Composition and properties of ASTM A387 grade 12 class 1 CrMo alloy steel

ASTM A387 Grade 12 Class 1 is a chromium-molybdenum (Cr-Mo) alloy steel plate specifically developed for boilers and pressure vessels operating at elevated temperatures. This steel grade is widely specified in ASME pressure vessel codes due to its excellent balance of strength, heat resistance, and long-term stability.

As a trusted pressure vessel steel plate supplier, GNEE Steel provides ASTM A387 Grade 12 Class 1 plates manufactured in China with strict quality control, full traceability, and international export experience. This material is commonly selected for power generation, petrochemical, and refinery equipment requiring reliable performance under high temperature and pressure.

Chemical Composition of A387 Grade 12 Class 1

The chemical composition of ASTM A387 Grade 12 Class 1 is carefully designed to enhance creep resistance, oxidation resistance, and mechanical strength. It belongs to the 1Cr-0.5Mo alloy steel family, optimized for medium-to-high temperature service.

Typical chemical composition (wt.%):

Carbon (C): ≤ 0.15

Silicon (Si): ≤ 0.50

Manganese (Mn): 0.30 – 0.60

Chromium (Cr): 0.80 – 1.25

Molybdenum (Mo): 0.45 – 0.65

Phosphorus (P): ≤ 0.035

Sulfur (S): ≤ 0.035

Chromium improves oxidation resistance and surface stability at elevated temperatures, while molybdenum significantly enhances creep strength and resistance to hydrogen attack. This alloy design makes A387 Grade 12 Class 1 particularly suitable for long-term high-temperature pressure service.

Heat Treatment Condition – Class 1 Explained

The "Class 1" designation indicates that the steel plate is supplied in the normalized and tempered (N+T) condition. This heat treatment process refines the grain structure, improves toughness, and ensures consistent mechanical properties throughout the plate thickness.

Normalized and tempered A387 Grade 12 Class 1 steel offers:

• Improved strength uniformity
• Enhanced impact toughness
• Better weldability for pressure vessel fabrication

This heat treatment is essential for meeting stringent boiler and pressure vessel design requirements.

Mechanical Properties of ASTM A387 Grade 12 Class 1

ASTM A387 Grade 12 Class 1 steel plate provides stable mechanical performance suitable for demanding service environments.

Typical mechanical properties:

Tensile Strength: 415 – 585 MPa

Yield Strength (min): 205 MPa

Elongation: ≥ 18%

Impact properties: Available upon request

These properties allow the steel to withstand high internal pressure and thermal stress, making it a dependable choice for critical pressure-bearing components.

Typical Applications of A387 Grade 12 Class 1 Steel Plate

ASTM A387 Grade 12 Class 1 is widely used in:

Power plant boilers and steam drums

Petrochemical and refinery pressure vessels

Heat exchangers and reactor shells

High-temperature separators and headers

Chemical processing equipment

Its combination of strength, heat resistance, and fabrication performance makes it a preferred material for ASME-coded pressure equipment.

Why Choose GNEE Steel for A387 Grade 12 Class 1 Plates

As a professional supplier of pressure vessel steel plates, GNEE Steel offers comprehensive solutions for ASTM A387 Grade 12 Class 1 CrMo alloy steel:

• Compliance with ASTM A387 / ASME SA387 standards
• Plate thickness range: 6mm – 150mm
• Customized cutting, testing, and inspection services
• EN 10204 3.1 / 3.2 Mill Test Certificates
• Third-party inspection support (SGS, TUV, BV)
• Strong export capability and stable delivery schedules

GNEE Steel supports global EPC contractors, boiler manufacturers, and pressure vessel fabricators with reliable material supply and technical expertise.

Conclusion

ASTM A387 Grade 12 Class 1 CrMo alloy steel is a proven and reliable material for high-temperature boiler and pressure vessel applications. Its optimized chemical composition, stable mechanical properties, and excellent high-temperature performance make it an ideal choice for demanding industrial environments.

If you are sourcing ASTM A387 Grade 12 Class 1 steel plates from China, GNEE Steel is your dependable partner.

📩 Contact GNEE Steel today for technical support, competitive pricing, and customized solutions tailored to your boiler and pressure vessel projects.

Request A Quote

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.