F.N.P.: Gorbenko Alexander Igorevich

Speciality: Treatment of Metals by Pressure

Master's degree work: Research of two-stage process of the «soft» reduction of continuously-cast blooms on the basis of physical design

                                                                                                                                                                                                         

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Permanent expansion of application domain of rental responsible setting produced from continuously-cast steel claims special attention to quality of continuously-cast ingot. One of technological methods which allow deciding these questions, is a technology of the controlled second cooling, the mandatory member of which is the method of «soft» reduction. This principle is taken to reduction of continuously-cast ingot which is in the diphasic state[1].

The lacks of all processes «soft» reduction, in which reduction execute by the smooth rollers on all width, is that the areas of ingot get reduction simultaneously and in an identical degree, which have a different temperature and different level of mechanical properties. Because lateral facet has more low temperature and more high level of mechanical properties, they in majority influence on strain resistance. For increase efficiency of penetration deformation in the middle of ingot it is necessary to multiply the rate of reduction that can result in appearance of internal and outward cracks. These failings stipulated the  appearance of new methods realization of «soft» reduction process. One of them is a method, which a patent is got on, was developed on the chair of the MF Donetsk national technical university [2].

A new method supposes the division of deformation in each reduction stand of «soft» reduction block on two interdependent stages. Central areas of ingot is reduced with the degree of deformation 0,6-1,2% on the first stage by the profiled rolling pairs of the first row on a width which is 80-90% from the width of liquid phase. Before undeformed edge areas of ingot is reduced with a rate of deformation 0,8-1,4% on the second stage by the smooth rolling pairs of the second row with ceiling on the width of ingot on a size which makes no less than half of  before undeformed central area with a liquid phase [3].

 

Continuously-cast blooms with cross-section 335*400 mm were chosen as object for the modeling. The blooms was produced in the conditions of continuous-casting machine on OJSK “Dneprovsky Iron & Steel Integrated Works named after F. Dzerzhinsky”. Accordingly to plan of experiment, there are three series of the special plasticines samples were made, which in scale 1:10 modelies the continuously-cast bloom with cross-section 335*400mm for three experiment factors. Research was conducted through the new method of modeling, which provides similarity of the thermal state of physical model and the nature object.

Special experimental mounting was created for providing of adequacy in distributing strain resistance (s_s) along the section of continuously-cast bloom and his physical model (by the condition of use new method modeling) [4]. During experiment implementation a sample 7 was placed on the special heat-insulating support 5 in the middle of calorimeter 3. Then tubular electro-heating element 2, which is fastened on support 1, entered in internal hole of sample. Hole of sample is filled by a oil 6. For the external cooling of sample the mixture 4 of ethyl spirit and carbon dioxide were used . For stabilizing of the temperature state on the height of modeling sample it was offered to make the forced interfusion of coolant (oil) by the way ground blowing with using a pump 11. Temperature was measured with using thermocouple 8 and fixed on an oscillograph 10. For realization of rolling the forming rolls are made by fiting of rings on the smooth body of roll. This rings was hard fixing for the first stage of deformation and the ring was made mobiled for the second stage.