What temperature is ASTM A387 Grade 11 Class 2 ?
ASTM A387 Grade 11 Class 2 is a chromium-molybdenum alloy steel for high-temperature service, specifically designed for medium temperature ranges, typically 350°C to 480°C (662°F to 896°F), offering excellent creep and corrosion resistance in pressure vessels and boilers, with Class 2 indicating higher strength through stricter heat treatment than Class 1. Its specified heat treatment involves tempering at a minimum of 620°C (1150°F).
ASTM A387 Grade 11 CL2 is a chromium-molybdenum alloy steel specifically engineered for weldable pressure vessels and boilers in elevated temperature service. It bridges the gap between standard carbon steels and high-alloy stainless steels, offering superior oxidation resistance and mechanical stability.
Technical Profile
The "Class 2" designation indicates enhanced mechanical properties achieved through a Normalized and Tempered heat treatment. This process refines the grain structure, allowing the material to handle higher operating stresses than Class 1.
P-Number: 4, Group 1 (Critical for determining welding procedures).
Density: Approximately 7.85 g/cm³ (490 lb/ft³).
Max Temperature: Typically used up to 593°C (1100°F) for pressure service.
Composition & Mechanical Requirements
While both Class 1 and Class 2 share the same chemical composition, their strength profiles differ significantly:
Fabrication & Service Performance
HTHA Resistance: The alloy is highly resistant to High-Temperature Hydrogen Attack, making it a staple for hydrocracking and catalytic reforming units in refineries.
Weldability: Due to its air-hardening characteristics, the material requires pre-heating and a minimum post-weld heat treatment (PWHT) temperature of 620°C (1150°F) to ensure joint integrity and stress relief.
Sour Service: The stable chromium oxide layer provides the necessary protection against hydrogen-induced cracking in sour gas environments.
Common Applications
Petrochemical: Hydrogenation reactors and heat exchangers.
Power Generation: High-pressure steam piping and boiler drums.
Oil & Gas: Thick-walled vessels operating in corrosive, high-heat environments.
What is ASTM A387 Grade 11 Class 2 equivalent to ?
ASTM A387 Grade 11 Class 2 is equivalent to ASME SA387 Grade 11 Class 2 (the ASME boiler and pressure vessel code version) and has international counterparts like EN 10028 13CrMoSi5-5 and British Standard BS 621B, all offering similar 1.25% Chromium, 0.50% Molybdenum alloy steel with specific higher tensile strength properties for high-temperature pressure applications.
What welding rod for ASTM A387 Grade 11 Class 2 ?
For ASTM A387 Grade 11 Class 2 (a 1.25Cr-0.5Mo alloy), use low-carbon chromium-molybdenum electrodes like E7018-B2L (SMAW/Stick), E8018-B2 or E8018-B3 (for P11 to P22), ER80S-B2 or ER90S-B3 (TIG/MIG), or appropriate flux-cored options like E9XT1-B3C, ensuring matching chemistry, proper preheat (around 150-200°C), and post-weld heat treatment (PWHT) for optimal performance in high-temperature pressure vessels.
What is the hardness of ASTM A387 Grade 11 Class 2 ?
ASTM A387 Grade 11 Class 2 steel's hardness isn't a single fixed number but varies with tempering, though it typically has a Brinell hardness of around 170-207 HBW (or roughly 190 HBW as one example), reflecting its higher strength Class 2 designation, with specified minimum tensile strength often around 515-690 MPa (75-100 ksi) after heat treatment for pressure vessels.
