A387 Grade 11 Class 1 is a chromium-molybdenum alloy steel plate specified under the ASTM A387 standard, widely used in the fabrication of pressure vessels and boiler components that operate at elevated temperatures. It belongs to the family of low-alloy steels containing a moderate amount of chromium and molybdenum, which imparts good strength, creep resistance, and resistance to hydrogen attack in high-temperature service environments. Class 1 indicates a normalized and tempered heat treatment condition, resulting in a refined microstructure that balances toughness and strength for reliable performance under thermal and mechanical stress. This grade is commonly employed in oil refineries, petrochemical plants, and power generation facilities where equipment is exposed to high-pressure and high-temperature fluids.
Equivalents
| BS | EN | ASTM/ASME | DIN |
| 621 B | ––– | A387-11-1 | ––– |
Specifications for ASTM A387 Grade 11 Alloy Steel Plates
| Designation | Nominal Chromium Content (%) |
Nominal Molybdenum Content (%) |
| A387 Grade 11 | 1.25% | 0.50% |
Tensile Requirements for ASTM A387 Grade 11 Alloy Steel Plates Class 1 Plates
| Designation: | Requirement: | Grade 11 |
| A387 Grade 11 | Tensile strength, ksi [MPa] | 75 to 100 [515 to 690] |
| Yield strength, min, ksi [MPa]/(0.2% offset) | 43 [310] | |
| Elongation in 8 in. [200mm], min % | 18 | |
| Elongation in 2 in. [50mm], min, % | 22 | |
| Reduction of area, min % | ––– |
Chemical Requirements for ASTM A387 Grade 11 Alloy Steel Plates
| Element | Chemical Composition (%) | |
| A387 Grade 11 | ||
| 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: | 0.50 - 0.80 |
| Product Analysis: | 0.44 - 0.86 | |
| Chromium: | Heat Analysis: | 1.00 - 1.50 |
| Product Analysis: | 0.94 - 1.56 | |
| Molybdenum: | Heat Analysis: | 0.45 - 0.65 |
| Product Analysis: | 0.45 - 0.70 |
manufacturing process
1. Primary Manufacturing
Steel Melting: The material is produced as killed steel (deoxidized) to prevent porosity and ensure structural integrity.
Refining: Processes like vacuum degassing may be used to remove impurities and gases.
Forming: Plates are typically manufactured using the Hot Rolled (HR) method.
2. Heat Treatment
This is the most critical phase for achieving specified mechanical properties:
Normalizing: Heating to 900–950°C (1650–1740°F) followed by air cooling to refine grain size.
Tempering: Reheating to at least 650°C (1200°F) to reduce brittleness and increase toughness.
Alternative (Q+T): Some applications may use Quenched and Tempered processing to enhance hardness.
3. Fabrication & Welding
Preheating: Necessary before welding to prevent thermal shock, typically between 121°C and 150°C (250–300°F).
Post-Weld Heat Treatment (PWHT): Often required for pressure vessel applications according to standards like ASME BPVC Section VIII to relieve residual stresses.
4. Quality Control
Standard tests include:
Tension Test: Verifies yield and tensile strength.
Non-Destructive Testing (NDT): Includes Magnetic Testing (MT), Ultrasonic Testing (UT), or Radiographic Testing (RT) for weld integrity.
Simulated PWHT: Supplemental testing may be performed to ensure the material remains within specifications after the customer's fabrication process.
applications
Pressure vessels and boilers
Used in the fabrication of pressure vessels, boilers, and related components that operate under high temperatures and pressures, where good creep resistance and strength retention are required.
Oil refinery equipment
Applied in refinery units such as reactors, heat exchangers, and piping systems that handle hot hydrocarbons and process fluids.
Petrochemical and chemical processing
Utilized in reactors, columns, and heat exchangers within petrochemical and chemical plants, particularly in services involving elevated temperatures and hydrogen-containing environments.
Power generation systems
Found in components of power plants, including boilers, steam generators, and associated pressure parts, where resistance to high-temperature oxidation and creep is essential.
Other high-temperature service equipment
Used in various industrial applications requiring steel plates with good elevated-temperature strength and resistance to hydrogen attack, such as in certain process heaters and furnace components.
Why Choose Us :
You can get the perfect material according to your requirement at the least possible price.
We also offer Reworks, FOB, CFR, CIF, and door to door delivery prices. We suggest you to do deal for shipping which will be quite economical.
The materials we provide are completely verifiable, right from raw material test certificate to the final dimensional statement.(Reports will show on requirement)
We guarantee to give a response within 24hours(usually in the same hour)
You can get stock alternatives, mill deliveries with minimizing manufacturing time.
We are fully dedicated to our customers. If it will not possible to meet your requirements after examining all options, we will not mislead you by making false promises which will create good customer relations.
Contact us at beam@gneesteelgroup.com for pricing, technical support, or customized solutions. We are always ready to support your project.
How does temperature affect the mechanical properties of A 387 Gr 11 CL 1?
At elevated temperatures (up to 593°C/1100°F), it retains excellent tensile strength, creep resistance, and fatigue strength compared to carbon steel. Beyond this temperature, its properties gradually degrade.
What is the Brinell hardness (HB) range of A 387 Gr 11 CL 1?
The typical Brinell hardness range is 130-180 HB, which reflects its moderate hardness and machinability.
What is the standard heat treatment for A 387 Gr 11 CL 1?
The standard heat treatment is normalizing and tempering. Normalizing is done at 899-954°C (1650-1750°F), followed by air cooling; tempering is at 593-704°C (1100-1300°F) to relieve stress and improve toughness.
Can A 387 Gr 11 CL 1 be welded?
Yes, it is weldable. However, preheating (typically 150-260°C/300-500°F) and post-weld heat treatment (PWHT) are required to prevent cold cracking and reduce residual stresses, ensuring weld joint integrity.
What are the main applications of A 387 Gr 11 CL 1?
It is widely used in the manufacture of pressure vessels, boilers, heat exchangers, and petrochemical equipment that operate at elevated temperatures, such as refinery reactors, steam generators, and catalytic crackers.
What is the maximum service temperature for A 387 Gr 11 CL 1?
Its maximum continuous service temperature is approximately 593°C (1100°F). Beyond this temperature, its creep and oxidation resistance decline significantly.
What is the difference between A 387 Gr 11 CL 1 and A 387 Gr 12 CL 1?
The main difference is the molybdenum content: Gr 11 CL 1 has 0.45-0.65% Mo, while Gr 12 CL 1 has 0.87-1.13% Mo. Gr 12 CL 1 offers better high-temperature strength and creep resistance but is more expensive.
What is the certification requirement for A 387 Gr 11 CL 1 plates?
Plates must be certified in accordance with ASME SA-387, including material test reports (MTRs) with chemical composition, mechanical properties, and heat treatment records. Third-party inspection (e.g., ABS, DNV) may be required for critical applications.
What is the typical thickness range of A 387 Gr 11 CL 1 plates?
The standard thickness range is 6 mm to 200 mm (0.24 inches to 7.87 inches). Thicker plates may be available on request but require special heat treatment to ensure uniform mechanical properties.