Valve design and material selection: working temperature of valve
One of the key issues to be considered in valve design and material selection is the working temperature of the valve. In order to regulate the suitable working temperature of valve body materials, the suitable working temperature and relevant requirements of valve body materials used in petrochemical, chemical, fertilizer, electric power and metallurgy industries in China are clearly specified from the material properties of various types of valve steel and alloy grades, which can be used in the design, manufacture and inspection of valve products. In addition, from the aspects of technical management, production management and material procurement, the steel with good comprehensive performance should be selected for each type of steel, and too many stainless steel grades and alloy grades should not be selected to avoid confusion.
Ultra-low temperature valve material
Ultra-low temperature valve (-254 (liquid hydrogen) ~-101 ℃ (ethylene)) the main 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, the low temperature impact toughness must meet the requirements of the standard.
The following austenitic stainless steel can be used to manufacture 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. The valve body, valve cover, Gate board or valve disc of ultra-low temperature valve must be treated with cryogenic in liquid nitrogen (-196 ℃) before finishing.
Cryogenic valve material
The main materials suitable for low temperature valves (-100 ~-30 ℃) are ferrite and martensite steel for Low Temperature austenitic stainless steel and low temperature pressure-bearing parts.
Low temperature austenitic stainless steel has ASTM A351 CF8M, CF3M, CF8 and CF3,ASTM A182 F316, F316L, F304 and F304L,ASTM A433 316, 316L, 304, 304L and CF8D.
Ferrite and martensite steel for Low Temperature Pressure-bearing parts are ASTM A352 LCA(-32℃), LCB, LCC(-46℃), LC1(-59℃), LC2, lc2111 (-73℃) and LC3(-100℃).
The primary price of the materials in the ASTM A352 standard is lower, but their chemical components must have reliable and strict factory internal control standards during smelting. Its heat treatment process is complicated, which requires many times of quenching and tempering, so it can meet the requirements of standard low temperature impact toughness, and the production cycle is long. When the impact toughness of low temperature does not meet the standard requirements, it is not allowed to be used as low temperature steel. Therefore, only when the production volume is large and it can be used in furnace smelting, and austenitic stainless steel is generally used.
Carbon steel is generally used when the working medium of the valve is water, steam, air, oil and other non-corrosive substances. Carbon steel for valves refer to WCB, WCC cast steel and ASTM A105 forged steel as specified in ASTM A216. The appropriate working temperature of carbon steel for valves is-29~425 ℃. But for the sake of safety, taking into account that the working temperature of the medium may fluctuate, therefore, the general carbon steel use temperature should not exceed 400 ° C.
Chromium-molybdenum high temperature steel
The Cr-Mo high temperature cast steel used for the valve is mainly WC6, WC9 and C5(ZG1Cr5Mo) of ASTM A217, and its corresponding rolled materials are F11, F22 and F5 of ASTM A182.
(1) Low chromium grade chromium-molybdenum steel
There are WC6, WC9, F11 and F22 low chromium-molybdenum steel. Its applicable working media are water, steam and hydrogen, which is not suitable for sulfur-containing oil products. The suitable working temperature for WC6 and F11 is-29~540 ℃, and the suitable working temperature for WC9 and F22 is-29~570 ℃.
(2) Chromium five molybdenum high temperature steel
The high-temperature chromium-molybdenum steel includes C5(ZG1Cr5Mo) and F5, and its applicable working mediums are water, steam, hydrogen, sour oil, etc.
C5(ZG1Cr5Mo) if used for steam, its maximum working temperature is 600 ℃. When used in sour oil and other working Media, its maximum working temperature is 550℃. Therefore, it is stipulated that the working temperature of C5(ZG1Cr5Mo) is ≤550℃.
Stainless acid-resisting steel
Stainless acid-resistant steel refers to Chrome-nickel or chrome-Nickel-molybdenum stainless acid-resistant steel used in petrochemical, chemical and chemical fertilizer industries to resist corrosion of nitric acid, sulfuric acid, acetic acid and organic acid. Stainless acid-resistant steel cast steel mainly adopts CF8, CF8M, CF3, CF3M, CF8C, CD-4MCu and CN7M in ASTM A743 or ASTM A744 standard, and their corresponding rolled materials are F304, f316, F304L, F316L, F347, F53 and United States UNS N08020.
