Selection of valve material for industrial application
One of the key considerations in valve design and material selection is the operating temperature of the valve.
In order to standardize the suitable working temperature of the valve body material, from various types of valve steel size and material performance of China's petrochemical industry, chemical industry, fertilizer, electricity, and metallurgical industries with the suitable working temperature of the valve body material and related requirements made clear rules, for valve product design, manufacturing and inspection. In addition, from the technical management and production management and material procurement and other aspects of consideration, for each type of steel should choose a good comprehensive performance, should not choose too many steel signs and signs, in order to prevent confusion.
Ultra-low temperature valve material ultra-low temperature valve (-254 (liquid hydrogen) ~ -101℃ (ethylene)) the main material must choose the face center cubic lattice of austenitic stainless steel, copper alloy or aluminum alloy, its heat treatment of low temperature mechanical properties, especially low temperature impact toughness must meet the standard requirements.
The following austenitic stainless steels can be used in the manufacture of 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). The body, bonnet, gate or disc of an ultra-low temperature valve must be cryogenically treated in liquid nitrogen (-196℃) before finishing.
Low temperature valve material is suitable for low temperature valves (-100 ~ -30℃) the main materials are low temperature austenitic stainless steel and low temperature pressure pieces for ferrite and martensite steel.
Austenitic stainless steels for low temperature use are ASTM A351 CF8M, CF3M, CF8 and CF3, ASTM A182 F316, F316L, F304 and F304L, and ASTM A433 316, 316L, 304, 304L and CF8D.
The ferritic and martensite steels for low temperature pressure parts are ASTM A352 LCA(-32℃), LCB, LCC(-46℃), LC1(-59℃), LC2, LC211(-73℃) and LC3(-100℃).
The materials in ASTM A352 have a lower primary price, but their chemical composition must be refined to a reliable and very strict factory control standard. The heat treatment process is complicated, and it needs to be tempered several times to meet the requirement of low temperature impact toughness required by the standard, and the production cycle is long. If the low temperature impact toughness is not up to the standard, it is not allowed to be used as low temperature steel. Therefore, only in the production of large quantities, and can be used in the furnace smelting, and in the general case of austenitic stainless steel.
Non-corrosive valve working medium for water, steam, air, oil and other non-corrosive substances, the general use of carbon steel. Carbon steels for valves refer to WCB, WCC cast steels and ASTMA105 forged steels in astm 216. Suitable operating temperature of carbon steel for valve is -29 ~ 425℃. However, in order to be safe, considering that the working temperature of the medium may fluctuate, the general carbon steel temperature should not exceed 400℃.
Cr-mo high temperature cast steel is mainly used in ASTM a217 standard WC6, WC9 and C5 (ZG1Cr5Mo). The corresponding rolled materials are F11, F22 and F5 in ASTM A182.
Low chromium grade chrome-molybdenum steel has WC6, WC9, F11 and F22, its suitable working medium for water, steam and hydrogen, not suitable for sulfur oil products.
The suitable operating temperature of WC6 and F11 is -29 ~ 540℃, while that of WC9 and F22 is -29 ~ 570℃.
Chromium pentamethmolybdenum high temperature steel is C5 (ZG1Cr5Mo) and F5, its suitable working medium for water, steam, hydrogen and sulfur containing oil products.
When C5 (ZG1Cr5Mo) is used for water vapor, its zui high operating temperature is 600℃. When used in working media such as sulfur-containing oil, its zui high working temperature is 550℃. Therefore, the working temperature of C5 (ZG1Cr5Mo) is defined as ≤550℃.
Stainless steel stainless acid steel is used in petrochemical and chemical industry, chemical fertilizer industry to resist nitric acid, sulfuric acid, acetic acid and organic acid and other corrosion resistant cr-ni or cr-ni-mo stainless acid steel.
