Análise da integridade superficial no torneamento endurecido do aço AISI 4317 cementado
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Dissertação
Data
2013
Autores
Branco, Felipe Kulig
Orientador
Delijaicov, Sergio
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Texto completo (DOI)
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Tornos mecânicos,Materiais duros,Tensões residuais
Resumo
Este trabalho teve como objetivo a analise da integridade superficial do material AISI 4317, cementado, temperado e revenido de dureza media de 59 HRC sujeito ao torneamento de acabamento utilizando pastilhas de CBN (nitreto cubido de boro), variando tres parametros de usinagem, sendo eles velocidade de corte, avanco e profundidade de corte. A caracterizacao da integridade superficial deu-se atraves do estudo da rugosidade media Ra, das tensoes residuais e analise da camada superficial afetada termomecanicamente devido ao processo de usinagem, correlacionadas com as respectivas forcas de usinagem. O planejamento experimental escolhido foi o central composto, comumente utilizado para experimento envolvendo processos de usinagem. As variaveis dependentes, esforcos de usinagem, rugosidade, tensoes residuais e camada superficial afetada, foram associadas estatisticamente as variaveis independentes, velocidade de corte, avanco e profundidade de corte, atraves do programa ¡§Statistica¡¨. As rugosidades medias obtidas variaram 0,32 a 2,80 Ým. O estudo das tensoes residuais indicou que o torneamento introduziu altas tensoes residuais compressivas na subsuperficie das amostras, caracteristica que aumenta a vida a fadiga e minimiza o aparecimento de trincas na superficie e subsuperficie do material. Camadas afetadas foram identificadas na superficie das amostras, verificadas a partir de ensaios metalograficos, apos a usinagem, fenomeno que tende a degenerar a integridade superficial, podendo ser eliminada utilizando processos de superacabamento, ja que pequenas camadas foram encontradas, variando de 1,1 a 5,1 Ým. Dentre as componentes da forca de usinagem, a forca de penetracao foi a que apresentou o maior modulo. Os menores valores das variaveis independentes representaram os parametros de usinagem responsaveis pelas condicoes otimizadas das variaveis dependentes que representam a integridade superficial do aco AISI 4317 torneado depois de cementado-temperado-revenido.
This work is based on the surface integrity analysis of hardened steel, AISI 4317 case carburized, quenched and tempered with 58 HRC, obtained by a turning operation executed with CBN (cubic boron nitride) tool, varying three basic cutting parameters (cutting speed, feed rate and cutting depth). The surface integrity characterization was conducted analyzing the behavior of the roughness Ra, residual stresses and with layer presence after turning. Also the cutting forces were measured. The experimental planning used was a central composite design, widely applied in many researchers related to machining experiments. The results and data were statistically treated by the Statistica software, enabling the generation of a mathematical model relating the dependent variables with the independent variables. The roughness values Ra obtained after the experiments ranged from 0.31 to 2.8 Ým, providing an indication that is possible to replace grinding process by hard turning using CBN tools, that could reduce machining time and costs. The hard turning process generated compressive residual stresses profiles and white layer formation, from 1.1 to 5.1 Ým, on the surface of the samples. The penetration force showed the highest values for the turning forces. The lowest values for the cutting parameters represented the optimized surface integrity of the AISI 4317 steel. Keywords: Hard Turning ¡V Surface Integrity
This work is based on the surface integrity analysis of hardened steel, AISI 4317 case carburized, quenched and tempered with 58 HRC, obtained by a turning operation executed with CBN (cubic boron nitride) tool, varying three basic cutting parameters (cutting speed, feed rate and cutting depth). The surface integrity characterization was conducted analyzing the behavior of the roughness Ra, residual stresses and with layer presence after turning. Also the cutting forces were measured. The experimental planning used was a central composite design, widely applied in many researchers related to machining experiments. The results and data were statistically treated by the Statistica software, enabling the generation of a mathematical model relating the dependent variables with the independent variables. The roughness values Ra obtained after the experiments ranged from 0.31 to 2.8 Ým, providing an indication that is possible to replace grinding process by hard turning using CBN tools, that could reduce machining time and costs. The hard turning process generated compressive residual stresses profiles and white layer formation, from 1.1 to 5.1 Ým, on the surface of the samples. The penetration force showed the highest values for the turning forces. The lowest values for the cutting parameters represented the optimized surface integrity of the AISI 4317 steel. Keywords: Hard Turning ¡V Surface Integrity