(1) Cr-Ni stainless steel
Cr-Ni stainless acid-resistant steel includes CF8, CF3, F304, F304L, CF8C and F347. Its maximum working temperature ≤ 200℃.
(2) Cr-Ni-Mo stainless steel
Cr-Ni-Mo stainless steel has CF8M, CF3M, F316 and F316L, which are suitable for reducing acids such as acetic acid.
CF8M,CF3M, etc. can replace CF8 and CF3, but CF8 and CF3 cannot replace CF8M and CF3M. Therefore, the stainless acid-resistant steel valves in the United States and other countries mainly use CF8M and CF3M, and their maximum working temperature is less than or equal to 200 ℃.
(3) CN7M alloy
CN7M alloy has good overall corrosion resistance. It is widely used under harsh corrosion conditions, including sulfuric acid, nitric acid, hydrofluoric acid, dilute hydrochloric acid, caustic alkali, seawater and hot chloride salt solution, etc, in particular, it can be used in sulfuric acid with various concentrations and temperatures ≤ 70 ℃. CN7M and UNS N08020 alloy use temperature is-29~450 ℃.
(4) Duplex stainless steel
Duplex stainless steel (Table 1) is precipitation hardened stainless steel, which contains 35% ~ 40% austenite in ferrite matrix, and its yield strength is about 2 times of 19Cr-9Ni austenitic stainless steel, it also has high hardness, good plasticity and impact toughness. It is especially suitable for use under corrosion working conditions with both abrasion and scouring, so it is widely used in strong acid working conditions of oxidation and reduction, there is a special ability to resist stress corrosion cracking in chlorine-containing environment. CD-4MCu, CD3MN, CE3MN and F53 duplex stainless steel temperature is-29~316 ℃.
Corrosion resistant nickel-based alloy
Corrosion resistant nickel-based alloy valve mainly uses cast Monel alloy (M35-1), cast nickel alloy (C Z-100), ingconel alloy (C Y-40), Hastelloy alloy B(N-12MV, n-7M) and Hastelloy C(C W-12MW, C W-7M, C W-6M, C W-2M).
The Monel alloy rolling stock used for the anti-corrosion Monel alloy valve is mainly UNS N04400(Monel 400) and UNS N05500(Monel K500). There is no corresponding rolled material for casting nickel alloy. The rolled material for ingconel alloy is Inconel 600 and Inconel 625, etc.
(1) Monel alloy
Monel alloy has higher strength and toughness, especially it has excellent performance of resisting reduction acid, strong alkali medium and seawater corrosion. Therefore, it is usually used for manufacturing equipment and valves that transport medium such as hydrofluoric acid, salt water, neutral medium, alkali salt and reductive acid, and also suitable for drying chlorine gas, hydrogen chloride gas, medium such as high temperature chlorine gas at 425 ℃ and high temperature hydrogen chloride gas at 450 ℃, but it is not resistant to corrosion of sulfur-containing medium and oxidizing medium (such as nitric acid and medium with high oxygen content). The whole is the valve material code of Monel alloy is M M, the inner part is the valve of Monel alloy, and the valve material code is C/M when the shell is carbon steel, when the shell is C F8, the valve material code is P/M; When the shell is C F8 M, the valve material code is R/M. The suitable working temperature of Monel alloy M35-1, Monel 400 and Monel K500 is-29 ~ 480℃.
(2) Cast nickel alloy
The chemical composition of cast nickel alloy (C Z-100) is 95% Ni and 1.00% C, and it has 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 chlor-alkali production with high corrosion concentration (including Molten anhydrous sodium) and in situations where metal pollution products such as copper and iron are not allowed. The material code of cast nickel alloy CZ-100 valve is Ni. The suitable working temperature of CZ-100 alloy is-29~316 ℃.
