What is A387 grade 11 material?

In high-temperature and high-pressure industrial applications, material selection is not a cost decision-it is a safety decision. Choosing the wrong steel plate can lead to premature failure, unplanned shutdowns, or even catastrophic accidents. Among chromium-molybdenum alloy steels, ASTM A387 Grade 11 has become one of the most widely specified materials for pressure vessels operating under elevated temperatures.

So, what is A387 Grade 11 material, and why is it trusted across power generation, petrochemical, and refining industries worldwide? This article provides a complete, practical explanation from composition to applications-helping engineers, EPC contractors, and procurement teams make informed decisions.

A387 Grade 11 is a chromium-molybdenum (Chrome Moly) alloy steel plate material, defined by the ASTM standard, used for high-temperature and high-pressure applications like pressure vessels, boilers, and heat exchangers, especially in the oil, gas, and chemical industries, due to its excellent corrosion and oxidation resistance. It contains approximately 1.25% Chromium (Cr) and 0.50% Molybdenum (Mo), with Class 1 and Class 2 variations, the latter requiring stricter heat treatment and impact toughness.

The carefully controlled alloying elements in A387 Grade 11 steel plate are the foundation of its performance.

Typical chemical composition (heat analysis, max %):

• Carbon (C): ≤ 0.15
• Silicon (Si): 0.50
• Manganese (Mn): 0.30–0.60
• Chromium (Cr): 1.00–1.50
• Molybdenum (Mo): 0.45–0.60
• Phosphorus (P): ≤ 0.035
• Sulfur (S): ≤ 0.035

The Cr-Mo alloy system improves oxidation resistance at elevated temperatures and enhances resistance to hydrogen attack-critical for refinery and hydrogen service.

A387 Grade 11 pressure vessel steel offers a balanced combination of strength, ductility, and toughness.

Typical mechanical properties:

• Yield strength: ≥ 310 MPa
• Tensile strength: 415–585 MPa
• Elongation: ≥ 18%
• Impact testing: As specified (often required for low-temperature service)

These properties allow the steel to maintain structural integrity under long-term thermal stress, making it suitable for continuous operation environments.

From a fabrication standpoint, A387 Grade 11 steel plate is well-suited for welding, provided proper procedures are followed.

Key welding considerations:

• Preheating is recommended (typically 150–250°C)
• Low-hydrogen welding consumables (e.g., E8018-B2)
• Controlled heat input
• Post-weld heat treatment (PWHT) is commonly required

When welded correctly, A387 Gr.11 exhibits excellent resistance to weld-related cracking and maintains strength in the heat-affected zone (HAZ).

GNEE Steel provides welding guidance and technical support to ensure smooth fabrication and compliance with project specifications.

Thanks to is balanced properties, A387 Grade 11 material is widely used in:

Oil & gas pressure vessels

Refinery reactors and separators

Heat exchangers and boilers

Hydrogen service equipment

Petrochemical storage vessels

Power plant pressure components

In many projects, A387 Gr.11 steel plate replaces carbon steel to extend equipment life while keeping alloy costs under control.

As an experienced pressure vessel steel plate supplier, GNEE Steel offers:

• ASTM A387 / ASME SA387 compliant plates
• N+T delivery condition as standard
• Thickness range up to 150 mm
• UT testing, impact testing, and MTCs
• OEM cutting, heat treatment, and export packaging

Our A387 Grade 11 steel plates are exported to refineries, EPC contractors, and equipment manufacturers across Europe, the Middle East, Southeast Asia, and South America.

If your project involves high-temperature pressure vessels, requires reliable long-term performance, and demands cost-effective alloy steel, A387 Grade 11 material is a proven and globally trusted solution.

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What is A387 11 material?

ASTM A387 is a specification for chromium-molybdenum alloy steel plates intended for welded boilers and pressure vessels designed for elevated temperature service. The Gr 11 and Gr 22 variants differ in chromium and molybdenum content, affecting their strength and corrosion resistance.

What is SA 387 Grade 11 Class 2 equivalent to?

Sa 387 Gr 11 Equivalent Material is the ASME SA387 in the US markets with the European Union having modules in 13CrMoSi5-5 grade. The Sa 387 Gr 11 Cl 2 Equivalent Material is the SA387-11-2 of the ASME and ASTM standard.

What temperature is SA 387 GR 11?

In the lower end of the temperature range SA 387 Gr 11 (1150 °F min tempering temperature) , and SA 387 Gr 22 (1250 °F min tempering temperature) are used. These grades can be specified in either class 1 or 2 and can also be provided in the Normalized & Tempered or Quenched and Tempered.

GNEE Steel also supplies a variety of boilers and pressure vessel steel plates, such as A204 Grade B,A515 Grade 70,A537 Class 1,SA387 Grade 11 Class 1,P265GH,S537 Class 2,P355Q,P275N,P355N,P690Q,Q345R, etc. If you want to know more about other types of steel plates, you can call the consultation hotline at +8615824687445 or send an email to alloy@gneesteelgroup.com. You are welcome to consult us, and we are very willing to answer your questions.