Shaped seamless steel pipe is a general term for seamless steel pipes with cross-sectional shapes other than round pipes. According to the shape and size of the cross-section of the steel pipe, it can be divided into special-shaped seamless steel pipes with equal wall thickness (code-named D), special-shaped seamless steel pipes with different wall thickness (code-named BD), and special-shaped seamless steel pipes with variable diameter (code-named BJ).

Shaped seamless steel pipe are widely used in various structural parts, tools and mechanical parts. Compared with round pipes, Shaped seamless steel pipe generally have a larger moment of inertia and section modulus, and have greater bending and torsion resistance, which can greatly reduce the structural weight and save steel.

Seamless square tubes and seamless rectangular tubes are also special-shaped seamless steel tubes.
Calculation method of theoretical weight of seamless torque management: (side length + side length) × 2 × wall thickness × 0.00785 × length;
Seamless square management theoretical weight calculation method: side length x4x wall thickness x0.00785 x length