Hole boring technology improvement of the freight car wheel hub

Abstract

The technological process of machining the wheel hub hole of a freight car is considered. Unreliable wheel and axle fit is one of the main reasons of rolling stock derailment. The reliability of the fit depends on several factors: interference, quality of the mating surfaces, the mechanical properties of the material. The roughness of the hole surface plays a very important role. In many ways, it determines the compressing force and fatigue strength, the roughness value should be within certain limits, which are strictly regulated by Russian National Standard GOST 4835-2013. The article describes in detail the requirements imposed in Russia and abroad to the amount of roughness of the mating surfaces provided by machining. The analysis of the chemical composition and mechanical properties of wheel steels of grades 1, 2, T and L. The article also discusses the technological process and equipment for boring holes in the wheel hub. The foreign experience of using boring technologies is analyzed. The arrangement of the cutting plates in the design of the boring head applied for boring the hub hole is considered. The application of round and prismatic carbide plates used in tools is also considered. The types of metal-cutting machines used are indicated. The main emphasis in the article is on ensuring the required roughness of Russian National Standard GOST 4835-2013 due to cutting modes that are optimal from the point of view of ensuring surface quality. Based on the production data and recommended in the reference literature on feed, speed and depth of cutting values, a full factorial experiment was carried out to determine the effect of each cutting mode on the roughness parameter. As a result of the analysis, diagrams of roughness changes were plotted and intervals of feed values, speed and cutting depth were established, ensuring minimal roughness of the machined surface. It was also found that the feed rate has the strongest effect on the surface roughness. The results obtained can be used when performing the operation of boring the hub hole at the enterprises of the railway industry.