A study of conditions of surface defects formation when bar rolling at a bar and wire mill and methods of their elimination

Quality of long products surface is an important consumer property of it. In the process of measures elaboration aimed at the increase of long products surface quality, in particular of bars produced at the mill 370/150 of ОJSC “BMZ – managing company of holding “BMK”, studies were accomplished by metallographic laboratory. It was established that defects being revealed at the bars finishing, don’t relate to the quality of continuously casted billet (CCB), but formed in the process of deformation. Studies of the mechanism of surface defects formation on hot-rolled bar of rolling origin – deformation fissure and wrinkles were carried out. Results of numerical simulation of rolling in roughing group of stands at various temperature-deformation parameters presented. Regularities of formation of surface defects on the bar in the finished product were revealed. It was shown that the reason of the surface defects of rolling origin – deformation fissure and wrinkles was a high temperature gradient between the core and the surface of billet, originated from local overheating of surface in the angles zone of CCB resulted in nonuniformity of drawing out of different layers of the billet being deformed. To eliminate the defects, minimum possible temperature gradient between the surface and the core of a billet by controlled rolls cooling should be provided. By calculation, the maximum permissible temperature of the working surface of the rolls of the rough group of stands was established, and empirically the actual temperatures of the rolls with the current production technology, as well as the temperature of the rolls support bearings seats of the rolls were measured. The technical and technological possibilities for improving of rolling technology on a bar and wire mill in order to improve the surface quality of rolled bars were demonstrated. The existing technology was adjusted and new technological modes of rolling with controlled cooling of the rolls were established, which made it possible to significantly reduce the rejection of the finished product due to defects in rolling production. A device was proposed for the roughing group of stands, which enables to minimize the ingress of coolant onto the bar rolled.

Research the Effect of Speed Mismatch during Continuous Rolling on the Plasticity Margin

The paper analyzes the influence of tension (dam) on the stress-strain stain and plasticity margin. For the analysis, a model of continuous rolling in three adjacent stands was developed using the Deform 3D software. The adequacy of the model was confirmed by comparing the experimental data from the small-section wire mill 150 and the simulation results. Further, a computational experiment was planned to identify the effect of mismatched of rolling speeds on stress-strain stain. It is shown that for small deviations of rolling speed from the matched mode, there is no significant change in the reserve plasticity along the specific trajectory of the particles movement.

Research into the Effect of Speed Mismatch during Continuous Rolling on the Process Parameters

The paper analyzes the influence of tension (dam) on the technological parameters of the rolling process (spreading, force and rolling torque). For the analysis, a model of continuous rolling in three adjacent stands was developed, using the Deform 3D software. The adequacy of the model was confirmed by comparing the experimental data from the small-section wire mill 150 and the simulation results. The error in determining the forming was 0.4%, and in determining the power parameters was 11%. Further, a computational experiment was planned, to identify the effect of mismatched of rolling speeds on technological parameters. According to the results of calculations, graphs of changes in technological parameters were constructed. It is established that, even small deviations of rolling speed from the matched mode lead to significant changes in technological parameters.

Mathematical and software for the study of the dynamics of the finished rolling mill block wire mill

The aim of the work is the development of mathematical and software for the study of transients arising from the management of the finishing unit of the mill of the rolling mill 150. The movements, speeds, accelerations and torques in various connections of the finishing unit were studied. The linear mechanical analogue in the form of an extensive system of discrete masses connected by elastic-dissipative elements was used to estimate the integral characteristics of the block load. Block design calculations include engines, a distribution gearbox, two transmission shafts for rolling rolls of horizontal and vertical stands of the block. The mathematical model for analyzing the oscillation frequencies of a block is represented by a system of second-order linear differential equations. The equations for changing the drive current in the armature circuit of the motor and in the excitation circuit, equalizing the motion of the armature (rotor) of the electric motor, the equations for determining the motor torque are presented. . According to the results of studies of the mill 150, the range of rolling speeds outside the resonant zones was established and the possibility of increasing the rolling speed by 10% was justified. Analysis of the frequencies, the level and nature of dynamic loads allowed us to develop a technical solution to reduce the dynamics of the drive line by changing the gear ratio of the gearbox. The study of the dynamics of the rolling unit of the first in Ukraine high-speed double-strand wire mill 150, put into operation at the Makeevka metallurgical combine, allowed an objective assessment of the optimality of the design parameters of its equipment, reliability and guaranteed life.

Research of Martensite Bands in the Core of 82B Wires

The character of microstructure in the segregation of 82B wire with two different stelmor control cooling procedures and kinetics of eutectoid transformation of segregation through thermal simulation in the range of 400-600°C were researched. The longitudinal section segregation microstructure and composition were analyzed by OMSEMWDS. The thermal simulation results show that the length of martensite segregation bands is decreased holding 10-40s above 500°C, and martensite band in the core of wire where the content of Mn and Cr elements is higher than matrix because of segregation. Furthermore, Stelmor control cooling experiments in the high speed wire mill confirms that there is a critical temperature500°C to 82B wire above which the eutectoid transformation in the segregation is possible, and enough time above the critical temperature in the Stelmor control cooling lids is the key to optimizing procedure.

Multi-Objective Optimal Design Roller of Y-Type Mill Using Ga Combined with FEM

Y-Type rolling mill with three roller is a new kind of wire mill. Because of its unique advantage, It is very important to optimize structure. Roller is important part of the rolling mill, whose size effects the strength, stiffness, as well as the rolling piece quality and service life of the rolling mill. Therefore, It is important to optimize the roller structure dimension of Y-type mill.A new structure optimizing method is set up combined the modified genetic algorithms with finite element method.This method can solve multi-objective problems with more complex constraints in the engineering. Compared with the zero order method and first order method companied with ANSYS, the result of this optimizing method is better. This method can solve multi-objective problems with more complex constraints in the engineering, providing a new and effective means for the engineering problems.

Influence of Stelmor Cooling Procedure on Eutectoid Transformation of Segregation in 82B Wires

The character of microstructure in the segregation of 82B wire with two different stelmor control cooling procedures and kinetics of eutectoid transformation of segregation through thermal simulation in the range of 400-600°C were researched. The longitudinal section segregation microstructure and composition were analyzed by OM、SEM、WDS. The thermal simulation results show that the length of martensite segregation bands is decreased as holding time increases above a certain temperature, and martensite band in the core of wire where the content of Mn and Cr elements is higher than matrix because of segregation. Furthermore, Stelmor control cooling experiments in the high speed wire mill confirms that there is a critical temperature to 82B wire above which the eutectoid transformation in the segregation is possible, and enough time above the critical temperature in the Stelmor control cooling lids is the key to optimizing procedure.