Large improvements in cutting tool design and technology, including the application of advanced surface engineering treatments on the cemented carbide insert, have been achieved in the last decades to enhance tool performance. However, the problem of improving the tool body material is not adequately studied. Fatigue is the most common failure mechanism in cutting tool bodies. Rotating tools, tool going in and out of cutting engagement, impose dynamic stresses and require adequate fatigue strength of the tool. Working temperatures of milling cutter bodies in the insert pocket can reach up to 600°C depending on the cutting conditions and material of the workpiece. As a result, steel for this application shall have good hot properties such as high temper resistance and high hot hardness values to avoid plastic deformation in the insert pocket of the cutting tool. Machinability of the steel is also essential, as machining of steel represents a large fraction of the production cost of a milling cutter. This thesis focus on the improvement of the cutting tool performance by the use of steel grades for tool bodies with optimized combination of fatigue strength, machinability and properties at elevated temperatures. The first step was to indentify the certain limit of the sulphur addition for improved machinability which is allowable without reducing the fatigue strength of the milling cutter body below an acceptable level. The combined effect of inclusions, surface condition and geometrical stress concentrator on the fatigue life of the tool steel in smooth specimens and in tool components were studied in bending fatigue. As the fatigue performance of the tools to a large extent depends on the stress relaxation resistance at elevated temperature use, the second step in this research was to investigate the stress relaxation of the commonly used milling cutter body materials and a newly steel developed within the project. Compressive residual stresses were induced by shot peening and their response to mechanical and thermal loading as well as the material substructures and their dislocation characteristics were studied using X-ray diffraction. Softening resistance of two hot work tool steels and a newly developed steel was investigated during high temperature hold times and isothermal fatigue and discussed of with respect to their microstructure. Carbide morphology and precipitation as well as dislocation structure were determined using transmission electron microscopy and X-ray line broadening analysis.

<p>Automobile and aero industries have an increasing interestin materials with improved mechanical properties. However, manyof these new materials are classified as difficult-to-cut withconventional tools. It is obvious that tools, cutting processesand cutting models has to be devel-oped parallel to materialsscience. In this thesis rotary cutting tools are tested as analternative toexpensive diamond or cubic bore nitridetools.</p><p>Metal matrix composites mostly consist of a light metalalloy (such as aluminium or titanium) reinforced with hard andabrasive ceramic parti-cles or fibres. On machining, thereinforcement results in a high rate of tool wear. This is themain problem for the machining of MMCs. Many factors affect thelife length of a tool, i.e. matrix alloy, type, size andfraction of the reinforcement, heat treatment, cuttingconditions and tool properties.</p><p>In tests, the Al-SiC MMC formed a deformation layer duringmilling, probably affected by lack of cooling. The dominatingfactor for tool life was the cutting speed. Water jet or CO2cooling of turning did not provide dramatic increase in toollife. With PCD, cutting speeds up to 2000 m/min were usedwithout machining problems and BUE formation. Tool flank wearwas abrasive and crater wear created an "orange-peel type" wearsurface. PCD inserts did not show the typical increase in flankwear rate at the end of its lifetime.</p><p>The use of self-propelled rotary tools seems to be apromising way to increase tool life. No BUE was formed on therotary tool at high cutting data. The measurements indicatethat the rotary tool creates twice as good surface as PCDtools. The longest tool life was gained with an inclinationangle of 10 degrees. Tool costs per component will beapproximately the same, but rotary cutting tool allows higherfeeds and therefore a higher production rate and thus a lowerproduction cost.</p><p>The rotary cutting operation might have a potential toincrease productiv-ity in bar peeling. The lack of BUE withrotary cutting gives hope on higher tool life. The test resultsshow that tool wear was 27% lower with rotary cutting tools.Increase of cutting speed from 22 to 44 m/min did not affectcutting forces. This indicates that the cutting speed canincrease without significant change in tool wear rate.</p><p>Issues related to rotary cutting like cutting models,cutting processes, standards, tools and models have beendiscussed. A tool wear model with kinetic energy has beendiscussed.</p><p><b>KEYWORDS:</b>Difficult-to-Cut material, Metal MatrixComposite (MMC), Machining, Machinability, Rotary Cutting Tool,Acoustic Emission</p>