Equivalents
| BS | EN | ASTM/ASME | DIN |
| 621 B | ––– | A387-11-2 | ––– |
| Designation | Nominal Chromium Content (%) | Nominal Molybdenum Content (%) |
|---|---|---|
| A387 Grade 11 | 1.25% | 0.50% |
Chemical Requirements:
| . | . |
|---|---|
| Carbon (C) | % |
| Heat Analysis: Product Analysis: |
0.05 - 0.17 0.04 - 0.17 |
| Manganese (Mn) | % |
| Heat Analysis: Product Analysis: |
0.40 - 0.65 0.35 - 0.73 |
| Phosphorus (P) | % |
| Heat Analysis: Product Analysis: |
0.035 0.035 |
| Sulphur (S) (Max) | % |
| Heat Analysis: Product Analysis: |
0.035 0.035 |
| Silicon (Si) | % |
| Heat Analysis: Product Analysis: |
0.50 - 0.80 0.44 - 0.86 |
| Chromium (Cr) | % |
| Heat Analysis: Product Analysis: |
1.00 - 1.50 0.94 - 1.56 |
| Molybdenum (Mo) | % |
| Heat Analysis: Product Analysis: |
0.45 - 0.65 0.45 - 0.70 |
ASTM A387 GR 11 CLASS 2 Plate Specification
| Property | Specification |
|---|---|
| Grade | ASTM A387 Gr 11 CL.2 Alloy Steel Plates |
| Standard | ASTM A387 / ASME SA387 |
| Width | 1000mm - 4500mm |
| Thickness | 5mm - 150mm |
| Length | 3000mm - 18000mm |
| Impact Tested | -52° C |
| Process | Hot-Rolled (HR) |
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 % | ––– |
1What is ASTM A387 Grade 11 Class 2 high speed steel?
ASTM A387 Grade 11 Class 2 is a specific type of chromium-molybdenum (Cr-Mo) alloy steel plate designed for high-temperature service in pressure vessels, boilers, and heat exchangers, featuring excellent creep resistance, corrosion resistance, and high-temperature strength due to its ~1% Chromium and ~0.5% Molybdenum content, with Class 2 having higher strength requirements than Class 1 but slightly less elongation,
2What are the typical application fields of ASTM A387 Grade 11 Class 2 ?
ASTM A387 Grade 11 Class 2 steel is primarily used for elevated temperature service in pressure vessels, boilers, and heat exchangers, especially within the oil, gas, petrochemical, and power generation industries due to its excellent strength, weldability, and resistance to corrosion and oxidation at high temperatures. Key applications include hydrogenation reactors, hydrocracking units, steam headers, and storage tanks in demanding environments.
3What is the difference between ASTM A387 Grade 11 Class 2 and ASTM A387 Grade 11 Class 1 ?
ASTM A387 Grade 11 Class 2 is a stronger, tougher version of Grade 11 Class 1, primarily differing in mechanical properties (higher tensile/yield strength) due to potentially different heat treatment, making Class 2 suitable for more demanding high-temperature/pressure applications than Class 1, while both share the same 1.25% Cr-0.5% Mo composition for pressure vessels.
4What is ASTM A387 Grade 11 Class 2 material?
ASTM A387 Grade 11 Class 2 is a chromium-molybdenum (Cr-Mo) alloy steel plate for high-temperature pressure vessels, offering higher strength than Class 1 due to stricter heat treatment, with around 1.25% chromium and 0.5% molybdenum for excellent high-temp strength, creep, and oxidation resistance, used in oil, gas, and chemical industries. It's known for applications like reactors and heat exchangers requiring elevated temperatures.
5Is ASTM A387 Grade 11 Class 2 carbon steel?
No, ASTM A387 Grade 11 Class 2 is not plain carbon steel; it's a chromium-molybdenum (Cr-Mo) alloy steel, specifically designed for high-temperature pressure vessels, with added chromium (around 1-1.5%) and molybdenum (around 0.5%) for enhanced strength, corrosion resistance, and creep resistance, distinguishing it from basic carbon steels. The "Class 2" designation indicates higher strength requirements achieved through specific heat treatment (normalized and tempered) compared to Class 1,
6What precautions should be taken when welding ASTM A387 Grade 11 Class 2?
When welding ASTM A387 Grade 11 Class 2 (a 1.25Cr-0.5Mo alloy), key precautions include thorough cleaning, mandatory preheating (around 149°C/300°F), using low-hydrogen electrodes (like E8018-B2), controlling interpass temperature, and applying Post-Weld Heat Treatment (PWHT) (around 690°C/1275°F) to prevent cracking due to its tendency to form brittle martensite, requiring adherence to ASME/AWS codes for specific parameters.
7What is the P number of ASTM A387 Grade 11 Class 2 ?
The P-Number for ASTM A387 Grade 11 Class 2 alloy steel, used in pressure vessels, is P-Number 4, which designates low alloy steels (Cr-Mo) that fall within specific compositional ranges for welding group classification. This material is characterized by its 1.25% Chromium and 0.5% Molybdenum content, differing from other grades by its mechanical properties (Class 2 having higher strength than Class 1) but sharing the same base chemistry,
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