20# steel pipe is made of steel 20# (consists of 0.2% C) and its regular state is seamless pipe.20# steel pipe has raw material of excellent carbon structural Steel which make the steel have great function of deformability when it’s in cold deformation, generally used for bending, calendering, crimping and hammer arching. The welding performance of arc welding and contact welding is good. The thickness is small during gas welding, and the shape is strict or the shape is complicated. The machinability cold drawn or normalized state is better than the annealed state, and is generally used to manufacture parts that are less stressed and have high toughness requirements.

Steel 45#:

The contents of C, Si, Mn, P, and S of 20# and steel 45# are different, and 45# is higher than 20#. 45# steel is commonly medium carbon tempered steel with good mechanical properties, low hardenability and easy cracking during water quenching. Small parts should be treated with quenching and tempering, and large parts should be normalizing. They are mainly used to manufacture moving parts with high strength, such as turbine impeller, compressor piston, shaft, gear, rack, worm and worm gear, etc.

27SiMn:

27SiMn steel has better performance than 16Mn and 25Mn. It has high hardenability and a critical hardenable diameter of 8-22mm in water. It has good machinability, moderate cold deformation deformability and weldability. In addition, the toughness of steel is reduced during heat treatment, at the same time, but it has quite high strength and wear resistance, especially water quenching still has high toughness; but this steel is sensitive to white point, when it is under heat treatment, it has temper brittle tendency and superheat sensitivity.

16Mn:

16Mn (Q345B) steel pipe is a low-alloy high-strength structural steel with a carbon content of 0.1-0.25%. The main alloy elements are manganese, silicon, vanadium, niobium, titanium, etc., and its total alloy content is less than 3%. According to the intensity, it is divided into 4 levels of 300, 350, 400 and 450 Mpa. There are mainly Q295, Q345, Q390, Q420, Q460. Q is yield strength, and the number after it is the minimum yield point (σs) value of the grade. Among them, A and B grade steels are usually called 16Mn.

25Mn:

25Mn refers to high-quality carbon structural steel. The strength of 25Mn is higher than steel20# and 20Mn. Other properties are similar to steel20# and 20Mn. It is used for carburizing and welding parts. Compared to steel 20# and 25Mn, have higher ratio. Strength and hardenability, good deformability in cold deformation, medium weldability, and good machinability. There is a tendency to temper brittleness and heat sensitivity during heat treatment.