As the name implies, duplex stainless steel flanges are flanges produced using duplex stainless steel raw materials like bars, ingots, or plates. People often simply refer to them as duplex steel flanges. A flange, also known as a flange plate or collar, connects pipes to each other, typically at the end of a pipe. Designers include bolt holes in flanges so users can insert bolts to tightly secure two flanges together. A gasket provides the seal between the flanges.
A flange connection consists of a pair of flanges, a gasket, and several bolts and nuts. The gasket is placed between the sealing1 faces of the two flanges.When the nuts are tightened, the specific pressure on the gasket’s surface reaches a certain value, causing it to deform and fill any unevenness on the sealing surfaces, creating a tight, leak-proof joint. Some pipe fittings and equipment come with pre-attached flanges, which also fall under the category of flange connections. Flange connections are a crucial method of joining in pipeline construction.
Feel free to contact us
Specification of Duplex Steel Flanges
| Size | 1/8″ NB TO 24″ NB |
| Standard | ANSI Flanges, ASME Flanges, BS Flanges, DIN Flanges, EN Flanges, etc. |
| Designation | ANSI B 16.5, BS 1560. BS 10, IS 6392, B-2.1 NPT, API, DIN, JIS. MSS SP 44 |
| Grade | ASTM A182 / ASME SA182 F51 / F52 / F53 / F54 / F55 / F60 , UNS S31803, UNS S32205,UNS32750,UNS32760 |
| Class | 150 LBS, 300 LBS, 600 LBS, 900 LBS, 1500 LBS, 2500 LBS |
| Flange Face Type | Flate Face (FF), Raised Face (RF), Ring Type Joint (RTJ) |
Duplex Stainless Steel Material Chemical Composition
| CHEMICAL | LIMITS | C | Mn | P | S | Si | Ni | Cr | Mo | N | Cu | W |
| ASTM A182 F51 | MIN | 4.50 | 21.00 | 2.50 | 0.08 | |||||||
| MAX | 0.03 | 2.00 | 0.030 | 0.020 | 1.00 | 6.50 | 23.00 | 3.50 | 0.20 | |||
| ASTM A182 F53 | MIN | 6.00 | 24.00 | 3.00 | 0.24 | |||||||
| MAX | 0.03 | 1.20 | 0.035 | 0.020 | 0.80 | 8.00 | 26.00 | 5.00 | 0.32 | 0.50 | ||
| ASTM F55 | MIN | 6.00 | 24.00 | 3.00 | 0.20 | 0.50 | 0.5 | |||||
| MAX | 0.03 | 1.00 | 0.030 | 0.010 | 1.00 | 8.00 | 26.00 | 4.00 | 0.30 | 1.00 | 1 | |
| ASTM F60 | MIN | 4.50 | 22.00 | 3.00 | 0.14 | |||||||
| MAX | 0.03 | 2.00 | 0.030 | 0.020 | 1.00 | 6.50 | 23.00 | 3.50 | 0.20 |
Duplex Stainless Steel Material Mechanical Property
| MATERIAL | ASTM A182 F51 | ASTM A182 F53 | ASTM A182 F55 | ASTM A182 F60 |
| T.S (MPA) | 620 min | 800 min | 750-895 | 655min |
| Y.S (MPA) | 450 min | 550 min | 550min | 450min |
| EL % | 25 min | 25 min | 25min | 25min |
| R/A % | 45 min | 15 min | 45min | 45min |
key Characteristics of Duplex Stainless Steel Flanges
High Strength: Duplex stainless steel flanges boast a yield strength more than double that of ordinary austenitic stainless steels, enabling them to withstand significantly higher pressures.
Excellent Corrosion Resistance: These flanges exhibit superior corrosion resistance in harsh environments, including oxidizing acids and chlorides. They are particularly notable for their remarkable resistance to stress corrosion cracking, especially in chloride-rich conditions.
Good Weldability: Duplex stainless steel flanges offer better welding performance than standard stainless steels. Their weld heat-affected zones maintain higher toughness and better corrosion resistance.
Wear and Fatigue Resistance: Compared to austenitic stainless steels, duplex stainless steel flanges show a distinct advantage in resisting wear corrosion and fatigue corrosion.
Different Types of Duplex Stainless Steel Flanges
Weld neck flange refers to a flange with a neck and a groove on the outside of the neck, which is used for butt welding with pipes or equipment.
2. Blind Flange
Blind flange is a type of flange connection. In fact, it is a flange without a hole in the middle. It is usually fixed to the flange of the pipe or equipment by bolts, and a gasket is used between the two to achieve sealing.
