Study on Control Strategies of Two-roll Straightening for Bar High Precision Straightening

High precision straightening roll design and process parameters control are the core technology of the two-roll straightener. In order to meet the requirements of bar high precision straightening, the design method of "three-stage concave roll and two-stage convex roll" is proposed based on wear state of straightening roll, elastic-plastic theory, hardening coefficient model of the plastic deformation and stress neutral layer offset theory. On these basis, according to the local contact state of bar and the straightening roll, the models of the roll angles and roll gap between bar and straightening roll are established, and the change rules and control strategies of two-roll straightening process parameters(roll angles, roll gap, straightening speed and plates spacing) are studied, and the specific example and finite element simulation analysis are put forward to verify the control strategies. From the straightening force, plastic deformation depth, straightness and residual stress, it is proved that the effectiveness of roll shape design method and process control strategies, the straightness of straightened bars is less than 1 mm/m in the field experiment, and the straightness fully meets the standard of high precision straightening.