Made available in DSpace on 2014-12-02T11:16:45Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-01-30Bitstream added on 2014-12-02T11:21:42Z : No. of bitstreams: 1 000750012.pdf: 56043843 bytes, checksum: 65a9d8f4fcf1fadbce747e43b1d073c2 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A utilização de fluido de corte geralmente é considerada uma solução para o aumento da produtividade por atuar na redução do desgaste da ferramenta. Contudo, os custos do sistema, manutenção, descarte e os danos à saúde e ao meio ambiente demandam uma evolução tecnológica sustentável. Alguns métodos de refrigeração, como a usinagem criogênica, o uso da mínima quantidade de lubrificante ou mesmo o corte a seco têm sido estudados, mas o desempenho destes métodos é restrito a condições específicas de usinagem. Esta pesquisa trata da concepção, do desenvolvimento e da análise de um método de um método de refrigeração ambientalmente correto, sem prejuízos à saúde, de simples integração em diversos equipamentos, sem alterar a estrutura das ferramentas de corte e tão ou mais eficiente que a aplicação de fluido de corte. Um porta-ferramentas foi adaptado com um canal interno de refrigeração por onde o refrigerante R141-b fluia e evaparava ao remover calor da ferramenta durante o torneamento, sendo em seguida condensado sem liberação para a atmosfera, criando um circuito fechado. Os resultados do método proposto foram comparados à aplicação convencional de fluído de corte e ao corte a seco no torneamento de aço ABNT 1045, utilizando ferramenta de corte de metal duro sem revestimento, bem como no torneamento do aço austenítico de difícil usinabilidade SAE XEV-F, utilizando-se ferramentas revistidas. Os testes mostraram que o novo sistema proporcionou vidas de ferramentas similares ou superiores às obtidas com fluido de corte e superiores ao corte a seco, sugerindo que a redução na temperatura da ferramenta foi capaz de atenuar os mecanismos de desgaste e as alterações na dureza e resistência do metal duro. No torneamento do aço inoxidável o fluído de corte propiciou a refrigeração e lubrificação do processo, superando o método concebido, já que a baixa condutividade térmica e desgaste... / The use of cutting fluid are generally considered a solution for the increase of productivity, reducing the cutting tool wear. However, the costs of the system, maintenance and disposal of the fluid, besides the damage to health and to the environment, make necessary the development of a sustainable technological evolution. Sme alternatives such as cryogenic machinig, the use of minimum quantity of lubrificant or even the dry cutting have been studied, but the performance of these methods is restricted to specific conditions. This work presents the conception, development and analysis of an environmental ly friendly method of cooling without health hazards, with integration, into several equipments, without changing the structure of the cutting tools and equally or even more efficient than the application of cutting fluid. A toolholder was desined with an internal cooling circuit in which cooling fluid R141-b flows and evaporates when removing the heat from the cutting tool, and then condensed, creating a closed circuit without release to the atmosphere. The results of using the proposed system were compared to conventional application of cutting fluid and dry cutting in turning of AISI 1045, using uncoated carbide, cutting tools, as well as in the turning of difficult to cut austenitic steel SAE XEC-F, using coated cutting tools. The tests indicated that the proposed system provided a tool life similar to cutting fluid application, suggesting that the reduction in temperature of the cutting tool was able to attenuate the wear mechanisms and the changes in hardness and toughness of the comented carbide. During the turning of stainless steel, the cutting fluid led to cooling and lubrification, exceeding the conceived method, since the low thermal conductivity and high abrasion are common when machining this material

Orientador: Luiz Eduardo de Angelo Sanchez / Banca: Vicente Luiz Scalon / Banca: Renato Goulart Jasinevicius / Resumo: A utilização de fluido de corte geralmente é considerada uma solução para o aumento da produtividade por atuar na redução do desgaste da ferramenta. Contudo, os custos do sistema, manutenção, descarte e os danos à saúde e ao meio ambiente demandam uma evolução tecnológica sustentável. Alguns métodos de refrigeração, como a usinagem criogênica, o uso da mínima quantidade de lubrificante ou mesmo o corte a seco têm sido estudados, mas o desempenho destes métodos é restrito a condições específicas de usinagem. Esta pesquisa trata da concepção, do desenvolvimento e da análise de um método de um método de refrigeração ambientalmente correto, sem prejuízos à saúde, de simples integração em diversos equipamentos, sem alterar a estrutura das ferramentas de corte e tão ou mais eficiente que a aplicação de fluido de corte. Um porta-ferramentas foi adaptado com um canal interno de refrigeração por onde o refrigerante R141-b fluia e evaparava ao remover calor da ferramenta durante o torneamento, sendo em seguida condensado sem liberação para a atmosfera, criando um circuito fechado. Os resultados do método proposto foram comparados à aplicação convencional de fluído de corte e ao corte a seco no torneamento de aço ABNT 1045, utilizando ferramenta de corte de metal duro sem revestimento, bem como no torneamento do aço austenítico de difícil usinabilidade SAE XEV-F, utilizando-se ferramentas revistidas. Os testes mostraram que o novo sistema proporcionou vidas de ferramentas similares ou superiores às obtidas com fluido de corte e superiores ao corte a seco, sugerindo que a redução na temperatura da ferramenta foi capaz de atenuar os mecanismos de desgaste e as alterações na dureza e resistência do metal duro. No torneamento do aço inoxidável o fluído de corte propiciou a refrigeração e lubrificação do processo, superando o método concebido, já que a baixa condutividade térmica e desgaste... / Abstract: The use of cutting fluid are generally considered a solution for the increase of productivity, reducing the cutting tool wear. However, the costs of the system, maintenance and