This standard is issued under the fixed designation A 268; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon ( ュ) indicates an editorial change since the last revision or reapproval.

1. Scope
1.1 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 ferromag-netic. Two of these grades, TP410 and UNS S41500 (Table1), are amenable to hardening by heat treatment, and the high-chromium, ferritic alloys are sensitive to notch-brit-tleness 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.

NOTE 1-TP329 (S32900) formerly in this specification. has been transferred to Specifications A 789/A 789M and 790/A 790M.

1.2 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 property 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].

1.3 The values stated in either inch-pound units or SIunits are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the specification. The inch-pound units shall apply unless the "M" designation of this specification is specified in the order.