B) and Hastelloy C are two types.
→Hastelloy B's cast alloy grades are N-12MV (N-12M-1) and N-7M in the ASTM A494 standard (some materials are called N-12M-2, also known as Chlorimet. (2 alloys), the rolling material is UNSN 10665 in the ASTM B 335 standard. Hastelloy B is resistant to various concentrations of hydrochloric acid and also resistant to non-oxidizing salts and acids. Hastelloy B corrosion valve, corrosion resistance and resistance to intergranular corrosion should consider the use of low carbon grade Hastelloy B (N-7M). Hastelloy alloy material code valve industry is not yet defined, Hastelloy B valve material code, can be directly used to indicate its alloy brand. Hastelloy B suitable working temperature is -29 °C ~ 425 °C.
→Hastelloy C has a cast alloy grade of CW-12MW (some materials are called CW-12M-1) and CW-7M (CW-12M-2, also known as Chlorimet 3 alloy) and Hastelloy C-276 alloy, its casting alloy grades CW-6 MC and Hastelloy C-4 alloy, the casting alloy grade CW-2M. Casting Hastelloy CW-7M, CW-12 MW, CW-6MC and CW-2M correspond to the UNS 10001, UNSN 10003, UNSN 10276 and UNSN 06455 respectively. Hastelloy C is resistant to oxidizing solvents and low concentrations of hydrochloric acid and nitric acid at room temperature.
→ The first generation of Hastelloy C (0Cr16Ni60Mo16 W4) is characterized by excellent corrosion resistance in highly corrosive oxidative and reducing acid media, but due to the high nickel corrosion resistance alloys are austenite because Ni is reduced C in the austenite solid solubility and other reasons. Therefore, both Hastelloy B and Ni-Mo-Cr Hastelloy C have severe intergranular corrosion tendencies or sensitivities, and can also cause stress corrosion and crevice corrosion at high temperatures. In order to overcome the intergranular corrosion, the second-generation Hastelloy C-276 (C is reduced from 0.03% to 0.02%) and Hastelloy C-4, the third-generation Hastelloy C, are introduced. Their characteristics are low. Si (Si ≤ 0.08%) and ultrafine C (C ≤ 0.015%), and reduced Fe and W content, and added stabilized alloying elements such as Ti.
→ Hastelloy C corrosion resistant valve, from corrosion resistance and resistance to intergranular corrosion, should use Hastelloy C-276 (CW-6MC) and Hastelloy C-4 (CW-2M). Hastelloy C valve has many material codes and its performance and operating temperature are very different, so CW-12MW, CW-7M, CW-6MC and CW-2M use HC-12, HC-7, HC-276 and HC-, respectively. 4 indicates, or directly represented by its cast alloy grade.
→ The suitable working temperature of Hastelloy CW-7M and UNSN10001 alloys is -29 to 425°C, and the suitable working temperature of Hastelloy CW-12MW and UNSN10003 alloys is -29 to 700°C. Hastelloy CW-6MC and UNSN 10276 alloys The suitable operating temperature is -29 ~ 676 °C, Hastelloy CW-2M and UNSN06455 alloy suitable working temperature is -29 ~ 425 °C.
4.4 Titanium alloy→Titanium (Ti) has high strength, light weight, sufficiently high heat resistance and low temperature toughness, and good processability and welding performance. For the production of valves, it is mainly cast pure titanium and forged pure titanium ZTA2.
→Titanium shows corrosion resistance, non-corrosion resistance, and even fire or explosion due to the difference in operating conditions such as temperature. Therefore, when ordering and designing, you should clearly specify the nature of the medium used (concentration, temperature, etc.).
→Titanium valves have excellent corrosion resistance in a variety of highly oxidizing aggressive media and neutral media.
→ Titanium has excellent corrosion resistance in the nitric acid below the boiling point and in concentrations of ≤80%. In the fuming nitric acid, when the NO2 content exceeds 2% and the water content is insufficient, titanium reacts with the fuming nitric acid to cause an explosion. Therefore, titanium is generally not used for nitric acid having a content of more than 80%.
