Abstract: One of the reasons for the occurrence of cracks on the surface of the slab is the low high-temperature plasticity caused by the coarse grains and grain boundary precipitation on the surface. In order to improve the slab plasticity, the high temperature confocal technology was used to research and develop the dual phase transformation control cooling technology for the slab surface structure.The grain size change and grain boundary precipitation state of steel grades under the dual-phase transformation controlled cooling process were studied by the Confocal Laser Scanning Microscope(CLSM), and the key technical parameters of the technology on the surface of the slab was put forward by simulation calculation. Through the transformation of cooling equipment, the requirements of dual-phase transformation controlled cooling technology was satisfied at the corner of the slab. In the field, peritectic steel was used to conduct industrial tests of steel grades. By analyzing the phase structure of the slab, it was found that the dual-phase transformation controlled cooling technology eliminated the grain boundary ferrite film and refined the surface grain size of the slab. The inspection results of slab corner scarfing also confirmed the effect of this technique on improving corner cracks for the peritectic steel.

Key words: dual-phase transformation controlled cooling process, grain refinement, precipitation, crack