ASTM A790/A790M Type 255 Introduce
ASTM A790/A790M is a specification for seamless and welded ferritic-austenitic (duplex) stainless steel pipe. The A790 specification covers several grades of austenitic-ferritic (duplex) stainless steel pipe. This type of stainless steel has a higher corrosion resistance than other forms of stainless steel due to its higher chromium content. The bi-metallic property of duplex stainless steel is highly resistive to general corrosion and stress corrosion.
Smelting temperature:1564°C - 1385°C
Application:Seamless and welded ferritic/austenitic stainless steel tube
ASTM A790/A790M Type 255 Material Chemical Composition
The chemical composition of the ASTM A790/A790M Type 255 steel are as follows:
| Element | Min | Max |
|---|---|---|
| Silicon (Si) | - | 1.0000 |
| Sulfur (S) | - | 0.0300 |
| PhOsphorus (P) | - | 0.0400 |
| Nickel (Ni) | 4.5000 | 6.5000 |
| Nitrogen (N) | 0.1000 | 0.2500 |
| Molybdenum (Mo) | 2.9000 | 3.9000 |
| Manganese (Mn) | - | 1.5000 |
| Copper (Cu) | 1.5000 | 2.5000 |
| Chromium (Cr) | 24.0000 | 27.0000 |
| Carbon (C) | - | 0.0400 |
ASTM A790/A790M Type 255 Material Mechanical Properties
The mechanical properties of ASTM A790/A790M Type 255 are determined by its chemical composition, which gives it an excellent combination of ductility and strength. The alloy has a yield strength of 260 MPA, which is relatively high for a stainless steel. It also has an ultimate tensile strength of 680 MPA, which is higher than many other common stainless steels. This alloy is also highly resistant to abrasion and is suitable for use in applications that require toughness and wear resistance.
The mechanical properties of the ASTM A790/A790M Type 255 steel are as follows:
| YieldRp0.2 | ≤ 166 (MPa) |
| TeileRm | ≤ 763 (MPa) |
| ImpactKV/Ku | 23(J) |
| ElongationA | 12% |
| Reduction in cross section on fractureZ | 24% |
| As-Heat-Treated Condition | Solution and Aging, Annealing, Ausaging, Q+T,etc |
| Brinell hardness (HBW) | 123 |
ASTM A790/A790M Type 255 Material Thermal Properties
The thermal performance parameters of the ASTM A790/A790M Type 255 steel are as follows:
| Temperature (°C) | 33 | 976 | 115 |
| Modulus of elasticity (GPa) | - | 451 | - |
| Mean coefficient of thermal expaion ×10-6/(°C) | - | - | 11 |
| Thermal conductivity (W/m·°C) | - | 12.3 | 13.2 |
| Specific thermal capacity (J/kg·°C) | - | 321 | - |
| Specific electrical resistivity (Ω mm²/m) | 0.34 | - | - |
| Deity (kg/dm³) | - | - | 413 |
| Poisson’s coefficient, ν | - | - | 233 |
ASTM A790/A790M Type 255 Material Machining Technology
When machining ASTM A790/A790M Type 255 steel, various machining processes can be used depending on the desired outcome. The most common machining processes used are turning, milling, and drilling, with an emphasis on the former two. Turning is a processes by which the steel is rotated and the cutting tool is fed into the material, allowing for a controlled cutting action with a higher amount of precision. Milling processes involve the same concept, but here the steel is moved into the cutting tool instead. Drilling is also used to create holes in the material with high accuracy, but is often used less than the other two processes.