Composite pipes are pipes based on a composite structure of metal and thermoplastic plastic. The inner and outer layers are made of non-metallic materials such as polyethylene and polypropylene. The middle layer is a metal structure, and the composite pipe is combined with special hot melt adhesive and has the advantages of metal pipes and non-metal pipes.

The deformation caused by the welding process directly affects the performance and use of the welded steel pipe, so it is necessary to use different welding processes to control and prevent the deformation of the steel pipe, and to correct the components that produce welding deformation.

The welding stress of the steel pipe is the stress generated by the welding of the seamless pipe or the welded pipe. Welding residual stress has six influences on steel pipes.

The production process of small-diameter thick-walled seamless steel pipes is the same as that of seamless pipes, and can be divided into four basic methods: cold drawing, cold rolling, hot rolling, and thermal expansion. Small-diameter thick-walled steel pipes are mostly used in large-scale steel structure construction as the main support part (steel pipe pile), such as bridge piling, submarine piling, and high-rise building piling.

Tapered pipe refers to a tapered seamless pipe designed and manufactured with seamless steel pipe as raw material through special equipment and technology. The main material of the seamless tapered steel pipe is mainly carbon steel, but also stainless steel and alloy steel.

Seamless steel pipes have a hollow cross-section and are widely used as pipes for transporting fluids, such as pipes for transporting oil, natural gas, gas, water, and certain solid materials. Special-shaped seamless steel pipe is a general term for seamless steel pipes with cross-sectional shapes other than round pipes. Seamless square pipes (such as a500 square tube) and seamless rectangular tubes (a500 rectangular tube) also belong to special-shaped seamless steel pipes.