SA 387 Gr. 11 Cl. 1 is a specific type of Chromium-Molybdenum (Cr-Mo) alloy steel plate defined by ASTM/ASME standards, designed for high-temperature service in welded pressure vessels and boilers, offering good oxidation/corrosion resistance due to its 1.25% Chromium content. Class 1 indicates a specific tensile strength level, with Class 2 having higher strength but Class 1 having better elongation, and both share the same chemical makeup but differ in mechanical properties and heat treatment requirements for different applications.
Chemical Requirements for ASME SA387 Grade 11 Alloy Steel Plates
| Element | Chemical Composition (%) | |
| SA387 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 |
Tensile Requirements
| ASME SA-387 Grade 11 Class 1 |
|
|---|---|
| Tensile Strength MPa [ksi] |
415-585 [60-85] |
| Yield Strength MPa [ksi], min. |
240 [35] |
| Elongation in 8", min. % |
19 |
| Elongation in 2", min. % |
22 |
| Reduction of area, min. % |
- |
process treatment
1. Delivery Heat Treatment
Per ASME SA-387 standards, the plates must undergo one of the following heat treatments to achieve Class 1 mechanical properties:
Normalized & Tempered (N+T): The most common condition for balancing strength and toughness.
Annealed (A): Provides maximum ductility and lowest hardness.
Accelerated Cooling: With the purchaser's consent, plates may be liquid quenched or air-blast cooled, followed by tempering.
Tempering Temperature: The minimum tempering temperature must be at least 1150°F (620°C).
2. Welding Process
Preheating: Essential to prevent hydrogen-induced cracking. For SA 387 Gr.11, the minimum preheat temperature is typically 250°F (121°C), though it may be higher for thick sections (>1 inch).
Filler Metals: Use electrodes matching the base metal chemistry, such as E8018-B2 or low-carbon versions like E7018-B2L.
Interpass Temperature: Should be maintained within the specified range (usually 121°C to 300°C) to ensure a stable microstructure.
3. Post-Weld Heat Treatment (PWHT)
PWHT is critical for stress relief and improving the ductility of the Heat Affected Zone (HAZ).
Holding Temperature: Generally performed between 1200°F (650°C) and 1300°F (705°C).
Heating/Cooling Rates: Above 800°F (427°C), the heating rate is limited to 400°F/hr (222°C/hr) divided by the wall thickness in inches.
Soak Time: Typically 1 hour per inch of thickness, with a minimum of 15–30 minutes depending on the specific code (ASME Sec VIII Div 1 or 2).
4. Mechanical Properties (Class 1)
| Property | Value |
|---|---|
| Tensile Strength | 60 – 85 ksi (415 – 585 MPa) |
| Yield Strength | ≥ 35 ksi (240 MPa) |
| Elongation (in 2") | ≥ 22% |
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What kind of material is SA387 GR 11 CLASS 1?
It's an ASME-standard Cr-Mo alloy steel plate (1.25% Cr, 0.5% Mo) for high-temperature pressure equipment.
What core properties does it have after heat treatment?
It has excellent high-temperature strength, toughness, creep resistance, good weldability and low internal stress.
What heat treatments are commonly used for it?
Normalizing+Tempering or Quenching+Tempering to refine microstructure and optimize mechanical properties.
What's the normalizing temperature range for it?
Heated to 890-920°C (above critical temp), held, then air-cooled to refine grains.
Which standard regulates its production and inspection?
It complies with ASME SA-387, a standard for high-temperature pressure vessel plates.
What's its main application?
It's mainly used to make components for high-temperature and high-pressure boilers and vessels.
Does it have good corrosion resistance?
It has moderate corrosion resistance, especially against hydrogen attack for petrochemical use.
What cooling medium is used for its quenching?
Oil or water is adopted for rapid cooling to form martensite and enhance hardness.
Can it make heat exchanger components?
Yes, it is suitable for heat exchanger parts like plates and tubes, thanks to its excellent heat transfer performance and thermal fatigue resistance for high-temperature service.
What inspections are needed after heat treatment?
It requires mechanical tests (tensile, impact), microstructure inspection and NDT like ultrasonic and radiographic testing, all complying with ASME standards.
Is it suitable for high-temperature piping flanges?
Yes, it resists thermal cycling and mechanical stress, ensuring leak-tight connections in high-temperature and high-pressure piping systems reliably.
Welding precautions for it?
Preheat before welding, control interpass temperature, adopt matching weld materials and perform PWHT to prevent cracks and maintain mechanical properties.