In a desulfurization project, since the chimney is made of 304 stainless steel, the air duct connecting the desulfurization tower and the chimney is also made of 304 stainless steel. Can it be anti-co

In a desulfurization project, since the chimney is made of 304 stainless steel, the air duct connecting the desulfurization tower and the chimney is also made of 304 stainless steel. Can it be anti-corrosion?

There are several metal materials you can consider: 1.4529, 254SMO, AL-6XN, 904L. The specific selection should be combined with the working conditions.

1.4529 is a desulfurization and denitrification six-molybdenum steel, super austenitic stainless steel:

1.4529 (Incoloy?926/UNS?N08926) has excellent properties in halide media and sulfur-containing hydrogen acidic environments. Very high resistance to pitting corrosion and crevice corrosion, can effectively resist chloride ion stress corrosion, also has good corrosion resistance in oxidizing and reducing media, good stability, mechanical properties slightly better than 904L, can be used in -196 to 400℃ pressure vessel manufacturing.

1.4529 Heat treatment:

Insulation between 980-1150℃ for 1-2 hours, rapid air cooling or water cooling.

Typical working conditions of 1.4529:

60% sulfuric acid, below 80℃, annual corrosion rate <0.1mm

1.4529 supporting welding materials and welding processes:

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It is recommended to use AWS?A5.14 welding wire ERNiCrMo-3 or AWS?A5.11 welding rod ENiCrMo-3 for welding of 1.4529 alloy.

1.4529 Application areas:

Fume desulfurization devices, evaporators, heat exchangers, filters and mixers for phosphoric acid production, sulfuric acid delivery devices, condensers, fire extinguishing systems, sea water Filtration systems, hydraulic and recharge piping systems in the offshore industry, pulp drift systems, salt evaporation condensers, broadcast contaminated cooling water piping systems, reverse osmosis seawater desalination units, corrosive chemical transport storage tanks, halogen acid catalyzed Organic production equipment, etc.

1.4529 Corrosion resistance:

1.4529 is an austenitic stainless steel with a similar chemical composition to Alloy 904L. Its nitrogen content is increased to about 0.2%, and its molybdenum content is about 6.5%. The increase in nitrogen and molybdenum content significantly improves the resistance to pitting and crevice corrosion in halide media. At the same time, nickel and nitrogen not only ensure the stability of the metallographic phase, but also reduce the tendency of intergranular phase precipitation during hot processing or welding than alloys with lower nickel and nitrogen content. The excellent resistance to localized corrosion combined with the 25% nickel content makes Alloy 1.4529 particularly resistant to corrosion in chloride ion media. Tests in various FGD systems with limestone slurries with chloride concentrations of 10,000-70,000 ppm, pH values ??of 5-6, and operating temperatures of 50-68°C showed that after a test period of 1-2 years, alloy 1.4529 No pitting corrosion or crevice corrosion occurred.

1.4529 alloy also has good corrosion resistance in other chemical media, as well as high temperature and high concentration media, including sulfuric acid, phosphoric acid, acidic gases, seawater, salt and organic acids. Alloy 1.4529 is the material of choice for Chapter 6 of the BAM catalog "Specifications for Storage and Transportation Containers of Dangerous Goods" of the German National Institute for Research and Testing of Materials (BAM) in Berlin. In addition, the best corrosion resistance can only be achieved when the material is in the correct metallurgical condition and ensures cleanliness.

Main specifications of 1.4529:

1.4529 seamless pipe, 1.4529 steel plate, 1.4529 round steel, 1.4529 forgings, 1.4529 flange, 1.4529 ring, 1.4529 welded pipe, 1.4529 steel strip, 1.4529 straight Strips, 1.4529 wire and supporting welding materials, 1.4529 round cake, 1.4529 flat steel, 1.4529 hexagonal rod, 1.4529 big and small heads, 1.4529 elbow, 1.4529 tee, 1.4529 processed parts, 1.4529 bolts and nuts, 1.4529 fasteners

254SMO is an austenitic stainless steel with six molybdenum steel.

Due to its high molybdenum content, it has extremely high resistance to pitting corrosion and crevice corrosion. This grade of stainless steel was developed for use in environments containing halides such as seawater. 254SMO also has good resistance to uniform corrosion. Especially in acids containing halides, this steel is superior to ordinary stainless steel. Its C content is <0.03%, so it is called pure austenitic stainless steel. (<0.01% is also called super austenitic stainless steel).

