Uralniti (Russia)

Analysis of the screw rolling process showed that change in axial speed of the roll along the length of the roll groove of cross rolling mill does not correspond to the required character of change in the speed of deformed billet. The process proceeds under intense axial compression, as a result of which a significant part of the metal crimped in the contact zone is displaced into the inter-roll area. It is shown that direction of the axial force in the corresponding zone of the roll groove depends on the value of inclination angle of the considered roll section generatrix to the rolling axis. The proposed modernization of screw rolling technology makes it possible to carry out deformation of the billet under the influence of intra-focal axial tension. The task is accomplished by rolls calibration when at the beginning there is a ridge section of the roll on which the axial force is directed against rolling direction; and behind it, a pulling one, on which the direction of the axial force coincides with rolling direction. Such a scheme of the axial forces action in the zone of intensive billet reduction creates the most favorable conditions for the metal flow in axial direction. A technical solution is proposed for the implementation of the stage of the billet gripping by rolls, and description of this stage and the process stationary phase is given. The cardinal change in the billet deformation condition after modernization makes it possible to reduce the power load on the work rolls, increase their efficiency and reduce energy costs during rolling. This will ensure the rolling of a solid billet in a roughing mill with a higher stretch, create the preconditions for expanding the size and grade assortment when obtaining rods in radial-displacement rolling mills and at production of pipes in rolling lines with the Assel mill. The range of finished products can be significantly expanded due to the production of thin-walled highprecision pipes.

An analysis of the helical rolling process shows that the change in the axial speed of the roll along the length of the groove of the cross-roller mill does not correspond to the required nature of the change in the speed of the deformed billet. The process proceeds under intense axial compression, as a result of which a significant part of the metal being compressed in the contact zone is displaced into the inter-roll zone. The direction of the axial force in the corresponding zone of the roll groove is shown to depend on the inclination angle of the generatrix of the considered section of the roll to the rolling axis. A modernization of the helical rolling technology, which makes it possible to deform the billet under the effect of intralesional axial tension, is proposed. The set problem is accomplished by applying the calibration of the rolls, at which the ridge section of the roll, on which the axial force is directed against the direction of rolling, is located at the beginning while the pulling section, on which the direction of the axial force coincides with the direction of rolling, is located behind it. This scheme of action of axial forces in the zone of intensive compression of the billet creates the most favorable conditions for the flow of metal in the axial direction. A technical solution for the implementation of the stage of gripping the billet by rolls is proposed, and a description of this stage and the stationary phase of the process is provided. The fundamental change in the deformation conditions of the billet due to the modernization makes it possible to reduce the force load on the operating rolls, increase their performance, and reduce energy costs during rolling. This will ensure the rolling of a solid billet in a swaging mill with a higher drawing, will create the prerequisites for expanding the size and grade range when producing bars in radial shear rolling mills. When producing pipes in rolling lines with an Assel mill, the range of finished products can be also significantly expanded due to the production of thin-walled high-precision pipes.

This is a comparative analysis of the operation of devices for heating dead-end offtakes of lines for live steam and hot intermediate heating steam in 300 – 800 MWpower units. The operating efficiencies of pressure pipes for live steam and intermediate heating steam are estimated for various operating modes. The most efficient schemes for heating of dead-end pipes for live steam and intermediate heating steam are developed. A specific device is proposed based on the conditions for ensuring heating of the dead-end pipelines.

The combustion of coal mixtures is regarded both as a necessary step and as a technology which offers noticeable technical, economic, and ecological advantages. The choice of an optimal, or even acceptable, mixture requires knowledge of the characteristics and properties of the coals being blended and of how their behavior changes in a mixture. With mixing, all the indicators characterizing a coal undergo changes and an improvement in one may be accompanied by the deterioration of others. Based on experimental and published data, we have analyzed the major characteristics of mixtures that control the operation of coal-dust thermal power plants, first the ones which are not additive, and then those whose additivity is not evident without experimental study.