Development of Finite Element Model of Reorientation of Cementite Lamellae in Pearlite Colonies in Wire Drawing Process for Wires Made from High Carbon Steel

摘要

Studies of properties of pearlitic steel wires used for production of metal cord or mining hoisting ropes have revealed a relationship between the orientation of cementite lamellas in the material and the mechanical properties of the wire and its resistance to cyclic loads. Influence of technological parameters on the orientation of cementite lamellas in wire was established. Experimental determination of the range of inclination angles of cementite lamellas in a given pearlite colony, at which their advantageous orientation, parallel to the wire axis, occurs, is not feasible in practice. Therefore, the only approach for solving this problem was to develop an appropriate mathematical model. Solution of the formulated problem proceeded in two stages. At first, the DRAWING2d program [3], modified and adapted to the needs of the task, was employed. The software incorporates a model based on the theory of plastic flow of the rigid-plastic medium. The boundary problem of the theory of plasticity is solved in this model considering the flow of heat and material heating due to plastic deformation and friction. Transfer of all strain tensor components data from draw to draw enabled simulation and optimization of the multi-stage drawing processes. Based on the model, strains fields and flow velocities were determined for the whole cross-section of the material being deformed in a particular draw. At the second stage, a program was developed to model the deformation of a single pearlite colony of dimensions corresponding to those of grains occurring in the actual structure of pearlitic steel after patenting. The mechanisms of deformation of the pearlite colony, the boundary conditions related to interaction of adjacent grains, and the rheology of cementite and ferrite were also accounted for.