OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 5 3 Finish milling of the working profile was carried out in the following modes: VC = 370 m/min; ap = 0.05 mm; ae = 20 mm; Vf = 250 mm/min. During machining, a universal cutting fluid (coolant) TECHCOOL 1000 with mineral oils was used. In the process of integrated workpiece processing, when its relocations between mechanical operations and surface heat treatment are leveled, the technological depth of hardening at the operation “Surface HEH HFC hardening” is AT = 0.52 +0.28 mm (finish allowance z min = 0). The absence of an additional workpiece positioning, and the fact that the premachining is carried out on non-hardened material, milling is carried out in a more intensive mode than with standard technology. Moreover, the use of hybrid technology makes it possible to intensify the cutting process of the workpiece during machining due to additional heating by a concentrated energy source. Preheating the product with high-frequency currents before using the cutting tool reduces the resistance during processing and makes the workpiece more conformable for shaping. Thus, an additional effect is achieved, which makes it possible to enhance the operation conditions during preliminary (rough) milling. At the same time, by the subsequent operation “Surface HEH HFC hardening” due to heating of the U10A carbon tool steel for hardening, it will be possible to balance the dangerous level of the stress-strain state of the workpiece surface layer. To determine the most effective modes of surface hardening in the framework of the use of hybrid processing, the relationship between the depth of hardening and process-dependent parameters for a given steel grade was established: 2 2 3 3 2 2 S S S S S S S S S S S S S S ( , ) h q V a bV cq dV eq fV q gV xq iV q jV q = + + + + + + + + + , (1) where for U10A steel the coefficients are: a = 0.906184; b = –12.343186; c = 1.851541 ∙ 10–9; d = 24.621030; e = 4.103625 ∙ 10–18; f = –1.571684 ∙ 10–8; g = –66.067377; x = –4.851607 ∙ 10–28; i = –2.040626 ∙ 10–17; j = 6.052463 ∙ 10–8. Fig. 7 shows the results of the research. Experimental data processingwas performed using STATISTICA6.0 and Table Curve 3D v 4.0 software products. It is important to note that the maximum error does not exceed 5 %, which indicates the reliability and accuracy of the results. This confirms the reliability of the study and allows taking its results into account when making decisions. When using HEH HFC, changing the geometric parameters of the source in the process of manufacturing a new inductor is a complex and spending process. In this regard, the specific power of the heating source and the speed of its movement were chosen as variable parameters. When applying induction heating, the size of the source is usually determined first, and then the other two process parameters. However, the results of mathematical and experimental studies [7, 14, 17, 21, 47, 61, 71–73, 75, 82–83, 87] showed that the obtained ranges of hardening modes do not guarantee the formation of a hardened layer Fig. 6. Processing area with high-energy heating by high-frequency currents: 1 – turntable; 2 – workpiece; 3 – self-centering vice chuck; 4 – loop inductor; 5 – adapter mandrel Fig. 7. Functional dependence h(qS, VS) for U10A steel
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