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.
ASTM A387 Grade 5 Class 1 Alloy Steel Sheets, Plates & Coils Specifications:
| Specifications | ASTM A387 / ASME SA387 |
| Standard | ASTM, ASME and API |
| Thickness | 4.0mm – 100mm |
| Specialize | Shim Sheet, Perforated Sheet, B. Q. Profile. |
| Form | Coils, Foils, Rolls, Plain Sheet, Shim Sheet, Perforated Sheet, Chequered Plate, Strip, Flats, Blank (Circle), Ring (Flange) |
| Finish | Hot rolled plate (HR), Cold rolled sheet (CR), 2B, 2D, BA NO(8), SATIN (Met with Plastic Coated) |
| Hardness | Soft, Hard, Half Hard, Quarter Hard, Spring Hard etc. |
| Grade | ASTM A387 GR.5 CL.1 |
Chemical Composition of ASTM A387 Grade 5 Class 1 Alloy Steel Sheets, Plates & Coils
| Grade | C | Si | Mn | P | S | Cr | Mo |
| A387 GR.5 CL.1 | 0.15 max | 0.55 max | 0.25-0.66 max | 0.035 max | 0.035 max | 3.90-6.10 max | 0.40-0.70 max |
Mechanical properties of ASTM A387 Grade 5 Class 1 Alloy Steel Sheets, Plates & Coils
| Grade | A387 GR.5 CL.1 | |||
| A387 GR.5 CL.1 | Thickness mm | Yield Min Mpa | Tensile Mpa | Elongation Min % |
| t≦50 | 205 | 415-585 | 18 | |
| 50<t≦200 | - | - | - | |
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.
Types of ASTM A387 Grade 5 Class 1 Alloy Steel Sheets, Plates & Coils
Alloy Steel ASME SA387 Plates
ASTM A387 GR.5 CL.1 Plates Exporter
Alloy Steel A387 GR.5 CL.1 Chequered Plate
Alloy Steel GR.5 CL.1 Plate Supplier
GR.5 CL.1 Alloy Diamond Chequered Plate
ASTM A387 GR.5 CL.1 Plates Manufacturers
Alloy Steel GR.5 CL.1 Plate Stockholder
Alloy Steel GR.5 CL.1 Cold Rolled Plates
A387 Alloy Steel Plate 2B Finish Dealer
#4 Finish GR.5 CL.1 Alloy Steel Plates
Cut to Size Alloy Steel GR.5 CL.1 Plates
Hot Rolled Alloy Steel GR.5 CL.1 Plates
Alloy Steel ASTM A387 CR Plates Stockist
Alloy Steel GR.5 CL.1 HR Plates Dealer
Leading Manufacturer Of Alloy Steel GR.5 CL.1 Plates
ASTM A387 High Quality CL.1 GR.5 Plates
ASME SA 387 GR.5 CL.1 Plates Distributors
GR.5 CL.1 Alloy Steel Plates Exporter
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.
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How is the weldability of A387 Grade 5 Class 1 different from A283 Grade C?
A387 Grade 5 Class 1 requires preheating before welding, unlike A283 Grade C which is easier to weld without strict preheating, due to alloy composition differences.
What's the contrast in maximum service temperature between A387 Grade 5 Class 1 and A387 Grade 22 Class 1?
Grade 5 Class 1's max service temp is 593°C, lower than Grade 22 Class 1's 649°C, as the latter has more chromium-molybdenum for heat resistance.
What is the hardness of A387 Grade 5 Class 1 after heat treatment?
After normalizing and tempering, its Brinell hardness is ≤207 HB, ensuring good machinability and toughness.
Does A387 Grade 5 Class 1 resist hydrogen embrittlement?
It has moderate resistance to hydrogen embrittlement, so proper heat treatment and welding processes are required in hydrogen-containing environments.
What is the melting point range of A387 Grade 5 Class 1?
Its melting point ranges from 1420-1480°C, similar to other chromium-molybdenum steels, suitable for high-temperature fabrication.
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.
How does the yield strength of A387 Grade 5 Class 1 compare with A487 Grade 2?
A387 Grade 5 Class 1 has a yield strength of ≥275 MPa, higher than A487 Grade 2's ≥240 MPa, offering better load-bearing capacity.
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.
What's the difference in chemical composition between A387 Grade 5 Class 1 and A387 Grade 11 Class 1?
Grade 11 Class 1 has 1.00-1.50% chromium, while Grade 5 Class 1 has 4.00-6.00% chromium, enhancing the latter's high-temp performance.