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ASTM A268 TP439 stainless steel tubes are manufactured using either seamless or welded processes, with no filler metal added during welding. All steel tubes must undergo reheating at a temperature of 1200°F [650°C] or higher followed by cooling. The surfaces of all tubes shall be free from excessive mill scale and shall be in a condition suitable for inspection. Minor surface oxide films shall not be regarded as mill scale.
For ASTM A268 TP439 welded tubes, advanced processes such as TIG welding and Post-Weld Heat Treatment (PWHT) are adopted to relieve residual stress and reduce the risk of Stress Corrosion Cracking (SCC). Our seamless tubes also feature a surface roughness of Ra < 0.6 μm, ensuring minimal fluid friction and excellent flow performance.
In addition, our TP439 heat exchanger tubes offer outstanding resistance to Stress Corrosion Cracking (SCC), with a service life in chloride environments far exceeding that of 304 stainless steel. With a thermal conductivity of up to 26 W/(m·K) and a linear expansion coefficient of 10.8×10⁻⁶/°C, the heat transfer efficiency is improved by 15% compared to conventional ferritic stainless steels. Furthermore, the tubes have an elongation of ≥25%, providing excellent ductility to withstand U-bending and complex forming operations.
ASTM A268 Stainless Steel Tubing Specification
| Standard | ASTM A268, ASME SA268 |
|---|---|
| Tube Type | Both Welded And Seamless |
| Grades | ASTM A268 TP 410, ASTM A268 TP 430, ASTM A268 TP 439 |
| Outside Diameter | 1/4″ (6.25mm) To 8″ (203mm) |
| Wall Thickness | 0.02″ (0.5mm) To 0.5″(12mm) |
| Application | Heat Exchanger, Heater, Condenser |
ASTM A268 TP439 stainless steel round pipe Chemical Composition
| Grade: | TP439 |
|---|---|
| UNS | S43035 |
| C, Max | 0.07 |
| Mn,Max | 1.00 |
| P, Max | 0.040 |
| S, Max | 0.030 |
| Si, Max | 1.00 |
| Ni | 0.50max |
| Cr | 17.00-19.00 |
| Mo | … |
| Al | 0.15 |
| Cu | … |
| N | 0.04 |
| Ti | 0.20+4(C+N)Min, 1.10max |
ASTM A268 Stainless Steel Tubing Sizes Tolerance
| Outside Diameter, In.[Mm] | OD Tolerance, In.[Mm] | Wall Thickness, % | Thin Wall Tubes |
|---|---|---|---|
| Up To1⁄2, [12.7], Excl | ±0.005 [0.13] | ±15 | |
|
1⁄2 To 11⁄2 [12.7 To 38.1], Excl/Td>
|
±0.005 [0.13] | ±10< | Less Than 0.065 In. [1.6 Mm] Nominal |
| 11⁄2 To 31⁄2 [38.1 To 88.9], Excl | ±0.010 [0.25] | ±10 | Less Than 0.095 In. [2.4 Mm] Nominal |
| 31⁄2 To 51⁄2 [88.9 To 139.7], Excl | ±0.015 [0.38] | ±10 | Less Than 0.150 In. [3.8 Mm] Nominal |
| 51⁄2 To 8 [139.7 To 203.2], Incl | ±0.030 [0.76] | ±10 | Less Than 0.150 In. [3.8 Mm] Nominal |
What is ASTM A268?
ASTM A268 is the "Standard Specification for Seamless and Welded Ferritic and Martensitic Stainless Steel Tubing for General Service." The grades covered by this standard include TP410, TP405, TP420, TP430, TP430Ti, TP403, TP409, TP444, TP439, and TP446, which are suitable for use in general corrosion-resistant and high-temperature environments; ASME SA268 serves as the corresponding equivalent standard.
Yield Strength of TP439 Stainless Steel Tube
The steel shall conform to the following tensile properties: tensile strength, yield strength, and elongation.
| Grade | Tensile Strength, Min, Ksi [MPa] | Yield Strength, Min, Ksi [MPa] | ELONGATION. MIN, % |
|---|---|---|---|
| TP410 | 55 [380] | 30 [205] | 20 |
| TP430 | 60 [415] | 35 [240] | 20 |
| TP439 | 60 [415] | 30 [205] | 20 |
The tubes shall have a hardness number that will not exceed the prescribed Brinell and Rockwell hardness values, TP410, TP430 and TP439 max Rockwell hardness 90, Test report required certification conform to Specification A1016/A1016M.
What is the difference between TP439 stainless steel tube and TP304?
The main difference is that TP304 is an austenitic, nickel-containing stainless steel (18/8) with superior, well-rounded corrosion resistance and higher ductility, while TP439 is a titanium-stabilized ferritic stainless steel (18% Cr) designed for high corrosion resistance and high-temperature strength, often used in automotive exhaust systems due to lower cost.
Several mechanical tests shall be conducted, namely:
Tension test;
Flaring test (for seamless tubes);
Flange test (for welded tubes);
Hardness test;
Reverse flattening test;
Intergranular corrosion test; and
Hydrostatic or nondestructive electric test.
Packaging and Marking:
The material shall be packaged in bundles or plywood crates, wrapped in plastic, and provided with appropriate protective measures to ensure seaworthy transport, or packaged as otherwise specified.
Marking shall comply with the requirements of Specification A1016/A1016M. The marking shall indicate whether the tubing is hot-finished or cold-finished, and shall includebut not be limited to the following information: standard, grade, dimensions, heat number, and lot number.
