Simulation Of Temperature And Internal Stress In Coiling Process Of Hot Rolled Strip

Carbon steel is gradually replaced by high strength steel in construction,transportation and navigation and the study of distribution of stress and temperature in the coiling process of high strength steel is an important basis for judging whether there will be flatness defects in the coil.This study derived the equations for calculating the increment of radial displacement in coiling process considering the anisotropy of the coil based on the axisymmetric characteristics of the coil.Firstly the force balance equation,geometric equation and physical equation were established based on the basic theory of elasticity by the calculated increment instead of the calculated total to compute the stress increment in the coiling process.Then the stress increment during coiling under three-dimensional condition was obtained by extending the convexity of the plate.Finally the distributions of radial compressive stress and circumferential stress under different relative convexity and convexity index conditions were analyzed when the coiling process finished.Two unloading methods obtained according to two different unloading theories and compared through the distribution of radial compressive stress and circumferential stress after unloading.The temperature field and stress field in coiling process of hot rolled steel was obtained by combining the temperature with the stress and then stress distribution at the end of coiling and after uncoiling was obtained considering the influence of temperature on coiling process.The temperature field in the coiling process of hot rolled steel was calculated by Laplace equation in three-dimensional unsteady cylindrical coordinate system combined with different boundary conditions according to the coiling process of coil.The initial tension and temperature were transformed the uniform distribution along the axis into the non-uniform distribution along the axis to obtain the distributions of radial compressive stress and circumferential stress after coiling and unloading under the nonuniform initial tension and the initial temperature along the axis,which considered the flatness defect of edge wave or medium wave formed during rolling and the influence of heat dissipation of hot rolled strip to air according to the actual coiling condition.Distribution of the radial compressive stress and circumferential stress at the end of coiling and after uncoiling in the coiling process of hot rolled steel with different influencing factors were analyzed which contained plate convexity,convexity index,temperature distribution and initial tension distribution.There will be a comprehensive understanding to the stress at the end of coiling and after unloading which provides preconditions for subsequent coil cooling and thermal stress calculation during cooling.