In conventional rolling, the axis of the billet is perpendicular to the axis of the rolling mill, and the movement trend of the workpiece is consistent with the direction of the rolling mill, which can be called longitudinal rolling. Roll forging is a longitudinal rolling process in which the length of the billet is less than the circumference of the rolling roller during plastic deformation. During roll forging deformation, a pair of reverse rotating molds are used to continuously produce local deformation of the blank. Flat roll deformation is a simple deformation situation in roll forging.
With the reverse rotation of the upper and lower rollers, the billet is compressed by the mold in the height direction, resulting in plastic deformation, a decrease in height, and an increase in length. This deformation process is similar to longitudinal rolling, and the area between the two dashed lines in the figure is the deformation zone. The main parameters of deformation include the length l of the deformation zone, the height h0 and width b0 of the inlet section of the billet, the height h1 and width b1 of the outlet section of the billet, and the center angle of the rolling roller corresponding to the deformation zone α (biting into the corner), etc.
Just like rolling, the deformation of the billet at any moment during roll forging can represent the entire deformation process, which is very stable. However, in actual production, during roll forging deformation, the axial cross-section of the billet generally changes and the deformation is unstable. The roll forging die is installed on the forging roller, and as the upper and lower forging rollers rotate in opposite directions, the billet undergoes continuous and local plastic deformation with the change of the mold groove. In actual production, the cross-section of the groove of the roll forging die is constantly changing, which leads to the deformation zone of the roll forging being subjected to force, the biting of the billet during the roll forging process, and the forward sliding, backward sliding, and widening during the roll forging process, all of which are constantly changing. This results in the roll forging process being more complex than the flat roll.