Study Of The Thermal Processes Dynamics In The Feedstuff Disinfection By Electric Contact Heating

The article is dedicated to the study of the heat transfer processes that occur in the feedstuff disinfection chamber that relies upon electric contact heating. The mechanism of the temperature gradient appearance, which is the main cause of the heat losses has been investigated. The basic equations of heat conduction are considered. A method is proposed for determining the key parameters of the heat transfer process. A functional diagram of the experimental setup with a description of the operation of individual units is presented. The dependence for the transient operating mode of the unit on the growth of heat losses has been established. Thermal images of different shapes of the unit dielectric chambers have been provided as well as temperature field distribution through the chamber wall.

An Investigation into the Effect of Electro-Contact Heating in the Machining of Low-Rigidity Thin-Walled Micro-Machine Parts

Low-rigidity thin-walled parts are components of many machines and devices, including high precision electric micro-machines used in control and tracking systems. Unfortunately, traditional machining methods used for machining such types of parts cause a significant reduction in efficiency and in many cases do not allow obtaining the required accuracy parameters. Moreover, they also fail to meet modern automation requirements and are uneconomical and inefficient. Therefore, the aim of provided studies was to investigate the dependency of cutting forces on cutting parameters and flank wear, as well as changes in cutting forces induced by changes in heating current density and machining parameters during the turning of thin-walled parts. The tests were carried out on a specially designed and constructed turning test stand for measuring cutting forces and temperature at specific cutting speed, feed rate, and depth of cut values. As part of the experiments, the effect of cutting parameters and flank wear on cutting forces, and the effect of heating current density and turning parameters on changes in cutting forces were analyzed. Moreover, the effect of cutting parameters (depth of cut, feed rate, and cutting speed) on temperature has been determined. Additionally, a system for controlling electro-contact heating and investigated the relationship between changes in cutting forces and machining time in the operations of turning micro-machine casings with and without the use of the control system was developed. The obtained results show that the application of an electro-contact heating control system allows to machine conical parts and semi-finished products at lower cutting forces and it leads to an increase in the deformation of the thin-walled casings caused by runout of the workpiece.

Phase and structural transformations when forming a welded joint from rail steel. Report 3. The use of thermokinetic and isothermal diagrams of austenite decomposition for selection of optimal modes of electric contact welding

During contact flash welding of rails, the metal is heated and continuously cooled in the zone of thermal influence. Accelerated heating and subsequent intensive cooling, implemented by the pulsed flashing-off method, lead to the formation of quenching structures. Subsequently, during the operation of the rails welded joint, this leads to the formation of cracks and to brittle destruction. We have investigated the possibilities of using contact heating after welding to avoid the formation of quenching structures in the metal of the welded joint made of R350LHT rail steel. The thermal cycles during welding and subsequent contact heating were recorded. The regularity of formation of the weld metal structure was established including the zone of thermal influence during pulsed contact heating for R350LHT rail steel. It is shown that contact pulse heating slows down the welded joint cooling and prevents the formation of quenching structures. However, contact pulse heating when using suboptimal modes can also lead to the opposite effect. It is determined that with a significant investment of heat by contact heating, cooling rate of the metal exceeds the critical one, transformation process passes through a diffusion-free mechanism with the formation of martensite coarse-grained structure. The use of thermokinetic and isothermal diagrams of austenite decomposition at known thermal welding cycles allows us to significantly narrow the search limits for optimal modes of contact butt welding of railway rails and subsequent contact heating. The use of optimal contact heating modes makes it possible to obtain a minimum length of heat-affected zones with reduced hardness without the formation of quenching structures in the welded joint of railway rails.

MICROHARDNESS OF BORIDE COATINGS OBTAINED ON 65G STEEL FROM DIFFERENT COMPOSITIONS OF BORATING MIXTURES

The surface of the working organs of tillage equipment is subject to wear during operation. To obtain a surface layer of a part with high hardness and strength, corrosion resistance and abrasive resistance, there are used methods of chemical-thermal treatment, which consist in simultaneously exposing the surface to temperature and substances that can react chemically with the organ material. In this article, we consider the method of diffusion boronizing in coatings using the method of non-contact heating by high-frequency currents to study the microhardness of various boride coatings. (Research purpose) The research purpose is in studying the mechanical properties of boride coatings obtained by boronizing by heating 65G steel with high-frequency currents using various borating mixtures. (Materials and methods) An HDTV-40AV furnace was used to study the processes of boronizing using high-frequency surface heating. The temperature of the boronizing process was 950-1250 degrees Celsius, and the saturation process time was 40-180 seconds. Boron-carbide-based compositions were used. (Results and discussion) As a result of the studies, the microhardness of samples with different compositions of boronizing mixtures was studied. 65G steel was boronized. (Conclusions) According to the results of the study, the greatest microhardness was obtained using composition 6, containing manganese boride crystals (HV100 of 27570 megapascals, coating thickness of 250 micrometers) for a time of 120 seconds. However, the most suitable and less expensive to use in the agricultural industry were compositions based on boron carbide.