Determine The Position For The Dynamic Soft Reduction Of Continuously Cast Bloom

The soft reduction technique at the solidifying terminal is one of the effective methods to decrease the center segregation and center porosity, and it has been widely used in many plants abroad and achieved obvious metallurgical effect. The VAI's soft reduction techn- ique were introduced in the new bloom caster at Panzhihua Iron&Steel Company, Panzhihua commissioned successfully in September 2003, Pan-steel is the first plant to use soft reduction in bloom caster(280 mm×380mm) to produce the heavy rail steel in china. The parameters and the mathematical model of soft reduction are a'black box'because of technique secrecy. The aim of this study is to definite the position of continuous casting bloom on the soft reduction so as to provide theory basis to detect the soft reduction.The soft reduction is a kind of forcing on the solidifying terminal to improve the internal quality in the continuous casting of bloom. In this study, according to the actual conditions (high-C steel), the numerical simulating of the solidifying process was carried out by Marcfinite element, defining the position of the solidifying terminal and the region of soft reduction so as to provide theory basis for soft reduction of baosteel bloom continuous casting .A heat transfer model was established and heat transfer process was carried by Marc finite element. According to the technological conditions of bao-steel bloom continuous casting of which material is U71Mn,casting section are 280mm×380mm and 280mm×325mm, of which material is 45钢,casting section are 280mm×380mm and 280mm×325mm, for the five typical technological conditions of casting speed 0.65m/min,superheat 25℃; casting speed 0.70m/min,superheat 15℃; casting speed 0.70 m/min,superheat 25℃; casting speed 0.70m/min,superheat 35℃; casting speed 0.75 m/min,superheat 25℃, the numerical simulating of heat transfer process was carried one by one. The position of the freezing terminal was worked out by calculating. The region of soft reduction was definited. The comparison were made between the result of numerical simulating and the result of the infrared temperature measuring equipment, all relative errors are less than 5%, these indicates the reliability and practicability of the result of numerical simulating, this model can be used to provide the solidification parameters for the soft reduction.The variational law of thickness of frozen layer with the variance of processing parameters was analysed. The result showed that raising pour temperature and aggrandizing drawing speed could delay the frozen speed. The shell's thickness leaving mould is thin, the surface temperature is increase, increasing of the shell's thickness is slow, liquid core is long and the position of the freezing terminal is move behind as drawing speed is increase.On the basis of heat transfer calculating, the heat-stress analysis of bloom continuous casting was worked out. The analysis could provide theoretical basis for which the soft reduction model is conbined with the solidification model and analysing the law of stress-strain with the soft-reduction press.