A387 Grade 11 Class 1 for pressure vessel

ASTM A387 Grade 11 Class 1 is a specific grade of chromium-molybdenum alloy steel plate used for welded boilers and pressure vessels, particularly in elevated temperature service. It's characterized by its 1.25% chromium and 0.5% molybdenum content, providing good strength and resistance to oxidation at high temperatures, according to Alloy Steel Plates and SSAB.

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Product Description

1.What are the chemical composition and mechanical properties of A387 Grade 11 Class 1?

A387 Gr.11 CL.1Chemical composition
Grade	The Element Max (%)
Grade	C	Si	Mn	P	S	Cr	Mo
A387 Gr.11 C1.1	0.04-0.17	0.44-0.86	0.35-0.73	0.035	0.035	0.94-1.56	0.40-0.70

Grade	A387 Gr.11 CL.1Mechanical Property
Grade	Thickness	Yield	Tensile	Elongation
A387 Gr.11 CI.1	mm	Min Mpa	Mpa	Min %
	t≤50	240	415-585	22
	50	240	415-585	19

2.What is the difference between A387 Grade 11 Class 1 and Class 2?

Heat Treatment

Class 1: Typically normalized and tempered (air-cooled after heating above the critical range, followed by tempering) .
Class 2: Requires quenching and tempering (accelerated cooling, often via water or air blast, followed by tempering at ≥620°C) . This process enhances strength and toughness.

Mechanical Properties

Tensile Strength:Class 1: 415–585 MPa (60–85 ksi) ;Class 2: 515–690 MPa (75–100 ksi) .
Yield Strength:Class 1: ≥240 MPa (35 ksi) ;Class 2: ≥310 MPa (45 ksi) .
Impact Toughness:Class 2 often requires stricter impact testing (e.g., ≥100 J at 0°C for thin plates) , while Class 1 may meet lower standards (e.g., ≥27 J at room temperature) .
Hardness:Class 2 may specify lower surface hardness (e.g., ≤190 HB) for improved formability in critical applications .

Application Focus

Class 1: Ideal for moderate-temperature/high-pressure vessels(e.g., boilers, heat exchangers) where balanced strength and cost are priorities .
Class 2: Suited for high-stress, elevated-temperature environments(e.g., reactors, hydrogen-processing equipment) due to its superior creep resistance and high-temperature strength . It is often preferred in ASME BPVC-compliant designs requiring higher allowable stress values .

3.What is the delivery condition of A387 Grade 11 Class 1?

The delivery condition of A387 Grade 11 Class 1 (as specified in ASTM A387 for pressure vessel steel plates) is typically normalized and tempered (N&T).

This involves heating the steel to a suitable temperature above the critical range, followed by air cooling (normalizing) to refine the microstructure, and then tempering at a lower temperature to improve toughness and relieve internal stresses.

This heat treatment ensures the material meets the required mechanical properties for high-temperature service, such as creep resistance and strength, in compliance with ASME BPVC standards for pressure vessels.

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