ASTM A387/A387M Grade 21 Class 1 Introduce
ASTM A387/A387M Grade 21 Class 1 steel is a heat-treated chromium-molybdenum alloy steel. It is mainly used for the construction of pressure vessels and boiler components. The steel is well-known for its superior resistance to corrosion, wear and tear, and fatigue. This is due to its excellent balance of properties and chemical composition, which combines a high strength-to-weight ratio, high hardness, and excellent weldability. ASTM A387/A387M Grade 21 Class 1 also offers good formability, machinability and good ductility, which make it suitable for a variety of applications.
Smelting temperature:1166°C - 1572°C
Application:Pressure vessel plate, alloy steel, chrome molybdenum
ASTM A387/A387M Grade 21 Class 1 Material Chemical Composition
The chemical composition of the ASTM A387/A387M Grade 21 Class 1 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 1 Material Mechanical Properties
The mechanical properties of ASTM A387/A387M Grade 21 Class 1 steel are some of the most important aspects of this material class. This alloy has excellent high temperature strength and oxidation resistance. At temperatures up to 815°C, the tensile strength of ASTM A387/A387M Grade 21 Class 1 steel is greater than 550MPa, while the yield strength is greater than 345MPa. Additionally, this material also has excellent resistance to oxidation, making it able to maintain its mechanical properties in temperatures up to 1000°C.
The mechanical properties of the ASTM A387/A387M Grade 21 Class 1 steel are as follows:
| YieldRp0.2 | ≤ 727 (MPa) |
| TeileRm | ≤ 366 (MPa) |
| ImpactKV/Ku | 34(J) |
| ElongationA | 43% |
| Reduction in cross section on fractureZ | 41% |
| As-Heat-Treated Condition | Solution and Aging, Annealing, Ausaging, Q+T,etc |
| Brinell hardness (HBW) | 221 |
ASTM A387/A387M Grade 21 Class 1 Material Thermal Properties
The thermal performance parameters of the ASTM A387/A387M Grade 21 Class 1 steel are as follows:
| Temperature (°C) | 23 | 333 | 411 |
| Modulus of elasticity (GPa) | - | 263 | - |
| Mean coefficient of thermal expaion ×10-6/(°C) | - | - | 41 |
| Thermal conductivity (W/m·°C) | - | 21.3 | 33.2 |
| Specific thermal capacity (J/kg·°C) | - | 321 | - |
| Specific electrical resistivity (Ω mm²/m) | 0.34 | - | - |
| Deity (kg/dm³) | - | - | 313 |
| Poisson’s coefficient, ν | - | - | 311 |
ASTM A387/A387M Grade 21 Class 1 Material Machining Technology
ASTM A387/A387M Grade 21 Class 1 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.