ASTM A234 WPB & WPC Carbon Steel Buttweld Fittings Manufacturer

Solitaire Overseas manufactures carbon steel buttweld fittings to ASTM A234, the governing material specification behind our ASME B16.9 fittings range. Grade WPB is the workhorse carbon steel material for moderate and high temperature pressure piping, while Grade WPC offers a higher strength option for thicker wall or higher pressure class requirements. This page also addresses Grade WPA, a designation still referenced in older piping specifications and some supplier catalogs, and clarifies its current status against the active ASTM A234/A234M specification.

Types of ASTM A234 Fittings

90° LR/SR Elbow
45° Elbow
Equal & Reducing Tee
Concentric / Eccentric Reducer
Cap
Straight & Reducing Cross
Lap Joint Stub End
Nipple & Coupling

Looking for the full ASME B16.9 dimensional range, or high yield MSS SP-75 fittings for pipeline service? See our Carbon Steel ASME B16.9 Pipe Fittings and Carbon Steel MSS SP-75 (WPHY) Pipe Fittings pages.

Technical Data

Specifications Chemical Composition Mechanical Properties Approximate International Equivalents

ASTM A234 Fittings Specifications

Parameter	Specification
Standard	ASTM A234 / A234M (material specification); dimensions per ASME B16.9, B16.11, MSS SP-79, SP-83, SP-95, SP-97
Grades Covered	WPB, WPC (current standard grades); WPA referenced for historical/legacy specification matching — see note below
Size Range	NPS 1/2" to 48"
Manufacturing	Killed steel; seamless or fusion welded pipe, plate, bar, sheet or forgings
Service	Moderate and high temperature pressure piping and pressure vessel fabrication
Heat Treatment	Not mandatory for standard hot formed fittings under 1800°F; required for cold formed or NPS 12+ locally heated fittings
Hardness	197 HBW max (WPB, WPC)
Certification	Mill Test Certificate EN 10204 3.1, 3.2 on request

Chemical Composition (ASTM A234, % — current grades)

Element	WPB max	WPC max
Carbon	0.30 (0.35 from bar/plate/forging)	0.35
Manganese	0.29 – 1.06	0.29 – 1.06
Phosphorus max	0.050	0.050
Sulfur max	0.058	0.058
Silicon min	0.10	0.10
Chromium max	0.40	0.40
Molybdenum max	0.15	0.15
Nickel max	0.40	0.40
Copper max	0.40	0.40
Vanadium max	0.08	0.08

Sum of Cu, Ni, Cr and Mo shall not exceed 1.00%. For each 0.01% reduction below the specified carbon maximum, manganese may increase 0.06% above the specified maximum, up to 1.65%. Grade WPA chemistry is not reproduced here as it is not defined in the current specification edition — see the technical note above.

Mechanical Properties (ASTM A234)

Grade	Tensile Strength min	Yield Strength min	Elongation min	Status
WPA (legacy reference)	330 MPa (48 ksi)*	205 MPa (30 ksi)*	—	Not in current A234/A234M
WPB	415 MPa (60 ksi)	240 MPa (35 ksi)	22%	Current standard grade
WPC	485 MPa (70 ksi)	275 MPa (40 ksi)	22%	Current standard grade

*WPA values are indicative, based on the matching ASTM A106 Grade A pipe properties referenced in older piping documentation, not on a current ASTM A234/A234M table.

Approximate International Equivalents

ASTM Grade	EN	JIS
A234 WPB	P235GH / P265GH (EN 10253-2)	STPG370 / SGP
A234 WPC	P280GH (EN 10253-2)	STPG410

Applications of ASTM A234 Fittings

Refinery and petrochemical process piping (WPB most common)
Power plant and boiler feed piping
Higher pressure or thicker wall pipe spools (WPC)
Oil and gas surface facilities and gathering systems
General industrial and utility piping

WPA vs WPB vs WPC - Grade Comparison

Buyers frequently search for all three designations together. This table summarizes where each one stands today.

Criteria	WPA (legacy)	WPB	WPC
Current A234/A234M Status	Not listed in current edition	Current standard grade	Current standard grade
Matches Pipe Grade	A106 Gr A / A53 Gr A	A106 Gr B / A53 Gr B	A106 Gr C / API 5L Gr B (higher strength)
Relative Strength	Lowest of the three	Standard	Highest of the three
Typical Use Today	Superseded — specify WPB	Most common carbon steel fitting grade	Higher pressure / thicker wall applications

Frequently Asked Questions

Q: What is the difference between ASTM A234 WPB and WPC?

A: WPC allows a higher maximum carbon content, 0.35% versus 0.30% for WPB, and carries higher minimum mechanical properties: 485 MPa tensile and 275 MPa yield versus 415 MPa and 240 MPa for WPB. WPC cannot be substituted with WPB unless the purchaser agrees, since WPC is the higher strength grade.

Q: Is ASTM A234 Grade WPA still a current designation?

A: No. Current editions of ASTM A234/A234M list only Grade WPB and Grade WPC as the standard carbon steel fitting grades. WPA appeared in earlier editions of the specification as a lower strength grade matching ASTM A106 Grade A pipe; purchase specifications that still call for WPA are generally satisfied by supplying Grade WPB, which meets or exceeds the historical WPA mechanical requirements.

Q: Can WPB and WPC be used interchangeably?

A: Not without agreement. If a drawing specifies WPC, WPB cannot be substituted because WPC carries higher tensile requirements. If WPB is specified, WPC may sometimes be offered as an upgrade with the buyer's consent, but this should be confirmed against the piping class and any stress corrosion cracking concerns.

Q: What pipe grade does ASTM A234 WPB match?

A: WPB is the standard buttweld fitting counterpart to ASTM A106 Grade B and ASTM A53 Grade B seamless or welded carbon steel pipe, and is also commonly paired with API 5L Grade B line pipe.

Q: Is heat treatment required for A234 WPB and WPC fittings?

A: Hot formed fittings finished between 1150°F and 1800°F and cooled in still air do not require heat treatment. Fittings finished above 1800°F, cold formed fittings, and NPS 12 and larger fittings that are locally heated during forming must be annealed, normalized, or stress relieved.

Q: What is the maximum hardness for A234 WPB and WPC fittings?

A: 197 HBW maximum for both grades, verified by hardness testing on a minimum of two pieces per batch or continuous production run.

Get a quote for ASTM A234 WPB or WPC carbon steel buttweld fittings from Solitaire Overseas, or visit our Carbon Steel Pipe Fittings hub to compare forged, buttweld, high yield and material grade options side by side.