→ Titanium is not resistant to corrosion in sulfuric acid and titanium has moderate corrosion resistance in hydrochloric acid. It is generally believed that industrial pure titanium can be used in the concentration of 7.5% at room temperature, 3% concentration at 60°C, and 0.5% concentration at 100°C. Titanium can also be used at 30% concentration at 35°C, 10% concentration at 100°C, and 100%. 3% phosphoric acid in °C.
→ Titanium is not resistant to corrosion in HF (hydrofluoric acid), titanium is not resistant to corrosion in acidic fluoride solutions, titanium is resistant to corrosion in boric acid and chromic acid, and can be used in both hydroiodic and hydrobromic acids.
→Titanium can be used at 60°C mixed acid of 10% sulfuric acid and 90% nitric acid, boiling acid mixture of 1% hydrochloric acid and 5% nitric acid, and aqua regia at room temperature (Note: Aqua regia is a mixture of 3 volumes of concentrated hydrochloric acid and 1 volume of concentrated nitric acid. )in.
→ Titanium is completely corrosion resistant at room temperature in various concentrations of barium hydroxide, calcium hydroxide, magnesium hydroxide, sodium hydroxide and potassium hydroxide solutions, but it cannot be used in boiling sodium hydroxide and potassium hydroxide. Alkali containing ammonia will exacerbate the corrosion of titanium.
→ The maximum working temperature of titanium in tap water, river water, and air is 300°C. Titanium can be used in seawater with a maximum flow rate of 20m/s. Titanium has high corrosion resistance in seawater at a temperature of ≤120°C. If the temperature is higher than 120°C, pitting corrosion and crevice corrosion may occur.
→ titanium In addition to formic acid, oxalic acid and concentrated citric acid (concentration ≥ 50%), titanium has excellent corrosion resistance for all organic acids, but when the water content in organic acids is too low (<0.1%) Prone to pitting corrosion.
→ Titanium has excellent corrosion resistance in hydrocarbons and chlorinated hydrocarbons. Titanium reacts violently in dry chlorine gas to produce TiCl4, and there is a danger of fire, but titanium has good corrosion resistance in wet chlorine (water content is 0.3 to 1.5%).
→ Titanium is stable in HCl dried at 20-160°C, but hydrochloric acid causes corrosion of titanium in wet hydrogen chloride.
→ The pitting potential of titanium in the chloride solution is higher than that of stainless steel. The pitting resistance of titanium against chlorine ions is better than that of stainless steel, so titanium has been widely used in chloride solutions.
→ At temperatures ≤ 80°C, titanium does not generally produce pitting, but at moderately high temperatures in chloride solutions (eg, 25% aluminum chloride solution at 100°C, 70% calcium chloride solution at 175°C, and 25°C at 25°C). The pitting is more likely to occur in % magnesium chloride solution and 75% zinc chloride solution at 200°C.
※High temperature conditions
→ High-temperature operating conditions Valves mainly refer to high-temperature valves used in refineries.
5.1 Sub-high temperature → Sub-high temperature means that the working temperature of the valve is in the range of 325 to 425°C. If the medium is water and steam, WCB, WCC, A105, WC6 and WC9 are mainly used. If the medium is a sulfur-containing oil, it is mainly used for anti-sulfide corrosion of C5, CF8, CF3, CF8M, and CF3M. They are mostly used in refinery atmospheric and vacuum units and delayed cokers. At this time, CF8, CF8M, CF3, and CF3M valves are not used for acid-resistant solution corrosion, but for sulfur-containing oils and oil and gas pipelines. In this case, the maximum operating temperature limit for CF8, CF8M, CF3, and CF3M is 450°C.
5.2 High Temperature Class I → The operating temperature of the valve is 425 to 550°C, which is a high temperature Class I (referred to as PI grade). The main material of the PI valve is the "high temperature grade I carbon chromium nickel rare earth titanium heat resistant steel" based on the CF8 in the ASTM A351 standard. Because the PI grade is a specific name, the concept of high-temperature stainless steel (P) is included here. Therefore, if the working medium is water or steam, although high-temperature steel WC6 (t ≤ 540 °C) or WC9 (t ≤ 570 °C) can also be used, high-temperature steel C5 (ZG1Cr5Mo) can be used in the sulfur-containing oil, but We cannot call them PI levels here.