Super stainless steel is a kind of special stainless steel. First of all, it is different from ordinary stainless steel in chemical composition. It refers to a high alloy stainless steel containing high nickel, high chromium and high molybdenum. The more famous one is 254SMo containing 6% Mo. This type of steel has very good local corrosion resistance. It has good pitting corrosion resistance (PI ≥ 40) and It has good stress corrosion resistance and is a substitute material for Ni-based alloys and titanium alloys. Secondly, in terms of high temperature resistance or corrosion resistance, it has better high temperature resistance or corrosion resistance, which is irreplaceable for 304 stainless steel. In addition, from the classification of stainless steel, the metallographic structure of special stainless steel is a stable austenite metallographic structure.

Since this special stainless steel is a high-alloy material, the manufacturing process is quite complex. Generally, people can only rely on traditional processes to manufacture this special stainless steel, such as pouring, forging, rolling, etc. .

Main components of 254SMO:

254SMo contains carbon (C) ≤ 0.02, manganese (Mn) ≤ 1.00, nickel (Ni) 17.5 ~ 18.5, silicon (Si) ≤ 0.8 phosphorus ( P) ≤ 0.03, sulfur (S) ≤ 0.01, chromium (Cr) 19.5 ~ 20.5, copper (Cu) 0.5 ~ 1.0, molybdenum (Mo) 6.0 ~ 6.5

254SMO national brands and standards:

UNS S31254, DIN/EN 1.4547, ASTM A240, ASME SA-240

254SMO physical properties:

Density: 8.24g/cm3, melting point: 1320-1390 ℃, magnetism: none

254SMO mechanical properties:

Tensile strength: σb≥650Mpa, yield strength σb≥310Mpa: elongation: δ≥40%, hardness: 182-223 (HB)

Corrosion resistance of 254SMO:

It is a highly corrosion-resistant super austenitic stainless steel, developed for halide and acid environments, and is widely used in high-concentration chlorine Harsh working conditions such as ionic media and sea water. In various industrial situations in acidic media, especially in acids containing halides, 254SMO is far superior to other stainless steels, and in some cases can be comparable to Hastelloy and titanium. The lower carbon content and high molybdenum content make it have good resistance to pitting corrosion and crevice corrosion, and excellent resistance to intergranular corrosion. It is a cost-effective stainless steel that is widely used in the fields of chemical industry, desulfurization and environmental protection at home and abroad. Widely used.

254SMO supporting welding materials:

ERNiCrMo-3 welding wire, ENiCrMo-3 welding rod

Main specifications of 254SMO:

254SMO seamless pipe , 254SMO steel plate, 254SMO round steel, 254SMO forgings, 254SMO flange, 254SMO ring, 254SMO welded pipe, 254SMO steel strip, 254SMO straight bar, 254SMO wire and supporting welding materials, 254SMO round cake, 254SMO flat steel, 254SMO hexagonal rod, 254SMO big and small heads, 254SMO elbows, 254SMO tees, 254SMO machined parts, 254SMO bolts and nuts, 254SMO fasteners

AL-6XN six-molybdenum super austenitic stainless steel?

AL -6XN Overview:

AL-6XN (N08367) super austenitic stainless steel is also a super austenitic stainless steel with excellent resistance to chloride ion pitting corrosion and crevice corrosion. As a kind of super austenitic stainless steel with good A cost-effective corrosion-resistant alloy, its comprehensive corrosion resistance has greatly improved compared to 316L. At the same time, its corrosion resistance is similar to other corrosion-resistant nickel-based alloys such as C-276, and its cost advantage is obvious. Because a significant nitrogen component is added to the alloy, the Al-6XN material has higher tensile strength than conventional austenitic stainless steel (such as 304, 316, 317, etc.), while maintaining excellent material toughness and impact strength, ASME standards The allowable stress value specified in Al-6XN is 40% higher than that of 316L, and nearly twice that of copper-nickel alloy.

AL-6XN international common name:

Al-6XN, desulfurization and denitrification alloy, UNS N08367, Cronifer1925hMo, Incoloy alloy25-6HN, NAS 254NM

AL-6XN Implementation standards:

ASTM B688, ASTM A240, ASTM B676, ASTM B675, ASTM B564

AL-6XN Chemical composition:

Carbon C: 0.03

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Magnesium Mg: 2.0

Phosphorus P: 0.04

Sulfur S: 0.03

Silicon Si: 1.0

Nickel Ni:23.5-25.5

Chromium Cr: 20.0-22.0

Molybdenum Mo:6.0-7.0

Nitrogen N: 0.18-0.25

Copper Cu:0.75

AL-6XN physical properties:

Density: 8.24g/cm3

Melting point: 1370-1398℃

Elastic modulus: 290GPa

Thermal conductivity: 90 W/(m?℃)?

