SA387 Grade 12 Class 1 is a chromium‑molybdenum alloy steel plate covered by the ASME SA‑387 standard, intended primarily for welded pressure vessels and boiler components that operate under high temperatures and pressures. The grade designation reflects its specific chromium and molybdenum content, which provides good high‑temperature strength, creep resistance, and oxidation resistance. Class 1 indicates that the material is supplied in the normalized condition, which refines the grain structure and enhances ductility and toughness, making the steel easier to form, weld, and fabricate. This material is commonly used in the oil, gas, and petrochemical industries, as well as in power generation applications where reliable performance at elevated temperatures is required.
Equivalents
| BS | EN | ASTM/ASME | DIN |
| 620 B | 13 CRMO 45 | SA387-12-1 | 13 CRMO 44 |
Specifications for ASME SA387 Grade 12 Alloy Steel Plates
| Designation | Nominal Chromium Content (%) |
Nominal Molybdenum Content (%) |
| SA387 Grade 12 | 1.00% | 0.50% |
Tensile Requirements for ASME SA387 Grade 12 Alloy Steel Plates Class 1 Plates
| Designation: | Requirement: | Grade 12 |
| SA387 Grade 12 | Tensile strength, ksi [MPA] | 65 to 85 [450 to 585] |
| Yield strength, min, ksi [MPa]/(0.2% offset) | 40 [275] | |
| Elongation in 8 in. [200mm], min % | 19 | |
| Elongation in 2 in. [50mm], min, % | 22 | |
| Reduction of area, min % | ––– |
Chemical Requirements for ASME SA387 Grade 12 Alloy Steel Plates
| Element | Chemical Composition (%) | |
| ASME SA387 Grade 12 | ||
| Carbon: | Heat Analysis: | 0.05 - 0.17 |
| Product Analysis: | 0.04 - 0.17 | |
| Manganese: | Heat Analysis: | 0.40 - 0.65 |
| Product Analysis: | 0.35 - 0.73 | |
| Phosphorus: | Heat Analysis: | 0.035 |
| Product Analysis: | 0.035 | |
| Sulphur (max): | Heat Analysis: | 0.035 |
| Product Analysis: | 0.035 | |
| Silicon: | Heat Analysis: | 0.15 - 0.40 |
| Product Analysis: | 0.13 - 0.45 | |
| Chromium: | Heat Analysis: | 0.80 - 1.15 |
| Product Analysis: | 0.74 - 1.21 | |
| Molybdenum: | Heat Analysis: | 0.45 - 0.60 |
| Product Analysis: | 0.40 - 0.65 |
processing flow
1. Procurement and Initial Inspection
SA387 Grade 12 Class 1 steel is first sourced from qualified suppliers, with verification of the mill test certificate to confirm compliance with the standard. Incoming inspection includes chemical analysis and mechanical testing to ensure the material's chromium‑molybdenum content and mechanical properties meet pressure vessel requirements.
2. Cutting and Edge Preparation
Once approved, the plates are cut to size using plasma, laser, or sawing. The edges are then prepared with the required groove-such as a V‑groove-and thoroughly cleaned to remove oil, rust, and other contaminants that could compromise weld quality.
3. Forming
Forming is done either cold or hot. Cold forming is suitable for moderate bends, while hot forming is used for thicker plates or complex shapes. Hot‑formed parts are typically normalized afterward to restore the desired microstructure and ensure consistent mechanical properties.
4. Assembly and Welding Preparation
The components are aligned and clamped into position. The weld area is cleaned again, and preheating is applied- a critical step for Cr‑Mo steels-to prevent cold cracking. Low‑hydrogen welding consumables are selected to further reduce cracking risk.
5. Welding
Welding proceeds with careful control of heat input and interpass temperature to avoid overheating and maintain the material's strength and toughness. Multi‑pass techniques are used to ensure good fusion and minimize stress concentrations.
