A pipe production process in which a heated solid ingot is rolled into a hollow pipe body with no seams around the perimeter. The hot rolling method can be used to produce carbon steel, alloy pipes, high alloy steel, and some non-ferrous metal seamless steel pipes, with outer diameters ranging from 16 to 1600mm and wall thicknesses from 2 to 200mm.

In addition to round cross-section pipes, there are also various special-shaped cross-section pipes and variable-section pipes. In addition to being used as finished pipes, hot-rolled seamless steel pipes can also be used as pipe materials for cold-drawn and cold-rolled pipes (see cold-rolled and cold-drawn pipes). Seamless steel pipes produced by hot rolling account for 80% to 90% of seamless steel pipe production.

The technological process of modern hot-rolled seamless steel pipes is: the tube blanks used for hot-rolled seamless steel pipes include ingots, continuous cast billets, rolled billets, forged billets, and hollow cast billets. The basic process of hot-rolled seamless steel pipe is:
(1) Pierce the ingot or billet into a hollow thick-walled capillary tube on a punching machine. The methods of piercing the tube blank are divided into two-roll cross-rolling piercing, pressure piercing, push-rolling piercing, three-roller cross-rolling piercing, etc.
(2) Thin the capillary tube on the stretching machine and extend it into a raw tube with a wall thickness close to that of the finished tube. The methods of capillary tube extension or capillary tube rolling include automatic tube rolling machine, continuous tube rolling machine, three-roller and two-roller cross-rolling (see pipe material rolling extension), periodic tube rolling machine, and Pipe jacking machine.
(3) Raw pipes are finely rolled into finished pipes in the finishing mill. Finish rolling of raw pipes includes pipe leveling and pipe sizing to improve quality, as well as pipe diameter reduction and pipe thermal expansion to expand product specifications.

The units for producing hot-rolled seamless steel pipes can vary depending on the production methods and equipment used in the three basic processes of piercing, stretching, and finishing rolling. Different units are named after the rolling mill that extends the capillary tube into the raw tube. For example, those with automatic pipe rolling machines are called automatic pipe rolling units, those with continuous pipe rolling machines are called continuous pipe rolling units, and those that roll raw tubes on a three-roller (or two-roller) cross-rolling stretcher are called three-roller (or two-roller) Pipe rolling units, those using periodic pipe rolling machines to roll pipes are called periodic pipe rolling units, and those using CPE pipe jacking machines to jack pipes are called CPE pipe jacking units.