ASTM A387 Grade 12 Class 2 is a high-performance chromium-molybdenum alloy steel plate specifically engineered for use in weldable pressure vessels and industrial boilers operating at elevated temperatures.
Equivalents
| BS | EN | ASTM/ASME | DIN |
| 620 B | 13 CRMO 45 | A387-12-2 | 13 CRMO 44 |
Specifications for ASTM A387 Grade 12 Alloy Steel Plates
| Designation | Nominal Chromium Content (%) |
Nominal Molybdenum Content (%) |
| A387 Grade 12 | 1.00% | 0.50% |
Tensile Requirements for ASTM A387 Grade 12 Alloy Steel Plates Class 2 Plates
| 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 for ASTM A387 Grade 12 Alloy Steel Plates
| 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 |
Primary Applications
The material is predominantly used in industries where equipment is subjected to high internal pressure and elevated heat.
Oil & Gas Refining:
Ideal for "sour service" applications due to its resistance to hydrogen sulfide (H2S). Specific equipment includes hydrocrackers, separators, and high-temperature storage tanks.
Power Generation:
Used extensively in the construction of industrial boilers, superheaters, and steam pipelines that must maintain structural integrity at temperatures up to 575°C.
Chemical Processing:
Construction of reactors, heat exchangers, and pressure vessels that handle corrosive media.
Specialized Industrial:
Fabrication of oxygen cylinders, large metallic tanks, and piping supports for hot gas transportation.
| Advantage | Description |
|---|---|
| High Tensile Strength | Class 2 has a higher tensile strength range (450–585 MPa) than Class 1, allowing for thinner plate designs in high-pressure vessels. |
| Superior Heat Transfer | Compared to Grade 11, Grade 12 has better thermal conductivity, making it more efficient for heat exchangers where minimizing temperature gradients is critical. |
| Corrosion Resistance | The chromium (1.00–1.50%) and molybdenum (0.45–0.60%) content provides robust resistance to oxidation, pitting, and chloride-induced stress corrosion cracking. |
| Cost Efficiency | Offers a lower-cost alternative to Grade 22 for applications with moderate pressure and temperature needs, providing the required stability without the higher price tag of more heavily alloyed steels. |
| Weldability & Fabrication | Despite its high strength, it maintains excellent weldability and formability, which simplifies the fabrication of complex pressure vessel components. |
| Durability in Sour Service | Specifically engineered to withstand harsh chemical environments, significantly extending the lifespan of equipment in the petrochemical sector. |
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Is it suitable for making pressure vessel shells?
Yes, it is widely used for pressure vessel shells in petrochemical plants, as it can withstand high internal pressure and stable high temperatures.
What is the hardness of A387 Grade 12 Class 2 after heat treatment?
After normalizing and tempering, its Brinell hardness is about 187-229 HB, balancing hardness and toughness for industrial applications.
Can it be cold-formed?
It can be cold-formed with proper procedures, but preheating may be required for thick plates to prevent cracking and ensure forming quality.
What is the main function of molybdenum in this alloy steel?
Molybdenum improves its high-temperature strength, creep resistance and corrosion resistance, making it adaptable to harsh working environments.
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.
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 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.