Hastelloy wire woven filter screen classification, chemical composition, performance

Hastelloy wire woven filter screen classification, chemical composition and performance introduction
Hastelloy wire woven filter screen is also known as Hastelloy filter screen, Hastelloy wire mesh, Hastelloy screen, Hastelloy woven mesh, Hastelloy wire square hole mesh, etc.
Hastelloy alloy (Hastelloyalloy)
is currently mainly divided into three series: B, C, and G. It is mainly used in strong corrosive media occasions where iron-based Cr-Ni or Cr-Ni-Mo stainless steel, non-metallic materials, etc. cannot be used.
Hastelloy alloy grades
In order to improve the corrosion resistance and cold and hot processing properties of Hastelloy alloy, Hastelloy alloy has undergone three major improvements, and its development process is as follows:
B series: B→B-2(00Ni70Mo28)→B-3
C series: C→C-276(00Cr16Mo16W4)→C-4(00Cr16Mo16)→C-22(00Cr22Mo13W3)→C-2000(00Cr20Mo16)
G series: G→G-3(00Cr22Ni48Mo7Cu)→G-30(00Cr30Ni48Mo7Cu)
Currently, the most widely used are the second-generation materials N10665(B-2), N10276(C-276), N06022(C-22), N06455(C-4) and N06985(G-3).

Chemical composition of Hastelloy alloy materialsNiCrMoFeCSiCoMnPSWVCuNb
Ta
N10665 (B-2) base≤1.026.0~30≤2.0≤0.02≤0.10≤1.0≤1.0≤0.04≤0.03
N10276 (C-276) base14.5~16.515.0~17.04.0~7.0≤0.01≤0.08≤2.5≤1.0≤0.04≤0.033.0~4.5≤0.035
N06007 (G-3) base 21.0~23.5 6.0~8.0 18.0~21 ≤0.015≤1.0≤5.0≤1.0≤0.04≤0.03≤1.5 1.5~2.5≤0.50

Introduction to the performance characteristics of commonly used alloys
1: Hastelloy B-2 alloy (Hastelloy B-2 alloy)

1. Corrosion resistance
Hastelloy B-2 alloy is a Ni-Mo alloy with extremely low carbon and silicon content. It reduces the precipitation of carbides and other phases in the weld and heat-affected zone, thereby ensuring good corrosion resistance even in the welded state. It is
well known that Hastelloy B-2 alloy has excellent corrosion resistance in various reducing media and can withstand corrosion of hydrochloric acid at any temperature and any concentration under normal pressure. It has excellent corrosion resistance in non-aerated medium-concentration non-oxidizing sulfuric acid, various concentrations of phosphoric acid, high-temperature acetic acid, formic acid and other organic acids, bromic acid and hydrogen chloride gas. At the same time, it is also resistant to corrosion by halogen catalysts. Therefore, Hastelloy B-2 alloy is usually used in a variety of harsh petroleum and chemical processes, such as distillation and concentration of hydrochloric acid; alkylation of ethylbenzene and low-pressure carbonyl synthesis of acetic acid and other production processes.
However, in the industrial application of Hastelloy B-2 alloy for many years, it was found that: (1) Hastelloy B-2 alloy has two sensitization zones that have a considerable influence on its resistance to intergranular corrosion: a high temperature zone of 1200~1300℃ and a medium temperature zone of 550~900℃; (2) The weld metal and heat-affected zone of Hastelloy B-2 alloy are more sensitive to intergranular corrosion due to dendritic segregation, intermetallic phases and carbides precipitate along the grain boundaries; (3) Hastelloy B-2 alloy has poor medium-temperature thermal stability. When the iron content in Hastelloy B-2 alloy drops below 2%, the alloy is sensitive to the transformation of β phase (i.e. Ni4Mo phase, an ordered intermetallic compound). When the alloy stays in the temperature range of 650~750℃ for a slightly longer time, β phase is generated instantly. The presence of β phase reduces the toughness of Hastelloy B-2 alloy, making it sensitive to stress corrosion, and even causes cracking of Hastelloy B-2 alloy during raw material production (such as hot rolling process), equipment manufacturing process (such as overall heat treatment of Hastelloy B-2 alloy equipment after welding) and Hastelloy B-2 alloy equipment in the service environment. At present, the standard test methods for the intergranular corrosion resistance of Hastelloy B-2 alloy designated by my country and other countries in the world are all atmospheric boiling hydrochloric acid method, and the evaluation method is weight loss method. Since Hastelloy B-2 alloy is an alloy resistant to hydrochloric acid corrosion, the atmospheric boiling hydrochloric acid method is quite insensitive to the intergranular corrosion tendency of Hastelloy B-2 alloy. Domestic research institutions have studied Hastelloy B-2 alloy using high-temperature hydrochloric acid method and found that the corrosion resistance of Hastelloy B-2 alloy depends not only on its chemical composition, but also on the control process of its thermal processing. When the hot working process is not properly controlled, the grains of Hastelloy B-2 alloy will not only grow, but also a high Mo σ phase will precipitate between the grains. At this time, the intergranular corrosion resistance of Hastelloy B-2 alloy will be significantly reduced. In the high-temperature hydrochloric acid test, the grain boundary etching depth of the coarse-grained plate and the normal plate is about twice as deep.
2. Physical properties
Density: 8.9g/cm3, melting point: 1330~1380℃, magnetic permeability: (℃, RT) ≤1.001 3.
Chemical composition
Chemical composition
ElementsNiCrFeCMnSiCuMoCoPSMinimum
Residue0.41.626.0Maximum1.02.00.011.00.080.530.01.00.020.010

