Seamless steel pipe is a steel pipe made by perforating a solid round bar, with no weld seams on its surface. Based on the production method, seamless steel pipe can be categorized as hot-rolled seamless steel pipe, cold-rolled seamless steel pipe, cold-drawn seamless steel pipe, extruded seamless steel pipe, and jacking pipe. Based on cross-sectional shape, seamless steel pipe is categorized as round or special-shaped. Special-shaped pipes include square, oval, triangular, hexagonal, melon-seed, star-shaped, and finned pipes. The maximum diameter is 900mm, and the minimum is 4mm. Depending on the application, thick-walled and thin-walled seamless steel pipes are available. Seamless steel pipe is primarily used as oil and geological drilling pipe, cracking pipes for the petrochemical industry, boiler pipes, bearing pipes, and high-precision structural steel pipes for automobiles, tractors, and aviation.

Seamless steel pipes are seamless along the perimeter of their cross-section. Depending on the production method, they are categorized as hot-rolled, cold-rolled, cold-drawn, extruded, and jacked pipes, each with its own process specifications.

Seamless steel pipes are made from materials such as ordinary and high-quality carbon structural steels (Q215-A to Q275-A and No. 10 to No. 50 steels), low-alloy steels (such as 09MnV and 16Mn), alloy steels, and stainless and acid-resistant steels.

Seamless steel pipes are categorized by application into general-purpose (for water and gas pipelines, structural components, and mechanical parts) and specialized (for boilers, geological exploration, bearings, and acid-resistant applications).