By material 

Quality steel tubing (steel) can be divided into: carbon and alloy tube, stainless steel pipe and so on. Carbon tubes can be divided into ordinary carbon steel tubes and high quality carbon structural tube. 

Tubes can be divided into: low alloy, high alloy structural tubing, alloy tube, high strength tube. Bearing acid-resistant stainless tubes, precision tubes, heat-resistant alloys (Kovar) tube and high temperature alloy etc.