Grey cast iron (GCI) is the most common material used in diesel engineCompact graphite iron is a material with intermediary properties between grey cast iron (GCI) and ductile cast iron (Sahm et al., 2002). Like in the GCI, the graphite particles in the CGI are flat, long, randomly oriented and interconnected. In the ductile iron they are in form of nodules (Warrick et al., 1999). However, as it can be seen in Fig. 1(b), the "worms" (as the graphite particles in the CGI are called) have something in common with the nodules of the ductile iron ( Fig. 1(a)), since both are much smaller than the graphite lamellas of the GCI (Fig. 1(c)). On the other hand, the morphology of CGI graphites is compact and with rounded tips, what makes the nucleation and growth of cracks more difficult than in the GCI. The sharp and lamellar graphites of the GCI with smooth surfaces (Fig. 1(c)) make this material more fragile than the other two (Löhe, 2005).The CGI alloys have good properties of mechanical strength, ductility, toughness, thermal shocks, damping and heat conductivity (Mocellin et al., 2004). These properties are better for the CGI part functioning, but make its machinability worse than the machinability of GCI.Compared with GCI, the CGI presents some advantages like reduction of the wall thickness of the parts for a same load, reduction of the safety factor due to a smaller variation of the cast properties, reduction of the fragile fractures during manufacturing, assembly and service due to its higher ductility and strength (Dawson, 1999).Compared with ductile cast iron, it can be said that with CGI it is easier to produce complex cast parts and the residual stresses are smaller due to the higher heat conductivity (what also helps to increase cutting tool life). Moreover, it presents smaller Young modulus and better machinability (Guesser, 2004). Milling of CGI engine blocksBesides the worm graphite particles, a certain percentage of spheroidal graphite nodules is also present in the CGI. As the nodularity increases, the material strenght also increases making the forces needed to cut the material higher. Moreover, with the nodularity growth, the heat conductivity decreases, decreasing machinabilty even more (Dawson, 2002).A factor that makes the engine blocks even more difficult to be machined is the great number of interruptions on the surface. Special care has to be taken in the mill cutter choice, because very positive tools reduce cutting force, but may generate tool life relatively lower when compared to the cutters with negative geometry, due to their small impact resistance.As the tool wears, workpiece surface roughness and flatness error increase. Besides tool wear, other important factors to obtain J. of the Braz. Soc. of Mech. Sci. & Eng.

GABALDO, Sander, A contribution to the improvement of the milling process machining compacted graphite iron -CGI, Campinas,: Mechanical Engineering Faculty, State University of Campinas, 2009. 136 p. Thesis (MSc).Since the beginning of this century, researches about the development of diesel engines have been intensified, aiming to increase its energy efficiency and to reduce the levels of emission of pollutants. One the way to increase this efficiency is to increase the peaks of pressure of fuel explosion in the combustion chamber. The grey casting iron material is the most common material used for the manufacturing of diesel engine blocks. However, to increase the pressures in the combustion chamber when this kind of alloy is used, it is necessary to increase the wall thickness of the blocks, what raises its weight and consequently, does not fulfill with the specified requirements. Thus, the compacted graphite iron (CGI) appears as an alternative material for such application. It has characteristics of heat conductivity and damping similar to the casting iron, however, with superior mechanical properties making possible the manufacturing of small and consequently, light engines and also with better performance, without considering the reduction of the environmental pollution for gases and noises. However the use of the CGI presents as disadvantage its worse machining when compared with the grey casting iron, stimulating research and development of machining techniques and, development of the cutting materials, where this thesis is inserted. The objective of this thesis is to analyze the influence of the micro geometries of the cutting edge (tested positive and flat geometry), cutting material (tested hard material, ceramic Si 3 N 4 with or without coating) and cutting speed in the finishing operation of the fire face of the engine made of CGI. As output variables we used tool life, cutting power and surface roughness of the workpiece. Among the main result we could say that the most negative tool presented the longest tool life and carbide material is better than ceramic (with or without coating) in terms of tool life in the milling of this kind of workpiece.x

A indústria metal mecânica em geral vêm testemunhando uma maior procura por materiais metálicos para fabricação de componentes críticos, tais como peças da indústria de extração de gás e petróleo para utilização de componentes em alto mar, palhetas de turbinas à vapor, tanques para produtos químicos, estruturas para construção civil, entre outras, fabricados em aços inoxidáveis, aços inoxidáveis duplex, ligas à base de titânio e à base de níquel, principalmente devido à relação resistência mecânica e peso, e à alta capacidade de manter propriedades mecânicas em temperaturas elevadas e em ambientes corrosivos. Variações e combinações de vários elementos de liga como o cromo, níquel, molibdênio, proporcionam uma excelente resistência à corrosão, uma alta taxa de encruamento e baixa condutividade térmica. Assim, gerou-se a necessidade da evolução dos processos de usinagem visto que a dificuldade da remoção de cavaco nestas ligas em função da baixa usinabilidade afeta diretamente os custos de produção destes componentes tornando-os extremamente caros e muitas vezes inviáveis. O objetivo deste trabalho é contribuir para o estudo de técnicas de usinagem na operação de torneamento longitudinal em acabamento da liga duplex SAF2205 (UNS S31803) com a utilização de fluido de corte tipo aquoso (emulsão) e fluido tipo gasoso (dióxido de carbono, CO2). Para cada tipo de fluido de corte, foram testados dois canais de direcionamento do fluido de corte para a região da interface cavaco-ferramenta e ferramentapeça com o objetivo de buscar o melhor desempenho da ferramenta de corte de metal duro.Como limitador do teste, por tratar-se de uma operação de acabamento, quando a rugosidade média (Ra) atingi 1,60 µm o teste era finalizado. A vida útil em minutos, taxa de remoção de cavaco, acabamento superficial, potência de corte e temperatura da peça-cavacoferramenta, e formação dos cavacos foram monitorados e analisados a fim de encontrar as melhores práticas e possibilidades para a operação de usinagem acabamento. Os melhores resultados foram obtidos na usinagem com CO2 e direcionamento do fluido na superfície de folga e ferramenta. Diferentes mecanismos de desgastes foram observados quando na usinagem por emulsão e CO2.