Предметом дослідження є процес теплоутворення при шліфуванні металів і сплавів, а об'єктом дослідження − визначення кількості теплоти, що виділяється при різанні металу окремими абразивними зернами, підсумовування теплових потоків від окремих зерен і формування потужності теплового джерела в зоні контакту шліфувального круга зі шліфованої деталлю. Знання теплонапруженостi процесу шліфування дає можливість не допускати шліфувальних прижогів і тріщин. Це різко знижує міцність, надійність і довговічність деталіКлючові слова: шліфування металів, кількість теплоти, теплові потоки, кількість теплоти, теплонапруженiсть процесу Предметом исследования является процесс теплообразования при шлифовании металлов и сплавов, а объектом исследования − определение количества теплоты, выделяющееся при резании металла отдельными абразивными зернами, суммирование тепловых потоков от отдельных зерен и формирование мощности теплового источника в зоне контакта шлифовального круга со шлифуемой деталью. Знание теплонапряженности процесса шлифования дает возможность не допускать шлифовочных прижогов и трещин. Это резко снижает прочность, надежность и долговечность деталиКлючевые слова: шлифование металлов, количество теплоты, тепловые потоки, теплонапряженность процесса UDC 621.791:621.926
Object of research. The article investigates the cutting forces when grinding martensitic-aging steels with highly porous grinding wheels. The problem to be solved is the regularities of the change in the magnitude of the cutting forces when grinding maraging steels with highly porous CBN wheels. Main scientific results. The studies were performed on martensiticaging steel H8K18M14. As a result of the experiments, it was found that when grinding wheels made of materials such as electrocorundum, CBN (borazon) and diamond, a significant role is played by the values of the cutting force, which increase during processing. During the experiment it was found out: the cutting forces Py and Pz in the width of the allowable modes, which are most often used in circular and flat grinding, can reach the following values: with the structure of the wheel 26 come to values from 2.714N to 30.721 and with the structure of the wheel 40 come to values from 2.49N to 28.185N. Reducing the grain size of the wheel, let’s obtain the effect of increasing the energy costs of the grinding process, by increasing the magnitude of the cutting forces. If to compare the cutting forces that occur when grinding different wheels, it is possible to note the following: in comparison with electrocorundum wheels when using wheels with KNB cutting forces are reduced by 20-25 %, and when grinding with diamond wheels, the effect of cutting forces is reduced by 25 - 30 %. When grinding with highly porous wheels, the cutting force is 15-20 % higher than when grinding with wheels of normal porosity. The area of practical use of research results-grinding technology for maraging steels. Innovative technological product – relationship between processing modes and the magnitude of cutting forces when grinding maraging steels. Scope of application of an innovative technological product-mechanical engineering technology
Cutting of natural and artificial building materials is most often carried out with diamond cutting wheels on a metal base at cutting speeds of about 50-80 m/s. The intensity of the cutting process causes a significant heat release, as a result of which the wheel temperature rises to unacceptable values. The value of these unacceptable temperatures is about 600 - 650°C At these temperatures, graphitization of diamond grains occurs, i.e. loss of diamond layer and loss of cutting properties. In addition, a thin diamond wheel (thickness 1 - 3 mm) is deformed, which leads to jamming and its tensile strength at these temperatures is reduced by half, which creates the risk of rupture by centrifugal forces. In this work, it is taken into account that during the rotation of the wheel, a boundary layer of air is created around it, which is stationary relative to the wheel. Consequently, contact heat transfer occurs between the wheel and the boundary layer, and then convective heat transfer occurs between the boundary layer and the surrounding air. This scheme allows you to more accurately determine the time of safe operation of the diamond wheel. Contact heat transfer between the wheel and the boundary layer is not effective enough to lower the temperature. When air with a negative temperature is introduced into the boundary layer by means of a Rank-Hillsch tube, the wheel temperature decreases by about 10%. When a sprayed coolant (fog cooling) is introduced into the boundary layer by means of an ejector tube, the wheel temperature decreases by 25%, which ensures an increase in the time of continuous operation.
The advantage of cutting stone building materials with SSM (synthetic superhard materials) wheels is that, first of all, it is possible to obtain high processing productivity and dimensional stability, which are 3..5 and 50…100 times higher than those of traditional tools based on carborundum, respectively. The study of the process of cutting stone materials with CBN (cubic boron nitrite) wheels is aimed at establishing force dependences, determining the cutting power and heating temperature of the cutting disc during operation. The forces were measured using a tensometric dynamometer UDM-50. To measure and calculate the cutting temperature, a thermoelectric method based on the formation of practically not inertial microthermocouples during cutting was used. The temperature to which the CBN cutting wheel on a metal base is heated is a limiting factor in processing, since when heated to a temperature of 600ºС, the strength of the wheel decreases by half, which can cause its rupture under the action of centrifugal forces, as well as loss of stability and jamming during cutting. In the present study, the wheel temperature was measured after one minute of continuous operation. The values of the component of the cutting force PY, depending on the processing modes, can reach values of the order of 70 N. The values of the component of the cutting force PZ, depending on the processing modes, can reach values of 45 N. The cutting power can be 2800W. The temperature resistance of the wheel (heating time of the wheel up to 600ºС) when cutting dry is maximum 28 minutes, when grinding with cooling of the cutting zone with negative temperature air from a Ranque-Hilsch tube, the temperature resistance is 35 minutes, with ejector cooling of sprayed coolant 37 minutes and with jet-pressure cooling it is 40 minutes. The maximum cutting length is respectively 0.7: 0.8; 0.9 and 2m. The cutting power is 600...2800W.
The object of research is the process of circular and surface grinding of titanium alloy and corrosion-resistant steel, namely, the cutting forces arising from mechanical processing. One of the most problematic areas in work is the selection of the required grinding modes, material and grinding wheel grain size. In the course of the experiment, we used samples of VT8 titanium alloy and 12Х18N9T steel, on which the grinding process was studied with wheels made of various materials (electrocorundum, cubic boron nitride (CBN), diamond). The values of the cutting forces Py and Pz were obtained in the latitude of permissible modes, which are most often used in circular and flat grinding, and can reach maximum values, respectively, Py=27 N, Pz=15.5 N. The data were obtained at a low wheel speed from electrocorundum, about 15 m/s and grain size 8. By reducing the grain size of the wheel, we get the effect of increasing the energy consumption of the grinding process, due to the increase in the values of the cutting forces. If we compare the cutting forces arising from grinding with different wheels, then the following can be noted. Compared to electrocorundum wheels, when using CBN wheels, the cutting forces are reduced by 20–25 %, and when grinding with diamond wheels (despite the high wear of the diamond wheel), the effect of cutting forces is reduced by 25–30 %. This is due to the fact that cutting conditions are the most favorable for diamond and CBN grains, which makes it possible to use more intense cutting conditions. The results of the study allow predicting the performance of the grinding wheel, reducing the energy consumption of production, and also adjusting the processing mode of the part to obtain the necessary quality indicators of the surface layer and the geometric dimensions of the part.