Hardness (HB): 280

Thermal expansion coefficient (20 -100℃): 8.5×10-6/℃

AL-6XN mechanical properties:

Tensile strength: σb≥650Mpa, yield strength σb≥295Mpa: elongation: δ ≥35%

AL-6XN heat treatment:

Hot between 980-1150℃ for 1-2 hours, rapid air cooling or water cooling.

Main features of AL-6XN:

AL-6XN (N08367, 1.4501) stainless steel has higher resistance to pitting corrosion, crevice corrosion and chloride ions than standard 300 series alloys. Pressure crevice corrosion ability. In stainless steel, Cr, Mo, Ni, and C have corrosion resistance to different media respectively. Cr is the representative of corrosion resistance in natural and oxidizing environments. The increase in the content of Cr, Mo, and Ni increases the resistance to pitting corrosion. Nickel provides an austenite structure. Nickel and molybdenum increase the pressure crevice corrosion ability of chloride ions and reduce the corrosion resistance. Environmental corrosion resistance. High nickel (24%), molybdenum (6.3%) AL-6XN stainless steel has good resistance to pressure crevice corrosion. Molybdenum has the ability to resist chloride ion pitting corrosion. Nickel further enhances the resistance to pitting corrosion and can provide higher strength than 300 austenitic stainless steel, so it is often used in thinner parts of equipment. In AL-6XN stainless steel, the higher levels of chromium, molybdenum, and nickel also provide corrosion resistance during the forming and welding of the stainless steel.

In addition, AL-6XN stainless steel also has the following characteristics

1. Excellent pitting corrosion resistance and crevice corrosion resistance in a medium environment containing chloride ions.

2. Excellent stress corrosion resistance in sodium chloride salt solution medium.

3. High strength and good toughness.

Main applications of AL-6XN:

AL-6XN’s high chromium, molybdenum, nickel and nitrogen make AL-6XN have good resistance to chloride ion pitting corrosion and crevice corrosion. AL-6XN is used in many environments:

Main specifications of AL-6XN:

AL-6XN seamless pipe, AL-6XN steel plate, AL-6XN round steel, AL- 6XN forgings, AL-6XN flanges, AL-6XN rings, AL-6XN welded pipes, AL-6XN steel strips, AL-6XN straight bars, AL-6XN wire and supporting welding materials, AL-6XN round cakes, AL- 6XN flat steel, AL-6XN hexagonal bar, AL-6XN large and small heads, AL-6XN elbows, tees, AL-6XNAL-6XN processed parts, AL-6XN bolts and nuts, AL-6XN fasteners

< p>Overview of 904L super stainless steel:

904L super austenitic stainless steel is a low-carbon, high-nickel, molybdenum austenitic stainless acid-resistant steel. It is a proprietary material imported from French H·S Company.

It has good activation-passivation transition ability, excellent corrosion resistance, good corrosion resistance in non-oxidizing acids such as sulfuric acid, acetic acid, formic acid, and phosphoric acid, and good corrosion resistance in neutral chlorine-containing media. Excellent resistance to pitting corrosion, as well as good resistance to crevice corrosion and stress corrosion. It is suitable for sulfuric acid of various concentrations below 70°C. It can withstand acetic acid of any concentration and temperature under normal pressure and has good corrosion resistance in mixed acids of formic acid and acetic acid. Super austenitic stainless steel 904L is a high-alloy austenitic stainless steel with low carbon content. It has good corrosion resistance in dilute sulfuric acid and is specially designed for environments with harsh corrosion conditions. It has a high chromium content and sufficient nickel content. The addition of copper makes it highly acid-resistant, especially highly resistant to chloride gap corrosion and stress corrosion cracking. It is not prone to corrosion spots and cracks, and is resistant to spots. Its corrosion resistance is slightly better than other steel types, it has good processability and weldability, and can be used for pressure vessels.

904L super stainless steel grades and standards:

00Cr20Ni25Mo4.5Cu (national standard), UNS N08904 (designed jointly by the American Society of Motor Vehicles Engineers and the American Society for Testing and Materials in 1967 Standard), DIN1.4539 (German standard), ASTM A240 (American Society for Testing and Materials standard; the new standard classifies it as a stainless steel series, and the original standard ASME SB-625 classifies it as a nickel-based alloy series), SUS890L.

