What is ASTM A387 Grade 11 Class 1 material?

What is ASTM A387 Grade 11 Class 1 material?

ASTM A387 Grade 11 Class 1 is a chromium-molybdenum (Cr-Mo) alloy steel plate for high-temperature pressure vessels, offering good high-temp strength, corrosion resistance (especially in sour gas), and weldability, with specific Cr (1.00-1.50%) and Mo (0.45-0.65%) content, typically supplied normalized or annealed, and used in boilers, reactors, and hydrogenation units. Class 1 denotes a lower tensile strength/toughness requirement compared to Class 2, emphasizing purity and flaw detection for critical applications.

ASTM A387 Grade 11 Class 1 is a chromium-molybdenum alloy steel plate specifically engineered for use in welded boilers and high-temperature pressure vessels. This material, often referred to in the industry as "1.25 Chrome 0.5 Moly," is supplied in the annealed or normalized condition to ensure structural integrity in environments where materials are subjected to constant thermal stress.

The "Class 1" distinction is a critical identifier of the material's mechanical property levels. Unlike Class 2, which aims for higher tensile strength, Class 1 is characterized by a specified tensile strength range of 60 to 85 ksi (415 to 585 MPa) and a minimum yield strength of 35 ksi (240 MPa). This lower strength profile translates into superior ductility and fracture toughness. Metallurgically, the manufacturing process typically involves controlled heat treatments such as normalizing and tempering or accelerated cooling from the austenitizing temperature followed by tempering. These processes ensure a refined grain structure-usually a mixture of ferrite and pearlite or bainite-which is vital for ensuring that the plates can withstand internal pressures without brittle failure.

Modern steel mills utilize vacuum degassing and ladle refining to minimize impurities like sulfur and phosphorus. This ensures that the steel maintains high cleanliness levels, which is crucial for preventing "temper embrittlement" during its service life in high-heat environments. The nominal chromium content (1.00% to 1.50%) provides primary defense against oxidation and corrosion by forming a stable oxide layer, while the molybdenum content (0.45% to 0.65%) enhances the steel's creep resistance-the ability to resist deformation under long-term mechanical stress at high temperatures.

Key Characteristics:

Material Type: Chromium-Molybdenum (Cr-Mo) Alloy Steel Plate.

Primary Use: Welded boilers and pressure vessels for elevated temperature service.

Performance: Excellent high-temperature strength, creep resistance, and resistance to hydrogen corrosion (HTHA).

Applications: Petrochemical plants (hydrogenation reactors, synthesis towers), power generation equipment, and other industries requiring reliable performance in hot, high-pressure environments.

Processing: Typically supplied normalized and tempered or annealed.

SA387 GR 11 CLASS 1 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)

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.

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.

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.

Equivalents

Dimension Range SA 387 GR. 11 CL. 1 Alloy Steel

Chemical Requirements

Tensile Requirements For Class 1 Plates

1 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.

2 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.

3 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.

4 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.

5 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.

6 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.

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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