Resumo:
Nodular cast iron is one of the most used ferrous materials by engineering currently, whether
as components for the automotive industry, for the basic sanitation industry or for the
component industries in general. One of the main raw materials for the production of cast iron
is steel scrap. Currently, this raw material is collected from different generating sources and is
composed of different types of steel with different chemical compositions. Many chemical
elements present in steel scrap, even in small percentage concentrations, are undesirable in the
production of cast iron, since some of them have the effect of causing significant changes in
their microstructure. The contribution of this study is to investigate the effect of the elements
copper, nickel, molybdenum and chromium, commonly present in steel scrap, as a promoter of
the martensitic matrix in a nodular cast iron in the as casted state. Contents lower than 1%w
were used for each element investigated and the pieces were produced by centrifugation casting
process. By analyzing the scanning electron microscopy images and semiquantitative analysis
via Energy Dispersive Spectroscopy, it was observed that nickel and copper were uniformly
distributed in the matrix, while chromium and molybdenum formed carbides in the intercellular
contours. Among the four elements investigated, molybdenum proved to be a strong promoter
of martensite formation and the fractions of this phase increased with the increase in the amount
added of this element (35%, 40% and 50%). The results obtained indicate the probable path to
obtain the totally martensitic matrix in as casted state and the possibility of eliminating costs
related to production on an industrial scale, such as the austenitization heat treatment followed
by quenching, which has an estimated operating cost of 26173.35 USD per month. It is
noteworthy that the analysis of the feasibility of eliminating the heat treatment should consider
the cost with the consumption of the ferro-molybdenum alloy and the particularities of the
process of each foundry
