Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Evaluation of recovery and recrystallization induced by heat treatment in deformed railway steel microstructures.
Submission Author:
Igor Ferreira Passinho Silva , MA
Co-Authors:
Igor Ferreira Passinho Silva, Andrei Bavaresco Rezende
Presenter: Igor Ferreira Passinho Silva
doi://10.26678/ABCM.COBEM2023.COB2023-2209
Abstract
The maintenance costs have demanded significant resources from companies, especially in areas like railways. Railway wheels operate under high load conditions on the contact surface with the rail and exhibit severe grain deformations beneath the contact surface. This load contributes to rolling contact fatigue, characterized by failure due to cyclic stress, which is one of the causes of surface deterioration of rails and railway wheels. The railway wheels, after a period of use, are machined for reprofiling via the turning process. The material layer thickness removed is sufficient to restore the original profile and remove the deformed layer to avoid grain heterogeneity on the new surface. In microstructures with grain deformation, restoration occurs through annealing and normalization treatments. Depending on the temperature and time, it is possible to obtain a recrystallized microstructure with smaller grains, which provides good mechanical strength. Based on this aspect of recovery and recrystallization, there is an opportunity to homogenize this deformed layer of the wheel through heat treatments, which would reduce cutting forces, machined thickness, and the volume of material removed while maintaining a microstructure with higher strength. These results would extend the wheel's lifespan and minimize the cost of purchasing new wheels. Thus, this work sought to perform thermal treatments to homogenize the deformed layer induced by twin-disc tests in Class C railway wheel steel. The holding temperatures were 600 and 650 °C with treatment time between 5 and 30 minutes. After heat treatment, the samples were prepared and analyzed by optical microscopy and Vickers hardness measurements. It was observed that the temperature of 650°C resulted in a more effective homogenization and lower hardness values. However, at 600°C, the hardness was slightly higher. Thus, the optimal treatment time was 10 minutes at a temperature of 650°C, demonstrating the homogenization of both hardness and microstructure.
Keywords
Railway, wheels, Heat treatment, hardening
