ASTM A387 Grade 12 Class 2 is a chromium-molybdenum alloy steel plate designed for high-temperature, pressurized applications like boilers, pressure vessels, and heat exchangers, offering excellent corrosion resistance due to its chromium content, good weldability, and robust mechanical strength in elevated temperature service. The "Class 2" signifies a higher tensile strength level compared to Class 1.
Equivalents
| BS | EN | ASTM/ASME | DIN |
| 620 B | 13 CRMO 45 | A387-12-2 | 13 CRMO 44 |
Specifications
| Designation | Nominal Chromium Content (%) |
Nominal Molybdenum Content (%) |
| A387 Grade 12 | 1.00% | 0.50% |
Tensile Requirements
| Designation: | Requirement: | Grade 12 |
| A387 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
| Element | Chemical Composition (%) | |
| ASTM A387 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
1. Steel Plate Manufacturing
Melting & Rolling: Produced via Electric Arc Furnace (EAF) or Basic Oxygen Furnace (BOF) with vacuum degassing.
Heat Treatment (Mandatory for Cl.2): To achieve the required mechanical properties, the plates must undergo specific heat treatments:
Method: Normalized & Tempered (N+T) or Accelerated Cooling & Tempered.
Tempering Temperature: Minimum tempering temperature must be 620°C (1150°F).
2. Pre-Fabrication & Cutting
Cutting: Thermal cutting (Oxy-fuel or Plasma) is common. Due to the Chromium and Molybdenum content, preheating the plate before cutting is highly recommended to prevent edge cracking.
Beveling: Mechanical machining or grinding is used to prepare welding grooves (V-shape or U-shape).
Cleaning: Ensure the bevel and at least 25mm of the surrounding area are free of oil, moisture, scale, and rust.
3. Welding Process
Welding Methods: Common methods include SMAW (Stick), SAW (Submerged Arc), and GTAW/GMAW (TIG/MIG).
Filler Metals: Consumables must match the base metal chemistry (e.g., E8018-B2 electrodes or ER80S-B2 wires).
Preheat & Interpass Temperature: This is critical to avoid cold cracking. A minimum preheat temperature of 120°C - 150°C (250°F - 300°F) is typically required depending on thickness.
4. Post-Weld Heat Treatment (PWHT)
Purpose: To relieve residual stresses and improve the ductility of the Heat Affected Zone (HAZ).
Parameters: The assembly is heated to a holding temperature (typically 593°C / 1100°F or higher as per ASME Section VIII). The soaking time is determined by the material thickness (usually 1 hour per inch of thickness).
5. Inspection and Testing (NDT)
Non-Destructive Testing: 100% Radiographic Testing (RT) or Ultrasonic Testing (UT) is performed on joints. Magnetic Particle (MT) or Penetrant Testing (PT) is used for surface cracks.
Mechanical Verification: Verification of Tensile Strength (450-585 MPa) and Yield Strength (≥275 MPa).
Hardness Testing: Often required to ensure the PWHT was successful and the material hasn't become too brittle.
applications
1. Energy and Power Generation
Boilers & Steam Systems: Used for manufacturing industrial boilers, boiler drums, and steam headers.
Heat Exchangers: A core material for shell-and-tube heat exchangers and heat recovery steam generators (HRSG).
Nuclear & Thermal Power: Utilized in nuclear reactor pressure vessels and turbine components due to its resistance to thermal fatigue.
2. Oil, Gas, and Petrochemical
Refinery Equipment: Found in hydrogenation reactors, hydrocracking units, and separators that operate under high pressure.
Sour Service: Ideal for environments containing high levels of hydrogen sulfide (
H2S)due to its excellent oxidation and corrosion resistance.
Storage & Transport: Used for large metallic tanks, vessels containing high-pressure gas, and oxygen cylinders.
3. Chemical Processing
Reactors and Separators: Construction of chemical reactors and pressure vessels that handle corrosive media at raised temperatures.
Piping Systems: High-temperature ducting, pipe supports, flanges, fittings, and clamps.
4. Specialized Industries
Aerospace & Defense: Applied in military vehicles, naval ships, and aircraft components where durability under high-stress and thermal conditions is required.
General Engineering: Used in diverse sectors such as fertilizer plants, sugar and paper mills, and textile manufacturing for heavy-duty pressure equipment.
Contact us at beam@gneesteelgroup.com for pricing, technical support, or customized solutions.
Does it have good fatigue resistance?
Yes, it has excellent fatigue resistance under cyclic loads, suitable for equipment parts that work continuously under alternating pressure and temperature.
Is heat treatment necessary after welding?
Yes, post-weld tempering at 620-670°C is essential to eliminate welding residual stress and restore the mechanical properties of the weld zone.
Can it be machined easily?
It has moderate machinability. Sharp tools and proper cutting parameters are needed, and cooling lubricants should be used to reduce tool wear.
What is the delivery condition of A387 Grade 12 Class 2?
It is usually delivered in normalized and tempered condition, ensuring stable mechanical properties and meeting industrial application requirements.
Can it be used in nuclear power plants?
It is not commonly used in core areas of nuclear power plants but can be used in auxiliary high-temperature and high-pressure pipelines and equipment.
What is the impact toughness of this steel at room temperature?
Its Charpy V-notch impact toughness is above 35 J at room temperature, ensuring good anti-impact performance in normal working conditions.
How to store A387 Grade 12 Class 2 to prevent corrosion?
It should be stored in a dry, well-ventilated place, away from moisture and corrosive media, and covered with waterproof cloth if necessary.
What welding methods are suitable for this alloy steel?
Common methods include shielded metal arc welding, gas tungsten arc welding and submerged arc welding, which adapt to different welding scenarios and quality requirements.
What is the maximum thickness of A387 Grade 12 Class 2 plates?
The maximum thickness of commercial plates can reach 200 mm, suitable for manufacturing thick-walled pressure vessels and heavy-duty equipment parts.
Can A387 Grade 12 Class 2 be welded?
Yes, it is weldable, but preheating (150-200°C) and post-weld heat treatment are required to avoid cold cracks and improve joint toughness.
What is the recommended preheating temperature before forging?
The recommended preheating temperature is 815-870°C, which softens the material and reduces deformation resistance during forging.