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Abstract(s)
Aços pré-tratados para moldes são muito utilizados nos dias de hoje dada a possibilidade de serem utilizados sem a necessidade de serem aplicados tratamentos antes e depois do processo de fresagem, visto que eles já apresentam a dureza necessária. No entanto a sua elevada dureza dificulta bastante a sua maquinabilidade, algo que proporciona às ferramentas de corte elevados níveis de desgaste e reduzidos tempos de vida. A deposição de revestimentos nas ferramentas de corte é um modo muito comum de colmatar esta adversidade, levando a um processo de fresagem com um melhor desempenho em termos de desgaste da ferramenta de
corte e da qualidade das superfícies maquinadas. A correta seleção dos parâmetros de corte também é um aspeto importante para o aumento da vida das ferramentas. O objetivo deste trabalho foi estudar o desempenho de ferramentas de corte compostas por carboneto de tungsténio e revestidas por TiAlN e AlCrN na fresagem de aço W 1.2711. Foram variados os valores de velocidade de corte, avanço por dente e profundidade de corte, enquanto a largura de corte foi mantida constante. Após cada ensaio de fresagem foram obtidos os valores de rugosidade superficial, desgaste acumulado e vibrações. Foi concluído que o aumento do avanço por dente apresenta uma influência negativa em todos os parâmetros estudados,
enquanto o aumento da velocidade de corte mostra um impacto negativo para certos valores de avanço por dente e um impacto positivo para outros valores de avanço por dente. Em geral, os principais mecanismos de desgaste nas ferramentas de corte foram desgaste adesivo, com a formação de arestas postiças em certos ensaios, desgaste abrasivo e lascagem, principalmente nos ensaios com valores de avanço por dente superiores. Também foram observadas fraturas, particularmente nas ferramentas 592 e 233 nos ensaios com avanço por dente de 0,1 mm/dente. Foi observada uma boa correlação entre o desgaste das ferramentas e as vibrações observadas no processo de fresagem. A monitorização da condição da ferramenta através da
análise da variação das vibrações ao longo do processo também mostrou ser um bom método de averiguar o fim de vida da ferramenta de corte. A ferramenta 591 mostrou o melhor desempenho em geral, enquanto a ferramenta 233 apresentou as piores características na fresagem do aço W 1.2711. O avanço por dente foi a condição de ensaio que mais influenciou o desempenho destas ferramentas no processo de fresagem.
Pre-hardened mould steels are commonly employed given the possibility of using them without the need to apply certain treatments before and after the milling process, since they already have the necessary hardness. However, this high hardness makes the milling process more difficult, generating high levels of tool wear and reduced tool life. The deposition of coatings on the cutting tools is a very common method of combating this adversity, giving the milling a better performance in terms of wear and quality of the machined surface. The correct selection of the cutting parameters is also an important aspect in regards to improving tool life. The objective of this work was to study the performance of carbide cutting tools coated with TiAlN and AlCrN in the milling of W 1.2711 steel. The values of cutting speed, feed per tooth and depth of cut were varied, while the width of cut was kept constant. After every milling test the values for surface roughness, wear and vibration amplitude were obtained. It was concluded that the increase in feed per tooth had a negative influence on the three parameters studied, while the increase in cutting speed showed a negative impact at certain values of feed per tooth and a positive effect at other feed per tooth values. In general, the main wear mechanisms observed were, adhesion wear, with the occurrence of BUE in some of the tests performed, abrasive wear and chipping, primarily in the tests with a high value of feed per tooth. Fractures were also observed in the 233 and 592 tools in the tests with a feed per tooth of 0,1 mm/tooth. A good correlation between the wear on the cutting tools and the vibrations registered in the milling process was also observed. The monitoring of the cutting tool condition by analyzing the vibration signals produced showed to be a good method of determining the end of life of the tool. The 591 cutting tool displayed the best performance, while the 233 tool showed the worst characteristics for milling W 1.2711 steel. Feed per tooth was the cutting parameter that had the highest influence on the performance of the milling process.
Pre-hardened mould steels are commonly employed given the possibility of using them without the need to apply certain treatments before and after the milling process, since they already have the necessary hardness. However, this high hardness makes the milling process more difficult, generating high levels of tool wear and reduced tool life. The deposition of coatings on the cutting tools is a very common method of combating this adversity, giving the milling a better performance in terms of wear and quality of the machined surface. The correct selection of the cutting parameters is also an important aspect in regards to improving tool life. The objective of this work was to study the performance of carbide cutting tools coated with TiAlN and AlCrN in the milling of W 1.2711 steel. The values of cutting speed, feed per tooth and depth of cut were varied, while the width of cut was kept constant. After every milling test the values for surface roughness, wear and vibration amplitude were obtained. It was concluded that the increase in feed per tooth had a negative influence on the three parameters studied, while the increase in cutting speed showed a negative impact at certain values of feed per tooth and a positive effect at other feed per tooth values. In general, the main wear mechanisms observed were, adhesion wear, with the occurrence of BUE in some of the tests performed, abrasive wear and chipping, primarily in the tests with a high value of feed per tooth. Fractures were also observed in the 233 and 592 tools in the tests with a feed per tooth of 0,1 mm/tooth. A good correlation between the wear on the cutting tools and the vibrations registered in the milling process was also observed. The monitoring of the cutting tool condition by analyzing the vibration signals produced showed to be a good method of determining the end of life of the tool. The 591 cutting tool displayed the best performance, while the 233 tool showed the worst characteristics for milling W 1.2711 steel. Feed per tooth was the cutting parameter that had the highest influence on the performance of the milling process.
Description
Keywords
Milling Wear mechanisms W 1 2711 steel PVD coatings Vibrational analysis Machined surface quality Fresagem Mecanismos de desgaste Aço W 1.2711 Revestimentos PVD Análise vibracional Qualidade da superfície maquinada Revestimentos TiAlN e AlCrN