engleski

Achieving specified properties of ductile cast iron by correction annealing

The paper presents the investigations of the process parameters for the correction heat treatment following casting process. The correction treatments are investigated for two different purposes: for achieving the specified impact toughness and for achieving good hardenability on the ferritic ductile iron. In both cases the optimal annealing parameters (time, temperature and cooling rate) are determined by applying modern statistical and quantitative methods on the results of microstructure analysis and tests of mechanical properties (determinations of strength, elongations and impact toughness). In the first case, by using the adequate annealing with slow cooling the impact toughness of the ferritic ductile iron (specified for the grade GGG 40.3) was increased from 4.2 J (as cast) to above 14 J after the correction annealing. In the second case, in order to achieve a satisfactory hardenability of the ferritic nodular iron (GGG 40) the graphite content was reduced from 7.9 % (as cast) to 3.4 % after a correction heat treatment. Subsequently, the hardness of about 58 HRC was obtained after quenching in oil.

ductile iron; ferritic ductile iron; correction heat treatment; hardenability

nije evidentirano