SA 387 Grade 5 Class 2 is a chromium-molybdenum alloy steel plate, conforming to ASTM/ASME standards, designed for weldable pressure vessels and boilers used in high-temperature service, offering excellent corrosion resistance and strength at elevated temperatures due to its chromium and molybdenum content. It's a high-quality, durable material used extensively in the oil, gas, chemical, and power generation industries for equipment like heat exchangers, refineries, and storage tanks.
Equivalents
| BS | EN | ASME | DIN |
| ... | ... | SA387-5-2 | ... |
Specifications ASME SA387 Grade 5 Alloy Steel Plates
| Designation | Nominal Chromium Content (%) |
Nominal Molybdenum Content (%) |
| SA387 Grade 5 | 5.00% | 0.50% |
Tensile Requirements for ASME SA387 Grade 5 Alloy Steel Plates Class 2 Plates
| Designation: | Requirement: | Grade 5 |
|
SA387 Grade 5 |
Tensile strength, ksi [MPA] | 75 to 100 [515 to 690] |
| Yield strength, min, ksi [MPa]/(0.2% offset) | 45 [310] | |
| Elongation in 8 in. [200mm], min % | ... | |
| Elongation in 2 in. [50mm], min, % | 18 | |
| Reduction of area, min % | 45 (measured on round specimen) 40 (measured on flat specimen) |
Chemical Requirements for ASME SA387 Grade 5 Alloy Steel Plates
| Element | Chemical Composition (%) | |
| SA 387 Grade 5 | ||
| Carbon: | Heat Analysis: | 0.15 max |
| Product Analysis: | 0.15 max | |
| Manganese: | Heat Analysis: | 0.30 - 0.60 |
| Product Analysis: | 0.25 - 0.66 | |
| Phosphorus: | Heat Analysis: | 0.035 |
| Product Analysis: | 0.035 | |
| Sulphur (max): | Heat Analysis: | 0.030 |
| Product Analysis: | 0.030 | |
| Silicon: | Heat Analysis: | 0.50 max |
| Product Analysis: | 0.55 max | |
| Chromium: | Heat Analysis: | 4.00 - 6.00 |
| Product Analysis: | 3.90 - 6.10 | |
| Molybdenum: | Heat Analysis: | 0.45 - 0.65 |
| Product Analysis: | 0.40 - 0.70 |
SA 387 Grade 5 Class 2 is a chromium-molybdenum alloy steel plate (5% Cr, 0.5% Mo) specifically designed for high-temperature pressure vessels and boilers. Given its high alloy content, the processing must strictly follow ASME Section II, Part A guidelines.
1. Heat Treatment Process
Heat treatment is critical to achieving the required mechanical properties for Class 2.
Delivery Condition: Usually supplied in an Annealed or Normalized and Tempered (N+T) condition.
Normalizing: Heating to approximately 900–950°C (1650–1740°F) to refine the grain structure.
Tempering: The standard mandates a minimum tempering temperature of 705°C (1300°F) to ensure ductility and toughness after the hardening effects of chromium.
Accelerated Cooling: Liquid quenching or forced air cooling is permitted followed by tempering to enhance specific mechanical properties.
2. Welding Procedure (WPS)
The 5% Cr content makes the material prone to air-hardening and cold cracking.
Preheating: Essential to prevent hydrogen-induced cracking (HIC). For Class 2, preheating is typically required at a minimum of 150°C to 200°C (300°F to 400°F) depending on thickness.
Interpass Temperature: Must be strictly controlled, generally maintained at the same level as the preheat temperature.
Post-Weld Heat Treatment (PWHT): Mandatory to reduce hardness in the Heat Affected Zone (HAZ) and relieve residual stresses. Typical PWHT temperature range is 705°C to 760°C (1300°F to 1400°F).
3. Mechanical Property Requirements (2026 Standards)
The "Class 2" designation signifies higher strength requirements compared to Class 1:
Tensile Strength: 75–100 ksi [515–690 MPa].
Yield Strength: Minimum 45 ksi [310 MPa].
Elongation: Minimum 18% (in 2 inches).
4. Key Processing Notes
Cold/Hot Forming: If hot forming is performed, the material must undergo a full re-heat treatment (Normalizing and Tempering) to restore its design properties.
Corrosion Resistance: The 5% Chromium provides excellent resistance to oxidation and sulfidation in refinery environments at temperatures up to 600°C.
applications
1. Oil, Gas, and Petrochemical Industry
This is the primary sector for SA 387 Grade 5. It is used for equipment that handles corrosive hydrocarbons at high temperatures:
Hydrocracking and Hydrotreating Units: Specifically in reactors and separators where resistance to high-temperature hydrogen attack is necessary.
