DEVELOPMENT OF THEORETICAL BASIS OF DETERMINING ENERGY-POWER PARAMETERS OF ROLLING WITH DEVELOPMENT OF NEW GRADES OF RAIL STEEL

The analysis of existing methods of theoretical determination of the resistance of steels plastic deformation revealed a number of significant shortcomings of the loading history, particularly, the lack of consideration the influence of chemical and phase composition of the steel. Due to limitations on the application of these drawbacks do not allow to consider these techniques as suitable for the preparation of reliable predictive values of energy-power rolling parameters according to the newly developed steel grades, in particular for complex-alloyed rail steel. Therefore, the conclusion about the necessity of experimental studies on plastic deformation resistance of steels at various combinations of temperature and speed of rolling, the degree of deformation and varying the chemical composition of steel was made. These studies applied to E78KhSF steel were performed using the complex for physical modeling for thermomechanical processes “Gleeble System 3800”. On the basis of mathematical processing of the experimental data the technique of numerical determination of the resistance of rail steel to plastic deformation under varying thermomechanical rolling parameters (temperature, speed and degree of deformation) and volatile chemical composition of steel was carried out. The nature of the experimental dependences indicates a decline in resistance to plastic deformation of E78KhSF steel with increasing temperature deformation in the rolling temperature range and improving the resistance to plastic deformation with increasing strain rate in the range of variation of this parameter in the rolling mill, which is consistent with the generally accepted views. Experimental evidence suggests the pronounced nonlinear character of dependence of the resistance of E78KhSF steel to plastic deformation on the degree of deformation that indicates the occurrence of dynamic recrystallization in addition to the dynamic recovery and polygonize. Analysis of the chemical composition of E78KhSF steel influence on the resistance to plastic deformation indicates an increase of this characteristic by increasing the concentration in the steel of carbon, manganese, sulfur and phosphorus, and decrease in resistance to plastic deformation by increasing the vanadium content in the steel. The obtained data on the absence of influence of the change in the concentration of silicon and chromium (within the interval of variation meeting the requirements of standards) on the resistance to plastic deformation of E78KhSF steel make it possible to draw a conclusion about the possibility of using the developed calculation technique for determining plastic deformation resistance of rail steels not alloyed by these elements. The adequacy of the proposed method was confirmed by studies of power parameters of rolling at the existing universal rolling mill of JSC “EVRAZ ZSMK” for steels with different chemical composition.

energy-power parameters of rolling, resistance to deformation, rail steel, experimental studies, thermomechanical rolling parameters, chemical composition of steel

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