This study includes examination of the machinability characteristics of two medium carbon steel types (SAE 1040 and SAE 1050) as a result of spherodizing treatment. Both steel types were handled into four categories according to their spherodizing treatment parameters (temperature and time). Microstructural investigation, hardness and ultrasonic sound velocity measurement (with both longitudinal and transverse waves) of these steels were performed, and effect of applied heat treatments on microstructure, hardness and ultrasonic sound velocity was investigated. Pulse-echo method has been used for ultrasonic sound velocity measurements, and measurements were performed with 5 and 10 MHz longitudinal and 5 MHz transverse wave probes. Tool life criterion was used for determining the machinability characteristics of the steels. For this purpose, flank wear land measurements were performed on the cutting tools. Results have showed that, by appliying heat treatment it is possible to change the microstructure, hardness, ultrasonic sound velocity and machinability characteristics of a steel.

Mica based glass - ceramics have been produced by subjecting the glasses in the SiO2 , Al2O3 , CaO , MgO, K2O , and F system to a controlled heat treatment called crystallization. TiO2 was added into the batch in the amount of 1 wt% of the glass as nucleating agent. B2O3 additions in the amounts of 1, 2, 4 and 8 wt% of the glass have been made in the batch to see and evaluate the effects of B2O3 additions on the texture of the mica glass ceramics. Crystallization was accomplished in two steps, nucleation and crystal growth. Nucleation temperature was 650 &amp / #61616 / C. Crystal growth temperatures were 850 and 1000 &amp / #61616 / C. The time for holding the specimens at the temperatures was 8 hours. The X-Ray diffraction analysis revealed that resultant glass ceramics possessed not only synthetic fluormica crystals called phlogopite which provide machinability, but also wollastonite crystals which provide biocompatibility. The scanning electron microscopy examinations have indicated that the amount and distribution of the crystalline phases varied as a function of B2O3 content and heat treatment schedule applied.

The manufacturing sector is one of the most rapidly growing sectors in the industrialized world today. Manufacturing industry is concerned with being more competitive and profitable. Profit margins are directly related to the productivity of the company, and productivity improvements can be achieved by making manufacturing processes more efficient and sustainable. Knowledge of cutting conditions and their impact on machined surface and tool life enable productivity improvement.  These days the main emphasis is not only to increase productivity, but also to make processes cleaner and more environmental friendly.  This research aims to study machinability of difficult to cut, titanium alloys, in close reference to the application of different cooling/ lubrication strategies and their environmental impact. Total energy consumed (kWh) and carbon dioxide (CO2) emissions produced in machining are common environmental indicators. In this research project environmental implications of the cutting process were calculated in terms of carbon dioxide (CO2) emissions and energy consumption analysis. The experimental work consisted of controlled machining tests with cutting force, surface roughness, power, and flank wear measurements under dry, mist, combination of vegetable oil mist and cooled air (MQL+CA) and flood cutting environments. The current study provides better understanding of the cutting performance of TiAlN coated and uncoated carbide tools. The study also investigated tool failure modes, tool wear mechanisms, surface roughness and energy consumption to improve machinability of Titanium alloys.  The study revealed the promising behaviour of minimum quantity lubrication (MQL) under specific ranges of cutting speed for both coated and uncoated tools.  Variation in the cutting force showed close link with built up edge (BUE) formation. MQL based systems have huge potential to improve machinability of Titanium alloys and should be investigated further. / <p>QC 20140407</p>