Stainless and acid-proof steels cast steel mainly adopts CF8, CF8M, CF3, CF3M, CF8C, cd-4mcu and CN7M in ASTMA743 or ASTMA744 standards, and the corresponding rolled steel is F304, F316, F304L, F316L, F34F53 and us UNSN08020 in ASTMA182 standards. Cr-ni stainless steel cr-ni stainless steel rustless acid resistant steel CF8, CF3, F304, F304L, CF8C and F347, it is suitable for working medium is nitric acid and other oxidizing acid. Its zui high operating temperature ≤200℃.
Cr-ni-mo stainless steel cr-ni-mo stainless steel has CF8M, CF3M, F316 and F316L, which is suitable for reducing acid such as acetic acid. CF8M and CF3M can replace CF8 and CF3, but CF8 and CF3 cannot replace CF8M and CF3M. Therefore, stainless steel valves in the United States and other countries mainly use CF8M, CF3M, its zui high operating temperature ≤200℃.
CN7M alloy CN7M alloy has a 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, seawater and hot chloride solution, especially for various concentrations and temperature ≤70℃ range of sulfuric acid. The working temperature of CN7M and UNS N08020 alloy is -29 ~ 450℃.
Biphase stainless steel biphase stainless steel is precipitation-hardened stainless steel, which contains 35% ~ 40% austenitic in the matrix of ferrite. Its yield strength is about twice that of 19cr-9ni austenitic stainless steel, and it has high hardness, good plasticity and impact toughness.
Especially suitable for use in both abrasion and erosion corrosion working conditions, so it is widely used in oxidation and reduction of strong acid working conditions, in the environment with chlorine has a special resistance to stress corrosion cracking performance. The operating temperatures of cd-4mcu, CD3MN, CE3MN and F53 are -29 ~ 316℃.
Dual-phase stainless steel material grade control grade casting material rolled material plate bar material 0cr25-ni5-mo-cu A8901A [CD4MCu] 00cr22-ni5-mo3-n A8904A A182 A240 A479 [CD3MN] F51 S31803 s3180300cr25-ni7-mo4-n A890 A182 A240 A479 [CE3MN] F53 S32750S32750 corrosion resistant nickel base alloy corrosion resistant nickel base alloy valves are mainly selected in ASTM A494 standard cast monel alloy (m35-1), cast nickel alloy (z-100), inkell alloy (cy-40), hastellae alloy B(n-12mv, n-7m) and hastellae alloy C(cw-12mw, cw-7m, cw-6mc, cw-2m).
Monel alloy rolling materials for corrosion resistant Monel alloy valves are mainly UNS N04400 (Monel 400) and UNS N05500 (Monel K500). Inconel 600 and Inconel 625 are rolled in Inconel.
Monel alloy has high strength and toughness, especially excellent resistance to corrosion by reducing acid and strong alkali medium and seawater.
Therefore, the equipment and valves usually used for transporting hydrofluoric acid, brine, neutral medium, alkali salt and reductive acid are also suitable for drying LV gas, LV oxidized hydrogen, LV gas at 425℃ and LV oxidized hydrogen at 450℃, but are not resistant to corrosion of sulfur-containing medium and oxidized medium (such as nitric acid and medium with high oxygen content). The valve material code is MM for the whole monel alloy, and the inner part is monel alloy valve. When the shell is carbon steel, the valve material code is C/M; when the shell is CF8, the valve material code is P/M; when the shell is CF8M, the valve material code is R/M. The suitable operating temperature of Monel alloys m35-1, Monel 400 and Monel K500 is -29 ~ 480℃.
Cast nickel alloy cast nickel alloy (cz-100) has chemical compositions of 95%Ni and 1.00%C, and no corresponding rolled material.
The cz-100 has excellent corrosion resistance when used in high temperature, high concentration or no alkali solution. The cz-100 is commonly used in chlor-alkali production with high corrosion concentrations (including molten anhydrous caustic soda) and in applications where metals such as copper and iron cannot be contaminated. Cast nickel alloy cz-100 valve material code Ni. The suitable operating temperature of cz-100 alloy is -29 ~ 316℃.
