Alloy seamless steel tubes refer to seamless steel tubes with cross-sectional shapes other than circular tubes. According to the different dimensions of the tube cross-section shape, they can be further divided into equal wall thickness alloy seamless steel tubes (code D), unequal wall thickness alloy seamless steel tubes (code BD), and variable diameter alloy seamless steel tubes (code BJ).

Extruded seamless steel tubes are widely used in various structural components, tools, and mechanical parts. Compared to round tubes, extruded tubes typically have larger inertia moments and section moduli, offering greater bending and torsional resistance. This can significantly reduce structural weight and save on steel usage.

The development of non-standard pipes primarily involves the expansion of product varieties, encompassing cross-sectional shapes, materials, and properties. Extrusion, oblique die rolling, and cold drawing are effective methods for producing non-standard pipes, suitable for creating pipes with various cross-sections and materials. To produce a wide range of non-standard pipes, it is essential to possess diverse production means. In the 1990s, China, building on the original cold drawing method, developed dozens of production techniques including roller drawing, extrusion, hydraulic, rolling, spinning, continuous rolling, rotating forging, and moldless drawing, while continuously improving and creating new equipment and processes.