Introduction of suitable working temperature of valve body parts

Issuing time:2019-12-05 09:06

One of the issues that must be considered during valve design and material selection is the operating temperature of the valve. In order to regulate the suitable working temperature of the valve body material, the suitable working temperature of the valve body material used in China's petrochemical, chemical, fertilizer, electric power and metallurgy industries and other related aspects from the material properties of various types of steel and alloy grades The requirements make clear regulations for valve product design, manufacture and inspection. In addition, from the perspective of technical management, production management and material procurement, for each type of steel, good comprehensive properties should be selected, and excessive steel and alloy grades should not be selected to prevent confusion.


One of the issues that must be considered during valve design and material selection is the operating temperature of the valve. In order to regulate the suitable working temperature of the valve body material, the suitable working temperature of the valve body material used in China's petrochemical, chemical, fertilizer, electric power and metallurgy industries and other related aspects from the material properties of various types of steel and alloy grades The requirements make clear regulations for valve product design, manufacture and inspection. In addition, from the perspective of technical management, production management and material procurement, for each type of steel, good comprehensive properties should be selected, and excessive steel and alloy grades should not be selected to prevent confusion.


2 Low temperature conditions

2.1 Ultra-low temperature valve materials

Ultra-low temperature valve [-254 (liquid hydrogen) ~ -101 ° C (ethylene)] The main material must be austenitic stainless steel, copper alloy or aluminum alloy with face-centered cubic lattice, and its low-temperature mechanical properties after heat treatment, especially low-temperature impact Resilience must meet standard requirements.


The following austenitic stainless steels can be used to make ultra-low temperature valves. ASTM A351 CF8M, CF3M, CF8 and CF3, ASTM A182 F316, F316L, F304 and F304L, ASTM A433 316, 316L, 304, 304L and CF8D (designed by Lanzhou High Pressure Valve Factory, factory standard code GFQ81-93). The valve body, bonnet, shutter or disc of the cryogenic valve must be cryogenically treated in liquid nitrogen (-196 ° C) before finishing.


2.2 Cryogenic valve materials

The main materials suitable for low temperature valves (-100 ~ -30 ℃) include low temperature austenitic stainless steel and ferritic and martensitic steel for low temperature pressure parts.


Austenitic stainless steels for low temperature use include ASTM A351 CF8M, CF3M, CF8 and CF3, ASTM A182 F316, F316L, F304 and F304L, ASTM A433 316, 316L, 304, 304L and CF8D.


Ferritic and martensitic steels for low temperature pressure parts are ASTM A352 LCA (-32 ° C), LCB, LCC (-46 ° C), LC1 (-59 ° C), LC2, LC211 (-73 ° C) and LC3 ( -100 ° C).


The primary price of materials in the ASTM A352 standard is low, but the chemical composition must have reliable and very strict factory internal control standards during smelting. The heat treatment process is complicated, and multiple quenching and tempering treatments are needed to meet the requirements of low temperature impact toughness required by the standard, and the production cycle is long. When the low temperature impact toughness fails to meet the standard requirements, it is not allowed to use the material for low temperature steel. Therefore, it is only used when the production batch is large and can be smelted in a furnace. In general, austenitic stainless steel is used.


3 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 ASTM A105 forged steel in the ASTM A216 standard. The suitable working temperature of carbon steel for valves is -29 ~ 425 ℃. However, for safety, considering that the working temperature of the medium may fluctuate, the use temperature of general carbon steel should not exceed 400 ° C.


4 Corrosion conditions

4.1 Chromium-Molybdenum High Temperature Steel

The Cr-Mo high-temperature cast steel selected for the valve is mainly WC6, WC9 and C5 (ZG1Cr5Mo) in ASTM A217 standard, and the corresponding rolling materials are F11, F22 and F5 in ASTM A182.


⑴ Low chromium grade chromium-molybdenum steel


Low-chromium chromium-molybdenum steels include WC6, WC9, F11, and F22. The applicable working medium is water, steam, and hydrogen. It is not suitable for sulfur-containing oil products. The suitable working temperature of WC6 and F11 is -29 ~ 540 ℃, and the suitable working temperature of WC9 and F22 is -29 ~ 570 ℃.


Chromium five molybdenum high temperature steel


Chromium five molybdenum high temperature steels include C5 (ZG1Cr5Mo) and F5. The applicable working medium is water, steam, hydrogen and sulfur-containing oil products.


When C5 (ZG1Cr5Mo) is used for water vapor, its maximum working temperature is 600 ° C. When used for working media such as sulfur-containing oils, the maximum working temperature is 550 ° C. Therefore, the operating temperature of C5 (ZG1Cr5Mo) is specified to be ≤550 ° C.


