Duplex Steel Flanges: Types, Specifications & Buying Guide
Duplex Steel Flanges: Types, Specifications & Buying Guide
If your piping system needssteel flanges that can resist corrosion while holding up under high pressure, duplex is the material worth specifying. These components are made of DSS, a material that exhibits excellent resistance to various types of corrosion. The name “duplex” comes from its two-phase microstructure, an equal composition of austenite and ferrite, which gives them higher strength than austenitic stainless steel products along with good weldability for easy fabrication and installation.
What Are Duplex Steel Flanges?
They display higher strength than standard austenitic stainless steel flanges while retaining the weldability needed for straightforward installation. This dual-phase structure is also what separates true duplex from single-phase alternatives, giving it a distinct edge in aggressive, chloride-rich environments where standard flanges tend to degrade faster.
Steel Flanges by Type: Weld Neck, Slip-On, Blind & More
Duplex flanges are available in several standard flange types, each suited to different piping requirements:
- Weld neck flange – features a tapered hub welded directly to the pipe, offering excellent strength and a smooth internal bore for high-pressure applications
- Slip-on flanges – slide over the pipe end before welding, a cost-effective option for lower-pressure systems
- Blind flanges – seal the end of a pipe run or vessel opening
- Threaded flanges – screw onto pipe without welding, useful where welding isn’t practical
- Reducing flanges – connect pipes of different diameters
- Socket weld flanges – ideal for smaller-diameter, high-pressure piping
Specifications & Size Range
Duplex Pipeline Solutions supplies these flanges to the following specifications:
- Size: 1/2″ – 48″
- Pressure class: 150 – 2500
- Face type: RTJ, RF, FF, T&G
- Yield strength: approximately 290 MPa
- Tensile strength: approximately 415 MPa
- Elongation: 50mm
- Coating: anti-rust painting
- Application: aerospace and industrial piping systems
Heat Treatment & Quality Testing
Manufacturers typically use optical microscopy and scanning electron microscopy (SEM) to examine heat-treated flanges, evaluating phase balance, grain structure, and the presence of any detrimental phases. Hardness tests such as Rockwell hardness are also conducted during manufacturing to measure resistance to indentation, ensuring every batch of flanges meets the required mechanical standard.
Advantages of Duplex Stainless Steel Flanges
- Excellent corrosion resistance – particularly strong in aggressive environments containing chloride solutions, which lowers the risk of material degradation and extends service life
- High yield, tensile, and fatigue strength – allows the use of thinner sections without sacrificing performance
- Long-term cost savings – higher initial cost than some other steel materials, offset by reduced maintenance and replacement over time
What Affects the Cost of a Duplex Flange?
The diameter (nominal pipe size) of a flange has a direct impact on weight and cost — larger-diameter flanges require more material and cost more to manufacture. Flange thickness has a similar effect: thicker flanges are heavier, require more material, and drive up overall cost.
Corrosion Resistance & Magnetism
Corrosion resistance in a duplex flange depends on its alloy composition — molybdenum content, for example, enhances resistance in chloride- and acid-containing environments — as well as service conditions like temperature, pH level, and chloride concentration. Because duplex is a two-phase alloy containing ferrite, DSS ring joint flanges are typically magnetic, though the exact magnetic strength varies with composition and heat treatment.
Why Choose Duplex Pipeline Solutions
- Leading supplier of DSS slip-on and weld neck flanges in India
- Available in custom sizes to fit your project needs
- Full chemical and mechanical documentation available on request
