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, and it covers standard specification for many 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, and be reheated to a temperature of 1200。F [650。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.
| Grade: | TP410 | TP430 | TP439 |
|---|---|---|---|
| UNS | S41000 | S43000 | S43035 |
| C, Max | 0.15 | 0.12 | 0.07 |
| Mn,Max | 1.00 | 1.00 | 1.00 |
| P, Max | 0.04 | 0.04 | 0.040 |
| S, Max | 0.03 | 0.03 | 0.030 |
| Si, Max | 1.00 | 1.00 | 1.00 |
| Ni | … | … | 0.50max |
| Cr | 11.5-13.5 | 16.0-18.0 | 17.00-19.00 |
| Mo | … | … | … |
| Al | … | … | 0.15 |
| Cu | … | … | … |
| N | … | … | 0.04 |
| Ti | … | … | 0.20+4(C+N)Min, 1.10max |
Other ASTM A268 Stainless Steel Grades
ASTM A268 TP 405, ASTM A268 TP 409, ASTM A268 TP 409S, ASTM A268 TP 410S, ASTM A268 TP 416, ASTM A268 TP 420, ASTM A268 TP 422, ASTM A268 TP 420, ASTM A268 TP 430F, ASTM A268 TP 430TI, ASTM A268 TP 440C, ASTM A268 TP 444, ASTM A268 TP 446.
ASTM A268 mainly contains 400 series Ferritic and Martensitic stainless steel grades, without or with slight Nickel element, so they have advantages in price compared to 304 or 316L stainless steel, which is the commonly 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 |
TP410, TP430 And TP439 Properties
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 |
ASTM A268 Test Requirements
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:
- Hydrostatic or nondestructive electric test.
- Tension test;
- Flaring test (for seamless tubes);
- Flange test (for welded tubes);
- Hardness test;
- Reverse flattening test;
- Intergranular corrosion test; and
ASTM A268 / A268M-10 (2016)
Standard Specification for Seamless and Welded Ferritic and Martensitic Stainless Steel Tubing for General Service
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
410 Stainless Steel
Grade 410 stainless steel is a general-purpose martensitic stainless steel containing 11.5% chromium, which provide good corrosion resistance properties. However, the corrosion resistance of grade 410 steels can be further enhanced by a series of processes such as hardening, tempering and polishing. Quenching and tempering can harden grade 410 steels. They are generally used for applications involving mild corrosion, heat resistance and high strength
430 Stainless steel
Stainless steel 430 combines good corrosion resistance with good formability and ductility, also has excellent resistance to nitric attack, which makes it well-suited to use in chemical applications. The most popular applications for 430 are in domestic appliances and decorative trim.
439 Stainless Steel
Stainless steel grade 439 is capable of being made into complex shapes such as tubular manifolds and exhaust system components, where temperatures tend to go beyond the oxidation limit of grade 409 steel. It is also preferred where wet corrosion resistance especially to chlorides is needed.
Stainless steel grade 439 has good weldability, brightness, and pitting corrosion resistance. It polishes well, and is good for deep drawing.
ASTM A268 Tensile Requirements
| Grade and UNS Designation | Tensile strength, min, | Yield strength, min, | ElongationA B , in 2 in. or 50 mm, |
|---|---|---|---|
| ksi [MPa] | ksi [MPa] | min, % | |
| TP405 S40500 | 60 [415] | 30 [205] | 20 |
| … S40800 | 55 [380] | 30 [205] | 20 |
| TP410 S41000 | 60 [415] | 30 [205] | 20 |
| TP429, TP430, and TP430 Ti S429000, S 43000, and S 43036 | 60 [415] | 35 [240] | 20 |
| TP443 S44300 | 70 [485] | 40 [275] | 20 |
| TP446-1 S44600 | 70 [485] | 40 [275] | 18 |
| TP446-2 S44600 | 65 [450] | 40 [275] | 20 |
| TP409 S40900 | 55 [380] | 25 [170] | 20 |
| TP439 S43035 | 60 [415] | 30 [205] | 20 |
| S43932 | 60 [415] | 30 [205] | 20 |
| … S41500 | 115 [795] | 90 [620] | 15 |
| TPXM-27 S44627 | 65 [450] | 40 [275] | 20 |
| TPXM-33 S44626 | 68 [470] | 45 [310] | 20 |
| 18Cr-2Mo S44400 | 60 [415] | 40 [275] | 20 |
| 29-4 and 29-4-2 S44700 and S44800 | 80 [550] | 60 [415] | 20 |
| 26-3-3 S44660 | 85 [585] | 65 [450] | 20 |
| 25-4-4 S44635 | 90 [620] | 75 [515] | 20 |
| … S44735 | 75 [515] | 60 [415] | 18 |
| 28-2-3.5 | |||
| S32803 | 87 [600] | 72 [500] | 16 |
| S40977 | 65 [450] | 41 [280] | 18 |
| S43940 | 62 [430] | 36 [250] | 18 |
| S42035 | 80 [550] | 55 [380] | 16 |
| TP468 S46800 | 60 [415] | 30 [205] | 22 |