IV. Manufacturing and heat treatment
1: Heating
For Hastelloy B-2 alloy, it is very important to keep the surface clean and away from contaminants before and during heating. If Hastelloy B-2 alloy is heated in an environment containing sulfur, phosphorus, lead or other low-melting-point metal contaminants, it will become brittle. The sources of these contaminants mainly include marker marks, temperature indicator paint, grease and liquid, and flue gas. This flue gas must have a low sulfur content; for example: the sulfur content of natural gas and liquefied petroleum gas does not exceed 0.1%, the sulfur content of urban air does not exceed 0.25g/m3, and the sulfur content of fuel oil does not exceed 0.5% to be qualified. The
gas environment requirement for the heating furnace is a neutral environment or a lightly reducing environment, and it cannot fluctuate between oxidizing and reducing. The flame in the furnace cannot directly impact the Hastelloy B-2 alloy. At the same time, the material must be heated to the required temperature at the fastest heating speed, that is, the temperature of the heating furnace must first be raised to the required temperature, and then the material must be placed in the furnace for heating.
2: Hot working
Hastelloy B-2 alloy can be hot worked in the range of 900~1160℃, and should be water quenched after processing. In order to ensure the best corrosion resistance, annealing should be performed after hot working.
3: Cold working
Cold worked Hastelloy B-2 alloy must be solution treated. Since it has a much higher work hardening rate than austenitic stainless steel, the forming equipment should be carefully considered. If the cold forming process is performed, it is necessary to perform interstage annealing. When the cold working deformation exceeds 15%, solution treatment is required before use.
4: Heat treatment
The temperature of solution heat treatment should be controlled between 1060~1080℃, and then water quenching or rapid air cooling can be performed when the material thickness is above 1.5mm to obtain the best corrosion resistance. In any heating operation, the surface cleaning of the material must be prevented in advance. When heat treating Hastelloy materials or equipment parts, pay attention to the following issues: In order to prevent the deformation of equipment parts during heat treatment, stainless steel reinforcement rings should be used; the charging temperature, heating and cooling time should be strictly controlled; before charging, the heat-treated parts should be pretreated to prevent thermal cracks; after heat treatment, the heat-treated parts should be 100% PT; if thermal cracks are generated during the heat treatment process, they need to be repaired after grinding and elimination, and a special repair welding process should be used.
5: Descaling
The oxides on the surface of Hastelloy B-2 alloy and the stains near the weld should be polished clean with fine grinding wheels.
Since Hastelloy B-2 alloy is sensitive to oxidizing media, more nitrogen-containing gases will be generated during the pickling process.
6: Machining
Hastelloy B-2 alloy should be machined in the annealed state, and its work hardening should be clearly understood. For example, a slower surface cutting speed should be used compared to standard austenitic stainless steel, and a larger feed rate should be used for the surface hardened layer, and the tool should be in a continuous working state.
7: Welding
Hastelloy B-2 alloy weld metal and heat-affected zone are prone to Mo-poor due to the easy precipitation of β phase, which is easy to cause intergranular corrosion. Therefore, the welding process of Hastelloy B-2 alloy should be carefully formulated and strictly controlled. The general welding process is as follows: ERNi-Mo7 is used as welding material; GTAW is used as welding method; the interlayer temperature is controlled to be no more than 120℃; the welding wire diameter is φ2.4, φ3.2; the welding current is 90~150A. At the same time, before welding, the welding wire, the groove of the welded parts and the adjacent parts should be decontaminated and degreased.
The thermal conductivity coefficient of Hastelloy B-2 alloy is much smaller than that of steel. If a single V-shaped groove is used, the groove angle should be around 70°, and a lower heat input should be used. Post-weld heat treatment can eliminate residual stress and improve stress corrosion cracking resistance.
2: Hastelloy C-276 alloy (Hastelloy C-276 alloy)
Corrosion resistance Hastelloy C-276 alloy belongs to nickel-molybdenum-chromium-iron-tungsten nickel-based alloy. It is one of the most corrosion-resistant modern metal materials. It is mainly resistant to wet chlorine, various oxidizing chlorides, chloride salt solutions, sulfuric acid and oxidizing salts, and has good corrosion resistance in low-temperature and medium-temperature hydrochloric acid. Therefore, in the past three decades, it has been widely used in harsh corrosive environments such as chemical, petrochemical, flue gas desulfurization, pulp and papermaking, environmental protection and other industrial fields.
The various corrosion data of Hastelloy C-276 alloy are typical, but cannot be used as a specification, especially in unknown environments, and materials must be selected after testing. There is not enough Cr in Hastelloy C-276 alloy to resist corrosion in strong oxidizing environments, such as hot concentrated nitric acid. This alloy is mainly produced for chemical process environments, especially in the presence of mixed acids, such as the discharge pipe of the flue gas desulfurization system. The following table shows the corrosion comparison test results of four alloys in different environments. (All welding samples are welded by self-fluxing tungsten inert gas argon arc welding)。