Stainless steel flange

Stainless Steel Flanges with 3 types

Stainless steel flanges connect with pipe and fittings to form a piping system that delivers air, water, natural gas, oil, and steam in plumbing applications and food and dairy processing.

Flanges provide easy access for cleaning, inspection, and modification. Flange types including blind, butt weld, lap joint, slip-on, socket weld, and threaded, are available in a variety of sizes and shapes. Stainless steel is durable, resists corrosion from caustic chemicals, corrosive fluids, oils, and gases, and withstands pressure and high temperatures.

Stainless steel flange simplified as SS flange, it refers to the flanges that made of stainless steel. Common material standards and Grades are ASTM A182 Grade F304/L and F316/L, with pressure ratings from Class 150, 300, 600 etc and to 2500. It used in more industries than carbon steel as stainless steel has better resistant performances on corrosion environment and always provides with a good appearance.

stainless steel flanges

Connections Types for Stainless Steel Flanges

Stainless steel flanges also ranged with slip on flange, weld neck flange, blind flange, socket weld flange and threaded pipe flange.

Generally they could be called stainless steel pipe flange, or stainless steel plate flange.

About Stainless Steel

In metallurgy, stainless steel also called as inox steel or inoxidizable steel. It is a steel material alloyed with high content of chromium and nickel, where

  • Minimum Cr at 10.5% 
  • Minimum Ni at 8% 
  • Maximum Carbon at 1.5%

As we know, stainless steel flange is impressed by it’s great corrosion resistance, which because of the elements of Chromium, and as Cr increased, better resistant performances will be gained. 

On the other hand, additions of Molybdenum will increase corrosion resistance in reducing acids and against pitting attack in chloride solutions. So there are different grades of stainless steel with varying Cr and Mo compositions to suit the environment with required to be alloyed. 


  • Resistant to corrosion and staining
  • Low maintenance
  • Bright familiar luster
  • Steel Strength

For stainless steel pipe flange, common use material is ASTM A182 F304/L and F316/L.

ASTM A182: It refers to forged and rolled alloy and stainless steel pipe flanges, fittings, valves and parts for high temperature service. And it includes several grades of austenitic and ferritic-austenitic stainless steels. 

Dimensions: 1/2” to 2”, 3”, 4”, 6” and up to 48”.
Wall thickness schedule: SCH 10S, SCH 40S, SCH STD, SCH 80S
Pressure ratings: 150#, 300#, 600#, 900#, 1500#, 2500#
Material Grade: F304, F316, F321 and more

Chemical Composition for F304 and F316 SS Flange

astm a182 f304 f316 stainless steel flange chemical composition

Mechanical Properties

astm a182 stainless flange mechanical properties

Welding Repair Requirements for Stainless Flange

astm a182 f304 f316 flange repair welding

304 Stainless Steel Flanges Features

304 is a relatively versatile stainless steel that is widely used to make equipment and parts that require good overall performance (corrosion resistance and formability). In China, 304 steel is called 0Cr19Ni9 or 0Cr18Ni9 stainless steel, as 304 contains 19% Cr and 9% Nickel. 

304 stainless steel flanges application

As 304 stainless steel is a widely used chromium-nickel stainless steel with good corrosion resistance, heat resistance, low temperature strength and mechanical properties. It has corrosion resistant in the atmosphere, if it is an industrial atmosphere or heavily polluted areas, it needs to be cleaned in time to avoid corrosion. Suitable for processing, storage and transportation of food. Has good processing properties and weldability. Used in plate heat exchangers, bellows, household goods, building materials, chemicals, food industry, etc.

316 Stainless Steel Flanges Features

Compared to 304 stainless steel, 316 stainless steel material have additionally of Nickel and Molybdenum, which in China called 18Cr-12Ni-2.5Mo steel. So normally it has extra Mo 2.0 to 3.0 percent than 304 steel. And this Mo is an element to offer better resistance for high temperature. 
Therefore, It is particularly good in corrosion resistance, atmospheric corrosion resistance and high temperature strength. It can be used under severe conditions which it has excellent work hardening property (non-magnetic).

Sulfuric acid is one of the largest tonnage industrial chemical manufactured. At room temperature Type 304 is only resistant to 3% acid while Type 316 is resistant to 3% acid up to 50 °C and 20% acid at room temperature. So Type 304 is rarely used in contact with sulfuric acid. Type 904L and Alloy 20 are resistant to sulfuric acid at even higher concentrations above room temperature.

316L stainless steel flanges application

316L stainless steel flange has good anti-corrosion effect, better than 304 in seawater and other various media. So it is also regarded as ”marine grade” stainless steel, but it is not resistant to warm sea water.

316 SS flange used for equipment resistant to sulfuric acid, phosphoric acid, formic acid and acetic acid. Applications include marine, pumping, chemical production, food industry, irrigation, and other stainless steel pipeline systems.

Manufacturing Types

Ranged with forged type and cast type. But in most of the cases forged type is adopted.

