Difference between A387 Grade 11 Class 2 and A387 Grade 22 Class 2

Jan 15, 2026 Leave a message

ASTM A387 Grade 11 Class 2 and Grade 22 Class 2 are chromium-molybdenum alloy steels for high-temperature pressure vessels, differing mainly in their alloy content, with Grade 22 having significantly higher Chromium (around 2.25%) and Molybdenum (around 1%) compared to Grade 11 (around 1.25% Cr, 0.5% Mo), making Grade 22 better for more severe elevated-temperature service, while Class 2 indicates higher strength (75-100 ksi tensile) than Class 1 for both grades.

A387 Gr.11 CL.2Chemical Composition

A387 Gr.11 CL.2 Chemical Composition
Grade	The Element Max (%)
	C	Si	Mn	P	S	Cr	Mo
A387 Gr.11 Cl.2	0.04-0.17	0.44-0.86	0.35-0.73	0.035	0.035	0.94-1.56	0.40-0.70

A387 Gr.22 CL.2 Chemical Composition

A387 Gr.22 CL.2 Chemical Composition
Grade	The Element Max (%)
Grade	C	Si	Mn	P	S	Cr	Mo
A387 Gr.22 Cl.2	0.04-0.15	0.50	0.30-0.60	0.035	0.035	1.88-2.62	0.85-1.15

A387 Gr.11 CL.2 Mechanical Property

Grade	A387 Gr.11 CL.2 Mechanical Property
	Thickness	Yield	Tensile	Elongation
A387 Gr.11 Cl.2	mm	Min Mpa	Mpa	Min %
	t≦50	310	515-690	18
50<t≦200	-	-	-

A387 Gr.22 CL.2 Mechanical Property

Grade	A387 Gr.22 CL.2Mechanical Property
Grade	Thickness	Yield	Tensile	Elongation
A387 Gr.22 Cl.2	mm	Min Mpa	Mpa	Min %
	t≦50	310	515-690	18
	50<t≦200	-	-	-

Key Differences:

Alloy Content:

Grade 11: ~1.25% Chromium, ~0.50% Molybdenum.

Grade 22: ~2.25% Chromium, ~1.00% Molybdenum.

Strength (Class 2): Both have higher strength than their Class 1 counterparts.

Grade 11 Class 2: 75-100 ksi (515-690 MPa) Tensile.

Grade 22 Class 2: 75-100 ksi (515-690 MPa) Tensile.

Performance: Grade 22's higher alloy content gives it superior high-temperature strength and creep resistance for more demanding applications than Grade 11.

Application: Used in boilers, pressure vessels, and piping for oil, gas, and power industries at elevated temperatures, with Grade 22 for harsher conditions.