Refinery Process Vessels: Including distillation columns and fractionation towers.
Heat Exchangers and Condensers: Handling aggressive media and high-pressure steam.
Sour Service Environments: Utilized in environments containing 𝐻2𝑆 due to its improved oxidation and sulfidation resistance.
2. Power Generation
In power plants, this grade is selected for its high-temperature tensile strength and creep resistance:
Industrial Boilers and Steam Generators: Used for boiler drums and piping that must maintain structural integrity under prolonged thermal stress.
Power Plant Superheaters: Components exposed to extreme steam temperatures.
Nuclear Power Industry: Used in specific secondary-side pressure vessel components where limited corrosion and elevated temperature are concerns.
3. Chemical and Heavy Processing
Chemical Storage Tanks: For holding various chemicals that require elevated temperatures to remain in a liquid or gaseous state.
Pharmaceutical Reactors: Used in high-pressure synthesis processes.
Pulp and Paper Industry: Components for digesters and other high-temperature processing equipment.
4. Specialized Industrial Equipment
Liners and Wear Plates: For chutes, bins, and truck bodies in mining or heavy construction that operate in high-heat environments.
Ducting and Pipe Supports: In high-temperature exhaust systems.
Furnace Equipment: Pins, shafts, and conveyors used within industrial furnaces.
Full specification and details are available on request. The above information is provided for guidance purposes only. For specific design requirements please contact our technical sales staff.
What type of material is SA 387 Grade 5 Class 2?
SA 387 Grade 5 Class 2 is a low-alloy chromium-molybdenum (Cr-Mo) steel plate, primarily designed for high-temperature and pressure applications.
What are the key alloying elements in SA 387 Grade 5 Class 2 and their typical ranges?
The main alloying elements are chromium (Cr: 1.00-1.50%) and molybdenum (Mo: 0.45-0.65%). It also contains carbon (C: max 0.18%), manganese (Mn: 0.40-0.70%), silicon (Si: 0.15-0.40%), and trace amounts of phosphorus (P) and sulfur (S) (each max 0.035%).
Which standard specifies SA 387 Grade 5 Class 2?
SA 387 Grade 5 Class 2 is specified by the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC), specifically in Section II, Part A (Ferrous Materials).
What is the maximum service temperature for SA 387 Grade 5 Class 2?
The maximum continuous service temperature for SA 387 Grade 5 Class 2 is approximately 593°C (1100°F), making it suitable for high-temperature industrial environments.
What heat treatment is typically required for SA 387 Grade 5 Class 2?
The standard heat treatment for SA 387 Grade 5 Class 2 includes normalizing (heating to 899-954°C / 1650-1750°F, followed by air cooling) and tempering (heating to 593-704°C / 1100-1300°F, then cooling).
What are the typical mechanical properties of SA 387 Grade 5 Class 2 after heat treatment?
The minimum yield strength is 207 MPa (30,000 psi), the minimum tensile strength is 414 MPa (60,000 psi), and the minimum elongation at break is 22% (in 50 mm / 2 inches).
In which industries is SA 387 Grade 5 Class 2 commonly used?
It is widely used in the oil and gas, petrochemical, power generation (boilers, turbines), and chemical processing industries, especially for pressure vessels, reactors, heat exchangers, and piping components.
What is the difference between SA 387 Grade 5 Class 1 and Class 2?
The main difference lies in thickness and heat treatment requirements. Class 2 is intended for thicker plates (usually above a certain thickness, e.g., >10 mm) and requires more stringent heat treatment (normalizing + tempering) to ensure uniform mechanical properties, while Class 1 may have simpler heat treatment for thinner sections.
Is SA 387 Grade 5 Class 2 weldable? If yes, what welding consumables are recommended?
Yes, it is weldable. Recommended welding consumables include E7018-B2 (for shielded metal arc welding, SMAW), ER80S-B2 (for gas metal arc welding, GMAW), and E8018-B2 (for flux-cored arc welding, FCAW), which match the Cr-Mo composition to maintain high-temperature strength.
What quality control tests are commonly performed on SA 387 Grade 5 Class 2 plates?
Common tests include chemical composition analysis (via spectroscopy), mechanical property tests (tensile, yield, elongation, impact), ultrasonic testing (UT) for internal defects, and visual inspection (VI) for surface quality. For critical applications, hardness testing and metallographic examination may also be required.