The Inconel (Inconel)CY-40 and Inconel 600(ASTM B564 N06600) are mainly used to resist stress corrosion, especially in high concentration chloride media. When Ni content is ≥45%, it has an "immune" effect to the stress corrosion of LV compounds.
In addition, it can also resist the corrosion of boiling concentrated nitric acid, fuming nitric acid, high temperature gas containing sulfur and vanadium and combustors.
Inconel has been widely used to make components for boiler feed systems in nuclear power plants because it is safer than stainless steel. At the same time, it is also suitable for high strength, high pressure sealing high corrosion resistance, and at high temperature with resistance to mechanical wear and oxidation resistance in industrial production. For example, large chemical fertilizer plants use Inconel 600 or Inconel 625 alloy (for the rolling grade of haselite cw-6mc) to manufacture high pressure (600 ~ 1500 LB) high concentration oxygen valves. The material code for cy-40 and Inconel 600 alloy valves is In. The suitable operating temperature is -29~650℃.
Hasloy Hasloy Hasloy is the trade name for Hasloy, which includes a series of combination Numbers, mainly Hasloy B and Hasloy C, used in corrosion resistant valves.
Hasloy B (Hasloy B) is n-12mv (n-12m-1) and n-7m (sometimes referred to as n-12m-2, also known as Chlorimet2) in ASTM A494, and its rolled material is UNS N10665 in ASTM B335. Haselloy B is resistant to various concentrations of hydrochloric acid and non-oxidizing salts and acids. For corrosion resistant valves of hardensite alloy B, low carbon hardensite alloy B (n-7m) should be selected for corrosion resistance and intercrystalline corrosion resistance. Haselloy alloy material code valve industry has not been specified, haselloy alloy B valve material code, can be expressed directly by its casting combination. The suitable working temperature of haselloy B is -29℃ ~ 425℃.
Hasloy C (Hasloy C) has cw-12mw (cw-12m-1 in some sources), cw-7m (cw-12m-2, also known as Chlorimet3 alloy) and Hasloy c-276 alloy, cw-6mc and Hasloy c-4 alloy, and cw-2m. The corresponding rolled material grades of cast hessian alloys cw-7m, cw-12mw, cw-6mc and cw-2m are UNS N10001, UNS N10003, UNS N10276 and UNS N06455, respectively. Hastelloy C is resistant to oxidizing solvents, low concentration room temperature hydrochloric acid and nitric acid.
* generation Hasloy C (0Cr16Ni60Mo16W4) is characterized by excellent corrosion resistance in highly corrosive oxidizing and reducing acid medium. However, the high nickel corrosion resistance alloy is austenitic because Ni reduces the solid solubility of C in austenitic and other reasons. Therefore, the Hasloy C alloys of ni-mo Hasloy B and ni-mo-cr have severe intergranular corrosion tendency or sensitivity, which will lead to stress corrosion and crack corrosion at high temperature. In order to overcome intergranular corrosion, Hasloy c-276 (C reduced from 0.03% to 0.02%) and Hasloy c-4 (third generation Hasloy alloy C) were introduced, characterized by low Si(Si≤0.08%) and ultrafine C(C≤0.015%), reduced Fe and W contents, and stabilized alloy elements such as Ti were added. For corrosion resistance valve of hardensite alloy C, considering corrosion resistance and intergranular corrosion resistance, it is advisable to choose hardensite alloy c-276 (cw-6mc) and hardensite alloy c-4 (cw-2m). Hcw-12mw, cw-7m, cw-6mc and cw-2m are represented by hc-12, hc-7, hc-276 and hc-4 respectively, or directly by their casting compound Numbers.
