| In the metaphase and anaphase of 20 century,foreign high efficient continuous casting which is a new metallurgical technology had developed with the technology of hot charging and hot carrying of continuous slab. High efficiency,high pulling and high quality are the cores of it. ROKOP caster is generated in this background. This kind of caster deals with the accident of the leak quickly and improves the efficiency. Because it doesn't have secondary cooling straightening roll. It is widely used in the world. In our country, square billet caster products more than 60% steel. On the other hand,without secondary cooling straightening roll in ROKOP caster and guide roll in operation,it has definite vibration,which makes the flaw of transverse crack appear clearly. Further more,our country's converter is in the transition from smelting plain carbon steel to smelting specific steel. The sensitivity of steel crack and the complexity of solidifying contraction are increased by increasing the alloy elements augment. Casting technology needs the support of new theory and new basic data. In the time of economical rapid development,structural steel dominates the market. Meanwhile,the demand of specific steel is increased quickly. Particularly, 20MnSi steel is an actual main kind of products. Using ROKOP caster producing this kind of structural steel, transverse cracks appeared. The work doesn't go on when it is severe. The technical and economical index of steel-making is affected severely. The aim of the study is to solve the quality problems which caused by the transition from plain carbon steel slab to specific steel slab.The subject studies the square billet and rectangular billet made by ROKOP caster,which widely used in our country. Solidifying and heat transferring model according to the actual conditions and extracts reasonable cooling strength and solidifying contraction for optimizing the cooling process of slab and making parabola crystallizer according to contractive rule are established. The vibrating parameters are optimized and the effect of the steel content on transverse crack are analyzed for bringing technical measures to solve transverse crack and the quality problems.On the base of academic analysis and actual operation,the factors which affect casting slab surface quality have been studied and effective measures to improve them have been brought out. The mechanism of transverse crack has been studied and controlling straightening temperature out of the range of brittle temperature has also been brought out. The crystallizer and the secondary cooling system have been optimized. In order to prevent slab surface quality at vibrating trace from deteriorating , the vibrated system of crystallizer has been studied. The vibrated system has been checked and cleaned. The depth of trace is controlled by high frequency and amplitude of vibration which can decrease negative slipping time. The surface quality of slab has been improved. By analyzing the chemical components of steel, moderate alloy element content and impurity content have been studied. The waste and degraded products caused by transverse crack are eliminated.
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