Abstract
	The forming factor QFv highlights influence of the mean stress exerting on the contact surface between the rolled metal and work rolls in the roll bite and in the rolling direction on the roll force size. The forming factor QFv enables conversion of the equivalent stress ?e value, obtained e.g. by means of plastometric measurements, to the roll force and predict load in forming. Generally, the QFv value is influenced by shape and geometry of the rolling stock in the roll gap, deformation conditions and friction conditions between the rolling stock and work rolls. Friction conditions are affected by roughness and hardness of work rolls, scaled surface of the rolling stock, temperature of the rolling stock, rolling speed and other factors. In evaluation for a particular mill stand we suppose that a value of the friction coefficient ?vs is constant in the course of the rolling process and may be directly integrated into the forming factor QFv. For determination of the forming factor it was necessary to carry out continuous torsion tests in the plastometric laboratory of Research and Development of Vítkovice and rolling of flat samples in the laboratory rolling mill Tandem in the Institute of Modelling and Controlling of Forming Processes. Comparing the obtained values of mean stress, forming factor for the applied rolling mill could be developed as a function of geometrical parameters of rolling. The experiment was carried out with samples from steel grades ČSN 11 523, 12 040, 17 153 and 17 251. A new model for the forming factor was developed in dependence on a wide range of values of aspect ratio .