Análise da influência do nióbio na microestrutura e propriedades mecânicas da barra chata temperada e revenida para aplicação em feixes de mola

• Ano de defesa: 2005
• Autor(a) principal: Eduardo de Oliveira Diniz
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: Engenharia Metalúrgica e de Minas; Engenharia metalúrgica; Metalurgia física; Niobio; Laminação (Metalurgia)
• Link de acesso: http://hdl.handle.net/1843/BUOS-8DUFC2

This dissertation aimed to evaluate the effect of niobium addition on the mechanic properties and structure of quenched and tempered flat bars applied to springs. Three different heats of ABNT 5160 steel were sampled with the following level of niobium: 0,0% Nb, 0,02% Nb and 0,04% Nb. The samples were extracted from flat bars rolled at BELGO Grande Vitória Plant and after quenched and tempered at customer springs manufacturer. The influences of different levels of niobium were evaluated in the rolled bars through measurement of the austenite grain size, characterization of structure, measurement of hardness and tensile strength. In the quenched and tempered bars, the structure was characterized and the hardness measured. In the springs, fatigue tests were made. The results showed that niobium doesnt have significative effect on mechanical proprierties and microstructure of steel after rolling or after thermal treatment, and the same happened to the results of fatigue tests. The results of fatigue test of heat with 0,02% of niobium were better than the ones of the heats without niobium and that heat with 0,04% of niobium. This absence or small influence of niobium on the mechanical proprierties, microstructure and fatigue life was attributed to the low austenitization temperature before rolling mill and before quench which cause merely a small solubilization of niobium.