Made available in DSpace on 2014-06-11T19:28:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-01-31Bitstream added on 2014-06-13T20:58:34Z : No. of bitstreams: 1 pimentel_mf_me_guara.pdf: 1070534 bytes, checksum: 041ac691a65005dd8019ca974206734b (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Nos componentes mecânicos em aço, a operação de usinagem pode representar mais de 50% do custo de produção. Por isso, tem-se procurado, com o desenvolvimento tecnológico, obter materiais que respondam adequadamente à solicitação de boa usinabilidade. No caso dos aços para construção mecânica, dentre os fatores que influenciam a usinabilidade, tem-se como principal fator a microestrutura do material, que por sua vez é definida pela composição química, tratamento térmico e o tipo, forma e distribuição das inclusões. No presente trabalho, o principal objetivo é avaliar a influência da composição química e da microestrutura, basicamente o tipo, a morfologia e a distribuição das inclusões, na usinabilidade do aço de corte fácil baixo-carbono com adição de chumbo. Para caracterização do material, foram realizadas análises químicas e executaram-se ensaios metalográficos. As análises químicas foram realizadas em amostras retiradas do lingotamento e em amostras retiradas do material laminado. Os ensaios metalográficos foram realizados para avaliar os principais tipos de microconstituintes e de inclusões presentes no aço estudado, por meio de microscopia óptica e eletrônica de varredura. Nos ensaios de usinabilidade, foi utilizada ferramente de corte de metal duro, sendo a usinabilidade avaliada pelo desgaste de flanco da ferramenta. Os resultados mostram que a maior usinabilidade foi obtida nas regiões dos corpos de prova com os maiores teores de carbono, enxofre e chumbo. Nestas regiões, também se verificou a maior quantidade de inclusões de sulfeto de manganês globulares e homogeneamente e distribuídas. / For mechanical steel components, the machinability could represent more than 50% of the production cost. Consequently, it's very important to develop steels with good performance in this kind of process. Microstructure is the main point, when it is analyzed all the factors that affect machinability. The microstructure can be defined by composition, heat treatment and inclusions type, shape and distribution. The present report has the target of evaluate how the chemical composition and microstructure influence the machinability of the leaded resulfurized low-carbon steel (leaded free-cutting steel). The material evaluation was based on chemical analysis and metallography of ladle and rolled samples. Metallography was used to iedentify the steel constituents and evaluate inclusions (type, shape and distribution). In machinability tests, the machinability was evaluated by flank wear of cutting tool. The results indicated that the machinability was easier in the test specimen regions with high contents of carbon, sulfur and lead. In these regions, it was verified high amount of globular manganese sulfide inclusions with homogeneous distribution.

Orientador: Marcelo dos Santos Pereira / Banca: Humberto Lopes Rodrigues / Banca: César Alves da Silva Leandro / Resumo: Nos componentes mecânicos em aço, a operação de usinagem pode representar mais de 50% do custo de produção. Por isso, tem-se procurado, com o desenvolvimento tecnológico, obter materiais que respondam adequadamente à solicitação de boa usinabilidade. No caso dos aços para construção mecânica, dentre os fatores que influenciam a usinabilidade, tem-se como principal fator a microestrutura do material, que por sua vez é definida pela composição química, tratamento térmico e o tipo, forma e distribuição das inclusões. No presente trabalho, o principal objetivo é avaliar a influência da composição química e da microestrutura, basicamente o tipo, a morfologia e a distribuição das inclusões, na usinabilidade do aço de corte fácil baixo-carbono com adição de chumbo. Para caracterização do material, foram realizadas análises químicas e executaram-se ensaios metalográficos. As análises químicas foram realizadas em amostras retiradas do lingotamento e em amostras retiradas do material laminado. Os ensaios metalográficos foram realizados para avaliar os principais tipos de microconstituintes e de inclusões presentes no aço estudado, por meio de microscopia óptica e eletrônica de varredura. Nos ensaios de usinabilidade, foi utilizada ferramente de corte de metal duro, sendo a usinabilidade avaliada pelo desgaste de flanco da ferramenta. Os resultados mostram que a maior usinabilidade foi obtida nas regiões dos corpos de prova com os maiores teores de carbono, enxofre e chumbo. Nestas regiões, também se verificou a maior quantidade de inclusões de sulfeto de manganês globulares e homogeneamente e distribuídas. / Abstract: For mechanical steel components, the machinability could represent more than 50% of the production cost. Consequently, it's very important to develop steels with good performance in this kind of process. Microstructure is the main point, when it is analyzed all the factors that affect machinability. The microstructure can be defined by composition, heat treatment and inclusions type, shape and distribution. The present report has the target of evaluate how the chemical composition and microstructure influence the machinability of the leaded resulfurized low-carbon steel (leaded free-cutting steel). The material evaluation was based on chemical analysis and metallography of ladle and rolled samples. Metallography was used to iedentify the steel constituents and evaluate inclusions (type, shape and distribution). In machinability tests, the machinability was evaluated by flank wear of cutting tool. The results indicated that the machinability was easier in the test specimen regions with high contents of carbon, sulfur and lead. In these regions, it was verified high amount of globular manganese sulfide inclusions with homogeneous distribution. / Mestre