The suitable working temperature of HCW -7m and UNS N10001 is -29 ~ 425℃; the suitable working temperature of cw-12mw and UNSN10003 is -29 ~ 700℃; the suitable working temperature of cw-6mc and UNSN10276 is -29 ~ 676℃; the suitable working temperature of cw-2m and UNSN06455 is -29 ~ 425℃.
Titanium alloy titanium (Ti) has high strength, light weight, high enough thermal resistance and low temperature toughness and good processing and welding performance.
Mainly used for casting pure titanium and forging pure titanium ZTA2 in valve production.
Titanium shows corrosion resistance, corrosion resistance and even fire and explosion to corrosive media due to different temperature and other working conditions. Therefore, the nature of the medium (concentration, temperature, etc.) should be clearly specified when ordering and designing.
Titanium valves have excellent corrosion resistance in a variety of oxidizing corrosive medium and neutral medium.
Titanium has excellent corrosion resistance in nitric acid with concentration less than or equal to 80% below boiling point. However, when the content of NO2 in fuming nitric acid exceeds 2% and the water content is insufficient, the reaction between titanium and fuming nitric acid will lead to an explosion. Therefore, titanium is generally not used for high-temperature nitric acid with a content of more than 80%.
Titanium has no corrosion resistance in sulfuric acid, while titanium has moderate corrosion resistance in hydrochloric acid. It is generally believed that industrial pure titanium can be used in hydrochloric acid with a concentration of 7.5% at room temperature, 3% at 60 ° c and 0.5% at 100 ° c. Titanium can also be used in phosphoric acid with a concentration of 30% at 35 ° c, 10% at 60 ° c and 3% at 100 ° 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 hydroiodic acid and hydrobromic acid.
Titanium can be used in mixture of 10% sulfuric acid and 90% nitric acid at 60℃, boiling mixture of 1% hydrochloric acid and 5% nitric acid, and room temperature aqua (note: aqua aqua is a mixture of 3 volumes of concentrated hydrochloric acid and 1 volume of concentrated nitric acid).
Titanium is completely resistant to corrosion at room temperature in solutions of various concentrations of barium hydroxide, calcium hydroxide, magnesium hydroxide, sodium hydroxide and potassium hydroxide, but cannot be used in boiling sodium hydroxide and potassium hydroxide. The presence of ammonia in the base increases the corrosion of titanium.
The zui high operating temperature of titanium in tap water, river water and air is 300℃. Titanium can be used in Marine water with high zui flow rate up to 20m/s. Titanium has high corrosion resistance in seawater with temperature ≤120℃. If the temperature is higher than 120℃, pitting corrosion and gap corrosion may occur.
Titanium has excellent corrosion resistance to all organic acids except formic acid, oxalic acid and concentrated citric acid (concentration ≥50%), but titanium is prone to pitting corrosion when the water content in organic acids is too low (<0.1%).
Titanium has excellent corrosion resistance in hydrocarbons and chlorinated hydrocarbons. Titanium can react violently in dry lv gas to form TiCl4 and has the risk of ignition, but titanium has good corrosion resistance in wet chlorine (water content is 0.3 ~ 1.5%).
Titanium is stable in 20 ~ 160℃ dry HCl, but hydrochloric acid causes corrosion in wet hydrogen chloride.
The pitting potential of titanium in chloride solution is higher than that of stainless steel, and the pitting resistance of titanium to chloride ion is better than that of stainless steel, so titanium has been widely used in chloride solution.
When the temperature is less than 80℃, titanium generally will not produce pitting corrosion, but in high temperature medium concentration of chloride solution (such as 25% aluminum chloride solution at 100℃, 70% calcium chloride solution at 175℃, 25% magnesium chloride solution at 200℃ and 75% zinc chloride solution at 200℃) is more prone to pitting corrosion.
High temperature operating conditions high temperature operating conditions mainly refers to the high temperature valves used in oil refineries.
Subhigh temperature subhigh temperature refers to the operating temperature of the valve in the 325 ~ 425℃ area.
