Valve body parts suitable for working temperature introduction
1 Overview
Valve design and material selection must be one of the key issues to consider the working temperature of the valve. In order to regulate the appropriate working temperature of the valve body material, suitable working temperature and related to the valve body material for petrochemical, chemical, fertilizer, electric power and metallurgical industries in China from the material properties of various types of valve steel and alloy grades Requirements made a clear provision for the valve product design, manufacture and testing purposes. In addition, from technical management and production management and material procurement considerations, the selection of each type of steel should be good overall performance, should not be used too much steel and alloy grades, to prevent confusion.
2 low temperature conditions
2.1 ultra-low temperature valve material
Cryogenic valve [-254 (liquid hydrogen) ~ -101 ° C (ethylene)] The main material must use face-centered cubic lattice austenitic stainless steel, copper alloy or aluminum alloy, the low temperature mechanical properties after heat treatment, especially low temperature impact Toughness must meet the standard requirements.
The following austenitic stainless steels can be used to make cryogenic valves. ASTM A351 CF8M, CF3M, CF8 and CF3, ASTM A182 F316, F316L, F304 and F304L, ASTM A433 316,316L, 304,304L and CF8D (Lanzhou High Pressure Valve Factory design, factory standard code GFQ81-93). Cryogenic valve body, bonnet, gate or valve flap and so on before finishing, must be in liquid nitrogen (-196 ℃) for cryogenic treatment.
2.2 low temperature valve material
Suitable for cryogenic valves (-100 ~ -30 ℃) of the main material is low temperature austenitic stainless steel and low temperature pressure parts ferritic and martensitic steel.
Austenitic stainless steels for low temperature are 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 pressure parts are ASTM A352 LCA (-32 ° C), LCB, LCC (-46 ° C), LC1 (-59 ° C), LC2, LC211 (-73 ° C) and LC3 -100 ° C).
The material in the ASTM A352 standard has a low primary price, but its chemical composition must have a reliable and very demanding factory-controlled standard for smelting. The heat treatment process is complex, requiring multiple quenching and tempering, in order to meet the requirements of the standard low temperature impact toughness, long production cycle. Low temperature impact toughness does not meet the standard requirements, not allowed to feed for low temperature steel. Therefore, only in the production of large quantities, and can only be used when the furnace smelting, and in general, the choice of austenitic stainless steel.
3 non-corrosive conditions
Valve working medium is water, steam, air and oil and other non-corrosive substances, the general use of carbon steel. Carbon steel for valves means WCB, WCC cast steel and ASTM A105 forged steel in ASTM A216. Valve with carbon steel suitable working temperature of -29 ~ 425 ℃. However, for safety, taking into account the working temperature of the medium may fluctuate, therefore, the general temperature of carbon steel should not exceed 400 ℃.
4 corrosion conditions
4.1 Chromium - Molybdenum high temperature steel
Valves used in the selection of high-temperature cast steel Cr-Mo mainly ASTM A217 standard WC6, WC9 and C5 (ZG1Cr5Mo), the corresponding rolling materials are ASTM F18 F11, F22 and F5.
⑴ low-chromium chromium - molybdenum steel
Low chromium chromium - molybdenum steel WC6, WC9, F11 and F22, the applicable working medium is water, steam and hydrogen, should not be used for sulfur-containing oil. WC6 and F11 suitable working temperature is -29 ~ 540 ℃, WC9 and F22 suitable working temperature is -29 ~ 570 ℃.
⑵ chrome molybdenum high temperature steel
Chrome five molybdenum high temperature steel C5 (ZG1Cr5Mo) and F5, the applicable working medium is water, steam, hydrogen and sulfur oil and so on.
C5 (ZG1Cr5Mo) if used for steam, the maximum operating temperature is 600 ℃. For sulfur-containing oil and other working medium, the maximum operating temperature of 550 ℃. Therefore, the provisions of C5 (ZG1Cr5Mo) operating temperature is ≤ 550 ℃.
