Faculty: Elektrotehnical
Speciality: Elektromechanical equipment energy-intensive industries
An important role in Ukraine's economy is the fuel and energy complex. Under the conditions of stable growth in prices of foreign energy sources, increasing the volume of coal is the key to energy security. For further development of the coal industry is necessary to introduce new technical equipment, a high degree of reliability and security. In the excavation complexes (harvester, conveyor and roof supports) used a large number of power cylinders (gidrostoyki, hydraulic jacks, etc.) working on water-oil emulsion. Working fluid contains up to 0.212% of contaminants, including pyrite and quartz particles with a microhardness is 3 times higher microhardness of the material cylinders, which leads to intensive corrosive damage of the latter and reducing their longevity. If you do not provide appropriate measures to ensure reliability and longevity of mining machinery and equipment, the economic effect of their use will be significantly reduced and the benefits of comprehensive mechanization of clearing works will not be fully utilized. Before the factories and coal-mining machinery repair companies set targets for improvement both new and reconditioned machines. To accomplish this task is possible when creating a new technical level of machinery and the use of advanced technology manufacturing and repair, including effective methods of surface hardening of parts. The development of modern technology surface treatment details, to increase the microhardness, corrosion resistance and reduce the surface roughness that increase durability of parts and the present paper.
Currently, the topic under consideration is quite interesting and relevant. Research and industrial laboratory electromechanical machining behalf BM Askinazi (Russia) is working on the development of electromechanical hardening equipment for construction, vehicles, agricultural enterprises. In particular, its staff Gustov SA, Fedorov, SK, Fedorova LV has published several articles on the topic of electromechanical hardening of agricultural machinery and various construction equipment [2,3,4]. Questions of increasing the longevity of hydraulic cylinders mining machines engaged in GP "Dongipruglemash. Ph.. VV Kosarev and forth so-called. N. Stadnyk propose to increase the purity of the working fluid through the introduction of a pumping station filter installations. Thus, proposing the deletion hit contaminants on the work surface and hydraulic cylinders to prevent them hydroabrasive wear [5]. Research has established that the main cause of failure of hydraulic and hydraulic jacks advancing conveyors is the pollution of the working fluid quartz and pyrite particles with a microhardness 8-10 kN/mm2. At the same time, the microhardness of the surface of cylinders (steel 30ÕÃÑÀ) is only 2,6 kN/mm2. So after hardening by electromechanical processing gidrostoyki with hardened mirror cylinders were not abrasive and corrosive damage worked without failure 12 months. Given these test results of hydraulic method of electromechanical treatment are useful for hardening cylinders jacks advancing conveyors. Based on the foregoing, the topic is relevant.
Audits in 6, 9 and 12 months of operation showed that the toughened glass cylinders had no abrasive and corrosive damage, while the mirror control cylinders was speckled with risks up to 0,8 mm in depth and had pockets of corrosion up to 20% of the working area cylinders. Gidrostoyki with hardened cylinders worked without failures more control of hydraulic commercially produced an average of 4000 hours. Given the high rates of technical parameters of hydraulic cylinders with hardened surfaces, the method of electromechanical treatment are useful for handling cylinders jacks advancing conveyors
According to the source [1], electromechanical hardening (EMU) is based on a combination of thermal and force action on the surface layer of the workpiece. The essence of this method is that the processing of a place of contact of the tool with the product passes a current of great strength and low voltage, thus projecting scallops surfaces exposed to strong heat, pressure tool deformed and smoothed, and the surface layer of metal uprochnyaetsya.Printsipialnaya scheme of electromechanical treatment (EMT) on the lathe is shown in Fig. 1.1 From the network voltage zheniem 220 ... 380 In the current passes through a step-down transformer, and then through the place of contact details of the tool. The strength of the current and secondary voltage regulated depending on the contact area, initial surface roughness and quality requirements of the surface layer For EMI rotary parts in small batch production and repair can be used by plant type UEMO-1. The unit consists of reducing transformer, lathe, circuit breaker to the patron, as well as stifle a caliper machine spring holder. The voltage from the network 380 is supplied via a rotary switch on the output pins of the magnetic starter magnetic field, managed portable keypad stations COP, is located on the workplace. Coil to the magnetic starter is fed through a small step-down transformer T2, the voltage is 36 V. When a magnetic starter voltage is applied to the plug plug switches to exclude any number of turns of the primary winding of the transformer T1. The other end of the secondary winding is connected to a spring sting 2, strengthened by isolation in the machine tool holders; n1-n2-n3-n4-n5 - respectively the number of turns of the primary winding of the transformer. The transformer provides voltage in the secondary circuit in 2 ... 6 with stepwise regulation of current. To change the current strength of the secondary circuit made taps in both primary coil. If you want a smoother control the current in the primary circuit is introduced rheostat secondary winding is made of a copper bus-section 640 mm2 and has a three-turn (two turns in one coil and one to the other). Transformers made under this scheme are widely used in repair shops for machining of parts such as bodies of revolution. Developed in USHI involving GOSNITI installation UEMO-2 (Fig. 1.3) differs from the installation UEMO-1 the presence of the voltage regulator RNO-250-5 and the possibility of increasing the secondary current to 1800 A.
Selected and justify the installation scheme for the electromechanical hardening of the outer and inner surfaces of cylinders, designed the current supply device and raskatnoy heads held hardening prototype cylinders, regression equations and selected the optimum conditions of hardening, defined corrosion resistance of the machined surface that is new in this field of research
A review of the literature found that a certain facility for electromechanical hardening of detail to be developed conductive device raskatnaya head for hardening of the outer and inner surfaces of cylinders jacks advancing conveyors. As it is not justified rational regimes of hardening. A raskatnaya head, cylinder differ by the presence of a unilateral action, for the clamping rollers. This design allows the hardening in different modes. The design of the conductive device, characterized the presence of three current collection brushes and conductive rings associated with the cartridge screws having contact elements. This design provides the necessary safety devices to regulate the current strength and speed of running in a wide range of values. Thus, it can provide the necessary micro-hardness and surface roughness. Based on experimental studies on the existing methods of the mathematical model of the influence of four variables on the value of the microhardness and surface roughness. The rational mode EMI: current density j = 500 ... 750 A/mm2, contact pressure rollers p = 300-500 N/mm2, the running speed V = 7 ... 14 m / min, at which the surface roughness in the range Ra = 0,6 ... 0,7 m along with high values of microhardness Nm = 6000 ... 7000 N/mm2. By the method developed in the IGD im. AA Skochinskiy accelerated tests were conducted on the corrosion resistance of materials. From the results of the study implies that a rational mode EMI, in which there is no corrosion of the tested samples, is a mode with a current density j = 600 ... 700 A/mm2
In writing this essay master's work was not completed. The final work you can be obtained from the author or supervisor since December 2010.