6. Post‑Weld Heat Treatment (PWHT)
After welding, PWHT is performed by heating the component to the appropriate temperature, holding it, and then cooling slowly. This step relieves residual stresses, tempers the microstructure, improves toughness, and helps prevent stress corrosion cracking.
7. Final Inspection and Testing
The completed welds and structure are inspected using non‑destructive methods such as radiographic and ultrasonic testing for internal defects, and penetrant or magnetic particle testing for surface flaws. Mechanical tests-including tensile, impact, and hardness examinations-may also be conducted, and the pressure vessel undergoes a hydrostatic test to confirm its integrity.
The fabrication process of SA387 Grade 12 Class 1 steel primarily involves cutting, forming (either cold or hot), weld preparation, welding, and post-weld heat treatment. The key objective is to ensure that the material's chemical composition-especially its chromium and molybdenum content-and its mechanical properties meet the requirements for pressure vessel applications. Special attention must be paid to welding, where strict preheating, careful control of interpass temperature, and proper post-weld heat treatment (PWHT) are essential to relieve welding stresses, prevent cracking, accommodate the characteristics of Cr-Mo steels, and ensure overall safety.
Key Applications:
Pressure Vessels:
For safe containment of liquids and gases under high temperatures and pressures.
Industrial Boilers:
Components in thermal power plants subjected to extreme heat.
Heat Exchangers & Condensers:
Facilitating efficient heat transfer in petrochemical and energy industries.
Oil & Gas Industry:
Used in equipment for sour service (containing H2S) and offshore drilling due to its corrosion resistance.
Chemical Equipment:
Fabrication of reactors and storage tanks in chemical processing plants.
Power Generation:
Components in various power-related equipment.
Request a professional quotation for SA387 Grade 12 Class 1 from GNEE Steel.
What is SA 387 GR 12 material?
Engineered for use in elevated temperature service, ASME SA387 Grade 12 is a chrome molybdenum carbon alloy steel for use in weldable pressure vessels and industrial boilers.
What are the key alloying elements in SA 387 Grade 12 Class 1?
It contains chromium (Cr) and molybdenum (Mo) as primary alloying elements, which enhance its high-temperature strength and creep resistance.
What is the typical chemical composition range for SA 387 Grade 12 Class 1?
Typically, it includes around 0.50–0.80% Cr, 0.45–0.60% Mo, along with controlled amounts of carbon, manganese, silicon, phosphorus, and sulfur.
What is the difference between SA 387 Grade 12 Class 1 and Class 2?
Class 1 has more restrictive chemical composition limits and tighter mechanical property requirements compared to Class 2, ensuring higher reliability in critical applications.
What is the maximum service temperature for SA 387 Grade 12 Class 1?
It is commonly used in applications with service temperatures up to approximately 900°F (482°C), depending on the specific design and loading conditions.
What are the typical mechanical properties of SA 387 Grade 12 Class 1?
Typically, it has a minimum yield strength of 30 ksi (205 MPa) and a minimum tensile strength of 60–80 ksi (415–550 MPa), with good ductility and impact resistance.
What heat treatment is required for SA 387 Grade 12 Class 1?
It is usually supplied in the normalized and tempered condition to achieve the required strength and toughness for high-temperature service.
Why is SA 387 Grade 12 Class 1 suitable for pressure vessels?
Its combination of high-temperature strength, creep resistance, and good weldability makes it ideal for pressure vessels operating under elevated temperatures and pressures.
What are common applications of SA 387 Grade 12 Class 1?
Common uses include boiler components, pressure vessel shells, headers, and other structural parts in refineries, petrochemical plants, and power generation facilities.
What is temper embrittlement, and how does it affect SA 387 Grade 12 Class 1?
Temper embrittlement is a reduction in toughness after exposure to certain temperatures, which can occur in Cr-Mo steels. Proper heat treatment and alloy control minimize this risk.