The Study On Cutting Precision Of Hot Rolled Rod By Crank Shear

Crank shear is a critical process equipment on continuous hot rolling line for wire and rod.Three kinds of cutting precision problems,including incorrect cutting length,jumping-up or bending problems after cutting head and plastic deformation after cutting head always occur during production,affect negatively the finished product quality,product yield and material-biting condition at downstream mill stand.Concerning the problem of incorrect cutting length and jumping-up or bending problems after cutting head,complex number vector analytical method is used to establish the kinematic model of crank shear and computing program is written for its prediction and calculation.The model is also verified by Creo/Mechanism,which can calculate crank shear process parameter correctly and eliminate incorrect cutting length and jumping-up or bending problems after cutting head.Concerning the problem of oversized head plastic deformation of hot rolled rod after cutting head which makes the biting condition of downstream mill stand worse,the optimized object of cutting swivel angle is firstly established and optimized by Matlab Fmincon function.After optimization procedure,the cutting swivel angle of a certain crank shear decrease to less than 1o,so the plastic deformation caused by it will be sucessfully eliminated.Secondly,the relations between head deformation after cutting head and knife parameters such as knife edge width,knife edge angle and knife gap are analyzed according to the formulae of rigid-visco-plastic mechanics and collapse depth,invasion depth and maximum cutting force are chosen as evaluation index of head deformation.Meanwhile,the cutting FEM model of DIN C45 hot rolled rod is established by deform-3D and used to simulate the value of collapse depth,invasion depth and maximum cutting force under the different knife parameter combinations in order to obtain the optimized knife parameters.The optimized parameters can reduce cutting deformation(invasion depth)by nearly 40%.Based on the study of cutting precision of crank flying shear for hot rolled rod,crank shear kinematic model,optimization method for decreasing cutting swivel angle and the optimized parameters for cutting knife are determined to provide logical thinking,theoretical method and optimization basis for its successful industry application.