Inconel CY-40 and Inconel 600(ASTM B564 N06600) are mainly used to resist stress corrosion, especially for high concentration Chloride Media, when Ni content ≥ 45%, it has an “immune” effect on stress corrosion of chlorides. In addition, it can also resist the corrosion of high temperature gas and burning materials of concentrated nitric acid, fuming nitric acid, sulfur and vanadium.
Inconel alloy has been widely used to manufacture components of boiler feed water systems in nuclear power plants because it is safer than stainless steel. At the same time, it is also suitable for high corrosion resistance performance requiring high strength and high pressure seals, as well as industrial production with mechanical wear resistance and oxidation resistance at high temperature. For example, large chemical fertilizer plant uses Inconel 600 or Inconel 625 alloy (the rolling stock brand of hastellok alloy CW-6MC) to manufacture high pressure (600 ~ 1500LB) high concentration oxygen valves, etc. The material code for CY-40 and Inconel 600 alloy valves is In. The suitable working temperature is-29 ~ 650℃.
Hastelloy is a commercial name, which includes a series of alloy brands. The main ones used for corrosion resistance valves are Hastelloy B and Hastelloy C. These two categories.
The cast alloy mark of Hastelloy B is N-12MV(N-12M-1) and N-7M in ASTMA494 standard (some materials call it N-12M-2, also call it Chlorimet2 alloy), its rolling material brand is UNS N10665 in ASTM B335 standard. Hastelloy B is corrosion resistant to hydrochloric acid of various concentrations, and also corrosion resistant to non-oxidizing salts and acids. The corrosion resistant valve of Hastelloy B, considering the corrosion resistance and intergranular corrosion resistance, low carbon grade Hastelloy B (N-7M). should be selected The material code of Hastelloy alloy is not stipulated 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 ℃.
The cast alloy brand of hasteloy C (hasteloy C) is CW-12MW (some materials call it CW-12M-1) and CW-7M(CW-12M-2, also called Chlorimet3 alloy) and Hastelloy C- 276 alloy, the cast alloy brand is CW-6MC and Hastelloy C- 4 alloy, and its cast alloy brand is CW-2M. The corresponding rolling grades of cast Hastelloy CW-7M, CW-12MW, CW-6MC and CW-2M are UNS N10001, UNS N10003, UNS N10276 and UNS N06455 respectively. Hastelloy C is corrosion resistant to oxidizing solvent, hydrochloric acid and nitric acid with low concentration and normal temperature.
The first generation of Hastelloy C(0C r16Ni60Mo16W4) is characterized by excellent corrosion resistance in strongly corroded oxidizing and reducing acid medium, but because the high nickel corrosion resistant alloy is austenite structure, because Ni reduces the solid solubility of C in austenite, etc. Therefore, Ni-Mo-series Hastelloy B and Ni-Mo-C r series Hastelloy C alloys have serious intergranular corrosion tendency or sensitivity, which can also lead to stress corrosion and gap corrosion at high temperature. In order to overcome the inter-Crystal corrosion, the second generation of Hastelloy –Hastelloy C- 276(C reduced from 0.03% to 0.02%) and the third generation of Hastelloy C –Hastelloy C- 4 were introduced, it is characterized by low Si(Si ≤ 0.08%) and ultra-micro C(C ≤ 0.015%), and reduces the content of Fe and W, adding stabilized alloy element Ti, etc.
The corrosion resistant valve of Hastelloy C, considering the corrosion resistance and intergranular corrosion resistance, should choose Hastelloy C- 276(CW-6MC) and Hastelloy C- 4(CW-2M). There are many material codes for Hastelloy C valve doors, and the performance and working temperature are very different, so CW-12MW, CW-7M, CW-6MC and CW-2M are expressed in HC-12, HC-7, HC-276 and HC-4 respectively, or directly expressed by 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 ℃, the suitable working temperature of Hastelloy CW-6MC and UNS N10276 alloy is-29 ~ ℃, and the suitable working temperature of Hastelloy CW-2M and UNS N06455 alloy is-29~425 ℃.
Titanium (Ti) has high strength, light weight, high heat resistance, low temperature toughness and good processability and welding performance. Used in valve production is mainly cast pure titanium and forged pure titanium zta2.
