Improving the efficiency of surface-thermal hardening of machine parts in conditions of combination of processing technologies, integrated on a single machine tool base

OBRABOTKAMETALLOV Vol. 23 No. 3 2021 technology Thus, the desired parameters are: the technological depth of quenching A T = 1.0 +0.1 mm; the size of the preprocess D 1 = 46.5 –-0.1 mm; the allowance for final processing z min = 0.431 mm. It should be noted that 5...8 % of the parts are rejected due to the presence of burns and microcracks on the surface (according to the company). To ensure this depth of the hardened layer when using a generator with a frequency of 440 kHz, it is necessary to implement a surface heating scheme, which is usually characterized by lower values of the specific power and speed of movement of the heating source in relation to the volumetric scheme. With the width of the active inductor wire R S = 12 mm – q s = 1.2×10 7 W/m 2 , V p = 2 mm/s. Two sections with a total length of 94 mm should be hardened on the parts. Both sections are processed in one axial movement of the part relative to the annular inductor. The total length of the part motion, taking into account the presence of a groove with a width of 6 mm and the entry and exit of the inductor with a continuously sequential heating scheme, is l = 114 mm. In this case, the processing time is T p = l/V p = = 57 s, while according to general machine-building standards for heat treatment on HFC installations with the specified method of basing the part (Fig. 9), the auxiliary time of the T aux = 20 s. Thus, the piece productivity is equal to P p = 1 / ( T p + T aux ) = 1 / (57 +20) = 0.013 s -1 and energy costs are equal to E = ( q s · π · D 1 · R s · l ) / V p = (1.2 · 107 · 0.0465 · 0.012 · 0.114) / 0.002 ≈ 0.333 kW ·h The final stage using the proposed integrated processing. In this case, the three finishing operations are replaced by one integrated, consisting of three transitions: 1. Turning (rough, semi-finishing, single finishing); 2. HEH HFC hardening; 3. Final finishing turning and diamond smoothing (Table 3). 1. HFC quenching is carried out according to the scheme (Fig. 10). In this case, the unevenness of the hardened layer in depth is determined by the accuracy of manufacturing the active inductor wire and its position relative to the axis of the processed product. Based on the experimental results and using the align- ment of the active inductor wire according to the indicator δ Т = 0.05 mm. Hence, δ t = δ K – δ Т = 0.4 – 0.05 = = 0.395 mm. 2. The quenching depth is 0.6...1.0 mm, hence the value of A P = 0.0048...0.010 mm, δ P = 0.0052 mm. Thus, 1 1 i i P − − ′d = d + d = 0.01 + 0.0052 = 0.0152 mm. Then the permissible value of the total spatial deviation will be equal to 1 0.025 0.0152 2 0.395 0.3749 2 2 i i e t − D ′ d + d + d = d − = − = mm. 3. The proposed finishing stage of the technological process is carried out without repositioning the workpiece, therefore, despite the fact that the same tooling is used, the positioning error is e P = 0. The first transition – rough, semi-finishing turning of the surface allows to eliminate errors that occurred at the previ - ous stage of the technological process and errors in the part positioning. This, in turn, ensures the constancy of the gap between the inductor and the treated surface, and, consequently, the uniformity of the depth of the hardened layer. In this case, the amount of warping after surface hardening is d и = 0. Then 2∑δ еi = 0. The real value of δ t is 1 0.025 0.0152 0 0.0201 2 2 i i t ei − ′ d + d + d = ∑ d + = + = мм. 4. The final finishing turning is carried out after quenching, therefore, T i- 1 = 0. Due to the fact that sur- face hardening is carried out without changing the surface roughness, and mechanical processing is car- ried out with a single grinding wheel, the achievement of the surface roughness specified by the drawing