What is the P number of ASTM A387 Grade 11 Class 1 ?
The P-number for ASTM A387 Grade 11 Class 1 steel, a chromium-molybdenum alloy, is P-Number 4, as it falls into the group of 1.25Cr-0.5Mo steels, similar to other materials like SA-213 T11 and SA-335 P11, used for high-temperature service.
The ASTM A387 specification is the Standard Specification for Pressure Vessel Plates, Alloy Steel, Chromium-Molybdenum intended primarily for use in welded boilers and pressure vessels designed for elevated temperature service. These plates are designed for applications that require improved mechanical properties and resistance to oxidation, making them suitable for use in high-temperature environments.
ASTM A387 Gr 11 CL 1 is a chromium molybdenum alloy steel plate within this specification, containing a Chromium (Cr) content of 1.25% and a Molybdenum (Mo) content of 0.5%. This specific composition enhances its performance in elevated temperature service.
ASTM A387 Grade 11 can be supplied to meet the distinct tension test requirements for Class 1 and/or Class 2, depending on the specific mechanical needs of the project.
Key Characteristics
Type: Alloy steel plate.
Application: Welded boilers, pressure vessels, heat exchangers, and equipment in oil, gas, and petrochemical plants.
Alloying Elements: Contains approximately 1.25% Chromium (Cr) and 0.5% Molybdenum (Mo) for enhanced high-temperature performance.
Properties: Excellent resistance to high-temperature creep, oxidation, and hydrogen attack.
Weldability: Good, suitable for high-temperature service.
Class 1 vs. Class 2 (Grade 11)
Chemistry: Both classes share the same chemical composition.
Mechanicals: Class 2 generally has higher tensile and yield strength, while Class 1 typically offers greater elongation (more ductility).
What is ASTM A387 Grade 11 Class 1 high speed steel?
ASTM A387 Grade 11 Class 1 is a Chromium-Molybdenum (Cr-Mo) alloy steel plate designed for welded boilers and pressure vessels used at elevated temperatures, offering good strength and excellent corrosion/oxidation resistance, particularly in oil, gas, and petrochemical industries, with Class 1 denoting specific mechanical properties and purity standards higher than Class 2. It contains about 1.0-1.5% Chromium and 0.45-0.65% Molybdenum, making it suitable for high-temperature service (around 350-480°C) in hydrogenation reactors and synthesis towers.
What temperature is ASTM A387 Grade 11 Class 1?
ASTM A387 Grade 11 Class 1 is a chromium-molybdenum steel for high-temperature service, often used in the range of 316°C to 593°C (600°F to 1100°F), with specific maximum use temperatures depending on the ASME code, such as around 649°C (1200°F) for some applications, but its minimum tempering temperature is typically 1150°F (620°C) for heat treatment to achieve desired toughness for elevated temperature use.
What precautions should be taken when welding ASTM A387 Grade 11 Class 1?
When welding ASTM A387 Grade 11 Class 1, prioritize low-hydrogen consumables (like E8018-B2), ensure thorough joint cleaning, apply preheat (minimum 250°F/121°C) to prevent cracking, control interpass temperature, and implement slow, controlled cooling post-weld, along with standard welding safety (PPE, ventilation) for this high-strength, high-temperature alloy used in pressure vessels.
SA387 GR 11 CLASS 1 / 2 Plate Specification :
Width: 1000mm-4500mm
Thickness: 5mm to 150mm
Length: 3000mm-18000mm
Supply Condition : As Rolled, Normalized Rolling, Furnace Normalizing, Vacuum Degassing, Simulated Post-Weld Heat Treatment or as per customer requirement.
