Abstract
	In the paper the method of calculation of sear stresses distribution in the deformation zone by spread of stock is proposed. In order to establish the dependence of friction coefficient on deformation conditions, the S235J2G3 steel strips were rolled at temperatures 900-1200 °C with 40% reduction on K350 laboratory rolling mill. For determination of friction variation the non direct method was used. Mathematic modeling was related to existing laboratory rolling conditions. The modified slab and finite element method was employed. The mathematic simulation of the process has been used to determine the variation of friction along the rolling contact interface. For initialization of the model the deformation zone geometrics and the hot forming properties of steel were specified. The finite element based model implements the calculation of strain, strain rate and temperature distributions, roll torques, forward slip, roll pressure and interfacial shear stress. The coefficients of friction for Coulomb and Tresca friction formulations were determined from the shear stress, the roll pressure and the yield stress distributions. The comparison of Coulomb and Tresca friction factor distributions was made. It was indicate that friction coefficient in both cases is not constant along the contact length. The differences between the Coulomb and Tresca friction factors were found more significant in the zone of slippage. The absolute value of the shear stress was found to decrease towards the neutral section.