Fittings made of forged steel connect pipes in plumbing systems. In a plumbing system carrying fluids or fluidized products,stainless steel forged fittings are used to lengthen, support, or change the flow direction. Assuring safety and reliability, forged pipe fittings provide the strongest connections.

Forged stainless steel fittings resist corrosion and rust better than plain iron or carbon steel fittings. A solid state forging process alters the product’s shape as well as refines and improves its metallurgy through thermal and mechanical processes.

Forged stainless steel has:

  • High impact toughness
  • Improved wear resistance
  • Directional material flow to provide added strength
  • Fine grained structure for best fatigue properties

In order to achieve success on a project, it is important to understand the differences between the various types of forged fittings. In the USA and other countries, ASTM A182 and ASME SA182 are the most commonly used standards when designing critical piping systems.

Stainless Steel Forged Fittings Dimensions

There are a variety of stainless steel forged fittings available in a variety of sizes, shapes, and compositions, but sometimes standard components are not sufficient. In case of special fittings that exceed standards or require unique construction, QC Forge offers forging design assistance.

Pressure and flow capacity are determined by the weld fitting dimensions of the stainless steel socket weld fittings. The team at QC Forge is ready to assist you if you cannot find the specific components you need in the standards.

Standard fittings are capable of handling 13.8 MPa, 20.7 MPa, 41.4 MPa, and 62 MPa (13.8, 3,000, 6,000, and 9,000 PSI). Depending on the diameter, the tubes can range from .125 inch (3.176 mm) to 4 inch (101.6 mm). For pipes, fittings are usually threaded or designed to be welded socked or butted.


The collar portion, raised pad, or raised boss portion of the forging must be permanently identified through raised letters, stampings, electro-etchings, or vibration toolings.  On cylindrical fittings, the marking must be placed on the outside diameter or end of the fitting so as to prevent the marking from being obliterated during welding. This standard does not require marking of bushings or plugs.

Marking specifics

Specific marks should include (but not be limited to):

Trademark or name of the manufacturer

Forgings shall comply with applicable ASME specifications A105, A182, A350, B160, B164 or ASME/ANSI B16.34 Table 1 (see section 5.1).

Compliance with product specifications.

To indicate compliance with this standard, the fittings in Section 1.1.1 shall be marked with the ASME Pipe Fitting Specification (e.g. “WP_”) or the symbol “B16”.

In Section 1.1.2, replaceable fittings bearing ASME forging marks (A105, A182, A350, etc.) shall not bear B16 markings.

In Section 1.1.2, replaceable fittings marked with ASME fittings (A234, A403, A420, and B366) shall be marked with the ASTM specification for special or non-standard fittings.

Class Designation

There are four levels of division based on the situation: 2000, 3000, 6000, and 9000. The designations 2M, 3M, 6M or 9M may also be used depending on the application, where M is 1000.

Material Standards Referred

Standard Material

Various materials can be used to make pipe fittings, including forgings, rods, seamless pipes, and tubes. WP seamless construction materials are required to comply with the ASTM Fitting Specifications A234, A403, A420, A815, or B366 for smelting, process, chemical composition, and mechanical properties, as well as ASTM Forging Specifications A105, A182, A350, B462, or B564.

Material that is not standard

This standard requires that non-standard pipe fittings manufactured from other materials be marked in accordance with the agreement between the manufacturer and the purchaser, but they should not include the identification marks specified in 4.1.1(b) and 4.1.1(c) of this standard.

Typical fitting shapes are:

  • Elbows with varying degrees of bend angle
  • Crosses – plain and reducing
  • Tees – plain and reducing
  • Couplings – generally for joining lengths of pipe
  • Unions – to create joints that can be opened.
  • And many special configurations to accommodate unique designs

What Are the Benefits of Using Rebar?

The shape configuration of stainless-steel forged fittings is determined by the service they are supposed to perform. Sensors and other equipment may require unusual connections that are not available in catalogs.

Fitting Types and configuration

This standard includes the following types of pipe fittings (differentiated by grade and specification):

The size of steel socket weld fittings and threaded fittings are specified in NPS inches. For example, the 45 and 90 degree elbows range in size from 1/2 inch to 4 inch, and their weight classes range from 3000 pounds to 6000 pounds.

Special Fitting

Suppliers and buyers can negotiate the manufacture of pipe fittings with special threads or flares. In addition to being properly marked (see Chapter 4 in ASME B16.11), these fittings must also comply with all other requirements of the standard.


The requirements for welding during installation are outside the scope of this standard. Welding must be carried out according to the applicable piping code or the operating procedures of the piping system in which the fitting is installed.

Standard Measurement Units.

Linear stainless steel weld fittings dimensions are measured in inches. In millimeters, only reference values are provided.

Pressure Rating for ASME B16.11 Forged Pipe Fittings

For threaded end fittings, Class 2000, 3000, and 6000 is designated, while for socket-weld end fittings, Class 3000, 6000, and 9000 is designated.

Minimum Wall Thickness Tolerance

Typically 12.5%, minimum wall thickness shall not less than this value.

Non-standard wall thickness

ANSI/ASME B36.10 M does not include pipe wall thickness series 160 (SCH160) nor extra strong thicknesses for NPS 1/8, NPS 1/4 and NPS 3/8. Therefore, the value listed below can be used for the nominal wall thickness of the pipe.

Combination End Fitting

Fittings with 150 stainless steel  socket weld fitting and threaded ends are graded according to their shape with a minimum rating.

Pressure Test Capability

Pressure testing is not required in this standard, but fittings must be able to withstand the hydrostatic test pressure required by the applicable pipe code to accommodate seamless pipes of the material equivalent to the fittings forging and of the schedule or wall thickness associated with the fitting grade and end connection of table.

Stainless Steel Forged Fittings Tolerances

The American Society of Mechanical Engineers (ASME) sets and controls standards for forged stainless steel pipe fittings. Among forged pipe fittings, ASME B16.9 and ASME B16.11 are the most commonly used standards.

Fittings with butt-welded connections, short radius returns, and elbows are covered by B16.9. This standard applies to factory-made butt-welded fittings that meet the following requirements:

  • Dimensions
  • Ratings
  • Testing
  • Tolerances
  • Markings

To ensure compatibility with all standard products with which the custom items will be used, these standards must be used in design.

Stainless Steel Forged Fittings Chemistry

Stainless steel components exposed to different chemical environments require different compositions, as outlined in ASTM A182 and ASME SA182. Some metal grades are better suited for welding to prevent cracks or other defects that may appear over time. There are some grades that offer a lower level of corrosion resistance than others, but a higher level of strength. Chemical compositions of alloys are adjusted according to application requirements. Understanding those requirements can help determine the best material choice.

It is based on the amount of iron, chrome, nickel, copper, and molybdenum in the steel, but additional elements and processing techniques provide a wide range of grades and capabilities.

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