In the cold drawing process of seamless steel pipe, the degree of deformation varies from the outer surface layer to the inner surface layer due to the non-uniformity of deformation. The additional bending deformation and shear deformation near the outer surface layer are larger, so the total deformation degree of the outer layer is larger than that of the inner layer. Therefore, the outer grain is finer and the hardness is higher, while the inner layer is opposite. The thicker of ASTM A106 Gr B 12 Inch Seamless Pipe wall is, the greater the friction coefficient is, and the bigger the cone angle of the die is.

　　The difference of total deformation degree between inner and outer layers will increase, and the degree of non-uniformity of structure and performance will increase. Because the deformation degree of inner and outer layers is different, the structure and properties of inner and outer layers of seamless steel pipe are different after deformation.

　　Seamless steel pipe is a high quality carbon structural steel with low hardness and easy cutting. It is often used as template, tip and guide post in die, but it needs heat treatment.

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