5.3 high temperature class II → valve operating temperature of 550 ~ 650 °C, set for high-temperature II grade (referred to as PII grade). The PII high temperature valve is mainly used in the heavy oil catalytic cracking unit of a refinery, and it contains a high temperature lining wear resistant gate valve used in the three-rotation nozzle and the like. The main material of the PII valve is CF8 based on ASTM A351 standard "High temperature grade II carbon chromium nickel rare earth titanium crucible reinforced heat-resistant steel."
5.4 The working temperature of the high-temperature III grade valve is 650-730°C, which is designated as high-temperature grade III (referred to as PIII grade). PIII high-temperature valves are mainly used in large-scale heavy oil catalytic cracking units in refineries. The main material of PIII high-temperature valve is CF8M based on ASTM A351 standard "High-temperature Class III medium carbon chromium nickel and molybdenum rare earth titanium cerium reinforced heat-resistant steel."
5.5 High Temperature Class IV → The operating temperature of the valve is 730 to 816°C, which is designated as High Temperature Class IV (referred to as PIV Grade). Limiting the operating temperature of the PIV class valve to 816°C is due to the standard ASMEB16.34 pressure-temperature rating used in the valve design that provides a maximum temperature of 816°C (1500). In addition, after the working temperature exceeds 816°C, the steel is close to entering the forging temperature zone. At this time, the metal is in the plastic deformation zone. The metal has good plasticity, and it is difficult to withstand the high working pressure and impact force without being deformed. The main material of the PIV valve is the CF8M in the ASTM A351 standard, which is based on the "high-temperature grade IV medium-carbon chromium nickel nickel molybdenum rare earth titanium-titanium reinforced heat-resistant steel." CK-20 and ASTM A182 standard F310 (where C content ≥ 0.050%) and heat-resistant stainless steel such as F310H.
5.6 High-temperature class V → valve operating temperature> 816 °C above, known as high-temperature grade V (referred to as PV grade). PV-type high-temperature valves (valves for shut-off, and valves for non-adjustable butterfly valves) must use special design methods such as lining the insulation lining or water or air cooling in order to ensure proper operation of the valve. Therefore, there is no provision for the upper working temperature limit of the PV-stage high-temperature valve. This is because the operating temperature of the control valve is not only determined by the material, but is solved by special design means. The basic principle of the design means is the same. PV grade high temperature valve can choose reasonable material that can satisfy the valve according to its working medium, working pressure and special design method. In the PV high temperature valve, usually the flute or butterfly plate of the flue plug or butterfly valve is often selected from the HK-30, HK-40 superalloy in ASTM A297, which can be used in oxidation and reducing gases below 1150°C. Corrosion, but can not withstand the impact and high pressure load.
※Conclusion
→ In the rapid development of technology today, the main material of the valve is increasingly diversified and highly parameterized. The working medium corresponding to the valve is also more complex and the operating temperature is more demanding. Understanding the performance of various types of valve steels and alloys and their appropriate operating temperatures is a must-know knowledge for scientists, technicians, and operators who design, manufacture, purchase, and use valves. In particular, the use temperature of the material must not exceed its suitable operating temperature, otherwise it may cause terrible serious accidents.
→ One of the major issues that must be considered when designing and selecting valves is the operating temperature of the valve. In order to regulate the suitable working temperature of the valve body material, the suitable working temperature and relevant conditions for the valve body materials used in the petrochemical, chemical, fertilizer, electric power and metallurgy industries in China are related to the material properties of various types of valve steels and alloys. Requirements have been made clear for the valve product design, manufacture and inspection. In addition, from the aspects of technology management, production management and material procurement, for each type of steel, a combination of good steel grades and alloy grades should not be used to prevent confusion.
※Low temperature conditions
2.1 Ultra-low temperature valve material → ultra-low temperature valve (-254 (liquid hydrogen) ~ -101 °C (ethylene)) The body material must use face-centered cubic lattice austenitic stainless steel, copper alloy or aluminum alloy, its low-temperature mechanical properties after heat treatment In particular, low temperature impact toughness must meet the requirements of the standard.
