I. Classification by material and model

1. Carbon steel pipe

Common carbon steel

Q195, Q215, and Q235: Commonly used in low-pressure fluid transportation (such as drainage pipes and ordinary brackets), they have low strength and are easy to weld.

Q275: It has relatively high strength and is used for mechanical parts (such as shafts and gears).

High-quality carbon steel

Steel 20# and 45# : Steel 20# has good toughness and is used for seamless steel pipes (such as fluid pipelines). 45# steel has high strength and is used in mechanical structures.

Low alloy high strength steel

Q345 (16Mn), Q460: High strength, low-temperature resistance, used in Bridges and pressure vessels.

2. Stainless steel pipe

Austenitic stainless steel

304 (06Cr19Ni10) : The most commonly used, it has good corrosion resistance and is applied in food and chemical pipelines.

316 (06Cr17Ni12Mo2) : Containing molybdenum, resistant to seawater and strong acids, suitable for Marine engineering and medical equipment.

310S (06Cr25Ni20) : High-temperature resistant (≤1200℃), used in boilers and heating tubes.

Ferritic stainless steel

430 (10Cr17) : It has better corrosion resistance than carbon steel, is low in cost, and is used for decoration and construction.

Martensitic stainless steel

410 (12Cr13) : High strength, average corrosion resistance, used in cutting tools and valves.

3. Alloy steel pipe

Cr-Mo steel: such as 15CrMo and 35CrMo, resistant to high temperature and high pressure, is used in power station pipelines and pressure vessels.

Cr-Ni steel: such as 12Cr1MoV, has strong oxidation resistance and is suitable for high-temperature steam pipelines.

Ii. Classification by structure and manufacturing process

Seamless steel pipe

Hot-rolled seamless pipe

Model: Φ10mm to Φ630mm (outer diameter), wall thickness 1mm to 40mm.

Common materials: 20#, 45#, 304, 316, 15CrMo.

Application: High-pressure pipelines (such as natural gas and oil), mechanical structures.

Cold-rolled/cold-drawn seamless tubes

High precision, outer diameter Φ6mm to Φ219mm, wall thickness 0.5mm to 12mm.

Used for precision instruments and hydraulic oil pipes (such as automotive brake pipes).

2. Welded steel pipe (seam pipe)

Straight seam welded pipe

Welded steel pipes for low-pressure fluid conveyance (GB/T 3091) :

Model: DN15 - DN200 (nominal diameter), such as DN25 (1-inch pipe, outer diameter 33.7mm).

Material: Q235, Q355, used for water and gas pipelines.

Spiral welded pipe

The outer diameter is Φ219mm to Φ2000mm, and the wall thickness is 6mm to 20mm.

Material: Q345, X52 (pipeline steel), used for long-distance oil and gas pipelines (such as the West-East Gas Pipeline project).

Iii. Classification by Application and Typical Models

Steel pipes for fluid transportation

Water supply pipe

Stainless steel water pipes: DN15 - DN100, material 304/316, in compliance with hygiene standards.

Galvanized welded pipe (GB/T 3091) : DN15 - DN150, Q235B galvanized, anti-corrosion.

Gas pipe

Seamless steel pipe: Φ25mm to Φ114mm, made of 20# steel, in compliance with GB 50028 standard.

Spiral welded pipe: Φ325mm to Φ1016mm, material Q355B, used for high-pressure gas transmission.

2. Structural steel pipes

Construction scaffolding pipe

The outer diameter is 48.3mm, the wall thickness is 3.6mm, the material is Q235B, and it complies with the JGJ 130 standard.

Mechanical structure tube

Seamless tubes: Φ20mm to Φ150mm, made of 45# steel, used for shaft parts.

Square and rectangular tubes: 10mm×10mm to 200mm×200mm, Q345B, used for steel structure frames.

3. Special-purpose steel pipes

Boiler tube

Seamless tubes, made of 20G (carbon steel for boilers) and 12Cr1MoVG (alloy tubes), with outer diameters ranging from Φ32mm to Φ159mm, are used for the heating surfaces of high-pressure boilers.

Petroleum cracking tube

Material: 20#, 15CrMo, outer diameter: Φ10mm to Φ168mm, used for oil refining equipment pipelines.

Hydraulic prop pipe

Seamless pipe, made of 27SiMn material, with an outer diameter ranging from Φ63.5mm to Φ159mm, is used for hydraulic supports in coal mines.