4.2 stainless steel acid
Stainless acid-resistant steel is used for petrochemical and chemical, fertilizer industry, anti-nitric acid, sulfuric acid, acetic acid and organic acid and other corrosion resistance of chromium-nickel or chromium-nickel-molybdenum stainless steel acid-resistant steel. Stainless steel acid-resistant steel is mainly used ASTM A743 or ASTM A744 standards CF8, CF8M, CF3, CF3M, CF8C, CD-4MCu and CN7M, etc., the corresponding rolling materials are ASTM A182 standard F304, F316, F304L , F316L, F347, F53 and the United States UNS N08020.
⑴ Cr-Ni stainless steel
Cr-Ni stainless steel acid-resistant stainless steel CF8, CF3, F304, F304L, CF8C and F347, which is suitable for working medium nitric acid and other oxidizing acids. The maximum operating temperature ≤ 200 ℃.
⑵ Cr-Ni-Mo stainless steel
Cr-Ni-Mo stainless steel acid-resistant stainless steel CF8M, CF3M, F316 and F316L, which applies to the working medium is a reducing acid such as acetic acid.
CF8M, CF3M, etc. can replace CF8 and CF3, but CF8, CF3 can not replace CF8M and CF3M. Therefore, the United States and other countries mainly stainless steel valve with CF8M, CF3M, the maximum operating temperature ≤ 200 ℃.
⑶CN7M 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, seawater and hot chloride salt solution, especially available In various concentrations and temperatures ≤ 70 ℃ range of sulfuric acid. CN7M and UNS N08020 alloy temperature of -29 ~ 450 ℃.
⑷ duplex stainless steel
Duplex stainless steel (Table 1) is precipitation-hardened stainless steel, which contains 35% -40% austenite in the ferritic matrix and has a yield strength of about 19Cr-9Ni austenitic stainless steel Times, and has high hardness and good ductility and impact toughness. It is particularly suitable for use in both corrosive and corrosive working conditions. It is therefore widely used in the presence of chlorine in environments with strong resistance to stress corrosion cracking in strong acid conditions of oxidation and reduction. CD-4MCu, CD3MN, CE3MN and F53 duplex stainless steel temperature of -29 ~ 316 ℃.
Table 1 duplex stainless steel grades control
Grade
Casting material
Rolled material
Plate
Bar
0Cr25-Ni5-Mo-Cu
A8901A
CD4MCu
00Cr22-Ni5-Mo3-N
A8904A
[CD3MN]
A182
F51
A240
S31803
A479
S31803
00Cr25-Ni7-Mo4-N
A8905A
[CE3MN]
A182
F53
A240
S32750
A479
S32750
4.3 corrosion-resistant nickel-based alloy
Corrosion-resistant nickel-based alloy valve is mainly used in the selection of the standard ASTM A494 Monel (M35-1), cast nickel alloy (CZ-100), British Cornell alloy (CY-40), Hastelloy B (N-12MV , N-7M) and Hastelloy C (CW-12MW, CW-7M, CW-6MC, CW-2M).
Monel alloy rolled for corrosion-resistant Monel valves are mainly UNS N04400 (Monel 400) and UNS N05500 (Monel K500). Cast nickel alloy without corresponding rolling, the British Cornell alloy rolled in Inconel 600 and Inconel 625 and so on.
⑴ Monel alloy
Monel has high strength and toughness, especially with excellent anti-reduction acid and alkali-resistant media and seawater corrosion performance. Therefore, the equipment and valves commonly used for the manufacture of hydrofluoric acid, salt water, neutral media, alkali salts, reducing acids and other media are also suitable for drying chlorine, hydrogen chloride gas, 425 ° C high temperature chlorine and 450 ° C high temperature hydrogen chloride gas Medium, but not resistant to sulfur-containing media and oxidizing media (such as nitric acid and high oxygen medium) corrosion. The overall Monel alloy valve codenamed MM, the inner part is a Monel alloy valve, the shell is carbon steel valve material code-named C / M, the shell is CF8 when the valve material code-named P / M, shell When the body is CF8M valve material code is R / M. Monel alloy M35-1, Monel 400 and Monel K500 alloy suitable working temperature is -29 ~ 480 ℃.