disposal of the fluid, besides the damage to health and to the environment, make necessary the development of a sustainable technological evolution. Sme alternatives such as cryogenic machinig, the use of minimum quantity of lubrificant or even the dry cutting have been studied, but the performance of these methods is restricted to specific conditions. This work presents the conception, development and analysis of an environmental ly friendly method of cooling without health hazards, with integration, into several equipments, without changing the structure of the cutting tools and equally or even more efficient than the application of cutting fluid. A toolholder was desined with an internal cooling circuit in which cooling fluid R141-b flows and evaporates when removing the heat from the cutting tool, and then condensed, creating a closed circuit without release to the atmosphere. The results of using the proposed system were compared to conventional application of cutting fluid and dry cutting in turning of AISI 1045, using uncoated carbide, cutting tools, as well as in the turning of difficult to cut austenitic steel SAE XEC-F, using coated cutting tools. The tests indicated that the proposed system provided a tool life similar to cutting fluid application, suggesting that the reduction in temperature of the cutting tool was able to attenuate the wear mechanisms and the changes in hardness and toughness of the comented carbide. During the turning of stainless steel, the cutting fluid led to cooling and lubrification, exceeding the conceived method, since the low thermal conductivity and high abrasion are common when machining this material / Mestre

The lubricants that are applied during metal cutting acts on the interface between the tool and the nascent surfaces generated by the cutting process. Dispersions of oil in water made using suitable emulsifier(s) are used as metal cutting lubricants. The efficiency of the emulsion in rendering a low friction layer on the freshly cut surface will depend on the composition of the emulsion and on the speed, load and temperature characteristics in the tribological system. A unique tribometer which can perform friction testing on freshly cut surfaces has been designed and built for the experimental investigation. In this experimental facility experiments are conducted by performing cutting operation inside a pool of the lubricant and friction force is measured in-situ. Experiments at different loads and speeds were performed. The surfaces were subsequently subjected to spectroscopic analysis using X-ray Photoelectron spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR). Lubricity of the base oils on nascent and preformed (oxidized) surfaces are compared by performing friction tests on surfaces which are cut and friction tested without exposing them to the environment, and on surfaces which were cut and exposed to the environment. While the freshly cut surfaces were seen to be sensitive to the structure of the base oil, the oxidized surfaces did not differentiate between the oil structures. Amongst the three base oils tested, aromatic oil was found to exhibit the least friction. This is attributed to tendency of the aromatic chains to react with the surface and form a film, due to the formation of radical anion-metal cation complexes. Results from spectroscopic investigations are presented to substantiate these arguments. The thesis then explores the differences in the tribological behavior promoted by an emulsion between, when it acts on a cut surface and is slid just once, and when it acts on a cut surface slid repeatedly. Due to repeated sliding, friction was found to decrease with sliding time (distance), and the transition from a freshly formed surface to a repeatedly slid one was found to follow a smooth transition. The improvement in lubricity is attributed to the formation of carboxylate type structures (C=O) which get generated due to the tribological action under repeated sliding conditions in the presence of water. Under repeated sliding conditions, the friction as a function of emulsifier concentration is found to exhibit a minimum at a value which is much below the critical micellar concentration of the emulsifier (CMC). However, the variation under continuous cutting followed a different pattern, with the friction undergoing a sharp decrease close to the CMC. The effect of speed on the tribological performance was investigated and friction was found to increase dramatically beyond a critical speed which is marked as the onset of starvation. The characteristic time required for a film to develop on a newly created surface, together with the contact pressure conditions dictated by the load and speed dictates starvation. The films formed at speeds corresponding to starvation conditions was found to have a significantly different chemical structure from that corresponding to a speed less than the starvation speed.. The effect of temperature was found to affect the lubricity adversely. At elevated temperature, the nature of the film was found to change to that to starved condition, even at a speed which does not register starvation when operating at a lower temperature. The effect of solubility of the emulsifier on the friction characteristics were explored by using emulsifiers of varying hydrophilic-lypophilic values (HLB). Lower HLB emulsifiers were found to exhibit lesser friction, than those corresponding to high HLB value. The variation in lubricity is examined in the light of the morphology of the micellar structures which evolve using these emulsifiers. The main conclusions of the thesis are: 1 Evaluation of lubricity of metal cutting fluids warrants a testing strategy which tests their lubricity on freshly cut surfaces. 2 The formation of carboxylate structures aids lubricity while using an emulsion; emulsions which can result in the formation of such structures exhibit better lubricity under cutting conditions. 3 Tribofilms which show characteristic peaks related to chemisorbed oxygen is found to exhibit good lubricity under the test conditions. 4 Emulsifiers which form lamellar micellar structures which aid easy shear give better lubricity in cutting than those which yield spherical micelles.