OBRABOTKAMETALLOV Vol. 24 No. 1 2022 technology This paper is devoted to the development of a theoretical method for calculating the temperature during milling for a group of nickel-based alloys. To achieve this purpose, it is necessary to develop a mathematical model that takes into account the effect of strain, strain rate and temperature on the change in the yield strength during milling and to confirm the results of theoretical prediction of cutting temperature experimentally (by non-contact method of temperature measurement). As an example, theoretical and experimental studies will be carried out for the 56% Ni-Cr-W-Mo-Co-Al heat-resistant alloy obtained by vacuum remelting. Research technique The first thing to consider when calculating the cutting temperature is the mechanical and physical properties of the material. Secondly, it is necessary to take into account the geometry of the cutting tool (back rake angle g°, front clearance angle α°, side cutting edge angle j°, rake angle λ°), as well as the schematization of the milling process, namely the infeed depth e, take into account the number of simultaneously working teeth, ratio of milling width to cutter diameter. The geometry of the cutting tool was taken into account through the Peclet criterion, which determines the heat exchange between the material being processed, the environment, and the tool, and through the Peclet coefficient, which takes into account the rate of heat removal [15]: 1 60 1000 v a Pe = ⋅ ⋅ w, (1) 1 1 exp( tg ) 1 tg y Pe y Pe K Pe − − ⋅ j = + ⋅ j , (2) sin cos z a S = ⋅ j ⋅ λ, (3) cos arctg sin y g j = z − g , (4) where a is the thickness of the cut layer in mm, ν is the cutting speed in m/s, w is the thermal diffusivity m2/s (reference value), S z is the feed per tooth in mm/tooth, j is the actual cutting edge angle in degrees, λ is the rake angle of the cutting edge in degrees, g is the back rake angle in degrees, jy is the angle of inclination of the conditional shear plane in degrees, z is chip shrinkage. Thirdly, it is necessary to take into account the influence of temperature itself on the change in the mechanical properties of the material. High temperatures during the cutting process can lead to a significant change in the mechanical properties of metals and alloys. It is known [16–18] that in the process of cutting under the influence of high strain rates, thematerial being processed can be significantly hardened, and under the influence of temperature, it can be softened. For the study, a group of heat-resistant alloys was selected, which obeys the same softening law (Figure 2), and therefore, the change in the yield strength of the above alloys can be described by one generalizing equation, and it is permissible to choose any of it for research. Fig. 2. Change in the mechanical properties of nickel based alloys during static tensile tests [15, 16]
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