Double-wall spiral welded pipe and manufacturing method thereof

A double-wall spiral welded pipe, formed by spiral roll welding of a double-layer composite steel belt, wherein the double-layer composite steel belt comprises a first steel belt layer (1) and a second steel belt layer (2) which have equal widths, are arranged in parallel and align with each other;

• at least two supporting steel bars (3) perpendicular to the first steel belt layer (1) and the second steel belt layer (2) are arranged between the first steel belt layer (1) and the second steel belt layer (2);
• the supporting steel bars (3) are arranged on end parts of two sides of the first steel belt layer (1) and the second steel belt layer (2) and extend together with the first steel belt layer (1) and the second steel belt layer (2);
• and the first steel belt layer (1), the second steel belt layer (2) and the supporting steel bars (3) on the end parts of the two sides are mutually welded to form a double-layer composite steel belt with a rectangular section in an extending direction.