Abstract
Surface cracking and the effect of predeformation on the cracking of continuously cast (CC) low carbon low alloy steel slabs have been studied by means of hot bending tests simulating a practical CC and the direct rolling process using the as-cast thin slabs. Two kinds of cracking, i. e., fine transverse cracks in microalloyed steels due to carbonitride precipitation during slow strain rate deformation of 10-3 s-1 and severe cracks in low carbon Al-killed steels due to sulfide precipitation during high strain rate deformation of 10 -1 s -1were easily simulated by the deformation in low temperature γ region. The both kinds of cracking were markedly suppressed by the slight predeformation on the slab surface during cooling to the deformation temperature. Since γ grain size was not changed by the predeformation, these results can be explained in terms of precipitation behavior of carbonitride or sulfide in each case. That is, the precipitates formed by the predeformation can grow into coarse particles during the cooling stage, resulting in marked suppression of fine precipitation which causes large ductility loss in the subsequent bending process.
