ASTM A 790 Seamless and Welded Ferritic/Austenitic Stainless Steel Pipe

This specification covers seamless and straight-seam welded ferritic/austenitic steel pipe intended for general corrosive service, with particular emphasis on resistance to stress corrosion cracking. These steels are susceptible to embrittlement if used for prolonged periods at elevated temperatures.

UNS number: S31803 (Ferritic/Austenitic steel)

Ordering Information

Orders for product under this specification should in-clude the following, as required, to describe the desired material adequately:

1 Quantity (feet, metres, or number of lengths),

2 Name of material (ferritic/austenitic steel pipe),

3 Process (seamless or welded),

4 Grade,

5 Size (NPS designator or outside diameter and schedule number of average wall thickness),

6 Length (specific or random),

7 End finish,

8 Optional requirements (product analysis; hydrostatic test or nondestructive electric test),

9 Test report required (section on certification of Specification A999/A999M),

10 Specification designation, and

11 Special requirements and any supplementary requirements selected.

Manufacture

The pipe shall be made by the seamless or an automatic welding process, with no addition of filler metal in the welding operation.

At the manufacturer’s option, pipe may be either hot-finished or cold-finished.

The pipe shall be pickled free of scale. When bright annealing is used, pickling is not necessary

Heat Treatment

Temperature: 1020-1100 °C

Quench: rapid cooling in air or water

Chemical requirements, %,

C: ≤0.030

Mn: ≤2.00

P: ≤0.030

S: ≤0.020

Si: ≤1.00

Cr: 21.0-23.0

Ni: 4.5-6.5

Mo: 2.5-3.5

N: 0.08-0.20

Tensile requirements

Tensile Strength: ≥620MPa

Yield Strength.: ≥450MPa

Elongation in 2 in. or 50 mm, %: ≥25

Hardness:

HBW: ≤290

HRC: ≤30

Each tube shall be subjected to the nondestructive electric test or the hydrostatic test.

Permissible Variations in Wall Thickness

The minimum wall thickness at any point shall not be more than 12.5 % under the nominal wall thickness specified.

Permissible Variations in Outside Diameter