4.2 Stainless acid-resistant steel

Stainless acid-resistant steel refers to chrome-nickel or chromium-nickel-molybdenum stainless acid-resistant steel used in petrochemical, chemical and fertilizer industries for resistance to nitric acid, sulfuric acid, acetic acid and organic acids. Stainless acid-resistant steel cast steel mainly adopts CF8, CF8M, CF3, CF3M, CF8C, CD-4MCu, CN7M, etc. in ASTM A743 or ASTM A744 standards. The corresponding rolling materials are F304, F316, F304L in ASTM A182 standard. , F316L, F347, F53 and United States UNS N08020.


⑴ Cr-Ni stainless steel


Cr-Ni stainless acid-resistant steels include CF8, CF3, F304, F304L, CF8C, and F347, which are applicable to oxidizing acids such as nitric acid. Its maximum operating temperature is ≤200 ° C.


⑵ Cr-Ni-Mo stainless steel


Cr-Ni-Mo type stainless acid-resistant steels include CF8M, CF3M, F316 and F316L, which are suitable for working media with reducing acids such as acetic acid.


CF8M, CF3M, etc. can replace CF8 and CF3, but CF8, CF3 cannot replace CF8M and CF3M. Therefore, stainless acid-resistant steel valves in the United States and other countries mainly use CF8M and CF3M, and their maximum operating temperature is ≤200 ° C.


⑶ CN7M alloy


CN7M alloy has good overall corrosion resistance, it is widely used in harsh corrosion conditions, including sulfuric acid, nitric acid, hydrofluoric acid and dilute hydrochloric acid, caustic alkali, sea water and hot chloride salt solution, etc., especially available In sulfuric acid of various concentrations and temperatures ≤70 ° C. CN7M and UNS N08020 alloys are used at temperatures from -29 to 450 ° C.


⑷ Duplex stainless steel


Duplex stainless corrosion-resistant steels (Table 1) are precipitation-hardened stainless steels. They are austenite containing 35% to 40% in the ferrite matrix, and their yield strength is about 2% of that of 19Cr-9Ni austenitic stainless steel. Times, and has high hardness and good plasticity and impact toughness. It is especially suitable for use under corrosive working conditions with both abrasion and scour, so it is widely used in the strong acid working conditions of oxidation and reduction, and has special stress corrosion cracking resistance in the environment with chlorine. CD-4MCu, CD3MN, CE3MN and F53 duplex stainless steel use temperature is -29 ~ 316 ℃.


Table 1 Comparison of grades of duplex stainless steel materials


Grade Casting Rolled Plate Sheet Bar

0Cr25-Ni5-Mo-Cu A8901A [CD4MCu]

00Cr22-Ni5-Mo3-N A8904A [CD3MN] A182F51 A240S31803 A479S31803

00Cr25-Ni7-Mo4-N A8905A [CE3MN] A182F53 A240S32750 A479S32750

4.3 Corrosion-resistant nickel-based alloy


Corrosion-resistant nickel-based alloy valves are mainly selected from cast Monel alloy (M35-1), cast nickel alloy (CZ-100), Inconel alloy (CY-40), Hastelloy B (N-12MV) , N-7M) and Hastelloy C (CW-12MW, CW-7M, CW-6MC, CW-2M).


Monel alloy rolled materials for corrosion-resistant Monel valve are mainly UNS N04400 (Monel 400) and UNS N05500 (Monel K500). There are no corresponding rolling materials for cast nickel alloys. Inconel 600 and Inconel 625 are the rolling materials for Inconel.


⑴ Monel alloy


Monel alloy has high strength and toughness, especially has excellent resistance to reducing acids and strong alkaline media and seawater and other corrosion properties. Therefore, it is generally used to manufacture equipment and valves for transporting media such as hydrofluoric acid, brine, neutral media, alkali salts, and reducing acids. It is also suitable for dry chlorine, hydrogen chloride, 425 ° C high-temperature chlorine, and 450 ° C high-temperature hydrogen chloride. Medium, but not resistant to sulfur and oxidizing media (such as nitric acid and high oxygen media). The valve code of the Monel alloy as a whole is MM, the valve of the Monel alloy is the internal part, the valve material code is C / M when the housing is carbon steel, and the valve material code is P / M when the housing is CF8. When the body is CF8M, the valve material code is R / M. The suitable working temperature of Monel M35-1, Monel 400 and Monel K500 alloys is -29 ~ 480 ℃.