→ The following austenitic stainless steels can be used to make cryogenic valves. ASTMA351 CF8M, CF3M, CF8, and CF3, ASTM A182F316, F316L, F304, and F304L, ASTM A433316, 316L, 304, 304L, and CF8D. The cryogenic valve body, bonnet, ram or flap must be cryogenically treated in liquid nitrogen (-196°C) before finishing.
2.2 Low-temperature valve materials → The main materials for low-temperature valves (-100～-30°C) include cryogenic austenitic stainless steel (low-temperature ball valve, low-temperature electric ball valve and low-temperature globe valve produced by Shanghai Yonglong Valve Factory) and low-temperature pressure-retaining parts. Ferritic and martensitic steels are used.
→ Austenitic stainless steels for low temperature use include ASTM A351CF8M, CF3M, CF8, and CF3, ASTM A182F316, F316L, F304, and F304L, ASTM A433316, 316L, 304, 304L, and CF8D.
→ Ferritic and martensitic steels for cryogenic pressure parts are available in ASTMA352 LCA (-32°C), LCB, LCC (-46°C), LC1 (-59°C), LC2, LC211 (-73°C) and LC3 (- 100 °C).
→ The primary price of the material in the ASTM A352 standard is low, but the chemical composition of the smelting must have reliable and demanding factory internal control standards. The heat treatment process is complex and requires multiple conditioning treatments to meet the requirements of the standard for low temperature impact toughness and long production cycle. When low-temperature impact toughness fails to meet the standard requirements, it is not allowed to use the material as cryogenic steel. Therefore, only in the production of large quantities, and can be used when the furnace smelting, and in general use of austenitic stainless steel.
※ Non-corrosive conditions
→ When the working medium of the valve is non-corrosive substances such as water, steam, air and oil, carbon steel is generally used. Carbon steel for valves refers to WCB, WCC cast steel and ASTMA 105 forged steel in the ASTM A216 standard. The suitable working temperature for carbon steel for valves is -29 to 425°C. However, for the sake of safety, considering that the operating temperature of the medium may fluctuate, the use temperature of carbon steel in general should not exceed 400°C.
※corrosion conditions
4.1 Chromium-molybdenum high temperature steel → Valves The Cr-Mo high temperature cast steels used in the valves are mainly WC6, WC9 and C5 (ZG1Cr5Mo) in the ASTM A217 standard. The corresponding rolling stocks are F11, F22 and F5 in ASTM A182 respectively.
(1) Low-chromium chromium-molybdenum steels → Low-chromium chromium-molybdenum steels have WC6, WC9, F11, and F22. Their applicable working media are water, steam, and hydrogen and should not be used for sulfur-containing oils. The suitable working temperature of WC6 and F11 is -29 ~ 540 °C, and the suitable working temperature of WC9 and F22 is -29 ~ 570 °C.
(2) Chromium five molybdenum high temperature steel → Chromium five molybdenum high temperature steel has C5 (ZG1Cr5Mo) and F5, the applicable working medium for water, steam, hydrogen and sulfur oil products.
→ C5 (ZG1Cr5Mo), if used in water vapor, has a maximum operating temperature of 600°C. When working media such as sulfur-containing oils, the maximum operating temperature is 550°C. Therefore, the working temperature of the specified C5 (ZG1Cr5Mo) is ≤550°C.
4.2 Stainless acid-resistant steel → Stainless acid-resistant steel is a chromium-nickel or chromium-nickel-molybdenum stainless acid-resistant steel that is used for corrosion resistance of nitric acid, sulfuric acid, acetic acid, and organic acids in petrochemical and chemical and fertilizer industries. The stainless acid-resistant steel cast steel mainly adopts CF8, CF8M, CF3, CF3M, CF8C, CD-4MCu and CN7M in the ASTM A743 or ASTM A744 standards, and the corresponding rolling materials are F304, F316, F304L, and F316L in the ASTM A182 standard. F347, F53 and United States UNSN08020.
(1) Cr-Ni stainless steel → Cr-Ni stainless steel acid-resistant steel CF8, CF3, F304, F304L, CF8C and F347, which applies to the working medium nitric acid and other oxidizing acids. Its maximum operating temperature is ≤200°C.
