ASTM A234 WPB Standard Specification

ASTM A234 is Standard Specification for steel pipe fittings includes carbon and alloy steel material for moderate and high temperature services.

Forging is the manufacturing process of ASTM A234 WPB pipe fittings.

  • W = WELDABLE / wrought

ASTM A234 Scope

1.1 This specification covers wrought carbon steel and alloy steel fittings of seamless and welded construction covered by the latest revision of ASME B16.9, B16.11, MSS-SP-79, MSS-SP-83, and MSS-SP-95. These fittings are for use in pressure piping and in pressure vessel fabrication for service at moderate and elevated temperatures. Fittings differing from these ASME and MSS Standards shall be furnished in accordance with Supplementary Requirement S58 of Specification A 960/A 960M.

1.2 Optional supplementary requirements are provided for fittings where a greater degree of examination is desired. When desired, one or more of these supplementary requirements may be specified in the order.

1.3 This specification does not cover cast welding fittings or fittings machined from castings. Cast steel welding fittings are governed by Specifications A 216/A 216M and A 217/A 217M.

1.4 This specification is expressed in both inch-pound units and in SI units. However, unless the order specifies the applicable “M” specification designation (SI units), the material shall be furnished to inch-pound units.

1.5 The values stated in either inch-pound units or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the specification.

GENERAL NOTE: All values are maximum unless otherwise indicated.

Chemical Composition (%) of ASTM A234

WP11 CL10.05-0.150.30-0.600.030.030.50-1.001.00-1.500.44-0.65----
WP11 CL2/30.05-0.200.30-0.800.040.040.50-1.001.00-1.500.44-0.65----

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 A234

Tensile RequirementsWPBWPC, WP11CL2WP11CL1 WP11CL3
Tensile Strength, min, ksi[MPa]60-8570-9560-85 75-100
(0.2% offset or 0.5% extension-under-load)[415-585][485-655][415-585] [520-690]
Yield Strength, min, ksi[MPa]32403045

Where the wall thickness lies between two values above, the min elongation value is determined by the following equations:

  • Longitudinal E=48t+15.00
  • Transverse E=32t+10.00
  • E = elongation in 2in [50mm], %
  • t = actual thickness of specimen, in [mm]

Steel elbow is used to be installed between two lengths of pipe or tube allowing a change of direction,usually these carbon steel elbows distinguished by connection ends, The ends may be machined for butt welding , threaded , or socketed , so the carbon steel elbows are consist of butt weld,thread elbow socket elbow and other series.the material is selected according to the application use such as high temperature use,sanitary fitting,regular industrial use etc.

What is the manufacturing process of ASTM A234 WPB pipe fittings?The WPB is not short hand for any process. It is simply an identifier developed by ASTM. The fittings in question are manufactured in the same manner as the companion pipe for this specification.

In very large sizes, the fittings may be manufactured in pieces and welded together as is the case for many large fittings.

The term used for the manufacturing is called “wrought” which means it is worked as opposed to being cast or forged.

As to the W standing for weldable, I’m not sure that is correct since that are many, many pipe fittings that are weldable but carry designations other than a W. Note the reference below.

Latest standard is:

  • ASTM A234 fittings material consist of killed steel, forgings, bars, plates, seamless or HFW (fusion welded) pipe products, with filler metal added.
  • ASTM A234 standard covers steel fittings of seamless and welded types. ASTM A234 Pipe fittings are applied in pressure pipelines and in pressure vessel fabrications.
  • ASTM A234/A234M-07 Standard Specification for Piping Fittings of Wrought Carbon Steel and Alloy Steel for Moderate and High Temperature Service

This standard covers wrought carbon steel fittings of seamless and welded construction which are manufactured to the dimensional specifications of ASME B16.9 and B16.28. These fittings are primarily for use in pressure piping and in pressure vessel fabrication for service at moderate and elevated temperatures.

Grades in ASTM A234

ASTM A234 specification has many grades, such as WPB, WPC, WP11, WP12, WP22, WP91 and so on.

In these standard Grade WPB is the most common material used for medium and high temperature pipelines. W means weldable, P means pressure, B is grade b, refer to the minimum yield strength.

The source raw material of ASTM A234 WPB steel pipe fittings may be from steel pipe, such as ASTM A106 Gr.B and C. Also from steel plate, as ASTM A285 Gr.C, ASTM A516 Gr 70, ASTM A572 etc.


Killed steel, with forgings, bars, plates, sheet, and seamless or fusion-welded tubular products with filler metal added. Forging or shaping operations performed by hammering, pressing, piercing, extruding, upsetting, rolling, bending, fusion welding, machining, or by a combination of two or more of these operations.

Heat Treatment

After forming at an elevated temperature, fittings are cooled to a temperature below the critical range under suitable conditions to prevent injurious defects caused by too rapid cooling, but in no case more rapidly than the cooling rate in still air. Heat treatment temperatures specified are metal (part) temperatures. Heat-treated fittings are to be treated according to paragraph 7 in Specification A960/A960M.