Orientador: Eduardo Carlos Bianchi / Coorientador: Anselmo Eduardo Diniz / Banca: Amauri Hassui / Banca: Nilson Cristino da Cruz / Resumo: O uso do fluído de corte é imprescindível para processos de usinagem em que há elevada geração de calor, principalmente no processo de retificação. A utilização de fluido de corte, no entanto, causa uma série de complicações, especialmente nos aspectos ambientais, econômicos e com relação à saúde dos operadores de máquinas. Assim, intensificaram-se estudos para novos métodos de aplicação e otimização do fluido de corte visando a sua redução, bem como os problemas ocasionados por esse. Sobre essa tendência, este trabalho analisa o comportamento de um método recente, até então aplicado somente em processos de usinagem com ferramenta de geometria definida, que consiste na adição de água no método da mínima quantidade de lubrificante (MQL). Foram avaliados três tipos de proporção na mistura óleo-ar e água (1:1, 1:3 e 1:5 parte de óleo de água). Para uma melhor avaliação desse método, os resultados obtidos foram comparados com outros dois métodos de lubri-refrigeração, a lubri-refrigeração convencional (fluído em abundância) e o MQL tradicional (óleo-ar). Os métodos de lubri-refrigeração foram avaliados com base nos resultados das variáveis de saída: rugosidade, circularidade, desgaste diametral do rebolo, tensão residual e microdureza. Os resultados obtidos para o método MQL com adição de água consuzem a melhorias significativas com relação ao método da MQL tradicional e estes resultados são bem próximos aos obtidos com a lubri-refrigeração convencional, para os resultados de rugosidade, circularidade e desgaste diametral do rebolo, além da isenção de danos térmicos às peças / Abstract: The use of cutting fluid is essential for the grinding process where there is high temperature, as in the grinding process. The use of cutting fluid, however causes a series of complication, especially in the environmental and economical aspects and in relation to the health of the machine operators. Therefore, there were more studies to develop new methods of application and optimization of fluid, aiming at the reduction, as well as the problems caused by the fluids. Regarding this trend, this paper has as an objective the analyzes of the behavior of a recent method, applied only to the grinding process with tools with defined geometry, it consists of the addition of water in the minimum quantity of lubrication method (MQL). This paper has analyzed three types of proportion in the mixture oil-air and water (1:1; 1:3 and 1:5). For a better assessment of this method, the obtained results were compared to other two lubri-cooling methods, the conventional method (fluid in abundance) and the traditional MQL (oil-air). The methods of the lubri-cooling studied were analyzed through the output of the variables of the grinding process: roughness, roundness, wear of the grinding wheel (relation G) and microhardness. The obtained results show that the minimum quantity of lubrification (MQL) with addition of water have a significant improvement in relation to the conventional method and these resuls are close to the obtained results with the conventional lubri-cooling (in abundance), for the results of roughness, roundness and wear of the grinding wheel, as well as examption of the thermal damage of pieces / Mestre

Made available in DSpace on 2015-12-10T14:22:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-12-19. Added 1 bitstream(s) on 2015-12-10T14:28:37Z : No. of bitstreams: 1 000852150_20160202.pdf: 256387 bytes, checksum: 4ef7991da4305b2ad879e52788744b73 (MD5) Bitstreams deleted on 2016-02-03T15:35:15Z: 000852150_20160202.pdf,. Added 1 bitstream(s) on 2016-02-03T15:35:55Z : No. of bitstreams: 1 000852150.pdf: 4573029 bytes, checksum: fb27ef52f4bb823b5d6820bb368b0d9d (MD5) / A utilização de ensaios de avaliação da usinabilidade dos materiais pode ser um fator determinante na viabilidade de processos de fabricação, contribuindo no planejamento dos custos, prazos e na busca pela qualidade do produto através de desenvolvimentos de estratégias e tecnologias de usinagem. Quando o produto usinado é um cilindro, que faz o papel de ferramenta no processo de laminação, a necessidade de tal desenvolvimento fica clara quando se analisa os requisitos para alta performance de cilindros de laminação e se identifica que eles são os mesmos requisitos para alta performance de insertos de usinagem: resistência ao desgaste, tenacidade e dureza. Assim esse trabalho propõe um ensaio de usinabilidade em laboratório para a avaliação de dois materiais de cilindros de laminação: o ferro fundido indefinido e o ferro fundido indefinido microligado. O ensaio foi executado através do fresamento com três arestas de metal duro em um centro de usinagem e a análise de usinabilidade foi feita pelo critério de fim de vida da ferramenta de usinagem. Foi constatado que a adição de elementos de liga na composição química dos cilindros influenciou diretamente na usinabilidade do ferro fundido indefinido microligado, pois a fração volumétrica de carbonetos VC aumentou em quase três vezes nesse material resultando em um desgaste abrasivo nas arestas das ferramentas de corte / The use of tests to evaluate the machinability of the material may be a determining factor in the viability of manufacturing processes, and contribute to planning the cost, time and in the search for the quality of the product through development of strategies and machining technologies. When the machined product is rolling mill roll, who played as a tool in the milling process the need for such development becomes clear when is examined the requirements for high performance rolling mill roll and identifies that they are the same requirements for high performance machining tools: wear resistance, toughness and hardness. So, this work proposes a machinability test in laboratory seeking the evaluation of two materials for rolling mill rolls: an indefinite chilled double poured cast iron and a microalloyed indefinite chilled double poured cast iron. The test was performed by milling with three edges of carbide on a machining center and the machinability analysis of this work was done by the criterion of end of life of the machining tool. The work found that the addition of alloying elements on the chemical composition of the rolling mill rolls directly influenced the machinability of microalloyed indefinite chilled double poured cast iron, because the volume fraction of carbides VC increased by almost three times in this material resulting in an abrasive wear on the edges of cutting tools

