Stainless steel flange

Stainless steel flange is made from stainless steel, a corrosion-resistant alloy that is known for its strength, durability, and aesthetic appeal.

Stainless steel flanges come in various grades, such as 304, 304L, 316, 316L, and 310, each with its own specific properties and applications.

Stainless Steel Flanges

Types of stainless steel flanges Which one is best for you?

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

Stainless steel flanges are available in various sizes, shapes, and designs, and they can be classified based on their face type or pressure class. Common types of stainless steel flanges include:

  1. Weld Neck Flanges: Weld Neck Flange has a long tapered neck that is welded to the pipe, providing excellent strength and support for high-pressure applications.
  2. Slip-On Flanges: Slip-On Flange slips over the end of the pipe and is then welded in place, making them easy to install and suitable for low-pressure applications.
  3. Blind Flanges: Blind Flange is used to seal the end of a pipe or fitting, rather than connecting it to another component.
  4. Threaded Flanges: Threaded Flange has threads on the inside bore, allowing them to be connected to pipes or fittings with matching threads.

Stainless steel flanges are commonly used in industries such as oil and gas, chemical processing, and food and beverage processing, where resistance to corrosion, high-temperature and pressure is required. The choice of stainless steel grade depends on several factors, including the application, the environment, and the required performance characteristics.

Overall, stainless steel flanges are an essential component of industrial piping systems, providing a means to connect pipes and other equipment components in a secure and leak-proof manner.

Why choose stainless steel flanges?

You want to get value for your money. Here is why stainless steel flanges are worth the investment.

Resistance to Corrosion

In every metal application, corrosion is an important consideration. In the U.S., around $9 billion goes to handling pipeline corrosion incidences. Metals are acted upon by rust, chemicals, as well as other environmental factors. Therefore, it would be best if you chose flanges that can withstand these factors. Stainless steel becomes a perfect choice since it has a high resistance to corrosion.


Stainless steel is durable and can withstand a lot of pressure. Although aluminum could be a cheaper option, it cannot withstand as much stress.

Withstanding High Temperatures

In industries, the temperatures could get a bit extreme. However, stainless steel flange fittings can withstand the temperatures without deformation or warping. Therefore, at no point will your system be compromised.

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

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. 


ASTM A182 - Popular Standard for Stainless Steel Pipe Flange

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

What is the ASTM A403?

ASTM A403 Stainless Steel Pipe Fittings refers to the material of forged and rolled austenitic stainless fittings for pressure pipes. Common grades are WP304/L, WP316/L. They can be used into many fields as engineering industry, energy conversion plants etc.

ASTM A403 Standard specification covers the standard for wrought austenitic stainless steel fittings for pressure piping applications.

ASTM A403/ WP304L Stainless Steel Pipe Elbow

ASTM A403 WP304L Stainless Steel Pipe Elbow

90 Degree A403 Stainless elbow

90 Degree A403 Stainless elbow

Chemical Composition (%) of ASTM A403

Steel No. Type C Si S P Mn Cr Ni Mo Other ób ós δ5
WP304 0.08 1 0.03 0.045 2 18-20 8-11 515 205 28
WP304H 0.04-0.1 1 0.03 0.045 2 18-20 8-11 515 205 28
WP304L 0.035 1 0.03 0.045 2 18-20 8-13 485 170 28
WP304LN 0.03 0.75 0.03 0.045 2 18-20 8-10.5 N2:0.1-0.16 515 205 28
WP304N 0.08 0.75 0.03 0.045 2 18-20 8-11 N2:0.1-0.16 550 240 28
WP309 0.15 1 0.03 0.045 2 22-24 12-15 515 205 28
WP310 0.15 1.5 0.03 0.045 2 24-26 19-22 515 205 28
WP316 0.08 1 0.03 0.045 2 16-18 10-14 2-3 515 205 28
WP316H 0.04-0.1 1 0.03 0.045 2 16-18 10-14 2-3 515 205 28
WP316LN 0.03 0.75 0.03 0.045 2 16-18 11-14 2-3 N2:0.1-0.16 515 205 28
WP316L 0.035 1 0.03 0.045 2 16-18 10-16 2-3 485 170 28
WP316N 0.08 0.75 0.03 0.045 2 16-18 11-14 2-3 N2:0.1-0.16 550 240 28
WP317 0.08 1 0.03 0.045 2 18-20 11-15 3-4 515 205 28
WP317L 0.03 1 0.03 0.045 2 18-20 11-15 3-4 515 205 28
WP321 0.08 1 0.03 0.045 2 17-20 9-13 Ti:5C-0.7 515 205 28
WP321H 0.04-0.1 1 0.03 0.045 2 17-20 9-13 Ti:4C-0.7 515 205 28
WP347 0.08 1 0.03 0.045 2 17-20 9-13 Nb+Ta:10C-1.1 515 205 28
WP347H 0.04-0.1 1 0.03 0.045 2 17-20 9-13 Nb+Ta:8C-1 515 205 28
WP348 0.08 1 0.03 0.045 2 17-20 9-13 Ta:0.1 515 205 28
WP348H 0.04-0.1 1 0.03 0.045 2 17-20 9-13 Ta:0.1 515 205 28


