Reutilização do cavaco do aço Vanadis ®8 pelo processo de metalurgia do pó utilizando a moagem de alta energia

Abstract

Vanadis®8 tool steel is a material manufactured by powder metallurgy, widely used in the manufacture of dies, punches, tools for cutting and cold forming. This high-performance steel has a high carbon content in its chemical composition combined with the alloy elements Chromium, Molybdenum and Vanadium, with mechanical properties of high wear resistance, high tenacity, excellent dimensional stability, being applied in tools that require high durability. Furthermore, Vanadis®8 has high value-added , and when this material is machined, the process generates chips that are sold as scrap to companies that use remelting in their processes, an expensive technique that degrades the environment environment. Thus, this study aims to reuse Vanadis R 8, using the powder metallurgy route. For this, it was realized the obtaining of the powders by the High Energy Milling in two phases. In the first phase of HEM, carbides of (Vanadium VC and Molybdenum Mo2C) were added during the milling process with a concentration of 3 %, in order to improve the mechanical properties. The parameters used were rotation 350 rpm, mass / ball ratio (1:15) and milling time 4, 8 and 12 hours. In order to technically determine the most efficient configuration, analyzes were made such as: MO, SEM, DRX, Laser Diffraction, average crystallite size and degree of crystallinity. In the second phase of HEM, the factorial DOE and the DOE RSM were used to define the most significant parameters and to equate the model obtained by the responses of the laser diffraction and screening experiments. The parameter ranges in the second phase of the HEM were rotation 300–400 rpm, mass / ball ratio (1:15) and grinding time 12–50 hours. The analysis of variance (ANOVA) of the experiments, showed that for the laser diffraction the adjustments for the answers were inconclusive, due to the low value of R2ad j. For the sieving experiment the adjustment of the responses showed a modeling within the acceptable limits, in which it is possible to obtain its equation. Through the results it was possible to conclude that the mixing of the powder of V®8 with the addition of 3%of VC was the most efficient configuration for the reduction of particles, and with DOE RSM, it was determined that rotation was the most significant parameter. In addition, it was possible to notice by the DOE RSM modeling, that the greater the rotation and the time, the smaller the particle size, being that in the rotation of 400 rpm and time of 50 hours of grinding, the process managed to transform 78 % of the powders in particles with the same characteristics as those sold commercially, while with 400 rpm and 28 hours of grinding the process managed to reach 60 % efficiency, this configuration being the most economically viable.