ASTM A387/A387M Grade 21 Class 2 Introduce
ASTM A387/A387M Grade 21 Class 2 is a low alloy steel plate for use in pressure vessels and boilers for welded construction. It is also suitable for use in heat exchangers, research reactors and organic and inorganic chemical reactors.
Smelting temperature:1876°C - 1127°C
Application:Pressure vessel plate, alloy steel, chrome molybdenum
ASTM A387/A387M Grade 21 Class 2 Material Chemical Composition
The chemical composition of the ASTM A387/A387M Grade 21 Class 2 steel are as follows:
| Element | Min | Max |
|---|---|---|
| Molybdenum (Mo) | 0.9000 | 1.1000 |
| Chromium (Cr) | 2.7500 | 3.2500 |
| PhOsphorus (P) | - | 0.0350 |
| Sulfur (S) | - | 0.0350 |
| Manganese (Mn) | 0.3000 | 0.6000 |
| Silicon (Si) | - | 0.5000 |
| Carbon (C) | 0.0500 | 0.1500 |
| Sulfur (S) | - | 0.0250 |
| PhOsphorus (P) | - | 0.0250 |
| Molybdenum (Mo) | 0.8500 | 1.1500 |
| Manganese (Mn) | 0.2500 | 0.6600 |
| Chromium (Cr) | 2.6300 | 3.3700 |
| Carbon (C) | 0.0400 | 0.1500 |
ASTM A387/A387M Grade 21 Class 2 Material Mechanical Properties
ASTM A387/A387M Grade 21 Class 2 steel requires either normalizing, tempered/quenched, or annealing treatments. Normalizing temperatures should be set between 845-925°C followed by air cooling. Tempered/quenched treatments involve heating the steel to 790-845°C and then quenching the steel in water or oil. Alternately, annealing treatments can be done at a temperature range of 760-845°C and air cooling.
The mechanical properties of the ASTM A387/A387M Grade 21 Class 2 steel are as follows:
| YieldRp0.2 | ≤ 864 (MPa) |
| TeileRm | ≤ 672 (MPa) |
| ImpactKV/Ku | 22(J) |
| ElongationA | 11% |
| Reduction in cross section on fractureZ | 23% |
| As-Heat-Treated Condition | Solution and Aging, Annealing, Ausaging, Q+T,etc |
| Brinell hardness (HBW) | 233 |
ASTM A387/A387M Grade 21 Class 2 Material Thermal Properties
The thermal performance parameters of the ASTM A387/A387M Grade 21 Class 2 steel are as follows:
| Temperature (°C) | 22 | 181 | 828 |
| Modulus of elasticity (GPa) | - | 257 | - |
| Mean coefficient of thermal expaion ×10-6/(°C) | - | - | 33 |
| Thermal conductivity (W/m·°C) | - | 41.3 | 31.2 |
| Specific thermal capacity (J/kg·°C) | - | 121 | - |
| Specific electrical resistivity (Ω mm²/m) | 0.31 | - | - |
| Deity (kg/dm³) | - | - | 222 |
| Poisson’s coefficient, ν | - | - | 322 |
ASTM A387/A387M Grade 21 Class 2 Material Machining Technology
ASTM A387/A387M Grade 21 Class 2 steel is a popular choice among manufacturers and machinists as it is corrosion and oxidation-resistant, tough, and affordable. It is also heat-treatable and can be machined with relative ease.