Definition and Manufacturing Process: Seamless steel pipes are made from solid billets such as round steel or square steel, which are heated and perforated to form hollow rough tubes, and then processed by rolling, sizing, straightening, and other steps. The production process of hot-rolled seamless steel pipes includes heating the pipe billet → perforation → three-roll skew rolling, continuous rolling or extrusion → pipe removal → sizing → cooling → straightening → hydrostatic testing → marking → warehousing; cold-drawn seamless steel pipes are made on the basis of hot-rolled pipes through steps such as heading → annealing → pickling → oiling → multiple passes cold drawing → heat treatment → straightening → hydrostatic testing → marking → warehousing.

• Classification: According to material, it can be divided into carbon steel seamless pipes, alloy steel seamless pipes, stainless steel seamless pipes, etc.; according to use, it can be divided into structural seamless pipes, boiler pipes, petroleum pipeline pipes, etc.; according to manufacturing process, it can be divided into hot-rolled seamless pipes and cold-drawn seamless pipes.

• Features: Seamless steel pipes have high strength and good pressure resistance, suitable for withstanding higher pressures; their material structure is relatively uniform, ensuring a more reasonable distribution of stress during use; they have good corrosion resistance, especially stainless steel seamless pipes, which are suitable for harsh environments; they have no welding seams, making them more reliable than welded steel pipes and giving them a longer service life.

• Specifications: The specifications of seamless steel pipes are expressed as the pipe's outer diameter multiplied by the wall thickness. The lengths are usually 3000-12000mm for hot-rolled pipes and 2000-10500mm for cold-drawn pipes.

• Standards: Common standards include GB/T 8162 for structural seamless steel pipes, GB/T 8163 for fluid seamless steel pipes, GB/T 5310 for high-pressure boiler pipes, etc.

• Application Areas: They are widely used in petroleum, chemical, power, machinery manufacturing, and other fields. For example, in the petroleum and natural gas industry, they are used for oil and gas pipelines and oil drilling pipes; in the power industry, they are used for boiler pipes, steam pipelines, etc.; in the chemical industry, they are used for pipelines transporting corrosive fluids.