The seamless square tube is a long strip of steel having a hollow section and no seam at the periphery, and is a square tube formed by a seamless tube passing through the four sides of the mold.

ASTM A210 standard covers minimum-wall-thickness, tubing sizes, boiler flues including safe ends, arch and stay tubes.

ASTM A213-Seamless ferritic and austenitic alloy-steel boiler, superheater and heat-exchanger tubes

ASTM A335-Seamless ferritic alloy-steel pipe for high-temperature service.

ASTM A519-Seamless carbon and alloy steel mechanical tubing.

ASTM A53-Pipe steel, black and hot-dipped, zinc-coated, welded seamless