ASTM A268 Standard Specification for Seamless and Welded Ferritic and Martensitic Stainless Steel Pipe for General Service. Covers standard specification for a number of grades of nominal wal thickness, welded ferritic and martensitic stainless steel tubing for general corrosion-resisting and high-temperature service.
The steel shall conform to the required chemical composition for carbon, manganese, phosphorus, sulfur, silicon, nickel, chromium, molybdenum, aluminum, copper, nitrogen, titanium, and columbium. The number of tubes in a lot heat treated by the continuous process shall be determined from the size of the tubes. The steel shall conform to the following tensile properties: tensile strength, yield strength, and elongation.
The tubes shall have a hardness number that will not exceed the prescribed Brinell and Rockwell hardness values. Several mechanical tests shall be conducted, namely: tension test; flaring test (for seamless tubes); flange test (for welded tubes); hardness test;flattening test; intergranular corrosion test; and hydrostatic or nondestructive electric test.
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.
Note 1-TP329 (S32900) formerly in this specification. has been transferred to Specifications A 789/A 789M and 790/A 790M.
An optional supplementary requirement is provided,and when desire, shall be so stated in the order.
Note 2-For tubing smaller than 1/2 in. [12.7 mm] in outside diameter, the elongation values given for strip specimens in Table 2 shall apply. Mechanical properties requirements do not apply to tubing smaller than 1/8 in. [3.2mm] in outside diameter or with walls thinner than 0.015 in. [0.4 mm].
| 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 |
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 |
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
Grade 410 stainless steels is 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
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.
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.
| 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 |
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.