⑵ cast nickel alloy
The chemical composition of the cast nickel alloy (CZ-100) is 95% Ni and 1.00% C, with no corresponding rolled stock. CZ-100 has excellent corrosion resistance when it is used in high-temperature, high-concentration or anhydrous alkaline solution. CZ-100 is commonly used in chlor-alkali production with high corrosive concentration (including molten caustic soda) and in applications where metal contaminated products such as copper and iron are not available. Cast nickel alloy CZ-100 valve material code-named Ni. CZ-100 alloy suitable working temperature of -29 ~ 316 ℃.
⑶ British Cornell alloy
Inconel CY-40 and Inconel 600 (ASTM
B564 N06600) are mainly used for stress corrosion resistance. They are especially suitable for high chloride concentration media. When Ni content is more than 45%, they have an "immune" effect on stress corrosion of chloride. In addition, it is resistant to boiling nitric acid, fuming nitric acid, high temperature gases containing sulfur and vanadium, and combustion products.
Inconel alloys have been used extensively in the manufacture of boiler feedwater system components for nuclear power plants because of their higher safety than stainless steel. It is also suitable for high corrosion resistance requiring high strength, high pressure sealing, as well as for industrial production with high resistance to mechanical wear and oxidation at high temperatures. Such as large fertilizer plant with Inconel 600 or Inconel 625 alloy (for the Hastelloy CW-6MC rolling material grades) manufacturing high pressure (600 ~ 1500
LB) high concentrations of oxygen valves. CY-40 and Inconel 600 alloy valve material code-named In. Suitable working temperature is -29 ~ 650 ℃.
⑷ Hastelloy
Hastelloy is a commercial name which includes a series of alloying grades for use on corrosion resistant valves primarily Hastelloy B
(Hastelloy B) and Hastelloy C (Hastelloy C).
Cast alloy grades for Hastelloy B are N-12MV (N-12M-1) and N-7M (some sources call N-12M-2, also known as Chlorimet 2 Alloy), the rolling material grades UNS N10665 ASTM standard ASTM B335. Hastelloy B corrosion of various concentrations of hydrochloric acid, non-oxidizing salts and acids are also corrosion-resistant. Hastelloy B corrosion valve, corrosion resistance and resistance to intergranular corrosion should choose low-carbon-grade Hastelloy B (N-7M). Hastelloy material code Valve industry there is no provision for the Hastelloy B valve material code can be directly cast alloy grades. Hastelloy B suitable for working temperature of -29 ℃ ~ 425 ℃.
Hastelloy C is a cast alloy of CW-12MW (some sources call CW-12M-1) and CW-7M (CW-12M-2, also known as Chlorimet3) and Hastelloy C -276 alloy, the casting alloy grades CW-6MC and Hastelloy C-4 alloy, the casting alloy grade CW-2M. Cast Hastelloy CW-7M, CW-12MW, CW-6MC and CW-2M The corresponding rolling grades are UNS N10001, UNS N10003, UNS N10276 and UNS N06455 respectively. Hastelloy C Corrosion resistance to oxidative solvents, low concentrations of hydrochloric acid and nitric acid at room temperature.
The first generation of Hastelloy C (0Cr16Ni60Mo16W4) is characterized by its excellent corrosion resistance in highly corrosive oxidizing and reducing acid media. However, since the high Ni corrosion resistant alloy is austenitic, because Ni reduces C in Austenitic solid solubility and other reasons. Therefore, Ni-Mo-based Hastelloy B and Ni-Mo-Cr-based Hastelloy C alloys have a more severe intergranular corrosion tendency or susceptibility to stress corrosion and crevice corrosion at elevated temperatures. In order to overcome the intergranular corrosion, Hastelloy C-276, the second generation Hastelloy (C is reduced from 0.03% to 0.02%) and the third generation Hastelloy C-4, is characterized by low Si (Si≤0.08%) and ultramicro C (C≤0.015%), and the contents of Fe and W are reduced, and the stabilized alloying element Ti and the like are added.
Hastelloy C corrosion valve, from the corrosion resistance and resistance to intergranular corrosion, should use Hastelloy C-276 (CW-6MC) and Hastelloy C-4 (CW-2M). Hastelloy C valve material code more, and the performance and operating temperature difference, so CW-12MW, CW-7M, CW-6MC and CW-2M, respectively, with HC-12, HC-7, HC-276 and HC- 4, or directly cast alloy grades to represent.