For each reduction of 0.01% below the specified C maximum, an increase of 0.06% Mn above the specified maximum will be permitted, up to a maximum of 1.35%.

The sum of Cu, Ni, Cr, and Mo shall not exceed 1.00%.

The sum of Cr and Mo shall not exceed 0.32%.

The maximum carbon equivalent (C.E.) shall be 0.50, based on heat analysis and the formula C.E.=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15.

Mechanical properties of ASTM A403

Grade UNS Tensile Strength, min Yield Strength,min Elongation min % in 4D
ksi MPa ksi MPa Longit % Trans%
ALL ALL 75 515 30 205 28 20
304L S30403 70 485 25 170 28 20
316L S31603 70 485 25 170 28 20
304N S30451 80 550 35 240 28 20
316N S31651 80 550 35 240 28 20
S31726 80 550 35 240 28 20
XM-19 S20910 100 690 55 380 28 20
S31254 94-119 650-820 44 300 28 20
S34565 115 795 60 415 28 20
S33228 73 500 27 185 28 20

Material Furnished to this specification shall conform to the requirements of specifications A960/A960M including any supplementary requirements that are indicates in the purchase order. Failure to company with the common requirements of Specification A960/A960M constitutes non-conformance with this specification . In case of conflict between this specification and Specification A960/A960M , this specification shall prevail.

Material Furnished to this specification shall conform to the requirements of specifications A960/A960M including any supplementary requirements that are indicates in the purchase order. Failure to company with the common requirements of Specification A960/A960M constitutes non-conformance with this specification. In case of conflict between this specification and Specification A960/A960M , this specification shall prevail.

What grade of steel is ASTM A403?

The standard includes several grades of austenitic stainless steel alloys, and uses the WP or CR prefix to mark the grade of steel, depending on the applicable ASTM or MSS size and rated pressure standards. ASTM A403 is designed for forged steel pipe fittings, Cast pipe fittings are not suitable.

304 stainless steel flanges

304 stainless steel flanges

304 Stainless Steel Flange 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. 


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.

ASTM A182 316Ti WN RF flange

ASTM A182 316Ti WN RF flange

316 SS Pipe Flange 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 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

Application of flanges


A flange is a method of connecting pipes, valves, pumps, and other equipment to form a piping system. It also provides easy access for cleaning, inspection, or modification.

When a piping joint requires to be dismantled, flanges are being used. These are primarily used on equipment, valves, and specialty items. Breakout flanges are provided at predetermined intervals in certain pipelines where maintenance is a regular occurrence. The flanges, gaskets, and bolting make up a flanged joint, which is made up of three separate but interconnected components. To achieve a leak-proof joint, special controls are required in the selection and application of all of these elements.

Here are the details of Flanges about their advantages and their applications.

Advantages of Flanges

Pipes, valves, pumps, and other parts are connected with flanges to form a piping system. Generally, flanges are welded or screwed together. The use of flanges makes pipe system maintenance and repair a breeze. Instead of taking the entire pipe for inspection, a small section of the pipe can be carefully investigated to use a flange to locate the fault.

