A widespread method exerting the influence on the homogeneous formation of the microstructure and enhancement of strength properties of Al-Si alloys is a modification by super- and nanodispersed particles of different chemical compositions. In spite of the significant advances in the studies of the influence of various modifying compositions on the structure and mechanical properties of casted silumins, the literature contains no data about the influence of nanodispersed W-powder on formation of the structural-phase state and mechanical properties of Al-Si alloys. The paper considers the influence of 0.01–0.5 mass % W nanopowder on the structural-phase state and mechanical properties of an Al-12%Si alloy. It has been established that 0.1 mass % of W is an optimal addition. It results in the uniform distribution of eutectic (α-Al + Si), a 1.5-time decrease in the size of the plates of eutectic Si, a change of the shape of coarse plates (coarse plate-like or acicular) into a fine fibrous one, and an enhancement of the mechanical properties by 16–20%.

ОСОБЕННОСТИ ФОРМИРОВАНИЯ ЭЛЕМЕНТАРНЫХ СКОЛОВ В ПРОЦЕССЕ РЕЗАНИЯ УГЛЕЙ И ИЗОТРОПНЫХ МАТЕРИАЛОВ ЭТАЛОННЫМ РЕЗЦОМ ГОРНЫХ МАШИН

The paper considers the advisability of continuous nonimpact regulation of powered support unit hydraulic props resistance to roof rock subsidence. It also examined the advisability of increasing the adaptability of the powered support within advanced high-powered mechanized longwall face complexes to mining-geological conditions that change as the blocks are extracted. A four-level characteristic with nonimpact regulation is proposed instead of a typical three-level operating characteristic of the support unit hydraulic prop with impact regulation of its resistance to roof rock subsidence. Such operation modes of hydraulic props with the power fluid displacement into the power support pressure pipe can be provided by a nonimpact resistance control unit. The paper presents the structure, connection diagram, and embodiment of the control unit. The production and in-mine testing of the MKYU 2SH13/27 powered support unit hydraulic prop equipped with a prototype control unit were carried out on OOO Zavod Krasny Oktyabr loading test bench and in the A. D. Ruban mine of AO SUEK-Kuzbass. The testing data is presented in the paper. The possibility of rock pressure energy recovery into the hydraulic system of the longwall power support has been proved.

The article discusses the possibility of adapting sections of mechanized roof supports to the variable geological and mining factors dealing with flat seams of medium thickness in longwall complex-mechanized coal face. Adaptation is provided by the rock pressure regulation of the pressure change rate in the piston cavities of hydraulic legs with static work load on the roof support. The proposed technical solution allows to separate process regulation function of rock pressure in the roof settling process from the protection function of the shields to be overloaded. Rock pressure regulation is provided by continuous regulation of fluid flow from the piston cavity into the complex hydraulic system which eliminates the sharp pressure drop in the elements of the hydraulic system sections, dynamic loads on the roof support in the regulating process. It also partly transfers potential energy of roof rock settling in the hydraulic system of the complex. Nonimpulsive rock pressure regulation leads to intensity decrease of crack formation processes directly in roof and rock caving in longwall face, to volume reduction of dangerous works stowing cavities formed over roof support, stability increase of coal mining technological process and safety works in coal faces. In the case of sharp roof block collapse at the limited capacity of an adjustable throttle, the piston emphasis in the top part of the pressure amplifier is provided in the block design. In this case pressure increase in piston cavity of hydraulic legs causing relief valve actuation in the protection mode against overloads is possible.