Abstract
         	The surface quality of the continuous cast slabs is important factor by the aspect of the surface quality final flat rolled product. The cross corner cracks are most important by the view branch of  the material volume.  For the initiation and crack propagation are very important conditions in the secondary zone of  cooling. In our work we have solved influence of secondary  cooling regime for the occurrence following cross corner cracks, in the manufacturer place U.S. Steel, Košice. The curve of the secondary cooling was analyzed for the  structural and  microalloyed steels. The statistical methods and comparison  were confirmed favourable impact decrease appearance the cross corner cracks by the decreasing volume of flow water and increasing the surface of  slab in single secondary cooling zones. Slab surface temperature has increased and decrease of occurrence cross corner cracks accomplished by decreasing of 10% flow water volume. This change of curve wasn‘t showed  very positive for microalloyed steels, because after changing the curve the changing of occurance trend to downward didn´t fall, only damping of increasing tendention happend. Therefore was suggested to test more soft curve of secondary cooling for microalloyed steels and than to use statistic detection for significance of applyed change. In account of the critical occurance area of cracks 750 – 900°C it is  needed to supercool the slab under critical area or increase the surface temperature of slab over critical area. The temperatures in range zone are in big influence of casting speed. According the higher is the casting speed, the more intense is the slab surface temperature.
         	The results of our investigation properly completing know-how presented by Acta Metallurgica Slovaca [1]  about  influence of  the speed on surface quality continuous cast slabs.