Chromium-Molybdenum Alloy Steel for Pressure Vessels & Elevated Temperature Service
Introduction
SA 387 Grade 11 and Grade 12 are chromium-molybdenum (Cr-Mo) alloy steel plates used primarily for pressure vessels, boilers, heat exchangers, and high-temperature equipment.
These grades are specified where strength retention at elevated temperatures, resistance to hydrogen attack, and long-term creep performance are critical.
At Sharoff Steel Suppliers, SA 387 Gr 11 & 12 plates are supplied to boiler manufacturers, EPC contractors, and heavy fabrication units where ASME compliance and traceability are mandatory.
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SA 387 is an ASME specification covering Cr-Mo alloy steel plates intended for welded pressure vessels designed to operate at moderately to high elevated temperatures.
The chromium and molybdenum content improves:
• High-temperature strength
• Resistance to oxidation
• Resistance to hydrogen-induced damage
• Long-term service reliability
SA 387 Grade 11
• Approx. 1.25% Chromium
• Approx. 0.5% Molybdenum
• Widely used for moderate temperature pressure service
SA 387 Grade 12
• Approx. 1% Chromium
• Approx. 0.5% Molybdenum
• Selected where specific design or code requirements apply
Grade selection depends on design temperature, pressure, and applicable code.
| Element | Gr 11 (%) | Gr 12 (%) |
|---|---|---|
| Chromium (Cr) | ~1.0 – 1.5 | ~0.8 – 1.25 |
| Molybdenum (Mo) | ~0.45 – 0.65 | ~0.45 – 0.65 |
| Carbon (C) | ≤ 0.15 | ≤ 0.15 |
| Manganese (Mn) | ≤ 0.60 | ≤ 0.60 |
Exact limits as per ASME SA 387. Always verify MTC.
• Designed for elevated temperature service
• Good creep resistance
• Improved resistance to hydrogen attack
• Suitable for thick pressure vessel fabrication
• Compatible with PWHT (Post Weld Heat Treatment)
Pressure Vessels
• Reactors
• Separators
• High-pressure drums
Boiler & Power
• Boiler components
• Steam drums
• Headers
Refinery & Process
• Heat exchangers
• Hydrogen service vessels
• Process equipment
SA 387 plates are typically supplied in:
• Normalized & Tempered (N+T) condition
Fabrication considerations:
• Mandatory preheating before welding
• Post Weld Heat Treatment (PWHT) generally required
• Use of matching Cr-Mo welding consumables
• Strict control over welding procedures
These steps are essential to maintain mechanical integrity and code compliance.
| Aspect | A516 Gr 70 | SA 387 Gr 11/12 |
|---|---|---|
| Alloying | Carbon-Manganese | Chromium-Molybdenum |
| Elevated temp strength | Limited | High |
| Hydrogen resistance | Lower | Higher |
| Typical service | Moderate temp | High temp / pressure |
SA 387 is selected where A516 Gr 70 reaches its design limits.
Sharoff Steel Suppliers supplies SA 387 Gr 11 & 12 plates in:
• Plates
• Cut-to-size segments
• Thicknesses suitable for pressure vessel fabrication
All supplies are supported with:
• Mill Test Certificates (MTCs)
• Heat number traceability
• Compliance to ASME SA 387
Before ordering SA 387 plates, confirm:
• ✅ Grade (Gr 11 or Gr 12)
• ✅ Plate thickness & size
• ✅ Delivery condition (N+T)
• ✅ PWHT requirements
• ✅ Code edition & inspection requirement
• ✅ MTC & traceability
Clear specification is essential for code approval and inspection clearance.
• Experience supplying boiler & pressure vessel grades
• Proper understanding of ASME code requirements
• Reliable sourcing with full documentation
• Guidance on grade selection vs A516 / 16Mo3
• Integration with APH pipes, boiler plates, and special steels
We support customers where material failure is not an option.
Is SA 387 required for all boilers?
No. It is required where operating temperature and pressure exceed carbon steel limits.
Is PWHT mandatory for SA 387?
In most pressure vessel applications, yes, as per code and thickness.
Can SA 387 replace A516 Gr 70?
Only when design conditions demand Cr-Mo alloy performance.
SA 387 Grade 11 and Grade 12 plates are essential materials for high-temperature, high-pressure service in boilers, refineries, and process industries. Correct grade selection, welding control, and documentation are critical for safe long-term operation.
At Sharoff Steel Suppliers, SA 387 plates are supplied with code clarity, technical discipline, and procurement confidence.