(2) Cr-Ni-Mo stainless steel → Cr-Ni-Mo stainless steel acid-resistant CF8M, CF3M, F316 and F316L, which applies to the working medium is acetic acid and other reducing acids.
→ CF8M, CF3M, etc. can replace CF8 and CF3, but CF8, CF3 cannot replace CF8M and CF3M. Therefore, stainless acid-resistant steel valves used in the United States and other countries mainly use CF8M and CF3M, and their maximum operating temperature is ≤200°C.
(3) CN7M alloy → CN7M alloy has a good overall corrosion resistance, and it is widely used in harsh corrosion conditions, including sulfuric acid, nitric acid, hydrofluoric acid and dilute hydrochloric acid, caustic alkali, seawater and hot chloride salt solutions, etc. In particular, it can be used in sulfuric acid in various concentrations and temperatures in the range of ≤70°C. The use temperature of CN7M and UNSN08020 alloys is -29 to 450°C.
(4) Duplex stainless steel → two-phase stainless corrosion-resistant steel (Table 1) is precipitation hardening stainless steel, which contains 35% to 40% of austenite in the ferrite matrix, and its yield strength is about 19Cr-9Ni. 2 times that of stainless steel, with high hardness and good plasticity and impact toughness. It is especially suitable for use in corrosion and erosive corrosive working conditions, so it is widely used in the oxidation and reduction of strong acid conditions, and has special stress corrosion cracking resistance in the presence of chlorine. The use temperature of CD-4MCu, CD3MN, CE3MN, and F53 duplex stainless steels is -29 to 316°C.
4.3 Corrosion-resistant nickel-base alloy → Corrosion-resistant nickel-base alloy valves are mainly made of cast Monel (M35-1), cast nickel (CZ-100), Inconel (CY-40), Hastelloy (ASTA494), and Hastelloy. Alloy B (N-12MV, N-7M) and Hastelloy C (CW-12MW, CW-7M, CW-6MC, CW-2M).
→ Monel alloys for corrosion-resistant Monel valves are mainly UNSN 04400 (Monel 400) and UNSN 05500 (MonelK 500). Cast nickel alloys have no corresponding rolling stock, and Inconel 600 and Inconel 625 are used for the British Cornell alloys.
(1) Monel → Monel (Monel) has high strength and toughness, in particular, it has excellent resistance to reducing acids and alkalis and seawater and other corrosive properties. Therefore, equipment and valves commonly used in the manufacture of media for the transport of hydrofluoric acid, brine, neutral media, alkali salts, and reducing acids are also suitable for drying chlorine, chlorinated hydrogen, high temperature chlorine at 425°C, and high temperature chlorinated gas at 450°C. Medium, but not corrosion of sulfur-containing media and oxidizing media (such as nitric acid and highly oxygenated media). The overall Monel alloy valve material code is MM, the internals are Monel alloy valves, the valve material code is C/M when the shell is carbon steel, and the valve material code is P/M when the shell is CF8. When the body is CF8M valve material code R/M. Suitable operating temperatures for Monel alloys M35-1, Monel 400 and MonelK 500 alloys are -29 to 480°C.
(2) The chemical composition of cast nickel alloy → cast nickel alloy (CZ-100) is 95% Ni and 1.00% C, and there is no corresponding rolled material. When CZ-100 is used in high temperature and high concentration or anhydrous alkali solution, it has excellent corrosion resistance. CZ-100 is commonly used in the production of chlor-alkali at high corrosion concentrations (including molten anhydrous sodium hydroxide) and in applications where metals such as copper and iron cannot be used to contaminate the product. The material code for cast nickel alloy CZ-100 valves is Ni. Suitable working temperature of CZ-100 alloy is -29 ~ 316 °C.
(3) Inconel-Inconel CY-40 and Inconel 600 (ASTMB 564 N 06600) are mainly used for stress corrosion resistance, especially for high-concentration chloride media. When the Ni content is ≥45%, Chloride stress corrosion has an "immune" effect. In addition, it is also resistant to corrosion of high boiling gases such as concentrated nitric acid, fuming nitric acid, sulfur and vanadium, and combustibles.