If the medium is water and steam, WCB, WCC, A105, WC6 and WC9 are mainly used. If the medium is sulfur-containing oil, mainly used with corrosion resistance to sulfide C5, CF8, CF3, CF8M and CF3M. They are mostly used in the constant pressure relief units and delayed coking units of refineries, where CF8, CF8M, CF3 and CF3M valves are not used for acid solution corrosion resistance, but for sulfur-containing oil products and pipelines. In this working condition, the upper limit of high operating temperature of zui for CF8, CF8M, CF3 and CF3M is 450℃.
High grade Ⅰ valve working temperature is 425 ~ 550 ℃ for high temperature when Ⅰ level (PI).
PI level in the body of the valve material for ASTM A351 standard CF8 as the fundamental form of "high temperature Ⅰ grade carbon chromium nickel titanium alloy steel rare earth". As the PI level 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℃) or WC9 (t≤570℃) is also available, while high temperature steel C5 (ZG1Cr5Mo) is also available when containing sulfur oil, but they cannot be called PI level here.
High grade Ⅱ valve working temperature is 550 ~ 650 ℃, as the high temperature Ⅱ level (hereinafter referred to as the P Ⅱ level).
P Ⅱ level high temperature valve is mainly used in heavy oil catalytic cracking unit of refinery, which contains three rotating nozzle used in the lining of parts such as high temperature wear gate valves. P Ⅱ level in the body of the valve material for ASTM A351 standard CF8 as the fundamental form of "high temperature level Ⅱ carbon chromium nickel and rare earth, titanium in tantalum type heat resistant steel".
High grade Ⅲ valve working temperature is 650 ~ 730 ℃, as the high temperature Ⅲ level (hereinafter referred to as the P Ⅲ level).
P Ⅲ level high temperature valves are mainly used on large heavy oil catalytic cracking unit in the refinery. P grade Ⅲ high-temperature valve body as ASTM A351 CF8M as the fundamental form of the standard of "high temperature grade Ⅲ carbon chromium nickel molybdenum in rare earth, titanium tantalum enhanced heat resistant steel".
High grade Ⅳ valve working temperature is 730 ~ 816 ℃, as the high temperature Ⅳ level (hereinafter referred to as the P Ⅳ level).
Will P level Ⅳ valve operating temperature limit at 816 ℃ because valve design selection standard ASME B16.34 pressure - temperature level provided in zui high temperature of 816 ℃ (1500 ℉). In addition, after the working temperature exceeds 816℃, 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 bear high working pressure and impact force without deformation. P Ⅳ level in the body of the valve material for ASTM A351 standard CF8M as fundamental form "high temperature grade Ⅳ carbon chromium nickel molybdenum in rare earth, titanium tantalum enhanced heat resistant steel". Ck-20 and ASTM A182 standard F310 (C content ≥0.050%) and F310H heat resistant stainless steel.
High temperature grade Ⅴ valve working temperature > 816 ℃ above, called heat Ⅴ level (hereinafter referred to as the P Ⅴ level).
P Ⅴ level high temperature valve (for cut off valve, rather than the external regulation butterfly valves) must be the use of special design method, such as lining insulation lining or water or air cooling, etc., can guarantee the normal work of the valve. So, level of P Ⅴ high temperature valve operating temperature limit does not make the rules, the working temperature of this is because the control valve is not only on the material, but with the special design method to solve, and the basic principle of design method is the same. P Ⅴ level high temperature valves according to the pressure of work and working medium and the special design methods and so on, choose reasonable, can meet the material of the valve. In P Ⅴ scale high temperature valve, normally the flue board flashboard valve or butterfly valve or butterfly plate often choose the HK - 30 A297 ASTM standard, HK - 40 high temperature alloy, they are able to under 1150 ℃ oxidation and corrosion in a reducing gas, but it can't withstand the impact and pressure load.