Impact tested: -52° C
Process of Manufacturing: Hot-Rolled (HR)
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% |
Dimension Range
|
Grade |
Product type |
Thickness |
Width |
Length |
|---|---|---|---|---|
|
Grade 11 |
Plate |
4.70 - 91.4 |
1500 - 3350 |
1900 - 15000 |
Alloy Steel ASTM A387 GR 11 CL. 1 / 2 Plates Chemical Composition :
| C | Mn | P | S | Si | Cr | Mo |
| 0.04 - 0.17 | 0.35 - 0.73 | 0.035 | 0.035 | 0.44 - 0.86 | 0.94 - 1.56 | 0.40 - 0.7 |
Alloy steel ASME SA387 GR. 11 CL. 1/ 2 Plates Mechanical Properties :
| Grade | Thickness | Yield strength | Tensile strength | Elongation in 2" 1) (min %) |
Elongation in 8" 1) (min %) |
|---|---|---|---|---|---|
| Grade 11 Class 1 | 0.185 - 3.60 4.70 - 91.4 |
35 | 60 - 85 | 22 | 19 |
1. What is the composition of ASTM A387 Grade 11 Class 1 ?
ASTM A387 Grade 11 Class 1 is a chromium-molybdenum alloy steel for high-temperature pressure vessels, containing approximately 1.00-1.50% Chromium (Cr), 0.45-0.65% Molybdenum (Mo), and balanced amounts of Carbon, Manganese, Silicon, Phosphorus, and Sulfur, offering enhanced creep and oxidation resistance compared to carbon steels, with Class 1 indicating the lower tensile strength range.
2. What welding rod for ASTM A387 Grade 11 Class 1 ?
For ASTM A387 Grade 11 Class 1 (1.25Cr-0.5Mo alloy steel), use low-hydrogen, chromium-molybdenum matched electrodes like E7018-B2L (SMAW/stick) or E71T1-B2L (FCAW), or for higher strength, consider E8018-B3 or matching ER80S-B3 (GTAW/MIG) filler wires, always ensuring proper preheat (around 149°C/300°F) and post-weld heat treatment (PWHT) for elevated temperature service.
3. What is the P number of ASTM A387 Grade 11 Class 1?
The P-number for ASTM A387 Grade 11, which is a chromium-molybdenum alloy steel (1.25Cr-0.5Mo), is P Number 4, a classification used in welding codes like ASME for grouping similar materials for welding procedures, despite variations in phosphorus content between Class 1 and Class 2.
4. What is ASTM A387 Grade 11 Class 1 equivalent to?
ASTM A387 Grade 11 Class 1 is a chromium-molybdenum alloy steel for high-temperature pressure vessels, equivalent to ASME SA387 Grade 11 Class 1 (its ASME counterpart) and also comparable to European standards like BS 621B and EN 10CrMo910, offering similar properties for global projects.
5. What is the hardness of ASTM A387 Grade 11 Class 1 steel?
ASTM A387 Grade 11 Class 1 steel typically has a Brinell hardness range of 143 to 217 HB, although it's primarily specified by its tensile properties (60-85 ksi tensile, 35 ksi yield) for high-temperature pressure vessel service, with Class 1 having lower strength but better elongation than Class 2.
6. What are the typical application fields of ASTM A387 Grade 11 Class 1?
ASTM A387 Grade 11 Class 1 steel is primarily used for welded pressure vessels and boilers in high-temperature service, especially in the oil, gas, and petrochemical industries, due to its excellent chromium-molybdenum alloy properties offering superior heat and corrosion resistance for transporting hot liquids and gases. Key applications include heat exchangers, flanges, piping, and high-temperature ducting where strength and resistance to oxidation are critical.
7. Is ASTM A387 Grade 11 Class 1 carbon steel?
No, ASTM A387 Grade 11 Class 1 is alloy steel, not plain carbon steel, specifically a chromium-molybdenum (Cr-Mo) steel designed for high-temperature pressure vessels, featuring significant chromium (around 1.25%) and molybdenum (around 0.5%) for enhanced oxidation and corrosion resistance, making it superior to basic carbon steels for demanding applications like boilers and reactors.
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