46 CFR §56.80-15

1. (a)Carbon-steel piping that has been heated to at least 1,650 °F (898 °C) for bending or other forming requires no subsequent heat treatment.
2. (b)Ferritic alloy steel piping which has been heated for bending or other forming operations must receive a stress relieving treatment, a full anneal, or a normalize and temper treatment, as specified by the design specification before welding.
3. (c)Cold bending and forming of carbon steel having a wall thickness of three-fourths of an inch and heavier, and all ferritic-alloy pipe in nominal pipe sizes of 4 inches and larger, or one-half-inch wall thickness or heavier, will require a stress-relieving treatment.
4. (d)Cold bending of carbon-steel and ferritic-alloy steel pipe in sizes and wall thicknesses less than specified in 129.3.3 of ASME B31.1 (incorporated by reference; see § 56.01-2) may be used without a postheat treatment.
5. (e)For other materials the heat treatment of bends and formed components must be such as to ensure pipe properties that are consistent with the original pipe specification.
6. (f)All scale must be removed from heat treated pipe prior to installation.
7. (g)Austenitic stainless-steel pipe that has been heated for bending or other forming may be used in the “as-bent” condition unless the design specification requires post-bending heat treatment.