铸 Cast nickel alloy


The chemical composition of the cast nickel alloy (CZ-100) is 95% Ni and 1.00% C, and there is no corresponding rolling material. When CZ-100 is used in high temperature or high concentration or anhydrous alkali solution, it has excellent corrosion resistance. CZ-100 is commonly used in the production of chlor-alkali in high corrosion concentrations (including molten anhydrous caustic soda) and in applications where products such as copper and iron cannot be polluted. The material code of the cast nickel alloy CZ-100 valve is Ni. The suitable working temperature of CZ-100 alloy is -29 ~ 316 ℃.


⑶ Inconel alloy


Inconel CY-40 and Inconel 600 (ASTM


B564 N06600) is mainly used for stress corrosion resistance, especially for high-concentration chloride media. When the Ni content is ≥45%, it has an "immunity" effect on the stress corrosion of chlorides. In addition, it is resistant to the corrosion of boiling concentrated nitric acid, fuming nitric acid, sulfur and vanadium-containing high-temperature gases and combustion materials.


Inconel alloy has been widely used to make boiler feedwater system components in nuclear power plants because it is more secure than stainless steel. At the same time, it is also suitable for industrial production that requires high strength, high pressure sealing and high corrosion resistance, as well as resistance to mechanical wear and oxidation at high temperatures. For example, the Dafei Fertilizer Plant uses Inconel 600 or Inconel 625 alloy (the rolling material grade of Hastelloy CW-6MC) to produce high pressure (600 ~ 1500


LB) High concentration oxygen valve. The material code for CY-40 and Inconel 600 alloy valves is In. Suitable working temperature is -29 ~ 650 ℃.


⑷ Hastelloy


Hastelloy is a commercial name. It includes a series of alloy grades. It is mainly used in corrosion resistant valves.


(Hastelloy B) and Hastelloy C (Hastelloy C).


Hastelloy B (Hastelloy B) casting alloy grades in the ASTM A494 standard are N-12MV (N-12M-1) and N-7M (some materials are called N-12M-2, also known as Chlorimet2 Alloy), and its rolled steel grade is UNS N10665 in the ASTM B335 standard. Hastelloy B is resistant to various concentrations of hydrochloric acid and non-oxidizing salts and acids. Hastelloy B corrosion resistant valve, from the consideration of corrosion resistance and resistance to intergranular corrosion, low carbon grade Hastelloy B (N-7M) should be used. The material code of Hastelloy has no regulations in the valve industry. The material code of Hastelloy B valve can be directly expressed by its cast alloy grade. The suitable working temperature of Hastelloy B is -29 ℃ ~ 425 ℃.


Hastelloy C (Hastelloy C) casting alloy grades are CW-12MW (some materials are called CW-12M-1) and CW-7M (CW-12M-2, also known as Chlorimet3 alloy) and Hastelloy C -276 alloy, its casting alloy grade is CW-6MC and Hastelloy C-4 alloy, and its casting alloy grade is CW-2M. Casting Hastelloy CW-7M, CW-12MW, CW-6MC and CW-2M, the corresponding rolling material grades are UNS N10001, UNS N10003, UNS N10276 and UNS N06455. Hastelloy C is resistant to oxidizing solvents, low concentrations of normal temperature hydrochloric acid and nitric acid.


The first generation of Hastelloy C (0Cr16Ni60Mo16W4) is characterized by excellent corrosion resistance in highly corrosive oxidizing and reducing acid media, but because the high-nickel corrosion-resistant alloy is an austenite structure, because Ni reduces Solid solubility in austenite and other reasons. Therefore, Ni-Mo-based Hastelloy B and Ni-Mo-Cr-based Hastelloy C alloys both have severe intergranular corrosion tendencies or susceptibility, and can also cause stress corrosion and crevice corrosion at high temperatures. In order to overcome intergranular corrosion, the second-generation Hastelloy C-276 (C has been reduced from 0.03% to 0.02%) and the third-generation Hastelloy C-Hastelloy C-4 have been introduced. Si (Si ≤ 0.08%) and ultrafine C (C ≤ 0.015%), and reduced the content of Fe and W, and added stabilized alloying elements Ti and so on.


Hastelloy C corrosion resistant valve, from the consideration of corrosion resistance and intergranular corrosion resistance, Hastelloy C-276 (CW-6MC) and Hastelloy C-4 (CW-2M) are suitable. Hastelloy C valve has many material codes, and the performance and working temperature are different. 4 means, or directly use its cast alloy grade.


The suitable working temperature of Hastelloy CW-7M and UNS N10001 alloy is -29 ~ 425 ℃, the suitable working temperature of Hastelloy CW-12MW and UNS N10003 alloy is -29 ~ 700 ℃, Hastelloy CW-6MC and UNS The suitable working temperature of N10276 alloy is -29 ~ 676 ℃, and the suitable working temperature of Hastelloy CW-2M and UNS N06455 alloy is -29 ~ 425 ℃.



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