ASTM A234 WPB | Butt Welding Fittings | ASME B16.9

Scope & Application

The butt welding fittings of seamless or welded construction, manufactured in accordance with ASME B16.9, can be made from the wrought carbon steel grade WPB of ASTM A234. These fittings are for use in pressure piping and in pressure vessel fabrication for service at moderate and elevated temperature.

Chemical Composition Requirements

Element	Composition, %
C	≤0.30
Mn	0.29-1.60
P	≤0.050
S	≤0.058
Si	≥0.10
Cr	≤0.40
Mo	≤0.15
Ni	≤0.40
Cu	≤0.40
V	≤0.08

*For ASTM A234 Gr. WPB, the carbon equivalent (C.E.), based on heat analysis and the following formula, shall be no greater than 0.50. C.E. = C + Mn / 6 + (Cr + Mo + V) / 5 + (Ni + Cu) / 15. The C.E. values shall be reported on the test report.
*ASTM A234 WPB fittings made from bar or plate may have 0.35 max carbon and that made from forgings may have 0.35 max carbon and 0.35 max silicon with no minimum.
*For each reduction of 0.01% below the specified carbon maximum, an increase of 0.06% manganese above the specified maximum will be permitted, up to a maximum of 1.65%.
*The sum of copper, nickel, chromium, and molybdenum shall not exceed 1.00%.

Mechanical Properties

Tensile Requirements	Values
T.S. min. MPa [ksi]	415 [60]
Y.S. min. MPa [ksi]	240 [35]
Hardness max. HBW	197
El.lg-1 min. %	22
El.tr-1 min. %	14
El.lg-2 min. %	30
El.tr-2 min. %	20

*T.S.: tensile strength; *Y.S.: yield strength.
*El._lg-1 & El._tr-1: longitudinal & transverse elongation of standard round specimen, or small proportional specimen in 4D.
*El._lg-2 & El._tr-2: longitudinal & transverse elongation of rectangular specimen for wall thickness 7.94 mm and over, and for all small sizes tested in full section; in 2″ [50 mm].
*For each 0.79 mm decrease in wall thickness below 7.94 mm of the rectangular specimen, a deduction of 1.5% for longitudinal and 1.0% for transverse from the values shown above is permitted.

Material, Manufacture & Heat Treatment

The starting material for ASTM A234 WPB fittings shall be fully killed steel, consisting of forgings, bars, plates, sheets, and seamless or fusion-welded tubular products and shall conform to the chemical requirements. The ASTM A234 WPB is a plain carbon steel and may be made to either coarse grain or fine grain practice. The fabrication operations may be performed by hammering, pressing, piercing, extruding, extruding, upsetting, rolling, bending, fusion welding, machining, or by a combination of two or more of these operations.

ASTM A234 WPB is the most prevalent carbon steel grade for ASME B16.9 pipe fittings. Hot-formed WPB fittings upon which the final forming operation is completed at a temperature above 1150°F [620°C] and below 1800°F [980°C] need not be heat treated provided they are cooled in still air. Hot-formed WPB fittings finished at temperature in excess of 1800°F [980°C] shall subsequently be annealed, normalized, or normalized and tempered. Cold-formed WPB fittings, upon which the final forming operation is completed at a temperature below 1150°F [620°C], shall be normalized, or shall be stress relieved at 1100 to 1275 °F [595 to 690 °C]. The WPB fittings produced by fusion welding and having a nominal wall thickness at the welded joint of 3/4″ [19 mm] or greater shall be post-weld heat treated at 1100 to 1250 °F [595 to 675 °C].

Protective Coating

Generally, ASME B16.9 butt welding fittings made of ASTM A234 Gr. WPB steel may be furnished with black primer coating, hot dipped galvanization, zinc flake coating (electro-galvanization), rust inhibition oil or varnish coating.