ASTM A299 Grade B is a manganese–silicon alloy pressure‑vessel steel plate designed for higher strength and improved thermal resistance in medium‑temperature service conditions. Compared with Grade A, A299 Grade B provides enhanced tensile performance and maintains stable weldability and forming behavior, making it suitable for boilers, heat‑exchangers, and industrial pressure vessels requiring stronger plate materials.
Its balanced mechanical properties and reliable fabrication characteristics support long‑term performance in petrochemical, power‑generation, and general industrial applications.
Chemical Composition

C	Mn	P	S	Si
≤0.27	0.90-1.50	≤0.035	≤ 0.035	0.15-0.30

 
Mechanical Properties

Property	Yield Strength	Tensile Strength	Elongation
Requirement	≥ 240 MPa	515-655MPa	≥ 19%

Dimensions

Thickness	3–150 mm
Width	1220–4200 mm
Length	5000–18000 mm
Supports custom cutting and shaping.

 Applications

• Medium‑temperature pressure vessels

• Boilers and heat‑exchangers

• Industrial tanks and welded containers

• Petrochemical and power‑plant equipment

• Fabricated components requiring higher strength than A285 and A299 Grade A