ASTM A387 Grade 11 Class 1 steel is a 1.25Cr‑0.5Mo alloy steel plate standardized under ASTM A387/A387M, engineered for welded pressure vessels, boilers and high‑temperature process equipment.It delivers stable creep strength, hydrogen resistance and good weldability, making it a widely used grade in oil, gas, petrochemical and power generation sectors.
Chemical Composition of A387 Grade 11 Class 1 Steel
| Element | Cr | Mo | C | Mn | Si | P | S |
|---|---|---|---|---|---|---|---|
| Range | 1.00–1.50 | 0.45–0.65 | ≤0.15 | 0.30–0.60 | 0.15–0.40 | ≤0.035 | ≤0.040 |
Mechanical Properties of A387 Grade 11 Class 1 Steel
|
Property |
Specification |
|---|---|
|
Tensile Strength |
515–690 MPa (75–100 ksi) |
|
Yield Strength (Min) |
310 MPa (45 ksi) |
|
Elongation (Min) |
18% |
|
Heat Treatment |
Normalized + Tempered |
|
Max Service Temperature |
Up to 550 °C (1022 °F) |
Key Features of A387 Grade 11 Class 1 Steel
Elevated Temperature Performance: Engineered for high-temperature service environments, providing reliable strength and oxidation resistance at elevated temperatures.
Optimal Alloy Composition: Contains 1.25% Chromium for excellent corrosion/oxidation resistance and 0.5% Molybdenum for superior high-temperature tensile strength.
Class 1 Tensile Strength: Specifically characterized by a lower, moderate tensile strength (typically 60-85 ksi) compared to Class 2, aiding in easier fabrication and toughness.
Weldability & Fabricability: Excellent weldability and, due to its moderate hardness, it is easier to handle during cutting, machining, and shaping processes.
Application-Specific: Ideal for boilers, pressure vessels, and piping systems within the petroleum, petrochemical, and power generation industries.
Surface Protection: The Cr-Mo composition forms a protective surface layer, providing good resistance to corrosion in high-temperature environments.
Key Applications & Industries of A387 Grade 11 Class 1 Steel
ASTM A387 Grade 11 Class 1 steel is a chromium-molybdenum alloy steel plate engineered for elevated temperature service, primarily used in welded pressure vessels, boilers, heat exchangers, and piping systems in the oil, gas, and petrochemical industries:
(1) Pressure Vessels & Boilers: Used in the fabrication of welded pressure vessels and boilers for high-temperature service.
(2) Oil & Gas Processing: Common in refineries for equipment handling high-temperature gases and liquids.
(3) Petrochemical Industry: Ideal for piping and storage tanks requiring resistance to oxidation and corrosion.
(4) Power Generation: Employed in heat exchangers and related equipment in power plants.
(5) Sour Gas Service: The 1.25% Chromium and 0.5% Molybdenum composition provides superior corrosion resistance.
What is the difference between A387 Grade 11 Class 1 and Class 2?
Both of these categories are chromium-molybdenum alloy steels, specifically designed for welded pressure vessels and boilers, ensuring high-temperature stability and corrosion resistance.The primary difference between ASTM A387 Grade 11 Class 1 and Class 2 lies in their mechanical strength. Although both share the same chemical composition, Class 2 possesses higher tensile and yield strengths compared to Class 1, making it better suited for more demanding high-pressure or high-temperature applications.
Comparison Summary
| Feature | Class 1 | Class 2 |
|---|---|---|
| Tensile Strength | Lower | Higher |
| Yield Strength | Lower | Higher |
| Typical Heat Treatment | As-rolled / Annealed | Normalized & Tempered / Q&T |
| Primary Usage | Moderate temp/pressure | Severe high-temp/pressure |
Why Choose Gnee's A387 Grade 11 Class 1 Steel?
Exceptional Quality and Compliance Assurance:Gnee supplies certified ASME SA387 Grade 11 Class 1 steel plates. And the products strictly adhere to all relevant international standards, ensuring consistently stable and reliable performance in the demanding industrial applications found within the oil, gas, and petrochemical sectors.
Direct-from-Manufacturer Advantage: As a direct manufacturer-rather than a mere trading company-Gnee offers a robust and stable quality control system, backed by extensive technical expertise and support.
Rapid Delivery and Stock Availability:With an inventory exceeding 50,000 tons, Gnee guarantees rapid dispatch (typically within 7 days), providing a reliable supply of materials to support urgent project requirements.
Comprehensive Service Solutions:Gnee offers a wide range of value-added processing services and dedicated technical support, designed to fully address the specific manufacturing and processing needs of diverse projects.
Contact now to get A387 Grade 11 Class 1 steel quote
| Standard: ASTM A387 Grade : A387 Gr 11 Class 1 |
| Thickness : 8mm-150mm Width : 1000mm-4000mm Length : 1000mm-20000mm |
| MOQ: 1 PC Product type : Steel plate Delivery time : Promptly ( Stock) or 10-40 days (Production) Payment Terms: L/C, T/T, etc Stock : Available MTC: Available |
| Delivery condition: Q+T or +N |
| MTC: Original |
What is ASTM A387 Grade 11 equivalent to?
ASTM A387 grade 11 equivalent steel is ASME SA387 grade 11. ASTM A387 grade 11 covers A387 grade 11 class 1 and A387 grade 11 class 2, which are equivalent to ASME SA387 grade 11 class 1 and SA387 grade 11 class 2 respectively.
What is ASTM A387 material?
ASTM A387 GR 22 CL 2 Plates is designed with chemical compositions like carbon, manganese, phosphorus, molybdenum, chromium, silicon, and sulfur. This A387 alloy is constructed with various classifications like area reduction, elongation, yield strength, and high tensile strength.
What is the maximum continuous service temperature for A387 Grade 11 Class 1?
The maximum continuous service temperature for A387 Grade 11 Class 1 is typically 540°C (1004°F), as the chromium-molybdenum alloy composition provides good creep strength at elevated temperatures. Operating above this limit for extended periods will accelerate creep deformation, potentially leading to excessive thinning or rupture of pressure vessel walls before the end of the designed service life. For applications requiring sustained temperatures above 540°C, higher grades such as A387 Grade 22 or Grade 91 should be considered.
Is post-weld heat treatment (PWHT) mandatory for A387 Grade 11 Class 1?
Yes, post-weld heat treatment is generally mandatory for A387 Grade 11 Class 1 due to its chromium-molybdenum content, which increases hardenability and the risk of martensite formation in the heat-affected zone after welding. PWHT, typically performed at 690–705°C (1275–1300°F), relieves residual welding stresses, tempers any hard microstructures, restores toughness, and prevents hydrogen-induced cracking, making it a standard requirement under ASME Section VIII and most pressure vessel construction codes for this alloy grade.