Lord Fin Tube--Ferritic and Martensitic Stainless Steel Tubing
ASTM A268/ASME SA268 specifications cover a variety of grades of stainless steel tubing that are designed for general corrosion-resistant and high-temperature service. These specifications include both seamless and welded ferritic and martensitic stainless steel tubing.
Ferritic Stainless Steel Tubing
Ferritic stainless steels are known for their high chromium content (typically 15-30%) and low carbon content. This composition provides excellent corrosion resistance, good oxidation resistance, and stress corrosion cracking resistance. They are generally less expensive due to the absence of nickel.
Ferritic Stainless Steel Tubing Characteristics:
- Chromium content: 15%-30%
- Generally does not contain nickel
- May include small amounts of Mo, Ti, Nb
- High thermal conductivity
- Low thermal expansion coefficient
- Good oxidation resistance
- Excellent resistance to stress corrosion
- Used for air, water vapor, water, and oxidation acid corrosion parts
Ferritic Stainless Steel Tubing Common Grades:
|
Grade |
C (max) |
Mn (max) |
P (max) |
S (max) |
Si (max) |
Cr (%) |
Ni (%) |
UTS (MPa) |
YS (MPa) |
Elongation (%) |
|
TP405 |
0.08 |
1.0 |
0.04 |
0.03 |
1.0 |
11.5-14.5 |
0.75 |
415 min |
205 min |
20 min |
|
TP409 |
0.08 |
1.0 |
0.04 |
0.02 |
1.0 |
10.5-11.75 |
0.5 |
380 min |
170 min |
20 min |
|
TP430 |
0.12 |
1.0 |
0.04 |
0.03 |
1.0 |
16.0-18.0 |
0.75 |
450 min |
205 min |
20 min |
|
TP439 |
0.03 |
1.0 |
0.04 |
0.03 |
1.0 |
17.0-19.0 |
0.75 |
450 min |
205 min |
20 min |
|
TP444 |
0.025 |
1.0 |
0.04 |
0.03 |
1.0 |
17.5-19.5 |
1.00 |
450 min |
205 min |
20 min |
Martensitic Stainless Steel Tubing
Martensitic stainless steels, on the other hand, contain higher levels of carbon, which allows them to be hardened by heat treatment. This makes them suitable for applications requiring high strength and hardness. However, they are less corrosion-resistant than ferritic grades.
Martensitic Stainless Steel Tubing Characteristics:
- Similar to ferritic but can be hardened by heat treatment
- Chromium content: typically around 12%-18%
- Ferro magnetic
- Can be hardened by heat treatment
- Sensitive to notch-brittleness on slow cooling to ordinary temperatures
- Used in applications requiring increased hardness and strength
Martensitic Stainless Steel Tubing Common Grades:
|
Grade |
C (max) |
Mn (max) |
P (max) |
S (max) |
Si (max) |
Cr (%) |
Ni (%) |
UTS (MPa) |
YS (MPa) |
Elongation (%) |
|
TP410 |
0.15 |
1.0 |
0.04 |
0.03 |
1.0 |
11.5-13.5 |
0.5 |
485 min |
275 min |
20 min |
|
TP429 |
0.12 |
1.0 |
0.04 |
0.03 |
1.0 |
14.0-16.0 |
0.5 |
380 min |
205 min |
20 min |
|
TP434 |
0.12 |
1.0 |
0.04 |
0.03 |
1.0 |
16.0-18.0 |
0.75 |
450 min |
205 min |
20 min |
|
TP436 |
0.12 |
1.0 |
0.04 |
0.03 |
1.0 |
16.0-18.0 |
0.75 |
450 min |
205 min |
20 min |
|
TP442 |
0.2 |
1.0 |
0.04 |
0.03 |
1.0 |
18.0-23.0 |
0.5 |
450 min |
205 min |
20 min |
|
TP446 |
0.2 |
1.0 |
0.04 |
0.03 |
1.0 |
23.0-27.0 |
0.75 |
450 min |
205 min |
20 min |
|
UNS S41500 |
0.05 |
1.0 |
0.04 |
0.03 |
1.0 |
11.5-14.5 |
0.5-1.5 |
515 min |
345 min |
20 min |
ASTM A268/ASME SA268 tubing includes several grades of tubing, each tailored to different operational environments and mechanical requirements. Ferritic stainless steels, with high chromium content and typically no nickel, offer excellent resistance to stress corrosion and oxidation, making them ideal for applications like automotive exhaust systems and heat exchangers. Martensitic stainless steels, known for their ability to be hardened by heat treatment due to higher carbon content, are preferred in applications that demand high strength and hardness, such as in cutlery and valves. The choice between these grades depends on the specific requirements of the application, including the need for corrosion resistance, strength, and formability.
