ASTM A387 Grade 5 Class 1 (often abbreviated as SA 387 Gr 5 Cl 1) is a high-quality chromium-molybdenum alloy steel plate. It is primarily used in the fabrication of weldable boilers and pressure vessels designed for elevated temperature service, such as those found in the oil, gas, and petrochemical industries.
Equivalents
| BS | EN | ASME | DIN |
| ... | ... | A387-5-1 | ... |
Specifications ASTM A387 Grade 5 Alloy Steel Plates
| Designation | Nominal Chromium Content (%) |
Nominal Molybdenum Content (%) |
| A387 Grade 5 | 5.00% | 0.50% |
Tensile Requirements for ASTM A387 Grade 5 Alloy Steel Plates Class 1 Plates
| Designation: | Requirement: | Grade 5 |
|
A387 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 ASTM A387 Grade 5 Alloy Steel Plates
| Element | Chemical Composition (%) | |
| A 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 |
processing
1. Heat Treatment (Thermal Processing)
The "Class 1" designation is achieved through specific cooling rates and tempering temperatures to prioritize ductility over high tensile strength.
Normalizing: Heating to 900°C – 950°C (1650°F – 1740°F) followed by air cooling to refine the grain structure.
Tempering: Performed at 675°C – 760°C (1250°F – 1400°F). For Class 1, the tempering duration is often longer to ensure the lower tensile range (60-85 ksi) and maximum toughness.
Annealing: Full annealing at 870°C – 930°C followed by slow furnace cooling is also an option for maximum softness.
2. Welding Procedures (WPS)
This grade is sensitive to hydrogen-induced cracking (HIC). Successful welding requires strict temperature control:
Preheating: Mandatory preheat of 150°C – 250°C (300°F – 480°F) depending on plate thickness.
Interpass Temperature: Must be maintained within the preheat range to prevent brittle martensite formation.
Post-Weld Heat Treatment (PWHT): Essential for all pressure vessel applications. Typically held at 700°C – 760°C (1300°F – 1400°F) to reduce hardness in the Heat Affected Zone (HAZ).
Filler Metal: Use low-hydrogen electrodes matching the chemistry, such as E8018-B6 or ER80S-B6.
3. Cutting and Forming
Thermal Cutting: Flame (Oxy-fuel) or Plasma cutting is standard. Due to the 5% Chromium content, the cut edges will harden significantly. It is recommended to grind away the hardened "heat-affected" edge before subsequent welding.
Cold Forming: Class 1 plates have excellent formability. However, if the strain exceeds 5%, a subsequent stress-relief or full heat treatment is often required by code (e.g., ASME BPVC).
Hot Forming: Performed between 850°C and 1050°C. If hot-formed, the plate must undergo a full Normalizing and Tempering cycle again to restore mechanical properties.
4. Surface Treatment & Inspection
Pickling or Blasting: Used to remove mill scale before fabrication to ensure high-quality welds.
Nondestructive Testing (NDT): Standard procedure for 2026 projects involves Ultrasonic Testing (UT) per ASTM A435 and Magnetic Particle Inspection (MPI) on weld seams to check for micro-cracks.
applications
1. Oil, Gas, and Petrochemical Industry
This is the most significant application area due to the material's resistance to corrosion and high-temperature oxidation.
Pressure Vessels: Used for the safe containment of pressurized gases and liquids at temperatures often reaching 316°C to 593°C.
Reactors: Specifically chosen for reactor vessels in petrochemical plants where high pressure and heat are used to initiate chemical reactions.
Refining Equipment: Applied in modules for transferring hot liquids and gases between processing stages.
Separators and Storage Tanks: Used for storing and separating volatile substances at elevated temperatures.
2. Power Generation
Industrial Boilers: Used in the fabrication of weldable boilers, specifically boiler steam drums and components subjected to sustained thermal stress.
Heat Exchangers: Indispensable for efficient heat transfer processes in thermal power plants.
Nuclear Power: Utilized in certain nuclear reactor pressure vessels and related high-pressure piping.
3. Specialized Processing Equipment
Chemical Manufacturing: Used in equipment handling corrosive media, such as sulfuric or citric acid solutions up to 343°C (650°F).
Gas Processing: Essential for condensers and high-pressure pipe work within gas processing facilities.
Heavy Machinery: Found in automotive components requiring heat resistance, such as exhaust systems and fuel pumps, as well as mining and cement industry equipment.
4. Marine and Offshore
Offshore Drilling: Applied in offshore drilling rigs and sea water equipment where a combination of tensile strength and salt-water corrosion resistance is required.
Shipbuilding: Used in specialized modules for marine vessels that handle hot or pressurized cargo.
If you want to learn more about A387 Grade 5 Class 1 GNEE's products, you can send an email to beam@gneesteelgroup.com. We are more than happy to assist you.
Is A387 Grade 5 Class 1 suitable for cryogenic services?
No, it is not ideal for cryogenic use. Its toughness decreases at low temps; cryogenic steels like A353 are preferred instead.
What is the molybdenum content of A387 Grade 5 Class 1?
The molybdenum content is 0.45-0.65%, which enhances high-temperature strength, creep resistance, and corrosion resistance.
Can A387 Grade 5 Class 1 be machined easily?
It has good machinability with proper tools and cutting parameters, though harder than carbon steel, requiring sharp tools and adequate lubrication.
What is the tensile strength range of A387 Grade 5 Class 1?
Its tensile strength ranges from 415-585 MPa, meeting the requirements of high-pressure and high-temperature industrial equipment.
What surface treatments are suitable for A387 Grade 5 Class 1?
It can undergo painting, galvanizing, or chrome plating to improve corrosion resistance, depending on the service environment.
Is A387 Grade 5 Class 1 used in the power generation industry?
Yes, it is widely used in power plants for boiler tubes, headers, and pressure vessels due to its excellent high-temp and high-pressure resistance.
What is the phosphorus content limit of A387 Grade 5 Class 1?
The maximum phosphorus content is 0.035%, as excessive phosphorus reduces toughness and increases brittleness in high-temperature services.
What distinguishes the application scope of A387 Grade 5 Class 1 from A242 Type 1?
Grade 5 Class 1 is for high-pressure boilers and vessels, while A242 Type 1 is for structural use, differing in pressure and temp resistance.
How is the heat treatment process of A387 Grade 5 Class 1 different from A387 Grade 7 Class 1?
Both need normalizing and tempering, but Grade 5 Class 1's tempering temp is 620-705°C, 20-30°C lower than Grade 7 Class 1, adapting to its alloy ratio.