→ Inconel alloys have been widely used in the manufacture of boiler feed water system components in nuclear power plants because of its higher safety than stainless steel. At the same time, it is also suitable for high-resistance, high-pressure seals that require high-strength seals, and industrial production that resists mechanical wear and oxidation at high temperatures. For example, large chemical fertilizer plants use Inconel 600 or Inconel 625 alloys (which are Hastelloy CW-6MC grades) to produce high pressures (600 to 1500)
→ LB) High concentration oxygen valve. The material code for the CY-40 and Inconel 600 alloy valves is In. Suitable working temperature is -29~650°C.
(4) Hastelloy → Hastelloy is a trade name, which includes a series of alloy grades, mainly for Hastelloy B on corrosion resistant valves.
→ (Hastelloy B) and Hastelloy C are two types.
→Hastelloy B's cast alloy grades are N-12MV (N-12M-1) and N-7M in the ASTM A494 standard (some materials are called N-12M-2, also known as Chlorimet. (2 alloys), the rolling material is UNSN 10665 in the ASTM B 335 standard. Hastelloy B is resistant to various concentrations of hydrochloric acid and also resistant to non-oxidizing salts and acids. Hastelloy B corrosion valve, corrosion resistance and resistance to intergranular corrosion should consider the use of low carbon grade Hastelloy B (N-7M). Hastelloy alloy material code valve industry is not yet defined, Hastelloy B valve material code, can be directly used to indicate its alloy brand. Hastelloy B suitable working temperature is -29 °C ~ 425 °C.
→Hastelloy C has a cast alloy grade of CW-12MW (some materials are called CW-12M-1) and CW-7M (CW-12M-2, also known as Chlorimet 3 alloy) and Hastelloy C-276 alloy, its casting alloy grades CW-6 MC and Hastelloy C-4 alloy, the casting alloy grade CW-2M. Casting Hastelloy CW-7M, CW-12 MW, CW-6MC and CW-2M correspond to the UNS 10001, UNSN 10003, UNSN 10276 and UNSN 06455 respectively. Hastelloy C is resistant to oxidizing solvents and low concentrations of hydrochloric acid and nitric acid at room temperature.
→ The first generation of Hastelloy C (0Cr16Ni60Mo16 W4) is characterized by excellent corrosion resistance in highly corrosive oxidative and reducing acid media, but due to the high nickel corrosion resistance alloys are austenite because Ni is reduced C in the austenite solid solubility and other reasons. Therefore, both Hastelloy B and Ni-Mo-Cr Hastelloy C have severe intergranular corrosion tendencies or sensitivities, and can also cause stress corrosion and crevice corrosion at high temperatures. In order to overcome the intergranular corrosion, the second-generation Hastelloy C-276 (C is reduced from 0.03% to 0.02%) and Hastelloy C-4, the third-generation Hastelloy C, are introduced. Their characteristics are low. Si (Si ≤ 0.08%) and ultrafine C (C ≤ 0.015%), and reduced Fe and W content, and added stabilized alloying elements such as Ti.
→ Hastelloy C corrosion resistant valve, from corrosion resistance and resistance to intergranular corrosion, should use Hastelloy C-276 (CW-6MC) and Hastelloy C-4 (CW-2M). Hastelloy C valve has many material codes and its performance and operating temperature are very different, so CW-12MW, CW-7M, CW-6MC and CW-2M use HC-12, HC-7, HC-276 and HC-, respectively. 4 indicates, or directly represented by its cast alloy grade.
→ The suitable working temperature of Hastelloy CW-7M and UNSN10001 alloys is -29 to 425°C, and the suitable working temperature of Hastelloy CW-12MW and UNSN10003 alloys is -29 to 700°C. Hastelloy CW-6MC and UNSN 10276 alloys The suitable operating temperature is -29 ~ 676 °C, Hastelloy CW-2M and UNSN06455 alloy suitable working temperature is -29 ~ 425 °C.
