ASTM A387 Standard Specification for CHROMIUM-MOLYBDENUM ALLOY STEEL PLATES FORPRESSURE VESSELS
The ASTM A387 specification is the Standard Specification for Pressure Vessel Plates, Alloy Steel, Chromium-Molybdenum plates used in the application of welded boilers and pressure vessels subjected to elevated temperatures. The two grades SSAB produces are available as Class 1 and/or Class 2.
ASTM A387 steel plate is a specification for chromium-molybdenum alloy steel plates intended primarily for use in elevated temperature service. These plates are designed for applications that require improved mechanical properties and resistance to oxidation, making them suitable for use in high-temperature environments.
Key Properties:
Composition: ASTM A387 steel plates typically contain chromium (up to 9% or more) and molybdenum (up to 2.25% or more), which enhance their strength and corrosion resistance at high temperatures.
Grades: The specification includes various grades, such as Grade 5, 9, 11, 12, 22, and 24, differentiated by their composition and intended use.
Applications:
ASTM A387 steel plates are commonly used in:
Pressure vessels
Heat exchangers
Power generation equipment
Piping systems in the oil and gas industry
Chemical processing facilities
Overall, ASTM A387 steel plates are essential for applications requiring materials that can withstand high temperatures and corrosive environments, offering reliable performance and durability.
ASTM A387 Chemical Composition
| Grade | Chromium (%) | Molybdenum (%) | Key Characteristics |
|---|---|---|---|
| A387 Gr. 11 | 1.00–1.50 | 0.45–0.65 | Good corrosion resistance, cost-effective choice |
| A387 Gr. 12 | 0.80–1.25 | 0.45–0.65 | Slightly lower Cr, stable at moderate temps |
| A387 Gr. 22 | 1.90–2.60 | 0.87–1.13 | High strength and heat resistance |
| A387 Gr. 91 | 8.00–9.50 | 0.85–1.05 | Enhanced creep strength at extreme temps |
ASTM A387 Mechanical Properties
| Property | Grade 11 / 12 | Grade 22 | Grade 91 |
|---|---|---|---|
| Tensile Strength (MPa) | 415–585 | 415–585 | 585–760 |
| Yield Strength (MPa) | ≥ 205 | ≥ 240 | ≥ 415 |
| Elongation (%) | ≥ 20 | ≥ 18 | ≥ 18 |
| Impact Resistance | Charpy V-notch Tested (Class 2) |
|
Features & Benefits
Withstands high-temperature, high-pressure environments
Excellent weldability and fabrication properties
Superior resistance to hydrogen-induced cracking and sulfide stress corrosion (H2S)
Long service life in harsh environments
Cost-effective for long-term boiler operations
Heat Treatment for A387 Chrom Moly Alloy Steel Plate
Chrome moly alloy steel plates under ASTM A387 must be killed steel and are thermally treated through processes such as annealing, normalizing, and tempering. Alternatively, if agreed upon by the buyer, the plates may undergo accelerated cooling from the austenitizing temperature via air blasting or liquid quenching, followed by tempering. The minimum tempering temperatures are outlined in the table below:
|
Grade |
Temperature, °F [°C] |
|---|---|
|
2, 12 and 11 |
1150 [620] |
|
22, 22L, 21, 21L and 9 |
1250 [675] |
|
5 |
1300 [705] |
Grade 91 alloy steel plates shall be heat treated by normalizing and tempering or by accelerated cooling by air blasting or liquid quenching, followed by tempering. Grade 91 plates need to be austenitized at 1900 to 1975°F [1040 to 1080°C] and shall be tempered at 1350 to 1470°F [730 to 800°C]
Grade 5, 9, 21, 21L, 22, 22L, and 91 plates ordered without heat treatment by above table, shall be finished in either the stress relieved or annealed condition.
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