Reduction of random seams in hot rolling through FEM based sensitivity analysis

In hot rolling, the thermomechanical design of the rolling sequence is often based on the design of the roll grooves and the selection of processing parameters. The sensitivity of this design to the variations in the processing parameters often results in the formation of random defects such as rolled seams. In this paper, a unique minimum sensitivity design approach is proposed that eliminates the formation of seams without affecting the finishes microstructure. Central to this approach is a microstructure based finite element model for simulating hot rolling, a seam formation criteria based on the groove underfill, and the manipulation of least constrained passes to find the design that least sensitive to process variations. The approach is applied to an industrial roll-pass design to demonstrate its efficacy. It is seen that the new robust design provides a wide working window for the roll-pass settings for seamless rolling of bars, and at the same time provides for acceptable microstructure.