4.4 Titanium alloy→Titanium (Ti) has high strength, light weight, sufficiently high heat resistance and low temperature toughness, and good processability and welding performance. For the production of valves, it is mainly cast pure titanium and forged pure titanium ZTA2.
→Titanium shows corrosion resistance, non-corrosion resistance, and even fire or explosion due to the difference in operating conditions such as temperature. Therefore, when ordering and designing, you should clearly specify the nature of the medium used (concentration, temperature, etc.).
→Titanium valves have excellent corrosion resistance in a variety of highly oxidizing aggressive media and neutral media.
→ Titanium has excellent corrosion resistance in the nitric acid below the boiling point and in concentrations of ≤80%. In the fuming nitric acid, when the NO2 content exceeds 2% and the water content is insufficient, titanium reacts with the fuming nitric acid to cause an explosion. Therefore, titanium is generally not used for nitric acid having a content of more than 80%.
→ Titanium is not resistant to corrosion in sulfuric acid and titanium has moderate corrosion resistance in hydrochloric acid. It is generally believed that industrial pure titanium can be used in the concentration of 7.5% at room temperature, 3% concentration at 60°C, and 0.5% concentration at 100°C. Titanium can also be used at 30% concentration at 35°C, 10% concentration at 100°C, and 100%. 3% phosphoric acid in °C.
→ Titanium is not resistant to corrosion in HF (hydrofluoric acid), titanium is not resistant to corrosion in acidic fluoride solutions, titanium is resistant to corrosion in boric acid and chromic acid, and can be used in both hydroiodic and hydrobromic acids.
→Titanium can be used at 60°C mixed acid of 10% sulfuric acid and 90% nitric acid, boiling acid mixture of 1% hydrochloric acid and 5% nitric acid, and aqua regia at room temperature (Note: Aqua regia is a mixture of 3 volumes of concentrated hydrochloric acid and 1 volume of concentrated nitric acid. )in.
→ Titanium is completely corrosion resistant at room temperature in various concentrations of barium hydroxide, calcium hydroxide, magnesium hydroxide, sodium hydroxide and potassium hydroxide solutions, but it cannot be used in boiling sodium hydroxide and potassium hydroxide. Alkali containing ammonia will exacerbate the corrosion of titanium.
→ The maximum working temperature of titanium in tap water, river water, and air is 300°C. Titanium can be used in seawater with a maximum flow rate of 20m/s. Titanium has high corrosion resistance in seawater at a temperature of ≤120°C. If the temperature is higher than 120°C, pitting corrosion and crevice corrosion may occur.
→ titanium In addition to formic acid, oxalic acid and concentrated citric acid (concentration ≥ 50%), titanium has excellent corrosion resistance for all organic acids, but when the water content in organic acids is too low (<0.1%) Prone to pitting corrosion.
→ Titanium has excellent corrosion resistance in hydrocarbons and chlorinated hydrocarbons. Titanium reacts violently in dry chlorine gas to produce TiCl4, and there is a danger of fire, but titanium has good corrosion resistance in wet chlorine (water content is 0.3 to 1.5%).
→ Titanium is stable in HCl dried at 20-160°C, but hydrochloric acid causes corrosion of titanium in wet hydrogen chloride.
→ The pitting potential of titanium in the chloride solution is higher than that of stainless steel. The pitting resistance of titanium against chlorine ions is better than that of stainless steel, so titanium has been widely used in chloride solutions.
→ At temperatures ≤ 80°C, titanium does not generally produce pitting, but at moderately high temperatures in chloride solutions (eg, 25% aluminum chloride solution at 100°C, 70% calcium chloride solution at 175°C, and 25°C at 25°C). The pitting is more likely to occur in % magnesium chloride solution and 75% zinc chloride solution at 200°C.
※High temperature conditions
→ High-temperature operating conditions Valves mainly refer to high-temperature valves used in refineries.
5.1 Sub-high temperature → Sub-high temperature means that the working temperature of the valve is in the range of 325 to 425°C. If the medium is water and steam, WCB, WCC, A105, WC6 and WC9 are mainly used. If the medium is a sulfur-containing oil, it is mainly used for anti-sulfide corrosion of C5, CF8, CF3, CF8M, and CF3M. They are mostly used in refinery atmospheric and vacuum units and delayed cokers. At this time, CF8, CF8M, CF3, and CF3M valves are not used for acid-resistant solution corrosion, but for sulfur-containing oils and oil and gas pipelines. In this case, the maximum operating temperature limit for CF8, CF8M, CF3, and CF3M is 450°C.
