SA 387 Grade 12 Class 2 is a chromium-molybdenum alloy steel plate specified under the ASME SA 387 standard, primarily designed for use in elevated-temperature service in pressure vessel and boiler applications. With a nominal composition containing chromium and molybdenum, this grade offers good creep resistance, high-temperature strength, and oxidation resistance, making it suitable for components operating at temperatures up to around 900°F (482°C). Class 2 indicates a normalized and tempered heat treatment, which provides improved toughness and ductility compared to Class 1. SA 387 Grade 12 Class 2 is commonly used in refineries, petrochemical plants, power generation facilities, and other industrial systems where reliable performance under high temperature and pressure is required.
Equivalents
| BS | EN | ASTM/ASME | DIN |
| 620 B | 13 CRMO 45 | SA387-12-2 | 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 2 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
Key Processing & Manufacturing Steps
Production Method: Plates are typically Hot-Rolled (HR). Manufacturing includes computer-controlled processing to meet specific customer requirements.
Heat Treatment: To achieve the "Class 2" mechanical properties, the steel must undergo thermal treatment, typically consisting of normalization and tempering or quenching and tempering. The minimum tempering temperature for Grade 12 is 1150°F.
Cutting Techniques: Recommended methods include plasma, water-jet, or flame cutting. For flame or plasma cutting, preheating the material is often necessary to prevent cracking.
Fabrication & Welding
Weldability: The material has good weldability, which is essential for fabricating complex pressure vessels.
Welding Procedures: Common processes include Shielded Metal Arc Welding (SMAW), Gas Tungsten Arc Welding (GTAW/TIG), and Submerged Arc Welding (SAW).
Filler Materials: Compatible fillers include E8018-B2 (SMAW) and ER80S-B2 (GTAW/GMAW).
Post-Processing: Preheating before welding is recommended to avoid cold cracking, followed by Post-Weld Heat Treatment (PWHT) to stabilize the structure.
Mechanical Properties (Class 2)
Processing must ensure the material meets the higher strength requirements of Class 2 compared to Class 1:
| Property | Value |
|---|---|
| Tensile Strength | 450 – 585 MPa (approx. 65 – 85 ksi) |
| Yield Strength | 275 MPa minimum (approx. 40 ksi) |
| Elongation | 20% minimum (in 2 inches) |
Standard Testing During Processing
To ensure reliability in high-pressure environments, the following tests are standard:
Non-Destructive Testing: Ultrasonic testing, Radiography (X-ray), and Magnetic Particle testing.
Mechanical Testing: Impact testing (often down to -52°C), Hardness, and Charpy tests.
Corrosion Testing: Intergranular corrosion (IGC) and Positive Material Identification (PMI) to verify chemical composition.
Core Industrial Applications
Oil & Gas and Petrochemical: Used extensively for fabricating separator vessels, refinery equipment, and storage tanks for high-pressure gases. Its resistance to oxidation makes it a standard for sour service applications (environments containing 𝐻2𝑆)
Power Generation: Essential for industrial boilers, boiler drums, and heat recovery steam generators (HRSG). It is also found in nuclear reactor pressure vessels and high-temperature ducting.
Heat Transfer Equipment: Commonly utilized in the manufacturing of heat exchangers, condensers, and superheaters due to its thermal stability.
Chemical Processing: Used for reactors and vessels designed to handle corrosive media at high temperatures.
Component Fabrication
Beyond large vessels, this grade is processed into specialized components:
Piping Systems: Steam pipelines, high-temperature ducting, and large-diameter pipe work.
Fittings: Flanges, valves, pipe clamps, and supports designed for high-stress environments.
General Industry: High-temperature storage tanks, oxygen cylinders, and liners for chutes or bins.
Full specification and details are available on request. The above information is provided for guidance purposes only. For specific design requirements please contact our technical sales staff.
What is the main material category of SA 387 Grade 12 Class 2?
It is a low-alloy chromium-molybdenum steel. Designed for high-temperature and pressure applications, it offers excellent creep resistance and structural stability in harsh industrial environments.
Which standard specifies SA 387 Grade 12 Class 2?
It is specified by the ASTM A387 standard, which covers alloy steel plates for welded boilers and pressure vessels. This standard defines its chemical composition and mechanical properties.
What is the typical carbon content range of this material?
Its carbon content ranges from 0.15% to 0.20%. This range balances hardness and weldability, making it suitable for fabrication of pressure-containing components.
What chromium content does SA 387 Grade 12 Class 2 contain?
It contains 0.80% to 1.15% chromium. Chromium enhances corrosion resistance and oxidation resistance, critical for high-temperature service conditions.
What is the molybdenum content range of this grade?
The molybdenum content is 0.45% to 0.60%. Molybdenum improves creep strength and heat resistance, enabling use in elevated-temperature industrial processes.
What is the minimum tensile strength of SA 387 Grade 12 Class 2?
Its minimum tensile strength is 415 MPa (60,000 psi). This ensures sufficient load-bearing capacity for pressure vessel and boiler applications.
What is the minimum yield strength of this material?
The minimum yield strength is 205 MPa (30,000 psi). It provides good ductility and structural integrity under high-pressure and temperature fluctuations.
What temperature range is SA 387 Grade 12 Class 2 suitable for?
It performs well between -29°C (-20°F) and 593°C (1100°F). Beyond this range, its mechanical properties may degrade significantly.
Is SA 387 Grade 12 Class 2 weldable?
Yes, it is readily weldable with proper procedures. Preheating and post-weld heat treatment are recommended to avoid cold cracking and relieve residual stresses.
What preheating temperature is recommended for welding this material?
The recommended preheating temperature is 150°C to 200°C (302°F to 392°F). This prevents hydrogen-induced cracking during and after welding.