|Author(s)||Collection number||Pages||Download abstract||Download full text|
|Kavyn Ya. M., Manko O. V.||№ 2 (57)||17-25|
In the article, the results of experiments of the process of rolling finishing of medium carbon steel, strengthened by the scheme “chemical coating + diffusion chromium”, have been considered. The physical surface of the steel is a diffusion layer with an outer composite zone consisting of a columnar chromium carbide colony placed in a plastic matrix of a solid chromium solution in α-iron.
The purpose of this work is to study the influence of the surface plastic deformation (SPD) of the coating with the outer composite zone on the roughness parameters of its physical surface.
The preconditions of the surface plastic deformation (PPD) of the diffusion layer have been considered. This diffusion layer represents a system of clearly separated deep zones, each of which has its own characteristics of microhardness and plasticity. It has been shown that surface plastic deformation, in contrast to the cutting process in these conditions, provides higher roughness (~ Ra 0.64 μm), which satisfies the conditions for the operation of tribo compounds. In the process of PPD a favorable stress-strain state is created in the zones of discrete contact of the friction pair. The contact load is evenly distributed, which reduces local peak voltages. In addition, the decarburized zone 4 is strengthened through its texturing.
The general ability to surface plastic deformation of the diffusion layer is determined by the presence of an external composite zone with its plastic matrix, as well as internal zones, which are also plastic, especially the degraded zone 4.
It has been established that the average arithmetic profile Ra reaches its minimum at tensiles of 0.10–0.20 mm, or at efforts of 700–900 N: it is reduced by 3–5 times for chrome steel 45 and 9–15 times for chrome steel 30 in relation to the to the initial value of Ra 5 microns.
The range of tensions of 0,15–0,20 mm during rolling allows the use of SPD in production without adherence to rigid technological processing regimes.
Keywords: rolling, chemical and thermal treatment, tribological compound, roughness, diffusion layer, diametrical gap, stress concentrators.