Effect of polarisation on surface longitudinal cracks of hypo-peritectic steel in non-sinusoidal oscillation

Mould oscillation monitoring was conducted on a slab continuous casting machine with a thickness of 170 mm, a width of 1500 mm, and a casting speed of 1.8 m/min. The measurements employed non-sinusoidal oscillation characterised by an amplitude of 3.95 mm, a frequency of 2.40 Hz, and a deflection ratio of 0.20. The force calculation model is established and optimised, and the polarisation in casting and width directions is found by the frequency analysis. Results show that the polarisation will gradually stabilise through 40 min after casting speed is unchanged. When the amplitude in casting and width directions decreases from 0.23 mm and 0.11 mm to 0.20 mm and 0.08 mm, the stress on the solidifying shell from is reduced from 4.32 MPa to 3.36 MPa, which is within the range of high-temperature strength of hypo-peritectic steel. Large mould polarisation changes the trajectory of the mould, increases tearing risk in positive strip time, and hinders crack healing in negative strip time, thereby facilitating crack initiation and propagation along the longitudinal direction.