一. Classification by production method
Steel pipes can be divided into two categories according to production methods: seamless steel pipes and welded steel pipes.
1. Seamless steel pipes can be divided into hot-rolled seamless pipes, cold-drawn pipes, precision steel pipes, hot-expanded pipes, cold-spun pipes and extruded pipes according to production methods.
Seamless steel pipes are made of high-quality carbon steel or alloy steel and are divided into hot-rolled and cold-rolled (drawn).
2. Welded steel pipes are divided into furnace welded pipes, electric welded (resistance welded) pipes and automatic arc welded pipes due to their different welding processes. They are divided into straight seam welded pipes and spiral welded pipes due to their different welding forms. They are divided into round welded pipes and special-shaped (square, flat, etc.) welded pipes due to their end shapes.
Welded steel pipes are made of steel plates rolled into a tube shape by welding with butt seams or spiral seams. In terms of manufacturing methods, they are divided into welded steel pipes for low-pressure fluid transportation, spiral seam electric welded steel pipes, direct rolled steel pipes, electric welded pipes, etc. Seamless steel pipes can be used for various liquid and gas pipelines. Welded pipes can be used for water pipes, gas pipes, heating pipes, etc.
二. Classification by material
Steel pipes can be divided into carbon pipes, alloy pipes, stainless steel pipes, etc. according to the material (i.e. steel type) of the pipe.
Carbon pipes can be divided into ordinary carbon steel pipes and high-quality carbon structural pipes.
Alloy pipes can be divided into low alloy pipes, alloy structural pipes, high alloy pipes, and high-strength pipes. Bearing pipes, heat-resistant and acid-resistant stainless pipes, precision alloy (such as Kovar) pipes, and high-temperature alloy pipes.
三. Classification by connection method
Steel pipes can be divided into plain pipes (without threads at the pipe ends) and threaded pipes (with threads at the pipe ends) according to the connection method of the pipe ends.
Threaded pipes can be divided into ordinary threaded pipes and thickened threaded pipes at the pipe ends.
Thickened threaded pipes can also be divided into threaded pipes with external thickening (with external threads), internal thickening (with internal threads), and internal and external thickening (with internal and external threads).
Threaded pipes can also be divided into threaded pipes with common cylindrical or conical threads and special threads according to thread types.
In addition, threaded pipes are generally delivered with pipe joints according to user needs.
四. Classification by coating characteristics
Steel pipes can be divided into black pipes (uncoated) and coated pipes according to surface coating characteristics.
Coated pipes include galvanized pipes, aluminum-coated pipes, chrome-coated pipes, aluminum-diffused pipes and other alloy-layer steel pipes.
Coated pipes include outer coating pipes, inner coating pipes, and inner and outer coating pipes. Commonly used coatings include plastics, epoxy resins, coal tar epoxy resins, and various glass-type anti-corrosion coating materials.
五. Classification by use
1. Pipes for pipelines. Such as: seamless pipes for water, gas pipes, steam pipes, oil pipelines, and oil and gas trunk pipes. Agricultural irrigation water taps and sprinkler pipes, etc.
2. Pipes for thermal equipment. Such as boiling water pipes and superheated steam pipes for general boilers, superheated pipes, large smoke pipes, small smoke pipes, arched brick pipes and high-temperature and high-pressure boiler pipes for locomotive boilers, etc.
3. Pipes for the machinery industry. Such as aviation structural pipes (round pipes, oval pipes, flat oval pipes), automobile half-axle pipes, axle pipes, automobile tractor structural pipes, tractor oil cooler pipes, square pipes and rectangular pipes for agricultural machinery, transformer pipes and bearing pipes, etc.
4. Pipes for petroleum geological drilling. Such as: oil drilling pipes, oil drill rods (square drill rods and hexagonal drill rods), drill braces, oil oil pipes, oil casings and various pipe joints, geological drilling pipes (core pipes, casings, active drill rods, drill braces, clamps and pin joints, etc.).
5. Pipes for the chemical industry. Such as: oil cracking pipes, pipes for heat exchangers and pipelines of chemical equipment, stainless acid-resistant pipes, high-pressure pipes for fertilizers, and pipes for conveying chemical media, etc.
6. Pipes for other departments. Such as: tubes for containers (tubes for high-pressure gas cylinders and general container tubes), tubes for instruments and equipment, tubes for watch cases, tubes for injection needles and other medical devices, etc.
