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The so-called Modified Martempering discussed in this work differs from the standard martempering by that the temperature of the quenching bath is below the Ms point. In spite of the fact the lower temperature increases the severity of quenching, this also usually avoids the bainite formation, and by this reason, it is possible to make a fair comparison between different processes, which result in different microstructures. The present study shows the results in terms of mechanical properties, impact resistance in special of a cold work tool steel class, after being heat treated by the isothermal modified martempering process, as well as a comparison with the conventional quenching and tempering process and the austempering as well.

Metal in general presents two distinct regions in tension by deformation curves, one elastic and other plastic. At the elastic region, there is a direct proportionality between applied load and correspondent deformation. This can be called an elastic linear behavior of the material. Considering graphite content cast iron with lamellar morphology this behavior does not follow the same pattern. Since the beginning of the loading those materials present non-linear behavior with the load applied. In this report will be presented microstructure analysis, micro and macro hardness tests and a precise determination of tension versus deformation curves of perlitic gray cast iron with predominant Type A graphite to get the real tension profile developed when flexion loads are applied.

The nitriding process improves in some applications the fatigue resistance of mechanical components. There is a lack of information about the nitriding process effect on the toughness of components. It is well known that the austempering heat treatment improves the toughness of the nodular cast iron. Some efforts have been made to find a compromise between the toughness of the bainitic structure of nodular cast iron and the high wear resistance undertaken by the nitriding process. Nitriding causes smaller dimensional problems if compared with other termochemical processes in steel and cast iron, but during exposure to the nitriding temperature the stabilized austenite of the nodular cast iron bainite may decompose, and induce component distortion. It is well known that the stabilized austenite is responsible for high toughness of the nodular cast iron.

The automotive industry has been increasing stainless steel consumption daily. Some important parts of a car should keep using carbon steel, however, the exhaust system must use stainless steel tubes since the gas from engine cannot corrode those tubes, avoiding catalytic conversor contamination. Among stainless steel groups, ferritic has been choosing due to costs and strong high temperatures resistance. This report starts studying ferritic stainless steel welded tubes mechanical properties (ABNT 409 stabilized), raw material for exhaust systems. Some welded tubes have been produced with internal bead rollers, to compare, afterwards, with tubes which were produced without bead hardening. The results shows that hardening induced by bead rolling causes material elongation reduction, that could lead problems on the tube forming operation during exhaust system production. Those materials have been analyzed by optical and electronic microscopy, Vickers micro hardness and tensile test.