Valve materials for oil circuit plate materials carbon steel valve materials for special bellows

Valve materials for oil circuit plate materials carbon steel valve materials for special bellows

The oil circuit plate, single flow valve and gate valve (piston valve) of most valves are more complex, so the casting parts are generally used. Only some caliber valves or valves with unique working condition standards use cast steel parts. Carbon steel can be used for non-corrosive substances, in some special conditions such as in a certain range of temperature, concentration value environment, can be used for some corrosive substances. Available temperature -29~425℃..
The oil circuit plate, single flow valve and gate valve (piston valve) of most valves are more complex, so the casting parts are generally used. Only some caliber valves or valves with unique working condition standards use cast steel parts.
Carbon steel can be used for non-corrosive substances, in some special conditions such as in a certain range of temperature, concentration value environment, can be used for some corrosive substances. 1. The execution standard for carbon cast steel parts used in our country is GB12229-89 “Technical standard for versatility Valve and carbon steel Casting parts”, and the material models are WCA, WCB and WCC. This standard is formulated in accordance with the standard ASTMA216-77 “Standard Specification for welded carbon steel Castings for high temperature” of the foreign Materials Experimental Association. The standard has been modified at least twice, but my GB12229-89 is still in use, and the newer version I see at the present stage is Astma216-2001. It differs from Astma 216-77 (that is, from GB12229-89) in three ways.
A: The 2001 requirements added a requirement for WCB steel, that is, for every 0.01% reduction in the very large carbon limit value, the very large magnesium limit value can be increased by 0.04% until the maximum value is 1.28%.
B: The sundries Cu of WCA, WCB and WCC models: 0.50% in 77, adjusted to 0.30% in 2001; Cr: 0.40% in 77 and 0.50% in 2001; Mo: It was 0.25% in ’77 and 0.20% in 2001.
C: The residue element synthesis should be less than or equal to 1.0%. In 2001, when there is a carbon equivalent standard, this clause is not suitable, and the maximum carbon equivalent of the three models is required to be 0.5 and its carbon equivalent calculation formula.
Common problems: A: Meet the requirements of the casting parts must meet the standards of organic chemical composition, structural mechanical properties are also up to the standards, and *** to meet the requirements, especially the residue element manipulation, otherwise harm the welding performance. B: The organic chemical composition specified in the code is still the maximum. In order to obtain good welding performance and achieve the required structural mechanical properties, it is necessary to establish the internal control standards of components and carry out the correct heat treatment process for the casting parts and test rods. Otherwise, the production of cast parts does not meet the requirements. For example, WCB steel carbon content standard ≤0.3%, if the smelter out WCB steel carbon content of 0.1% or lower from the composition to see is in line with the requirements, but the structural mechanical properties do not meet the requirements. If the carbon content is equivalent to 0.3%, but the welding performance is poor, the carbon content control is more appropriate to 0.25%. Want to be an “entry and exit,” some investors will clearly put forward carbon control regulations.
C: Temperature categories relating to carbon steel valves
(a) JB/ T5300-91 “Materials for Universal valves” requires that the available temperature of carbon steel valves is -30℃ to 450℃.
(b) SH3064-94 “petrochemical equipment steel universal valve adoption, testing and engineering acceptance” requirements of carbon steel valve available temperature of -20℃ to 425℃ (the application of low limit provisions for -20℃ is in order to unify with GB150 steel pressure vessel)
(c) ANSIB16·34 “flange and butt welding end valve” working pressure – temperature rated current value standard requirements WCB A105 (carbon steel) available temperature range including -29℃ to 425℃, can not be used above 425℃ for a long time. Solid carbon steel tends to graphitize at about 425℃. Special bellows valve materials Bellows,Ni-Cu alloy,Ni-Cr-Mo alloy,NI-Fe-Cr alloy, two-phase steel, titanium and other different unique materials,Ni-Cu alloy about 70%N i and 30%Cu nickel copper alloy has been known as Monel (M onel) name. The composition of the most typical M onel400 alloy is shown in Table 2. Monel alloy is mainly used in weak oxidizing organic solvents, especially hydrochloric acid, strong acid and liquid seawater also has excellent corrosion resistance. Monel alloy is also suitable for..
Special bellows for valve materials
(1)N i-Cu alloy
A nickel-copper alloy containing about 70%N i and 30%Cu has long been known as M onel. The composition of the most typical M onel400 alloy is shown in Table 2. Monel alloy is mainly used in weak oxidizing organic solvents, especially hydrochloric acid, strong acid and liquid seawater also has excellent corrosion resistance. M onel alloy is also suitable for dry hydrogen gas, hydrogen chloride gas, continuous high temperature hydrogen gas (425℃) and continuous high temperature hydrogen chloride gas (450℃) and other materials.
Mone l is subject to amphoteric oxides, fluoride, and ammonia salts in humid environments, and is therefore resistant to corrosion in reducing solutions. In addition, he will cause intergranular corrosion when melting caustic soda. The suitable working temperature of Mo2nel alloy is below 480℃.