Orientador: Alessandro Roger Rodrigues / Banca: Hidekasu Matsumoto / Banca: Otávio Villar da Silva Neto / Resumo: Este trabalho apresenta um estudo sobre a influência das condições de fresamento na formação de cavaco, microestrutura, dureza e rugosidade da peça. Foi ensaiado um aço baixo carbono 0,15%C com dois tamanhos de grão distintos. Para ambos os materiais da peça, empregou-se 8 condições de usinagem variando a velocidade de corte, o avanço da ferramenta e a profundidade de usinagem visando à aplicação da Análise de Variância (ANOVA), dando-se destaque à usinagem considerada como alta velocidade de corte e convencional. Os ensaios de fresamento de topo concordante a seco foram conduzidos em um centro de usinagem CNC de 11 kW de potência e rotação do eixo-árvore de 7.500 rpm. Utilizou-se ferramenta de diâmetro 25 mm com dois insertos de metal duro revestidos com Al2O3. Os resultados apontam para uma influência dos parâmetros de corte sobre todas as variáveis de resposta, exceto a macrodureza. Velocidades de corte e profundidades de usinagem maiores causaram deformação da microestrutura do material "como recebido" próxima à superfície fresada. Os mesmos parâmetros governaram o aumento da microdureza superficial e da profundidade da camada endurecida. O material com grãos ultrafinos não apresentou deformação da microestrutura próxima à superfície fresada nem aumento de microdureza superficial. A velocidade de corte influiu apenas na profundidade da camada endurecida. A rugosidade foi inversa e diretamente influenciada pela velocidade de corte e avanço da ferramenta, respectivamente, sendo dependente também do tamanho de grão do material da peça. Os mesmos parâmetros de corte influíram de forma significativa no ângulo de deformação da microestrutura dos cavacos, cuja classificação foi dependente do material e das condições de usinagem. / Abstract: This work deals with the influence of milling conditions on chip formation, microstructure, hardness and roughness of workpiece. A 0.15%C low carbon steel with two different grain sizes was milled. For both workpiece materials eight milling conditions were employed where cutting speed, tool feed and depth of cut varied and combined aiming at Analysis of Variance application. The machining conditions considered as High-Speed Cutting (HSC) and Conventional were focused. The milling tests considering down-milling and dry conditions were carried out in a CNC machining center with 11 kW power and 7,500 rpm spindle rotation. A 25 mm diameter endmill with two inserts coated of Al2O3 was used. The results indicated the cutting parameters influenced on all output variables except the macrohardness. Greater cutting speed and depth of cut caused deformation of workpiece microstructure with 10.8 um grain size near milled surface. The same parameters governed the increase of surface microhardness and hardened layer depth. Refined grain material did neither present deformation of microstructure near milled surface nor increase of microhardness. The cutting speed influenced only on depth of hardened layer. Roughness was inverse and directly influenced by cutting speed and tool feed, respectively, and dependent on grain size of workpiece material. These parameters also influenced on deformation angle of chip microstructure which were classified as continuous for 10.8 um grain size and segmented for the ultrafine grain, in this case just for some milling conditions. / Mestre