Estudo sobre o torneamento de aços inoxidáveis

• Ano de defesa: 2021
• Autor(a) principal: Jorge Dayvison Celestino Duarte
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; Brasil; ENG - DEPARTAMENTO DE ENGENHARIA MECÂNICA; Programa de Pós-Graduação em Engenharia Mecanica; UFMG
• Palavras-chave em Português: Aços inoxidáveis; Usinabilidade; Torneamento; Engenharia mecânica; Aço inoxidável
• Link de acesso: http://hdl.handle.net/1843/39224

Stainless steels are widely used in daily life in domestic and industrial items and are considered difficult to machine materials due to characteristics such as: high ductility, low thermal conductivity, formation of long chips and a tendency to form built-up edge. This work presents the state of the art on the influence of chemical composition and both physical and mechanical properties of stainless steels on their machinability, specifically in the turning operation. It is intended to identify the most suitable machining conditions in terms of machinability (considering tool life and wear, surface finish, process forces, cutting temperature and subsurface alterations). Results obtained with the use of tools with different geometries, substrates and coatings are also evaluated. The results point to a greater difficulty in turning austenitic stainless steels due to their low thermal conductivity, strong tendency to hardening and formation of long chips. The most frequently observed wear mechanisms were attrition, abrasion and diffusion. Due to the high hardness of martensitic stainless steels, deformation under compression was the most relevant wear mechanism. For duplex and austenitic steels, the presence of built-up edge was observed in a wide range of cutting speeds. Turning of martensitic stainless steels promoted high process forces, associated with the high hardness of this grade. Duplex stainless steels that have higher Ni and Cr amounts and elevated values of tensile strength and hardness also presented high process forces. The use of cutting fluid helped to reduce machining temperature and the cryogenic method showed best efficiency due to the direct application of N2 in the cutting zone. With regard to surface integrity, the increase in feed resulted in higher surface roughness for all grades. Microstructural changes in stainless steels are associated with high temperatures and high deformation during turning. The increase in feed and depth of cut in austenitic steels caused work hardening and the increase of microhardness, while the increase in temperature and material deformation contributed to the induction of tensile residual stresses, which negatively affect the fatigue life.