Flatness evolution of cold-rolled high-strength steel strips during quenching process

Drastic flatness changes in high-strength steel strips during water quenching cause problems for both their subsequent manufacture and final products. In this work, a temperature–microstructure–stress coupled finite element model is established to simulate the quenching process of cold-rolled high-strength steel strips using a UMAT subroutine in ABAQUS. The evolution mechanisms of two main forms of flatness defects, including C warping defect and edge wave defect, are investigated. Our simulations reveal that the temperature gradients of the strips induce their extension differences along transversal/thickness direction and the sequential phase transformation, both of which finally cause the flatness changes. Furthermore, flatness control strategies are proposed according to the integrated effects of the tension and initial temperature differences during quenching. In addition, quenching experiments are implemented to validate the numerical results.