Análise do torneamento do aço AISI 4340 endurecido com ferramentas de metal duro recobertas com TiAlN-TiN
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Data
2020-12-01
Autores
Silva, Vivian Martins Ferreira da
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Este estudo visa avaliar o processo de torneamento do aço AISI 4340 endurecido, com ferramenta de corte de metal duro revestida com TiAlN e TiN, em substituição à etapa de retificação. Eliminar a retificação traz melhorias no processo, tais como diminuição de custo e de complexidade, além da remoção de fluídos de corte, o que possibilita a usinagem a seco e, com isso, torna o processo menos agressivo tanto para o meio ambiente quanto para o operador da máquina. Em contrapartida, também existem desvantagens no torneamento duro, dentre elas o maior desgaste da ferramenta de corte, daí a importância em selecionar materiais apropriados para cumprir essa função. Atualmente, são utilizadas ferramentas de PCBN para a usinagem de aços endurecidos, porém a mesma custa até oitenta vezes mais do que ferramentas de metal duro. Neste trabalho, será avaliada a ferramenta de corte de metal duro revestida, contemplando propriedades extremamente atrativas e antagônicas entre si, como por exemplo a resistência ao desgaste das camadas externas, enquanto o seu núcleo possui elevada tenacidade. Para analisar o processo, foi feito o acompanhamento do comportamento das variáveis de saída do mesmo, ao longo dos ensaios, tais como rugosidade, emissão acústica, potência consumida, vibração, além de observações microscópicas qualitativas e quantitativas dos desgastes da ferramenta de corte e também estudos dos cavacos formados. Foi realizado um planejamento de experimentos fatorial completo variando-se os parâmetros de velocidade de corte, avanço e profundidade de corte de forma que fosse possível entender a interferência de cada fator individualmente e suas interações, através de análises estatísticas. De modo geral, o avanço mostrou-se o parâmetro mais significativo nas respostas das variáveis de saída do processo. O resultado final em termos de qualidade superficial da peça usinada ficou dentro da faixa de rugosidade adequada ao processo de retificação. Os cavacos formados foram contínuos, em sua maioria, o que pode interferir em variáveis como emissão acústica, mas não foi o suficiente para que o material retirado enroscasse na máquina e na peça, portanto a rugosidade da peça usinada não foi comprometida.
This study evaluate the turning process of hardened AISI 4340 steel, with a carbide cutting tool coated with TiAlN and TiN, replacing the grinding step. Eliminating grinding brings improvements in the process such as cost and complexity reduction, in addition to the removal of cutting fluids, which enables dry machining, making the process less aggressive for both the environment and the machine operator. On the other hand, there are also disadvantages in hard turning, including the increased wear of the cutting tool, hence the importance of selecting appropriate materials to fulfill this function. Currently, PCBN tools are used for machining hardened steel, but it costs up to eighty times more than carbide tools. In the case of the present work, the coated carbide cutting tool will be evaluated, considering extremely attractive and antagonistic properties, such as the wear resistance of the outer layers, while its core has high toughness. To validate the process, the behavior of important output variables was monitored throughout the tests, such as roughness, acoustic emission, consumed power, vibration, in addition to qualitative and quantitative microscopic observations of the cutting tool wear and also studies of the formed chips. A full factorial design was carried out by varying the cutting speed, advance and depth of cut parameters so that it was possible to understand the interference of each factor individually and their interactions, through statistical analysis. In general, the advance was shown to be the most significant parameter in the responses of the process output variables. The final result was satisfactory in terms of the surface quality of the machined part, as well as in the life of the tool when subjected to softer cutting parameters. The chips formed were mostly continuous, which can interfere with variables such as acoustic emission, but it was not enough for the material removed to curl on the machine and the part, so the roughness of the machined part was not compromised.
This study evaluate the turning process of hardened AISI 4340 steel, with a carbide cutting tool coated with TiAlN and TiN, replacing the grinding step. Eliminating grinding brings improvements in the process such as cost and complexity reduction, in addition to the removal of cutting fluids, which enables dry machining, making the process less aggressive for both the environment and the machine operator. On the other hand, there are also disadvantages in hard turning, including the increased wear of the cutting tool, hence the importance of selecting appropriate materials to fulfill this function. Currently, PCBN tools are used for machining hardened steel, but it costs up to eighty times more than carbide tools. In the case of the present work, the coated carbide cutting tool will be evaluated, considering extremely attractive and antagonistic properties, such as the wear resistance of the outer layers, while its core has high toughness. To validate the process, the behavior of important output variables was monitored throughout the tests, such as roughness, acoustic emission, consumed power, vibration, in addition to qualitative and quantitative microscopic observations of the cutting tool wear and also studies of the formed chips. A full factorial design was carried out by varying the cutting speed, advance and depth of cut parameters so that it was possible to understand the interference of each factor individually and their interactions, through statistical analysis. In general, the advance was shown to be the most significant parameter in the responses of the process output variables. The final result was satisfactory in terms of the surface quality of the machined part, as well as in the life of the tool when subjected to softer cutting parameters. The chips formed were mostly continuous, which can interfere with variables such as acoustic emission, but it was not enough for the material removed to curl on the machine and the part, so the roughness of the machined part was not compromised.
Descrição
Palavras-chave
Aço AISI 4340, Torneamento duro, Ferramenta de metal duro revestida, TiAlN, TiN, Aço de alta resistência, Ferramentas de corte, Usinagem, AISI 4340 steel, Hard turning, Coated carbide tool