Model of head sag of round bars in rolling process

The head sag of a minimum-size round bar in rolling process was investigated to prevent it from crooking and heaping in front of a flying shear. The temperature of bar, rolling force and power of mill drive motor were thus modeled to analyze the causes of bar crooking/heaping, such as the decreasing internal stress due to reduced bar size enables the head of running bar to be lower than the baffle of flying shear, crook and heap. Solving the function of deflection of round bar, a mathematic model was developed for its head sag. Some in-situ rolling experiments were conducted for various small-size round bars to check how the theoretically calculated results conform to the actuality. They showed that the calculated results in accordance to the head sag model are in conformity to experimental results in case there is or no flying shear.