Comprehensive Classification of Seamless Steel Pipes (Industry Standard; Common in Foreign Trade & Procurement)

I. By Production Process (Primary Classification)

1. Hot-Rolled Seamless Steel Pipe

- Billet heating and piercing → Rolling/forming

- Large dimensions, thick walls; moderate precision; surface scale present

- Applications: Fluid pipelines, structural piping, thick-walled boiler tubes

2. Cold-Rolled Seamless Steel Pipe (Cold-drawn pipes are also considered cold-processed)

- Cold processing of hot-rolled raw tubes (no heating)

- High-dimensional precision, uniform wall thickness, smooth inner and outer surfaces

- Cold-rolled: Thinner walls, higher precision. Cold-drawn: Simpler equipment, ideal for small batches.

- Collectively known as precision seamless steel pipes

II. By Material

1. Carbon Seamless Steel Pipe

- 10#, 20#, 45# (GB Standard)

- A106 Gr.B, A53 Gr.B (ASTM Standard)

2. Alloy Seamless Steel Pipe

- Low-alloy: 16Mn (Q345B), 12Cr1MoV, 15CrMo

- Medium/High-alloy: 42CrMo, 4 0Cr

3. Stainless Seamless Steel Pipe

304, 316L, 321, TP310S, etc. (Chemical/Corrosion-resistant)

III. By Application (Most Common Order Classification)

1. Structural Seamless Steel Pipe (GB/T 8162)

Supports, mechanical components, construction machinery; non-pressure-bearing

2. Seamless Steel Pipe for Fluid Transport (GB/T 8163)

Water, oil, and gas transportation; requires flaw detection; suitable for low-pressure applications

3. Seamless Steel Pipe for High-Pressure Boilers (GB 5310 / ASME SA213)

High-temperature/high-pressure boilers, superheaters (alloys such as 12Cr1MoVG))

4. Oil Country Tubular Goods (OCTG)

- Tubing, casing, and drill pipe (API standards) 5CT

5. Precision seamless steel pipes for hydraulic applications

Cold-rolled bright tubes, high precision, hydraulic cylinder barrels

6. Seamless steel pipes for gas cylinders

High-pressure shells for oxygen and nitrogen cylinders

7. Bearing steel pipes (GCr15)

8. Seamless steel pipes for shipbuilding (GB/T 5312)

IV. By wall thickness

1. Thin-walled seamless pipes

2. Standard wall thickness

3. Thick-walled seamless steel pipes (wall thickness > 10% of outer diameter)

V. Surface Treatment

- Black pipe (as-rolled/hot-rolled surface)

- Bright cold-worked pipe (cold-rolled bright finish)

- Pickling and passivation (stainless steel)

- Galvanized seamless steel pipes (hot-dip or electro-galvanized; anti-corrosion)

VI. Standards systems

- Chinese National Standards (GB)

- US Standards (ASTM/ASME, API)

- German Standards (DIN) / European Standards (EN)

- Japanese Industrial Standards (JIS)