WPB and WPC are very similar to each other. Both are grades of weld fitting specified in ASTM A234.

Element	Content, %
	ASTM A234 WPB	ASTM A234 WPC
Carbon [C]	≤0.30	≤0.35
Manganese [Mn]	0.29-1.06	0.29-1.06
Phosphorus [P]	≤0.050	≤0.050
Sulfur [S]	≤0.058	≤0.058
Silicon [Si]	≥0.10	≥0.10
Chromium [Cr]	≤0.40	≤0.40
Molybdenum [Mo]	≤0.15	≤0.15
Nickel [Ni]	≤0.40	≤0.40
Copper [Cu]	≤0.40	≤0.40
Vanadium [V]	≤0.08	≤0.08

The chemical requirements are identical except for the Carbon (C) content. WPB has a maximum of 0.30% and WPC has a maximum of 0.35%. In other words, every WPB will meet the chemical requirements of WPC.

ASTM A234 Grades	Tensile Strength, min.		Yield Strength, min.		Elongation %, min
	ksi	MPa	ksi	MPa	Longitudinal	Transverse
WPB	60	415	35	240	22	14
WPC	70	485	40	275	22	14

WPC has a slightly higher Tensile and Yield strength minimum requirements than WPB. Since these requirements have an overlap, it is possible for a material to meet the requirements of WPB and WPC. If the WPB material’s tensile and yield strength exceed the WPC minimums, it can be dual certified as WPC.