The following are the five most important benefits of The following are the five most important benefits of flanges:

A flange is a method of connecting pipes, valves, pumps, and other equipment to form a piping system. It also provides easy access for cleaning, inspection, or modification. Flanges are usually welded or screwed.

In many applications, engineers need to find a way to close off a chamber or cylinder in a very secure fashion, usually because the substance inside must differ from the substance outside in composition or pressure.

They do this by fastening two pieces of metal or other material together with a circle of bolts on a lip. This “lip” is a flange.


You can connect two sections of metal piping by soldering or welding them together, but pipes connected in this way are very susceptible to bursting at high pressures. A way of connecting two sections of pipe more securely is by having flanged ends that you can connect with bolts. This way, even if gases or liquids build up to high pressures inside the pipe, it will often hold with no problem.


In order to connect two sections of a large, enclosed area, it is often best to used flanges and bolts. An example of this is the connection between the engine and the transmission in an automobile. In this case, both the engine and the transmission contain a number of moving parts that can easily get damaged if they get dust or other small objects inside of them. By connecting the outer casings of the engine and transmission in this way, engineers protect the inner workings of both.


Flanges have a specific purpose in cameras and other electronic devices. Though flanges in such items do not usually have to sustain high pressures, they do have to hold tight so they can keep out harmful particles. These flanges are usually found connecting two different materials, such as the glass of a lens and the rest of the body of the camera.

Flanged connection

There are many ways to connect flanges, including threading, welding or bolting. The threaded flange is best for low pressure or smaller pipelines because it can maintain its seal. When your pipeline is larger or high pressure, then the welded flange is preferable. A boiler room is one place where welded blind flanges might be used, due to the high pressure involved.

Flanged joints: flanges, bolts and nuts and gaskets

A flange is a external rib at the end of pipes, valves and other flow devices to assemble them.

Dimensions of the flanges are up to specific Standards : DIN, ANSI, AS, BS, JIS

Flanged connection

A flanged connection requires two flanges (the “main” and the “companion”), a set of bolts and nuts (whose number depends on the flange diameter and class) and two sealing gaskets. Flanged connections have to be executed and supervised by trained personnel, as the quality of the joint has a critical impact on the performance of the piping system / pipeline (the standard TSE – TS EN 1591 Part 1-4, “Flanges and their joints”, defines a number of requirements for the execution of proper flanged connections). Whereas all elements of the joint are critical, experience shows most leaks are originated by the improper installation of the sealing elements, i.e. the gaskets.

The typical pipe to flange connections are welded or threaded. Welded flanges are used for pipelines and piping systems with high pressures and temperatures, and with diameters above 2 inches.

Threaded connections are instead used for installations of smaller diameter and not subject to severe mechanical forces such as expansion, vibration, contraction, oscillation (forces that would crack the threaded joint). In all these critical cases, butt weld connections are recommended.


Pipe flanges are manufactured in all the different materials like stainless steel, cast iron, aluminium, brass, bronze, plastic etc. but the most used material is forged carbon steel and have machined surfaces.

Flanges are welded to pipe and equipment nozzle. Accordingly, it is manufactured from the following materials;

The list of materials used in manufacturing is covered in ASME B16.5 & B16.47.

Commonly used Forged material grads are

Frequently used astm grades

Material Fittings Flanges Valves Bolts & Nuts
Carbon Steel A234 Gr WPA A105 A216 Gr WCB A193 Gr B7
A194 Gr 2H
A234 Gr WPB A105 A216 Gr WCB
A234 Gr WPC A105 A216 Gr WCB
Carbon Steel
A234 Gr WP1 A182 Gr F1 A217 Gr WC1 A193 Gr B7
A194 Gr 2H
A234 Gr WP11 A182 Gr F11 A217 Gr WC6
A234 Gr WP12 A182 Gr F12 A217 Gr WC6
A234 Gr WP22 A182 Gr F22 A217 Gr WC9
A234 Gr WP5 A182 Gr F5 A217 Gr C5
A234 Gr WP9 A182 Gr F9 A217 Gr C12
Carbon Steel
Alloy Low-Temp
A420 Gr WPL6 A350 Gr LF2 A352 Gr LCB A320 Gr L7
A194 Gr 7
A420 Gr WPL3 A350 Gr LF3 A352 Gr LC3
Austenitic Stainless Steel A403 Gr WP304 A182 Gr F304 A182 Gr F304 A193 Gr B8
A194 Gr 8
A403 Gr WP316 A182 Gr F316 A182 Gr F316
A403 Gr WP321 A182 Gr F321 A182 Gr F321
A403 Gr WP347 A182 Gr F347 A182 Gr F347