5.2 High Temperature Class I → The operating temperature of the valve is 425 to 550°C, which is a high temperature Class I (referred to as PI grade). The main material of the PI valve is the "high temperature grade I carbon chromium nickel rare earth titanium heat resistant steel" based on the CF8 in the ASTM A351 standard. Because the PI grade is a specific name, the concept of high-temperature stainless steel (P) is included here. Therefore, if the working medium is water or steam, although high-temperature steel WC6 (t ≤ 540 °C) or WC9 (t ≤ 570 °C) can also be used, high-temperature steel C5 (ZG1Cr5Mo) can be used in the sulfur-containing oil, but We cannot call them PI levels here.
5.3 high temperature class II → valve operating temperature of 550 ~ 650 °C, set for high-temperature II grade (referred to as PII grade). The PII high temperature valve is mainly used in the heavy oil catalytic cracking unit of a refinery, and it contains a high temperature lining wear resistant gate valve used in the three-rotation nozzle and the like. The main material of the PII valve is CF8 based on ASTM A351 standard "High temperature grade II carbon chromium nickel rare earth titanium crucible reinforced heat-resistant steel."
5.4 The working temperature of the high-temperature III grade valve is 650-730°C, which is designated as high-temperature grade III (referred to as PIII grade). PIII high-temperature valves are mainly used in large-scale heavy oil catalytic cracking units in refineries. The main material of PIII high-temperature valve is CF8M based on ASTM A351 standard "High-temperature Class III medium carbon chromium nickel and molybdenum rare earth titanium cerium reinforced heat-resistant steel."
5.5 High Temperature Class IV → The operating temperature of the valve is 730 to 816°C, which is designated as High Temperature Class IV (referred to as PIV Grade). Limiting the operating temperature of the PIV class valve to 816°C is due to the standard ASMEB16.34 pressure-temperature rating used in the valve design that provides a maximum temperature of 816°C (1500). In addition, after the working temperature exceeds 816°C, the steel is close to entering the forging temperature zone. At this time, the metal is in the plastic deformation zone. The metal has good plasticity, and it is difficult to withstand the high working pressure and impact force without being deformed. The main material of the PIV valve is the CF8M in the ASTM A351 standard, which is based on the "high-temperature grade IV medium-carbon chromium nickel nickel molybdenum rare earth titanium-titanium reinforced heat-resistant steel." CK-20 and ASTM A182 standard F310 (where C content ≥ 0.050%) and heat-resistant stainless steel such as F310H.
5.6 High-temperature class V → valve operating temperature> 816 °C above, known as high-temperature grade V (referred to as PV grade). PV-type high-temperature valves (valves for shut-off, and valves for non-adjustable butterfly valves) must use special design methods such as lining the insulation lining or water or air cooling in order to ensure proper operation of the valve. Therefore, there is no provision for the upper working temperature limit of the PV-stage high-temperature valve. This is because the operating temperature of the control valve is not only determined by the material, but is solved by special design means. The basic principle of the design means is the same. PV grade high temperature valve can choose reasonable material that can satisfy the valve according to its working medium, working pressure and special design method. In the PV high temperature valve, usually the flute or butterfly plate of the flue plug or butterfly valve is often selected from the HK-30, HK-40 superalloy in ASTM A297, which can be used in oxidation and reducing gases below 1150°C. Corrosion, but can not withstand the impact and high pressure load.
※Conclusion
→ In the rapid development of technology today, the main material of the valve is increasingly diversified and highly parameterized. The working medium corresponding to the valve is also more complex and the operating temperature is more demanding. Understanding the performance of various types of valve steels and alloys and their appropriate operating temperatures is a must-know knowledge for scientists, technicians, and operators who design, manufacture, purchase, and use valves. In particular, the use temperature of the material must not exceed its suitable operating temperature, otherwise it may cause terrible serious accidents.
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