The aim of this work consisted of evaluate the influence of heat treatment on sintered valve seat inserts (VSI) obtained with the AISI M2 high-speed steel powder. The AISI M2 high-speed steel powder was mixed with iron powder and additives such as manganese sulphide, zinc stearate, graphite and carbides. The heat treatment of the VSI consisted of air quenching followed by double tempering it in seven different equidistant temperatures, from 100 °C until 700 °C. The mechanical property was measured regarding the VSI apparent hardness. The results indicated that the VSI obtained with the AISI M2 high-speed steel powders mixtures showed the best results regarding its apparent hardness after air quenching and double tempering it at 600 °C.Keywords: powder metallurgy, air quenching, valve seat insert, AISI M2 high-speed steel.
ResumoO objetivo deste trabalho consistiu em avaliar a influência do tratamento térmico em insertos de assentos de válvulas (do inglês valve seat insert, VSI) obtido com o pó de aço rápido AISI M2. O pó de aço rápido AISI M2 foi misturado com pó de ferro e aditivos como o sulfeto de manganês, estearato de zinco, grafite e carbetos. O tratamento térmico dos VSI consistiu em temperá-los ao ar e duplamente revení-los em sete temperaturas equidistantes diferentes, de 100 °C a 700 °C. A propriedade mecânica foi medida em relação à dureza aparente dos VSI. Os resultados indicaram que o VSI obtido com a mistura de pós do aço rápido AISI M2 obtiveram os melhores resultados em relação à sua dureza aparente depois de temperados ao ar e duplamente revenidos a 600 °C.Palavras-chave: metalurgia do pó, têmpera ao ar, inserto de assento de válvula, aço rápido AISI M2.
Many engineering specifications, manufacturing procedures, inspection and quality controls require the evaluation of the residual stress of critical parts of components. The finite elements analysis (FEA) provides a simulational advantage and it is very helpfully in projects aiming manufacturing improvements, thus reducing costs in terms of time and money. This study had as proposal to improve the database of the analysis systems using FEA extending the knowledge of the residual stresses phenomena in wheels using extensometers. To this work were use strain gage to acquire and make available this information available. The residual stress values obtained from the experimental tests by drilling method with rosette type strain gages. The region to test is a critical region (the spokes), showed on FEA simulations. The relevance of the present study and research on residual stresses meets the required effort towards the safety improvements in car's wheel industry.
Many engineering specifications, manufacturing procedures, inspection and quality controls have begun to require that the residual stress analysis of a particular component is evaluated. This is becoming as common place as the demands on the mechanical properties. In the country there are few research laboratories qualified to perform these tests and also found a disturbing lack of skilled labor. The relevance of the study and research on residual stresses, stresses the development of science, technology and innovation in manufacturing components for the industry. New tools and instrumentation for the investigation of microstructure of materials available in research laboratories both in governmental institutions such as private facilities in need of qualified researchers which is associated with the training of specialists dedicated to measurements of residual stresses, the development of experimental procedures and sample preparation techniques involving gages. The residual stress in metal and alloy components arises as a result of manufacturing processes (casting, heat treatment, machining and mechanical forming) by which to obtain the structural form of the desired component. Study the formation and arrangement of residual stress fields may allow, among other gains, the development of mathematical modeling simulations more refined. Thus it can be inferred, in more detail the behavior of these components by adding gains in resilience to fatigue, survival, security and operational cost reduction of equipment and machinery. The use of strain gage in the investigation of residual stresses in automotive wheels contribute to the formation of a larger database that will allow for FEM simulation software, with a better index of mathematical modeling with respect to the real physical component. vii LISTA DE SIGLAS a; aₒ , ac Comprimentos da amostra b Dimensão da amostra B Espessura da amostra C Constante de material D Dimensão do círculo preenchendo um defeito e Flexibilidade ep ; eq Deformações principais h Altura hp Zona plástica K Constante de barreiras microestruturais k' Parâmetro determinado por elementos finitos K Fator de intensidade de tensão K Constante do material Kres Fator de intensidade de tensão no campo de tensões residuais Ko Limiar do fator de intensidade de tensão Kg Constante de material K Fator de concentração de deformação inelástica L Comprimento da trinca
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