Referred Standards:

  • B16.5 Dimensional standard for steel pipe flanges and flanges fittings
  • B16.34 Valves connect by flanges, threaded and welding end
  • B16.47 Large diameter steel flanges
stainless steel flange

Features And Maintenance Methods Of Stainless Steel Flanges

Stainless steel flanges are a common type of flange and are widely used due to their ability to withstand high pressures and the properties of stainless steel, which are appreciated by industry experts. Let’s take a look at thecharacteristics of stainless steel flanges and precautionsfor use.

The flange is also called a flange or flange. This is a tube-to-tube connection. Connect to the end of the pipe. There are holes in the flanges that can be screwed in so that the two flanges are well connected. Flanges are sealed with gaskets. Pipe fittings are pipe fittings with flanges (flanges or adapters). It can be melted, threaded or welded. Flange connections consist of a pair of flanges, a washer, and several bolts and nuts. The joints are placed between the sealing surfaces of the two flanges. After tightening the nut, the washer consists of a washer, a washer, and various bolts and nuts.

The joints are placed between the sealing surfaces of the two flanges. After tightening the nut, the washer consists of a washer, a washer, and various bolts and nuts. The joints are placed between the sealing surfaces of the two flanges. After tightening the nut, the specific pressure between the joint surface and the top surface will deform after reaching a certain value, and the irregular part of the sealing surface and the top will be filled to ensure a tight connection. Some fittings and piping equipment have their own flanges, which are also flanged connections. It is an important connection method in pipeline construction. It is easy to use, can withstand high pressure, and the connection is widely used in industrial pipes.

At home, the diameter of the pipe is small, the pressure is low, and it is not visible to connect. If you are on a production site in a boiler room,flanged tubesand equipment are everywhere. Generally speaking, the function of the flange is to fix and seal the joint of pipe fittings.

Maintenance of stainless steel flanges

The stainless steel flange designs the flange body and bushing into an integrated structure, preventing leakage caused by dislocation of the welded joint during welding. The structure is simple, the use is convenient, and the sealing performance is good.

Rust treatment methods include:

  1. Clean with emery cloth and wire brush.
  2. Use a tungsten steel shovel to remove large areas of rust.
  3. Use a file to remove bumps such as welding slag and various burrs.
  4. Use a scraper and wire brush to remove rust from the corners.
  5. Clean with a clean cloth or apply the primer in time with a solvent-dampened cloth.
  6. Pay attention to the sturdy coating that has not yet failed, which can be retained. 

Duplex 2205 Flanges

Duplex 2205 flanges are made from an austenitic-ferritic stainless steel, which was designed to deliver higher strength and corrosion resistance than 300 series stainless steels. It helps users to avoid stress corrosion cracking that is typically seen with 316 and 317. Duplex 2205 flanges combine the qualities of stress corrosion cracking resistance and high strength derived from being a ferritic alloy along with its austenitic fabrication capabilities.

duplex 2205 flanges
2205 Duplex stainless steel flanges

Key Benefits

  • Good general corrosion resistance
  • High resistance to chloride stress corrosion cracking, as well as pitting and crevice corrosion
  • Good sulfide stress corrosion resistance
  • High strength and good fatigue resistance
  • Good weldability and workability
  • High energy absorption
  • Low thermal expansion

Duplex 2205 Strength
In comparison to SS316, Duplex 2205 has been tested under reverse bending stresses at room temperature. The results show that the fatigue limit/yield strength is about twice as high for Duplex 2205.

Duplex 2205 Temperature Capabilities
Duplex 2205 flanges have a a ductile to brittle transition at -50°C and can also become embrittled at temperatures of 300-1000°C, therefore recommended use is -50°C to 300°C. Exposure above 300°C will not only cause the embrittlement of 2205 flanges, but also reduced corrosion resistance.

Duplex 2205 Corrosion Resistance
Providing industry with an improved corrosion solution to stainless, Duplex 2205 flanges offer good sulfide corrosion resistance, as well as chloride pitting and crevice corrosion resistant superior to 317L. The combination of chromium, molybdenum and nitrogen give Duplex 2205 flanges good protection from chloride pitting and crevice corrosion, which makes them useful for marine environments, brackish water, bleaching operations, closed loop water systems and some food processing applications. Though it is important to keep in mind that pitting corrosion can be a concern in chloride solutions when oxidizing media is present. In these conditions, the passive (protective) layer of the Duplex 2205 material may be compromised in localized pitting may occur.

Physical Properties
Density: 7,860 kg/m3
Ultimate Tensile Strength: 110 ksi
Yield Strength: 80 ksi
Thermal Conductivity at room temperature: 8.7 (BTU/hr•ft•°F)
Electrical Resistivity at room temperature: 33.5 (in x 10-6)

Duplex 2205 Uses

  • Chemical industries use Duplex 2205 flanges on processing equipment, storage vessels and piping.
  • Pulp and paper look to Duplex 2205 flanges for use in digesters, bleaching equipment, stock-handling systems and liquid tanks.
  • Marine as well as oil & gas extraction and processing uses 2205 flanges in chloride and hydrogen sulfide environments