Titanium shows corrosion resistance, non-corrosion resistance, even fire and explosion, etc. to corrosive medium due to different temperature and other working conditions. Therefore, the properties (concentration, temperature, etc.) of the Applied Media should be definitely stipulated when ordering and design.
The valve made of titanium has excellent corrosion resistance in a variety of highly corrosive and neutral media.
Titanium has excellent corrosion resistance in nitric acid whose concentration is below boiling point and is less than or equal to 80%. However, when the content of O2 in fuming nitric acid is over 2% and the water content is insufficient, titanium will explode from the reaction of fuming nitric acid. Therefore, titanium is generally not used for high temperature nitric acid with a content of more than 80%.
Titanium is not corrosion resistant in sulfuric acid, and titanium has medium corrosion resistance in hydrochloric acid. It is generally considered that industrial pure titanium can be used in hydrochloric acid with a concentration of 7.5% at room temperature, 3% at 60 ℃ and 0.5% at 100 ℃. Titanium can also be used at 35 ℃ with a concentration of 30%, in phosphoric acid with concentration of 10% and 3% at 60 ℃ and 100 ℃.
Titanium is not corrosion resistant in HF (hydrofluoric acid), titanium is also not corrosion resistant in acidic fluoride solution, and titanium is corrosion resistant in boric acid and chromic acid; It can be used in hydroiodic acid and hydrobromic acid.
Titanium can be used at 60 ℃, mixed acid of 10% sulfuric acid and 90% nitric acid, mixed acid of boiling 1% hydrochloric acid and 5% nitric acid and room temperature Aqua (note: wang Shui is a mixture of 3 volumes of concentrated hydrochloric acid and 1 volume of concentrated nitric acid).
Titanium is completely corrosion resistant in various concentrations of barium hydroxide, calcium hydroxide, magnesium hydroxide, sodium hydroxide and potassium hydroxide solutions at room temperature, but cannot be used in boiling sodium hydroxide and potassium hydroxide. Ammonia in alkali will aggravate the corrosion of titanium.
The highest working temperature of titanium in tap water, river water and air is 300℃. Titanium can be used for the highest flow rate up to 20m/s in seawater. Titanium has high corrosion resistance in seawater whose temperature is below 120℃. If the temperature is higher than 120℃, it may cause spot corrosion and gap corrosion.
Except for formic acid, oxalic acid and concentrated citric acid (concentration ≥50%), titanium has excellent corrosion resistance to all organic acids. However, the water content in the organic acids is too low (<0.1%). When Titanium is prone to point corrosion.
Titanium has excellent corrosion resistance in hydrocarbon compounds and chlorinated hydrocarbon compounds. Titanium can react intensively in dry chlorine to generate TiCl4 with the danger of fire, but titanium has good corrosion resistance in wet chlorine (water content is between 0.3 and 1.5%).
Titanium is stable in dry HCl at 20 ~ 160℃, but hydrochloric acid corrodes titanium in wet hydrogen chloride.
The pitting potential of titanium in chloride solution is higher than that of stainless steel, and the pitting corrosion resistance of titanium in chloride solution is better than that of stainless steel. Therefore, titanium has been widely used in chloride solution.
When the temperature is less than or equal to 80℃, titanium generally does not produce pitting corrosion, but in high temperature and medium concentration chloride solution (such as 25% aluminum chloride solution at 100℃, 70% calcium chloride solution at 175 ℃, 25% magnesium chloride solution of 200 ℃ and 75% zinc chloride solution of 200 ℃) are more prone to pitting.
High temperature condition
The valve under high temperature condition mainly refers to the high temperature valve used in the refinery.
Sub-high temperature refers to the working temperature of the valve in the area of 325~425 ℃. If the medium is water and steam, WCB, WCC, A105, WC6 and WC9 are mainly used. If the medium is sour oil, it mainly uses C5, CF8, CF3, CF8M and CF3M with sulfide corrosion resistance. They are mostly used in the atmospheric and vacuum distillation unit and delayed coking unit of the oil refinery, when valves made of CF8, CF8M, CF3 and CF3M are not used for corrosion of acid-resistant solution, but for sour oil products and oil pipelines. In this working condition, the maximum working temperature limit of CF8, CF8M, CF3 and CF3M is 450℃.