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 N10276 alloy suitable working temperature is -29 ~ 676 ℃, Hastelloy CW-2M and UNS N06455 alloy suitable working temperature is -29 ~ 425 ℃.
4.4 Titanium
Titanium (Ti) with high strength, light weight, high enough heat resistance and low temperature toughness and good processing and welding performance. For the production of valves is mainly cast titanium and forged titanium ZTA2.
Titanium corrosive medium due to temperature and other conditions showed corrosion, corrosion and even fire, explosion and so on. Therefore, when ordering and design options should be used to deal with the nature of the media (concentration, temperature, etc.) to give clear provisions.
Titanium valves have excellent corrosion resistance in a wide range of oxidizing corrosive and neutral media.
Titanium has excellent corrosion resistance in nitric acid with a boiling point below 80%. In fuming nitric acid, when the NO2 content exceeds 2% and the water content is insufficient, the reaction between titanium and fuming nitric acid will explode. Therefore, titanium is generally not used for high-temperature nitric acid content of more than 80%.
Titanium is not corrosion-resistant in sulfuric acid and titanium has moderate corrosion resistance in hydrochloric acid. Generally believed that the industrial pure titanium can be used for 7.5% concentration at room temperature, 3% at 60 ℃ and 0.5% concentration of hydrochloric acid at 100 ℃, titanium can also be used at 35 ℃ concentration of 30%, 60 ℃ concentration of 10% and 100 ℃ 3% concentration of phosphoric acid.
Titanium is not corrosion-resistant in HF (hydrofluoric acid), titanium is not corrosion-resistant in acidic fluoride solutions, titanium is corrosion-resistant in boric acid and chromic acid, and is used in hydroiodic acid and hydrobromic acid.
Titanium can be used for mixed acid of 10% sulfuric acid and 90% nitric acid at 60 ° C, mixed acid of boiling 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 vol of concentrated nitric acid) in.
Titanium is completely corrosion resistant at various concentrations of barium hydroxide, calcium hydroxide, magnesium hydroxide, sodium hydroxide and potassium hydroxide at room temperature but can not be used in boiling sodium hydroxide and potassium hydroxide. Alkali containing ammonia will aggravate the corrosion of titanium.
Titanium in tap water, river water and air maximum operating temperature of 300 ℃. Titanium can be used for seawater maximum flow rate of 20m / s, titanium in seawater temperature ≤ 120 ℃ have a high corrosion resistance, if the temperature is higher than 120 ℃, may produce pitting corrosion and crevice corrosion.
Titanium has excellent corrosion resistance to all organic acids except formic acid, oxalic acid and concentrated citric acid (concentration ≥50%), but the organic acid is too low in water content (
Titanium has excellent corrosion resistance in hydrocarbons and chlorinated hydrocarbons. Titanium can react violently to produce TiCl4 in dry chlorine gas, which is dangerous for fire. However, titanium has good corrosion resistance in wet chlorine (water content 0.3-1.5%).
Titanium is stable in 20-160 ° C dry HCl but corrodes titanium in wet hydrogen chloride.
The pitting potential of titanium in chloride solution is higher than that of stainless steel. Titanium anti-chloride ion has better pitting corrosion resistance than stainless steel. Titanium has been widely used in chloride solution.
Titanium generally does not cause pitting at temperatures of <80 ° C but is not resistant to pitting corrosion at high temperature in moderate concentrations of chloride solutions (eg 25% aluminum chloride solution at 100 ° C, 70% calcium chloride solution at 175 ° C, 25% Magnesium chloride solution and 75% zinc chloride solution at 200 ° C).
5 high temperature conditions
High temperature condition valve is mainly used in high temperature oil refinery valves.
5.1 sub-high temperature
Sub-high temperature is the working temperature of the valve 325 ~ 425 ℃ area. If the medium is water and steam, the main use of WCB, WCC, A105, WC6 and WC9. If the medium is sulfur-containing oil, the main use of anti-sulfide corrosion C5, CF8, CF3, CF8M and CF3M and so on. They are often used in refinery units of atmospheric and vacuum coking units and delayed, when CF8, CF8M, CF3 and CF3M valve material is not used for acid solution corrosion, but for sulfur-containing oil and oil and gas pipelines. In this condition, the maximum operating temperature for CF8, CF8M, CF3 and CF3M is 450 ° C.