(2)Ni-Cr-Mo alloy
Nickel – based alloy containing molybdenum, also known as Hastelloy alloy. Hastelloy C-276 alloy has excellent comprehensive properties, which can be used to oxidize substances in air and restore medium in natural environment, so it is used. C-276 alloy key wet chlorine, a variety of reducing fluoride, sodium cyanate solution, hydrochloric acid and reducing salt, low temperature environment and atmospheric pressure sulfuric acid have very good corrosion resistance. C-276 does not have sufficient heat resistance. After long-term timability in the temperature range of 650 ~ 1 090℃ (exceeding 10m in), it will mistakenly precipitate cementates or intermetallic compounds, leading to stress corrosion. The composition of C-276 alloy is shown in Table 3. Incone l625 alloy is a nickel-ferric martensitic variant alloy containing more chromium (20W t% ~ 25W t%), molybdenum (8W t% ~ 10W t%), iron (5W t%), and niobium (315W t% ~ 415W t%) as the basic additive element. The composition is shown in Table 3. The addition of niobium to 625 alloy improves the heat resistance to stress corrosion. The chromium content is higher than that of the C-276 alloy, which improves the corrosion resistance of the alloy in many oxidizing substances, such as boiling sodium cyanide. 625 alloy with molybdenum and niobium as the basic reinforcing elements of fine crystal hardening alloy, the application temperature is generally not more than 650℃. Special bellows material for valves
(3)NI-Fe-Cr alloy
Incoloy825 is a nickel-iron-chromium fine-grain reinforced alloy with molybdenum, copper and titanium. The composition is shown in Table 4. In general, the mass concentration of nickel is not less than 30%, and the mass concentration of (nickel-iron) is not less than 65%, so 825 alloy is sometimes referred to as nickel-iron base alloy. Alloy 825 is mainly used for oxidation resistant media etching. Due to the addition of titanium in the material, its reliability is improved, and due to the relatively low carbon content, it reduces the corrosion caused by cementite deposition in the welding heat affected zone in the corrosion environment of normal startup. The nickel content of the alloy is sufficient to resist the stress corrosion cracking of martensite. The application temperature of 825 is generally not more than 550℃, and 650 ~ 760℃ is a very serious sensitization temperature range of materials.
Inconel718 alloy is an aging enhanced Ni-ferro chromium based modified continuous superalloy. It is a continuous superalloy at the strength of 650℃ and has good heat resistance fatigue, oxidation resistance, radiation resistance, cold and heat treatment properties. It is one of the superalloys with high temperature, and its composition is shown in Table 4. The alloy should be developed under the premise of solid solution treatment, according to the addition of more classical A, l, Ti and N b. In addition to strengthening the ionic crystal, these elements also fuse with nickel to produce colattice stable and complex intermetallic compounds. At the same time, aluminum, copper, boron elements and carbon produce a variety of cementites to improve the thermal strength of the alloy. The strength of the alloy is mainly derived from the strengthening phase γ “and a small amount of γ ‘distributed in the substrate, which has better structural mechanical properties, corrosion resistance and creep resistance at 650℃. The main strengthening phase γ” in the alloy used above 650℃ is easy to be passivated and converted into δ phase, which can reduce or ineffective the alloy properties.
(4) two-phase steel
Duplex stainless steel is composed of martensite and metallography of about 50% each, the appearance of martensite reduces the brittle fracture and alkali embrittlement of high chromium ferrite steel, and improves the ductility of duplex steel. The microstructure of martensitic steel improves the yield strength, stress corrosion resistance and intergranular corrosion resistance.
The two-phase steel has strong resistance to stress corrosion cracking in fluoride and sulfate, which has effectively overcome the ineffective problem of low alloy steel caused by local corrosion. The composition of SA F2205 biphase steel in large demand is shown in Table 5. The material has a ductility temperature zone of 475℃, and the application temperature is generally not more than 300℃. Valves used in several classes of special materials bellows fifth
(5) Titanium
Titanium is a kind of metal material with strong passivation tendency, which is very easy to reflect with oxygen and form an oxide layer on the surface. In many corrosive media, this kind of oxide layer is very relatively stable, relatively difficult to melt, even if damaged, as long as there is enough oxygen, it can quickly recover by itself. Therefore, titanium has excellent corrosion resistance in reducing and neutralizing media. The composition of industrially produced titanium alloy TA 2 is shown in Table 6. Valves use bellows of several special materials
ASME has set the operating temperature limit of variant industrial-produced titanium alloys and low-alloy titanium alloys at 316℃.
Forming characteristics
The method of cold forming production of bellows by hydraulic press provides that the material has good plasticity, and the strong toughness and compressive strength are obtained by the following processing method. However, many unique materials do not have such characteristics, which brings some difficulties to the design and production of bellows. For example, two-phase steel has high tensile strength (tensile strength/compressive strength), larger cold-formed springback strength than 300 series low-alloy steel, and more serious strain hardening tendency than 300 series low-alloy steel. When the bellows diameter and nominal diameter ratio exceeds a certain value, the bellows should be formed by two times forming and two times aging treatment. Similarly, the compressive strength of titanium is not so close as the tensile strength, and the shape changes poorly when the bellows are formed. At the same time, the ratio between the strength limit of titanium and the elastic die is large, which makes the resilience of titanium forming strong. It is difficult to predict and measure the rebound force of the bellows made of this material, and it is also difficult to meet the initial design scheme according to the method of plastic surgery. As a result, there are some unique materials that can be used in the production of bellows but do not find widespread use. Customers in the use of bellows, should give full consideration to the valve medium corrosion performance, temperature, working pressure, as far as possible to choose a better performance of the material.
Welding characteristics of electric welding
The seamless steel tube billet or longitudinal weld of the corrugated pipe of the hydraulic press is made of welded pipe material. The tensile strength and elongation of the butt weld are very similar to that of the original material. Electric welding bellows is made by welding the cold-squeezed annular valve plate along its inside and outside edges. Valve with bellows on both sides of the general need to use a variety of interface forms and flange or seat components such as welding, such parts and sometimes bellows material is not the same. Therefore, the material of valve bellows itself should have better electric welding performance, and the valve seat and other parts should have malleable welding. And bellows welding parts should be as far as possible to choose the same material with bellows or performance close, good malleability of different materials.