Hydraulic system on the fluid tube in the domestic standard is close to the standard GB3639-83. Introduction to hydraulic steel pipe: hydraulic equipment with high dimensional accuracy and good surface finish cold drawn or cold rolled precision seamless steel pipe. Selects precision seamless steel pipe to manufacture mechanical structure or hydraulic equipment, precision steel pipe is a kind of high precision seamless steel pipe after cold drawing or cold rolling treatment. Because the inner and outer wall of the precision steel pipe has no oxidation layer, no leakage under high pressure, high precision, high finish, no deformation in cold bending, flared, flattened and no crack, etc., it is mainly used to produce pneumatic or hydraulic products.