Desenvolvimento de um modelo de transferência de calor e solidificação de placas no processo de lingotamento contínuo

• Ano de defesa: 2019
• Autor(a) principal: André Afonso Nascimento
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; Brasil; ENG - DEPARTAMENTO DE ENGENHARIA METALÚRGICA; Programa de Pós-Graduação em Engenharia Metalúrgica, Materiais e de Minas; UFMG
• Palavras-chave em Português: Solidificação; Lingotamento contínuo; Modelo matemático; Transferência de calor; Engenharia metalúrgica; Metalurgia extrativa; Calor - Transmissão; Fundição continua; Modelos matemáticos
• Link de acesso: http://hdl.handle.net/1843/31563

Surface and internal defects in slabs produced in the continuous casting process are usually related to four aspects: (i) primary and secondary cooling condition; (ii) machine alignment; (iii) flow of steel in the mold and (iv) physico-chemical properties of steel. Among the mentioned aspects, the cooling conditions of the slab are of paramount importance for the solidification process, since they affect parameters such as the shell thickness, the temperatures as a function of the position in the strand and the solidification end point of the slab. Such parameters are essential for any failure or adequacy analysis in the continuous casting process and can be obtained by heat transfer and solidification models of the slab. Thus, in the present study a model will be developed by the 2½ D method, which consists of following a transverse section of the slab, in a transient scheme, throughout the extension of the machine, adjusting the boundary conditions for each region. The model can be adapted to continuous casting machines casting shapes with rectangular cross sections. The profile of heat fluxes in mold faces were as a function of the distance of the meniscus taking the flow rate of water and the difference between inlet and outlet temperature of water. In the secondary cooling, routines were implemented to consider extraction of heat by roller, by radiation, by the convection due to the spray and by the water accumulator in the rollers. For a convection boundary condition, a specific water flow fraction was applied to the marge of slab, on the wide face, in function of the central water flow. To validate the model, thermocouples were inserted between the rollers and the slab to measure the surface temperature. In one point of the machine was measure the temperature of slab in function of the wide face, with optical pyrometer. To validate the shell thickness was measure breakout shell in mold and bender regions. Therefore, the objective of this study was to develop a mathematical model to simulate the cooling conditions during solidification in the slab continuous casting. The experimental results were compared with those obtained in the simulations and showed excellent agreement. Thus, the developed model has been validated and can be used to assist in process changes aimed at improving the internal and surface quality of slabs for continuous slab casting machine from Gerdau Ouro Branco.