High temperature level I
When the working temperature of the valve is 425 ~ 550℃, it is high temperature Class I (PI level for short). The main material of grade PI valve is “high temperature grade I Medium carbon, chromium-nickel rare earth titanium high-quality heat-resistant steel” based on CF8 in ASTM A351 standard “. Because grade PI 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 ℃) can also be used, although high temperature steel C5(ZG1Cr5Mo) can also be used in sulfur-containing oil products, they cannot be called PI grade here.
High temperature level II
The working temperature of the valve is 550 ~ 650℃ and is classified as high temperature Class II (referred to as PII for short). The pⅱ high-temperature valve is mainly used in the heavy oil catalytic cracking unit of the refinery, which contains the high-temperature lining wear-resistant gate valve used in the three-Rotating nozzle and other parts. The main material of P Grade II valve is “high temperature grade II medium carbon chromium nickel rare earth titanium tantalum reinforced heat-resistant steel” based on CF8 in ASTM A351 standard “.
High temperature grade III
The working temperature of the valve is 650~730 ℃, which is defined as high temperature Class III (referred to as pⅲ). The pⅲ high temperature valve is mainly used in the large heavy oil catalytic cracking unit of the refinery. The main body material of P Ⅲ high temperature valve is “high temperature Ⅲ grade medium carbon chromium nickel molybdenum rare earth titanium tantalum reinforced heat-resistant steel” based on CF8M in ASTM A351 standard “.
High temperature class Ⅳ
The working temperature of the valve is 730 ~ ℃, which is classified as high temperature Class IV (referred to as class PIV). Setting the upper limit of working temperature of P Class IV valve at ℃ is because the maximum temperature provided in the standard ASME B16.34 pressure-temperature level selected by the valve design is ℃ (1500f). In addition, when the working temperature exceeds ℃, the steel will enter the region of forging temperature, and at this time, the metal will be in the range of plastic deformation with good plasticity, it is difficult to bear high working pressure and impact force while keeping shape. The main material of P class Ⅳ valve is CF8M in ASTM A351 standard, which is “high temperature class IV medium carbon chromium nickel molybdenum rare earth titanium tantalum reinforced heat-resistant steel”. Heat-resistant stainless steel such as F310 (C content ≥ 0.050%) and F310H in CK-20 and ASTM A182 standards.
High temperature Class V
If the operating temperature of the valve is higher than ℃, it is called high temperature level V (referred to as P level V). P Grade V high temperature valves (as valve for cutting off, not as butterfly valves of adjustable type) must adopt special design means, such as heat insulation lining, water or air cooling, etc, only in this way can the normal work of the valve be guaranteed. Therefore, there is no regulation on the upper limit of the working temperature of the PV level high temperature valve, because the control of the working temperature of the valve is not only based on materials, but also solved by special design methods, the basic principle of design means is the same. The P V-level high temperature valve can choose reasonable materials that can meet the valve according to its working medium, working pressure and the adopted special design method. In the pⅴ high-temperature valve, the HK-30 of ASTM A297 standard is usually used for the plug-in plate valve of flue pipe or the plug-in plate or butterfly plate of butterfly valve, HK-40 high-temperature alloy, they can resist corrosion in antioxidant and reductive gases below 1150 ℃, but cannot withstand impact and high pressure load.
Today, with the rapid development of technology, the main material of the valve is becoming more and more diversified and highly parameterized. The working medium corresponding to the valve is also more complicated, and the working temperature requirements are higher. Understanding the performance and appropriate working temperature of various valve steel and alloy is a necessary knowledge for relevant scientific and technical personnel and operators who design, manufacture, purchase and use valves. In particular, the use temperature of the material cannot exceed its suitable working temperature, otherwise it will cause terrible serious accidents.
Source: China Valve Manufacturer – Yaang Pipe Industry Co., Limited (www.steeljrv.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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