Fluid pipes are pipes (mostly seamless steel pipes) that are specially used to transport media with fluid properties. The media with fluid properties, in addition to liquid media such as water, oil, solution, etc., solid media such as cement, grain, coal powder, etc., can also flow under certain conditions. Fluid pipes can be made of steel, non-ferrous metals such as copper and titanium, or even non-metallic materials such as plastics.

Special-shaped seamless steel pipe is a general term for seamless steel pipes with cross-sectional shapes other than round pipes. Special-shaped seamless steel pipes are widely used in various structural parts, tools and mechanical parts. Compared with round pipes, special-shaped pipes 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.

Steel pipes have a hollow section whose length is much greater than the diameter or circumference of steel. According to the cross-sectional shape, it is divided into round, square, rectangular and special-shaped steel pipes.

Plastic-coated steel pipe, also known as plastic-coated pipe, steel-plastic composite pipe, and plastic-coated composite steel pipe. The steel-plastic composite steel pipe is based on a seamless pipe or a welded steel pipe, and a plastic anti-corrosion layer is welded on the inner surface of the steel pipe (bottom pipe) by spraying, rolling, dipping, and suction processes, or a plastic anti-corrosion layer is welded on the inner and outer surfaces.

The surface quenching and tempering heat treatment of ERW straight seam welded pipe is usually carried out by induction heating or flame heating. The main technical parameters are surface hardness, local hardness and effective hardened layer depth.

Seamless steel pipe is a steel pipe without weld seam manufactured by hot processing methods such as piercing and hot rolling. If necessary, the hot-worked pipe can be further cold-worked to the required shape, size and performance. At present, seamless steel pipe is the most widely used pipe in petrochemical production equipment (such as octg casing).