This standard is issued under the fixed designation A 791; 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 welded, unannealed, ferritic stainless steel tubing intended for high-temperature and corrosive serice where post-weld heat treatment is not necessary for corrosion resistance. These grades are com-monly known as the "straight-chromium" types and are characterized by being ferromagnetic. 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 thest materials.The user requiring additional testing or examination is referred to the Supple-mentary Requirements or Ordering Information Section, or both. Users requiring a tubular product with post-weld heat treatment are referred to Specification A 2668 /A 268M.

1.2 The values stated in either inch-pound units or SI units 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; theerfore, 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.

NOTE 1-For tubing smaller than 1/2 in. [12.7 mm] in outside diameter, the elongation values given for strip specimens in Table 1 shall apply. Mechanical property requirements do not apply to tubing smaller than 1/8 in. [3.2 mm]in outside diameter or with walls thinner than 0.015 in.[0.4mm].