Efeito do tratamento térmico nas propriedades mecânicas e resistência ao desgaste de um ferro fundido branco multicomponente
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Data
2010-08-06
Autores
Xavier, Renato Rufino [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A exigência crescente por melhoria de qualidade, aumento de produtividade e redução de custos tem imposto contínua evolução aos processos de laminação e, consequentemente, aos processos e materiais empregados para a fabricação de cilindros. O desempenho dos cilindros é avaliado basicamente pelo tempo de permanência no laminador durante a operação, pelo consumo específico e pela qualidade superficial dos produtos laminados, todos relacionados a propriedades como resistência mecânica, tenacidade e resistência ao desgaste. Nesse trabalho foram avaliadas as propriedades mecânicas e a resistência ao desgaste abrasivo de um ferro fundido branco multicomponente empregado na fabricação de cilindros de laminação, submetido a diferentes condições de tratamento térmico. Foram propostas duas condições de tratamento térmico para essa avaliação, utilizando-se diferentes taxas de resfriamento após austenitização. Em cada condição proposta foram retiradas amostras durante as principais etapas do ciclo de tratamento térmico: após têmpera, após o primeiro revenimento e após o segundo revenimento. A microestrutura, as propriedades mecânicas obtidas pelos ensaios de flexão, dureza e tenacidade à fratura utilizando a metodologia chevron, assim como a resistência ao desgaste abrasivo obtida pelo ensaio pino-contra-disco, foram comparadas e correlacionadas nas diferentes condições de tratamento térmico. As características microestruturais da matriz foram modificadas conforme as taxas de resfriamento utilizadas após a austenitização. As amostras resfriadas dentro do forno apresentaram menor dureza, menor resistência ao desgaste e maior tenacidade à fratura que as amostras resfriadas ao ar. Não houve diferença significativa nas propriedades mecânicas após o primeiro revenimento para ambas as condições de resfriamento estudadas...
The growing demand for quality improvement, productivity increase, and costs reduction has been imposing a continuous evolution on the rolling processes and, as a consequence, on the processes and materials used in the rolls manufacturing. The rolls performance is basically evaluated by the available time during mill operation, by the specific consumption and by the surface quality of the rolled products, all of which related to properties such as mechanical resistance, toughness and wear resistance. In this work the mechanical properties and resistance to abrasive wear of a multicomponent white cast iron for rolling mill rolls, submitted to different heat treatment conditions were evaluated. Two heat treatment conditions were proposed for this evaluation, using different cooling rates after austenitization. During each proposed condition, samples were collected during the main stages of the heat treatment cycle: after quenching, after the first tempering and after the second tempering. The microstructure, the mechanical properties obtained from the bending, hardness and fracture toughness utilizing chevron-notch methodology, as well as the resistance to abrasive wear obtained from the pin-on-disc test, were compared and correlated in the different heat treatment conditions. The matrix microstructural characteristics were modified according to the cooling rates utilized after austenitization. The samples cooled inside the furnace showed lower hardness, lower wear resistance and higher fracture toughness than those air cooled samples. No major differences in the mechanical properties were noticed after the first tempering cycle for both cooling conditions under study. The results obtained from the bending tests were similar in the different heat treatment conditions. The wear rate showed a strong correlation with the matrix hardness. The same behavior was observed... (Complete abstract click electronic access below)
The growing demand for quality improvement, productivity increase, and costs reduction has been imposing a continuous evolution on the rolling processes and, as a consequence, on the processes and materials used in the rolls manufacturing. The rolls performance is basically evaluated by the available time during mill operation, by the specific consumption and by the surface quality of the rolled products, all of which related to properties such as mechanical resistance, toughness and wear resistance. In this work the mechanical properties and resistance to abrasive wear of a multicomponent white cast iron for rolling mill rolls, submitted to different heat treatment conditions were evaluated. Two heat treatment conditions were proposed for this evaluation, using different cooling rates after austenitization. During each proposed condition, samples were collected during the main stages of the heat treatment cycle: after quenching, after the first tempering and after the second tempering. The microstructure, the mechanical properties obtained from the bending, hardness and fracture toughness utilizing chevron-notch methodology, as well as the resistance to abrasive wear obtained from the pin-on-disc test, were compared and correlated in the different heat treatment conditions. The matrix microstructural characteristics were modified according to the cooling rates utilized after austenitization. The samples cooled inside the furnace showed lower hardness, lower wear resistance and higher fracture toughness than those air cooled samples. No major differences in the mechanical properties were noticed after the first tempering cycle for both cooling conditions under study. The results obtained from the bending tests were similar in the different heat treatment conditions. The wear rate showed a strong correlation with the matrix hardness. The same behavior was observed... (Complete abstract click electronic access below)
Descrição
Palavras-chave
Ferro fundido, Desgate mecânico, Ferro - Tratamento termico, Heat treatment, Mechanical properties, Wear
Como citar
XAVIER, Renato Rufino. Efeito do tratamento térmico nas propriedades mecânicas e resistência ao desgaste de um ferro fundido branco multicomponente. 2010. 95 f. Dissertação (mestrado) - Universidade Estadual Paulista, Faculdade de Engenharia de Guaratinguetá, 2010.