Avaliação das condições de transferência de calor na simulação do ciclo de recozimento contínuo da gleeble

• Ano de defesa: 2007
• Autor(a) principal: Ricardo Machado Cabral
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: Gleeble; Recozimento contínuo; Simulação; Engenharia metalúrgica; Engenharia de minas $x
• Link de acesso: http://hdl.handle.net/1843/MAPO-7RCNEN

The application of laboratory scale equipment for the simulation of industrial processes in scientific studies is usual and necessary as a result of the high costs and operational problems involved in industrial scale experiments. However, in order to produce adequate results, the real process conditions must be closely simulated by the equipment. The Gleeble is a thermo-mechanical simulator which has been frequentlyused for the simulation of continuous annealing cycles in research works. However, it has been verified that the samples subjected to thermal cycles during soaking, fast cooling and overaging show temperature variations along the testing area, which impairs their use for research studies because: (i) the results do not correspond to thedesired conditions; (ii) a new variable is introduced into the simulation and (iii) the mechanical properties of the material are changed.In the present study, the characterization of the current situation of the assays of continuous annealing in the Gleeble was realized using samples with 0,77mm and 2,03mm thickness. Also, the adequate test conditions for the simulation of the desired cooling rates were determined and the temperature distribution over the sample wasevaluated. It was concluded that the temperature variation over the sample is influenced by the cooling of the jaws, during the soaking and overaging phases of the cycle, and by the pressure of the atomization gas, during the fast cooling phase. The area of the sample where the temperature can be considered homogeneous, with a maximumvariation of 10°C in relation to the desired temperatures during the simulation, is of 14mm x 10mm in samples with 0,77mm of thickness and 12mm x 8mm for samples with 2,03mm thickness. To extend this area, one must use: (i) longer samples (200mm length); and (ii) lower air pressure for atomization. Along the study several devices were developed, including the one which measured the impact force of the atomization water during fast cooling, allowing the correlationbetween the convection coefficient and the impact pressure of the water jet