During the rolling process, the relative movement between the roll and the rolling produces a resistance to contact with the surface of the metal particle, which is called external friction. Its resistance is called frictional resistance or friction, the direction of friction and the opposite direction of motion. And plastic deformation occurs when the plastic, gold M internal particles produce relative movement (slip) caused by friction called internal friction. The internal friction of solids is a direct consequence of the motion of the whole molecule. These molecules are in close contact with each other, showing a strong mutual attraction and repulsion between each other. The internal friction causes the metal body to cut inside and causes internal heat. So far, the study of internal friction of metal materials is not enough, the information is also very poor. Thus, the friction discussed in the rolling process usually refers to the external friction between the roll and the roll.