Socket welding flange is a type of flange that is welded by inserting the end of the pipe into the socket hole of the flange and then performing annular fillet weld.
Threaded flange is a non-welded flange that processes the inner hole of the flange into a pipe thread and connects it with a threaded pipe.
Slip on flange refers to a type of flange that is welded by putting the flange on the end of the pipe and then performing annular fillet welds on the inside and outside of the flange.
The lap joint flange is not directly welded to the pipe, but is connected to the pipe through a flanged nipple.
Packaging
Protective Caps or Rings:
Plastic or wooden protective caps/rings are typically used on the sealing surface and bevel ends of the flange. These protective devices effectively prevent scratches, dents, or deformation during handling and transportation.
Anti-corrosion Coating or Rust Preventive Oil:
To avoid surface contamination or slight oxidation during long-term storage in humid or special environments, users may apply a thin layer of rust preventive oil or a peelable anti-corrosion coating to the sealing surface, even though duplex stainless steel is corrosion-resistant.
Stretch Film or Bubble Wrap:
Individual flanges may be wrapped with stretch film or bubble wrap before being packed into crates to provide extra physical protection.
Fully Enclosed Wooden Crates:
Used for export, long-distance transportation, or environments with high moisture and dust protection requirements. Wooden crates offer the highest level of protection and can withstand significant external pressure and impact.
Wooden Pallet with Wooden Frame or Cover Boards:
For flanges with regular shapes or in larger quantities, they can be stacked on wooden pallets, secured with a wooden frame or cover boards, and strapped with packing bands. This method is forklift-friendly and suitable for bulk handling.
Heat Treatment
Solution Annealing
Solution annealing involves heating a material to its solutionizing temperature, allowing the solid to dissolve, and then cooling it. This process can increase the material’s hardness and strength, and ensures a uniform distribution of austenite and ferrite.
Quenching
Quenching is the rapid cooling of a material after it has been heated to its solutionizing temperature. It can increase the material’s hardness and strength, but it will reduce its toughness.
Solution Annealing + Quenching (with Cold Treatment)
After solution annealing, the material undergoes quenching, often followed by a cold treatment (or “cold quenching”), to further increase its hardness and strength while maintaining a certain level of toughness.
Advantages of Duplex Stainless Steel
High Strength: Duplex stainless steel typically boasts a yield strength more than double that of common austenitic stainless steels (like 304/316L). This means you can use thinner wall thicknesses for the same pressure requirements, leading to reduced material costs and equipment weight.
Resistance to Pitting and Crevice Corrosion: Its higher chromium, molybdenum, and nitrogen content provides superior resistance to pitting and crevice corrosion in chloride-containing environments.
Resistance to Uniform Corrosion: It shows good corrosion resistance to various acidic and alkaline media.
Good Weldability: Compared to some ferritic stainless steels, duplex stainless steel has better weldability, often without the need for pre-heating or post-weld heat treatment.
Good Ductility and Toughness: While not as ductile as austenitic stainless steel, it is significantly better than ferritic stainless steel.
Application of Duplex Stainless Steel Flanges
Oil and Gas Industry
Offshore platforms and marine engineering
Onshore oil and gas extraction and refining
Chemical and Petrochemical Industry
Fertilizer production
Water Treatment and Desalination
Seawater desalination plants
Wastewater treatment facilities
Pulp and Paper Industry
Environmental Protection and Pollution Control
Flue Gas Desulfurization (FGD) systems
Construction and Infrastructure
Chemical Tankers and Oil Tankers
Frequently Asked Questions (FAQs)
1. What is the difference between 304 and 2205 duplex stainless steel?
The main difference between 304 and 2205 duplex stainless steels is their microstructure and corrosion resistance, which makes them suitable for different environments and applications. 304 stainless steel is a typical austenitic stainless steel, and its microstructure is mainly composed of austenite. 2205 duplex stainless steel is an austenite-ferrite duplex stainless steel, which has the characteristics of both austenite and ferrite phases.
2205 duplex stainless steel has excellent corrosion resistance, especially in environments containing chloride ions. Its resistance to chloride stress corrosion cracking (SCC), pitting and crevice corrosion is significantly better than 304 stainless steel because it contains higher chromium, molybdenum and nitrogen.
2. Is duplex stainless steel expensive?
Yes, duplex stainless steel is usually more expensive than ordinary austenitic stainless steel (such as 304, 316L). However, although the initial material price of duplex stainless steel is higher, due to its high strength (and excellent corrosion resistance (extending equipment life and reducing maintenance and replacement costs), in many specific applications, the use of duplex stainless steel may be more economical from a life cycle cost perspective.
We are professional in manufacturing and exporting flanges in various materials.
