Análises de inclusões não metálicas no aço inoxidável ferrítico 409

• Ano de defesa: 2015
• Autor(a) principal: Marcio Nascimento Cunha
• 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 Materiais e de Minas; Engenharia metalúrgica
• Link de acesso: http://hdl.handle.net/1843/BUBD-AEAKX9

Non metallic inclusions make part of the steel production and are impossible to remove all of them. Several quality and operational problems in the production are linked with these inclusions. The knowledge about the process of production together a good investigationmethod is an important step to find the possible inclusions sources. It helps to problems analysis and to find solutions quickly. Some methods to obtain inclusion in order to improve the steel quality have been used. Inclusions with low melting point after calcium treatment have showed good results. The propose of this study was to obtain the chemical composition of the non metallic inclusions in specifics steps of production of the ferritic stainless steel 409 type in the Melt Shop, to identify the steps that effect the cleanness, to evaluate the inclusions constitution evolution during the process and to evaluate the possibility to modify the inclusions with calcium addition in the Ladle Furnace.Samples of the liquid steel and slag were taken in specifics process in two steps. In the first step samples were obtained from a standard heat and in the second one was used a heat with Ca-Si addition in the Ladle Furnace. Optical microscopy examination with image analyzer was carried out in the samples. The worst areas were divided by fields and every inclusion was quantified in these particular fields. Inclusions with size 2Zm had the chemical composition analyzed in a Scanning Electron Microscope with EDS (MEV/EDS). The results showed that the cleanness condition is more affected after the blowing step inthe VOD process, after titanium addition in the Ladle Furnace and in the tundish of the continuous casting. The chemical composition of the inclusions was changed according to the treatment in each process and the effect of the Ca-Si addition in order to obtain inclusions with low melting point depend on the CaO variation in a narrow range withdifficult control.