Vol 47, No 11 (2017)

To minimize the manufacturing costs of parts with specified operational properties, the machining processes must be optimized. Cutting accounts for at least 70% of such processes. To that end, tool materials with distinctive properties may be developed and utilized. Analysis of manufacturing components—in particular, power components in gas-turbine engines—shows the need for higher quality of the machined surfaces and more efficient use of expensive equipment with numerical and adaptive control systems, so as to ensure a wide range of cutting conditions, including high-speed cutting. To obtain products that are domestically and internationally competitive, we need to optimize cutting processes, in which the tool is the weakest link in the technological chain. Defects of the cutting tool impair the productivity and product quality. In the present work, the wear of cutting tools produced by the sintering of high-speed steel powder is studied. Tool materials based on high-speed steel with additional alloying by titanium carbide (carbide steel) are shown to be highly wear-resistant. They may be classified as a new category of self-organizing tool materials. The results indicate the expediency of additional alloying by two methods to modify the tool friction and wear: (1) alloying with compounds that considerably reduce the self-organization by decreasing the frictional coefficient at working temperatures; (2) alloying to expand the range of self-organization. Both methods result in lower frictional forces and temperatures, as confirmed by the change in wear resistance and frictional characteristics. The wear resistance of such tools is found to be 2–3.5 times that of regular high-speed steel tools.

Orientation microscopy (electron back scatter diffraction, EBSD) is used to investigate the structural and textural states of low-carbon, low-alloy pipe steel (resembling 06Г2MБ steel) after thermomechanical controlled processing (TMCP): heating to 1000°C with subsequent quenching in water; isothermal quenching with holding at 300°C; and slow cooling in the furnace. The heat treatment is associated with double phase recrystallization: α → γ → a_ht, where a_ht is martensite, bainite, or ferrite. The texture obtained after TMCP is mainly formed by two strong scattered orientations from {112}〈110〉and two weaker scattered orientations close to {110}〈223〉. Despite the double phase recrystallization, the main crystallographic orientations of the bainite after TMCP and after isothermal quenching are the same. That indicates structural and textural inheritance in the material. The structures obtained after other thermal treatments of the structure (both martensite and ferrite) also include complex multicomponent textures, which are nevertheless distinct. Some of the main textural components of martensite and ferrite are the same as bainitic components. All the structures after heat treatment have a similar spectrum of large-angle boundaries, with strongly expressed boundaries of the coincidence site lattices (CSL): Σ3, Σ11, Σ25b, Σ33c, and Σ41c. The orientations forming the texture of all the structures obtained are related to the main orientation of the deformed austenite grains formed on hot rolling in TMCP, in accordance with orientation relations intermediate between the Kurdjumov–Sachs and Nishiyama–Wasserman types. In all cases, the orientation relationship of the textural components of the initial material and the structure obtained by heat treatment may be explained in terms of the onset of phase transformations (both shear and diffusional transition) at crystallographically determined boundaries (including special boundaries) similar to the CSL boundaries Σ3 and Σ11.

In a new mathematical model of the stress–strain state of steel strip in the course of cooling, the nonplanarity, surface roughness, and transverse thickness variation (convexity of the cross section) are taken into account. The stress–strain state of a coil of thin steel sheet has a significant influence on factors such as the temperature distribution in the coil; the scale formation on cooling in the course of hot rolling; the adhesion of adjacent turns in the annealing of cold-rolled strip; and the shape of the coil itself. The mathematical model is based on representation of the coil as individual nested hollow cylinders of finite length. The cylinders are divided into sections over the width. The sum of solutions of the Lame equation for individual sections is shown to converge to the solution for the cylinder as a whole. The model permits calculation of the coil’s stress–strain state, taking account of gap formation between adjacent turns as a result of the transverse variation in strip thickness. The modeling results show how the radial and tangential stress formed in strip winding is distributed within the coil. The model permits calculation of the stress–strain state of the coil in the winding of even strip; in the winding of convex even strip with no tension; in the loose winding of convex even strip with tension less than that in tight winding; in tight winding of even convex strip with the correct tension; and in the winding of convex uneven strip without tension. The decrease in distance between contacting rough surfaces is calculated on the basis of a probabilistic approach. An algorithm is presented for calculation of the coil’s stress–strain state. The result obtained for the stress distribution in the coil is typical for the winding of steel strip. The model is verified for the winding of hot-rolled strip, in terms of the size of the region with tight contact of adjacent turns. The tightness of contact is assessed on the basis of the temper color on the edges of the hot-rolled strip. The discrepancy between the calculated and measured size of the region with tight contact is 3%.

The electrical asymmetry in the operation of arc furnace with an asymmetric triangular configuration of the electrodes is noted. Experimental data from the DSP-100 furnace permit analysis of how the electrical parameters affect the arc characteristics. Nonuniform power distribution over the phases of the electrofurnace decreases the component of the useful power consumed in heating the metal and slag. The power consumption by the furnace may potentially be reduced by 7.4% and the electrode consumption by 9%. The results confirm the need for research on phase-by-phase regulation of the power of ac arc furnaces.

The influence of the rheological properties of the lubricant in pipe pressing is investigated. The dynamic viscosity of lubricants used in laboratory and industrial conditions is determined. The frictional coefficient in pipe pressing is determined by a hybrid method based on calculation and experiment.

The influence of cyclic flexural deformation of thick low-alloy and carbon steel sheet on its structure and mechanical properties is investigated over a broad temperature range. In plastic flexure, the deformational amplitude is 1–6%. Permissible parameter ranges corresponding to the best mechanical properties of the steel, without irreversible structural damage, are selected. Strengthening treatment for thick steel sheet is developed, and permissible parameter ranges are proposed.