Low carbon steel: The carbon content is less than 0.25%. It has good plasticity and toughness and is easy to process. It is often used to make chains, rivets, bolts, etc. Medium carbon steel: The carbon content is between 0.25% and 0.6%, and its strength and hardness are higher than low carbon steel. It is used to manufacture moving parts such as axles, worms, and gears. High carbon steel: with a carbon content of more than 0.6%, high strength and hardness, but poor weldability and plasticity, it is used to make springs, wear-resistant parts and cutting tools.

Hot rolled seamless steel pipe. The outer diameter is usually greater than 38mm, and the wall thickness is between 3~80mm. Cold rolled seamless steel pipe. The outer diameter can be up to 6mm and the wall thickness can be up to 0.25mm. High pressure seamless steel pipe. The outer diameter ranges from 10 to 159mm, and the wall thickness ranges from 2 to 45mm. Precision seamless steel pipe. The outer diameter ranges from 10 to 377mm, and the wall thickness ranges from 1 to 25mm. stainless steel pipe. The outer diameter range is from 6 to 530mm, and the wall thickness is from 0.5 to 15mm.

Steel pipes made of a single piece of metal with no seams on the surface are called seamless steel pipes. Materials include ordinary and high-quality carbon structural steel (Q215-A ~ Q275-A and 10 ~ 50 steel), low alloy steel (09MnV, 16Mn, etc.) Seamless steel pipes are made from steel ingots or solid tube blanks that are perforated into capillary tubes, and then hot rolled, cold rolled or cold drawn.

Elastic stage: The deformation in this stage is completely elastic, and it returns to its original state after being stressed, and no plastic deformation occurs. If all loads are removed, its original length can still be restored.