Study On The Formation Reasons Crack In Tang Steel FTSC Thin Slab

The FTSC technology developed by Danieli Company was first adopted by Tang Steel. Some inevitably problems were encountered because of lacking of operation experiences. Thin slab surface cracks, slag, bonded and breakout phenomena in which a larger proportion of surface crack defects have occurred by normal casting speed, the normal operation of the production was serious constraints. In order to improve the product quality and market competitiveness, it is to study the causes of thin slab surface cracks.The reasons of thin slab SS400 surface cracks were studied by SEM test, metallogra- -phic analysis, system of sampling and actual production data because of process and conditions of Tang Steel. Ltd. It was found that the high content of inclusions in steel, roll steel slag, iron oxide into the leather and high sulfur are the main reasons which cause thin slab surface cracks. The main inclusions of crack are silicates, calcium aluminum and sulfur, thin slab surface cracks owing to high content of inclusions account for 54.6%; molten slag entrapment account for 30.4%, iron oxide pressed into the skin account for 10.6%, higher S accounts for about 3.4% and some scratches on the surface crack take about 1% of the total testing. Secondly, lower Mn/S is one of the reasons of formation surface crack.The Mn/S of 93.5% of crack furnaces are less than 50 by analysis, it should be adjusted to fewer than 50. The water inlet temperature in crystallizer is instability and water inlet temperature which lower than 30℃account for 8.3%, the water inlet temperatures high must high then 30℃.The ZT3 is relatively good by testing three kinds of thin slab slag which were used now, Because of the ZT3 have low melting temperature and melting faster speed possess, but the viscosity and crystallization temperature of ZT3 must be adjusted in order to achieve better effects.