ASTM standards define the specific manufacturing process of the material and determine the exact chemical composition of pipes, fittings and flanges, through percentages of the permitted quantities of carbon, magnesium, nickel, etc., and are indicated by "Grade".

The usual materials of flanges include stainless steel, carbon steel, aluminum and plastic. The choice of the material largely depends on the purpose of the flange. For example, stainless steel is more durable and is necessary for heavy use. On the other hand, plastic is more feasible for use in the home because of its reasonable price and easy installation. The materials used for flanges are under the designation of the American Society of Mechanical Engineers.

Flange materials acc. to ASTM

The most common materials for pipe flanges (forged grades) are: ASTM A105 (carbon steel high temperature to match A53/A106/API 5L pipes), A350 Grades LF1/2/3 (carbon steel low temperature to match A333 pipes), A694 Grades F42 to F80 (high yield carbon steel to match API 5L pipe grades), ASTM A182 Grades F5 to F91 (alloy steel flanges to match A335 pipes), A182 Grade F304/316 (stainless steel flanges to match A312 SS pipes), A182 Gr. F44/F51/F53/F55 (duplex and super duplex to match A790/A928 pipes) and various nickel alloy grades (Inconel, Incoloy, Hastelloy, Monel).

The material qualities for these flanges are defined in the ASTM standards.

What are ASTM Grades?

For example, a carbon steel pipe can be identified with Grade A or B, a stainless-steel pipe with Grade TP304 or Grade TP321, a carbon steel fitting with Grade WPB etc.


Pipe Flange Standards mainly include three systems in the world, ANSI/ASME flange system(American), DIN flange system(European system), JIS flange system, other system made according to this three systems, like GB flange standard, which mainly made according to ANSI/ASME and DIN flange standard, Duwa Piping supplies those flanges with top quality and soonest delivery time.

ASME standards

ASTM standards

AWWA standards

ISO standards

MSS standards

Pipe bend


The most frequently asked questions regarding flanges and flange fittings have to do with how flanges fit on specific steel tube and steel pipe ends.

How flanges operate?

Flange process

Flanges have flat or flush surfaces that are vertical to the pipe to which they are attached. The attachment process involves mechanically joining two or more faces using bolts, adhesives, collars, or welds. Due to the attachment requirements, a flange must fit the equipment or pipe that it’s designed. That’s why it’s necessary to check all the possible specifications and dimensions to ascertain that it’s of the right size, type, and material.

What are the three parts of a flanged connection?

Pipe flanges, gaskets, and bolts are the three parts that comprise a flanged connection. Gaskets and bolts are typically made of the same flange materials or a material approved for the pipe components. Each component comes in various materials that suit specific applications and must be matched correctly for proper functioning. The gaskets come in two conventional types: full-face gaskets and ring gaskets. Full-face gaskets have the bolt holes visible and pair up with raised-face gaskets. Ring gaskets tend to be smaller rings minus the bolt holes and pair up with flat-faced flanges. Securing the flange components requires matching the surfaces evenly and plumb, adjusting as needed for a uniform fit. Once all surfaces match, bring the flanges together and secure at least two of the bolts. Refine the alignment, so the remaining bolt holes match and their corresponding bolts are tightly secured.

How do I properly size a flange for pipe use?