904L super stainless steel metallographic structure:?

904L is a completely austenitic structure. Compared with the general austenitic stainless steel with high molybdenum content, 904L has no effect on ferrite and It is not sensitive to the precipitation of α phase.

904L super stainless steel processing performance:

Welding performance

Like general stainless steel, 904L can be welded using a variety of welding methods. The most commonly used welding methods are manual arc welding or inert gas shielded welding. The welding rod or wire metal is based on the composition of the base metal and has higher purity, and the molybdenum content is required to be higher than the base metal. Preheating is generally not required before welding, but in cold outdoor operations, in order to avoid condensation of water vapor, the joint part or adjacent area can be heated evenly. Pay attention to the local temperature not exceeding 100°C to avoid carbon accumulation and intergranular corrosion. When welding, small linear energy, continuous and fast welding speed should be used. Generally, heat treatment is not required after welding. If heat treatment is required, it must be heated to 1100~1150℃ and then cooled quickly.

Supporting welding materials and welding processes: ER385 welding wire and E385 electrode are used for welding 904L

Machining performance

The machining characteristics of 904L are similar to other austenitic ones Made of stainless steel, there is a tendency for tool sticking and work hardening during processing. Carbide tools with positive rake angles must be used, and vulcanized and chlorinated oils should be used as cutting coolants. The equipment and processes should be based on reducing work hardening. Slow cutting speeds and feed rates should be avoided during the cutting process.

Corrosion resistance and main use environment of 904L:

904L is an austenitic stainless steel with very low carbon content and high alloying designed for environments with harsh corrosion conditions. , has better corrosion resistance than 316L and 317L, takes into account both price and performance, and has high cost performance. Due to the addition of 1.5% copper, it has excellent corrosion resistance against reducing acids such as sulfuric acid and phosphoric acid. It also has excellent corrosion resistance against stress corrosion, pitting corrosion and crevice corrosion caused by chloride ions, and has good resistance to intergranular corrosion. In pure sulfuric acid in the concentration range of 0-98%, the service temperature of 904L can be as high as 40 degrees Celsius. In pure phosphoric acid in the concentration range of 0-85%, its corrosion resistance is very good. In industrial phosphoric acid produced by wet processes, impurities have a strong impact on corrosion resistance. Among all kinds of phosphoric acid, 904L has better corrosion resistance than ordinary stainless steel. In strongly oxidizing nitric acid, 904L has lower corrosion resistance than highly alloyed steels that do not contain molybdenum. In hydrochloric acid, the use of 904L is limited to lower concentrations of 1-2%. within this concentration range. The corrosion resistance of 904L is better than that of conventional stainless steel. 904L steel has high resistance to pitting corrosion. Its resistance to crevice corrosion in chloride solutions. The force is also very good. The high nickel content of 904L reduces the corrosion rate in pits and crevices.

Ordinary austenitic stainless steel may be sensitive to stress corrosion in a chloride-rich environment at temperatures above 60 degrees Celsius. This sensitivity can be reduced by increasing the nickel content of the stainless steel. Due to the high nickel content, 904L has high resistance to stress corrosion cracking in chloride solutions, concentrated hydroxide solutions and hydrogen sulfide-rich environments.

904L application areas:

Petroleum and petrochemical equipment, such as reactors in petrochemical equipment, sulfuric acid storage and transportation equipment, such as heat exchangers, power plant flue gas desulfurization The main parts used in the device include: tower body, flue, door panel, internal parts, spray system, etc. of the absorption tower, scrubbers and fans in the organic acid treatment system, seawater treatment devices, seawater heat exchangers, and papermaking industry equipment. , sulfuric acid, nitric acid equipment, sulfuric acid, pharmaceutical industry and other chemical equipment, pressure vessels, food equipment, pharmaceutical factories: centrifuges, reactors, etc., plant foods: soy sauce tanks, cooking wine, salt tanks, equipment and dressings, for dilute sulfuric acid 904L is a matching steel grade for highly corrosive media.

904L main specifications:

904L seamless pipe, 904L steel plate, 904L round steel, 904L forgings, 904L flange, 904L ring, 904L welded pipe, 904L steel strip, 904L straight Strips, 904L wire and supporting welding materials, 904L round cakes, 904L flat steel, 904L hexagonal rods, 904L big and small heads, 904L elbows, 904L tees, 904L processed parts, 904L bolts and nuts, 904L fasteners

The space is limited, if you need more detailed introduction, please feel free to inquire.