5.2 high temperature Ⅰ level
Valve operating temperature is 425 ~ 550 ℃ for high temperature Ⅰ (referred to as PI level). The main material of the PI-class valve is CF8-based "High Temperature Grade I Medium Carbon, Chromium-Nickel Rare Earth Titanium High-Quality Heat-Resistant Steel" in the ASTM A351 standard. As PI is a special designation, the concept of high temperature stainless steel (P) is included here. Therefore, if the working medium is water or steam, the high-temperature steel C5 (ZG1Cr5Mo) may be used for the sulfur-containing oil although the high-temperature steel WC6 (t≤540 ℃) or WC9 (t≤570 ℃) Here we can not call them PI level.
5.3 high temperature Ⅱ level
Valve operating temperature of 550 ~ 650 ℃, as high temperature Ⅱ level (referred to as P Ⅱ level). P Ⅱ grade high temperature valve is mainly used in heavy oil refinery catalytic cracking unit, which contains the use of high-temperature lining in the three rotary nozzle and other wear-resistant gate valve. P Ⅱ-level valve body material for the ASTM A351 standard CF8-based "high temperature Ⅱ grade carbon chromium-nickel-titanium rare earth titanium tantalum heat-resistant steel."
5.4 high temperature Ⅲ level
Valve operating temperature is 650 ~ 730 ℃, as a high temperature Ⅲ (referred to as P Ⅲ level). P Ⅲ level high temperature valve is mainly used in large oil refinery catalytic cracking unit. PⅢ grade high-temperature valve body material for the ASTM A351 standard CF8M-based "high-temperature medium-grade carbon chromium chromium nickel molybdenum rare earth titanium tantalum reinforced heat-resistant steel."
5.5 high temperature Ⅳ level
Valve operating temperature of 730 ~ 816 ℃, as a high temperature Ⅳ (referred to as P Ⅳ level). The upper limit of the working temperature of the PⅣ -level valve is set at 816 ° C because the highest temperature available in the standard ASME B16.34 pressure-temperature class for valve design is 816 ° C (1500 ° F). In addition, the working temperature exceeds 816 ℃, the steel is close to the forging temperature range, then the metal in the plastic deformation range, good plasticity of the metal, it is difficult to withstand the high working pressure and impact and remain unchanged. P Ⅳ-level valve body material for the ASTM A351 standard CF8M-based "high-temperature grade IV carbon chromium chromium nickel molybdenum rare earth titanium tantalum reinforced heat-resistant steel." CK10 and ASTM A182 standard F310 (which C content ≥ 0.050%) and F310H and other heat-resistant stainless steel.
5.6 high temperature Ⅴ level
Valve operating temperature> 816 ℃ above, called the high temperature Ⅴ level (referred to as P Ⅴ level). P Ⅴ-class high-temperature valves (for cut-off valves, non-regulating butterfly valve) must adopt special design methods, such as liner insulation lining or water or gas cooling, etc., to ensure the normal operation of the valve. Therefore, the P Ⅴ temperature valve high temperature limit is not provided, this is because the control valve temperature is not only by material, but by special means to solve the design, and the basic principle of the design is the same. P Ⅴ-temperature valve according to their working medium and working pressure and the use of special design methods, the selection of reasonable, to meet the valve material. In the P class high-temperature valve, usually flapper or butterfly valve flapper or butterfly plate often use ASTM A297 standard HK-30, HK-40 superalloy, they can be below 1150 ℃ antioxidant and reducing gas In the corrosion, but can not withstand the impact and high pressure load.
6 Conclusion
In the rapid development of technology today, the valve of the main material is increasingly diverse, high parameterization. Valve corresponding to the working medium is also more complex, higher operating temperature requirements. Understand the performance of various types of valve steel and alloy and its suitable operating temperature, is the design, manufacture, procurement and use of valves related to scientific and technical personnel and operators must master the knowledge. In particular, the temperature of the material can not exceed its suitable operating temperature, otherwise it will cause terrible serious accident.
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