Seamless carbon steel pipe (Seamless carbonsteel pipe) is made of steel ingot or solid tube blank through perforation to make capillary, and then hot-rolled, cold-rolled or cold-drawn.

It is made by rolling low-carbon carbon structural steel or low-alloy structural steel strip according to a certain spiral angle(called forming angle) into a tube blank, and then welding the tube seam together.

Square and rectangular pipe is a name for square pipe and rectangular pipe, that is, steel pipes with equal and unequal side lengths.