Properly sizing a flange for pipe use depends not only on the type of flange but its compatible piping. The pipe must slip into the flange’s inside diameter easily and securely, and the outside diameter should cover wall holes. Once you determine the specific flange type and material you need for the job, you’ll need to take several measurements. The four measurements you’ll need are the inside diameter, outside diameter, bolt hole count, and bolt hole center. You’ll need to align each of these measurements from opposing bolt holes to get the most accurate readings. Take all measurements from edge to edge and try to get as precise as possible to match the correct product. Round up bolt diameter to the next half or whole step since bolts measure half or whole inches. Once you have all four measurements, check them against the manufacturer’s table to find the correct flange. Most manufacturers list these specifications on their websites for easy reference.

Flange Inspection

Before dispatching from manufacture each flange is inspected to ensure quality. During an inspection you have to check the following;

ASME B16.5 and B16.47 standards cover permissible tolerances for inspection.

Flange material standards

Flanges are used to connect pipes or other equipment components in various industries, and they come in a variety of materials and sizes. Flange material standards are developed by standard-setting organizations and describe the properties and characteristics of different materials that can be used to make flanges. Some examples of commonly used flange material standards include:

  1. ASTM A105: This standard covers forged carbon steel piping components, including flanges, that are suitable for use in high-pressure applications.
  2. ASTM A182: This standard covers forged or rolled alloy steel pipe flanges, forged fittings, and valves and parts intended for high-temperature service.
  3. ANSI B16.5: This standard specifies the dimensions, tolerances, and markings for steel pipe flanges and flanged fittings.
  4. DIN 2632-2638: This standard defines the dimensions and tolerances for flanges made from steel, including carbon steel, stainless steel, and other alloys.
  5. ASME B16.47: This standard covers large diameter steel flanges, typically used in high-pressure applications where larger bore sizes are needed.
  6. BS 4504: This British standard covers circular flanges for pipes, valves, and fittings, with nominal sizes ranging from 15 to 600 mm.

The choice of flange material standard will depend on various factors such as the application, the environment, the fluid being transported, and the required performance characteristics. For example, high-pressure applications may require flanges made from materials with high strength and durability, while corrosive environments may require flanges made from materials with good resistance to corrosion.


Steel flanges must be packed with seaworthy packing method then delivery to customers, usually the packing way include wooden box, wooden pallet, iron & steel cage, iron & steel pallet etc.

PMI-raw material inspection

Flange raw material PMI
Flange raw material PMI
Flange raw material PMI

Flange Marking

Flange markings are governed by ANSI ASME codes. Flange marking includes;

  • Manufacturer logo
  • ASTM material code
  • Material Grade
  • Service rating (Pressure-temperature Class))
  • Size
  • Thickness (Schedule)
  • Heat No
  • Special marking if any QT (Quenched and tempered) or W (Repair by welding)
Flange Marking

Size inspection

ASME B16.5 and B16.47 standards cover permissible tolerances for inspection.

Flange size inspection
Flange size inspection
Flange size inspection
Flange size inspection
Flange size inspection
Flange size inspection


Because of the normal wooden boxes or wooden pallets have to do fumigation treatment, we usually use plywood pallet or plywood case or box to pack steel flanges without fumigation treatment.

Flange size inspection
Flange size inspection
Flange size inspection

【H】 Ceramic lined pipe

Ceramic lined pipe is made through self-propagating high-temperature synthesis (SHS) technique.

【H】 Cast basalt lined steel pipe

Cast basalt lined steel pipe is composed by lined with cast basalt pipe, outside steel pipe and cement mortar filling between the two layers.

【H】 Ceramic Tile Lined Pipes

Ceramic tile lined pipes have very uniform coating of specially formulated ceramic material that is affixed to the inner of the pipe.

【H】 Rare earth alloy wear-resistant pipe

The material of the rare earth alloy wear-resistant pipe is ZG40CrMnMoNiSiRe, which is also the grade of rare earth alloy steel.

【H】 Tubes Erosion Shields

Tubes Erosion Shields are used to protect boiler tubing from the highly erosive effects of high temperatures and pressures thereby greatly extending tube life.

【H】 ASTM A213 T91 Alloy Tube

The ASTM A213 T91 seamless tubes are primarily used for boiler, superheater, and heat-exchanger.

Ni-Hard Wearback Pipes Ni-Hard Wearback Pipes