ASTM A268 is Standard specification for Seamless and Welded Ferritic and Martensitic Stainless Steel Tubing for General Service, the grades contain TP410, TP405, TP420, TP430, TP430Ti, TP403, TP409, TP444, TP439 and TP446, it covers standard specification for a number of grades of nominal-wall-thickness, welded ferritic and martensitic stainless steel tubing for general corrosion-resisting and high-temperature service, ASME SA268 is alternative standard.
The tubes shall be made by the seamless or welded process with no filler metal added, tubes shall be reheated to a temperature of 1200。F [650。澳门凯发娱乐C] or higher and cooled to meet the requirements of this specification, All tubes shall be free of excessive mill scale, suitable for inspection. A slight amount of oxidation will not be considered as scale.
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 TP410, TP430, TP439 Chemical Composition
The steel shall conform to the required chemical composition for carbon, manganese, phosphorus, sulfur, silicon, nickel, chromium, molybdenum, aluminum, copper, nitrogen, titanium, and columbium, most of these grades are commonly characterized by being ferromagnetic.
ASTM A268 mainly contains 400 series Ferritic and Martensitic stainless steel grades, without or with slight Nickel element, so they have advantages on price compared to 304 or 316L stainless steel, that is the common used grade。
ASTM A268 Stainless Steel Tubing Sizes Tolerance
Variations in outside diameter, wall thickness, and length from those specified shall not exceed the amounts prescribed below。
|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|
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 ||30 ||20|
|TP430||60 ||35 ||20|
|TP439||60 ||30 ||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。
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.
ASTM A268 / A268M-10 (2016)
This specification covers a number of grades of nominal-wall-thickness, stainless steel tubing for general corrosion-resisting and high-temperature service. Most of these grades are commonly known as the “straight-chromium” types and are characterized by being ferromagnetic. Two of these grades, TP410 and UNS S 41500 in the specification (Table 1), are amenable to hardening by heat treatment, and the high-chromium, ferritic alloys are sensitive to notch-brittleness on slow cooling to ordinary temperatures. These features should be recognized in the use of these materials. Grade TP439 is used primarily for hot-water tank service and does not require post-weld heat treatment to prevent attack of the heat affected zone.
TP410 Stainless Steel
TP430 Stainless steel
TP439 Stainless Steel
Stainless steel grade 439 has good weldability, brightness, and pitting corrosion resistance. It polishes well, and is good for deep drawing.