This paper shows how it is possible to obtain an ausferrite in compacted graphite iron (CGI) without heat treatment of castings. Vermicular graphite in cast iron was obtained using Inmold technology. Molybdenum was used as alloying additive at a concentration from 1.6 to 1.7% and copper at a concentration from 1 to 3%. It was shown that ausferrite could be obtained in CGI through the addition of molybdenum and copper in castings with a wall thickness of 3, 6, 12 and 24 mm. Thereby the expensive heat treatment of castings was eliminated. The investigation focuses on the influence of copper on the crystallization temperature of the graphite eutectic mixture in cast iron with the compacted graphite. It has been shown that copper increases the eutectic crystallization temperature in CGI. It presents how this element influences ausferrite microhardness as well as the hardness of the tested iron alloy. It has been shown that above-mentioned properties increases with increasing the copper concentration.
The paper presents the results of studies of the effect of chromium concentration on the solidification process, microstructure and selected
properties of cast iron with vermicular graphite. The vermicular graphite cast iron was obtained by an Inmold process. Studies covered the
cast iron containing chromium in a concentration at which graphite is still able to preserve its vermicular form. The effect of chromium on
the temperature of eutectic crystallization and on the temperature of the start and end of austenite transformation was discussed. The conditions
under which, at a predetermined chromium concentration, the vermicular graphite cast iron of a pearlitic matrix is obtained were
presented, and the limit concentration of chromium was calculated starting from which partial solidification of the cast iron in a metastable
system takes place. The effect of chromium on the hardness of cast iron, microhardness of individual phases and surface fraction of carbides
was disclosed.
The paper presents the results of the research on the effect of copper on the crystallization process, microstructure and selected properties
of the compacted graphite iron. Compacted graphite in cast iron was obtained using Inmold process. The study involved the cast iron
containing copper at a concentration up to approximately 4%. The effect of copper on the temperature of the eutectic crystallization as well
as the temperature of start and finish of the austenite transformation was given. It has been shown that copper increases the maximum
temperature of the eutectic transformation approximately by 5C per 1% Cu, and the temperature of the this transformation finish
approximately by 8C per 1% Cu. This element decreases the temperature of the austenite transformation start approximately by 5C per
1% Cu, and the finish of this transformation approximately by 6C per 1% Cu. It was found that in the microstructure of the compacted
graphite iron containing about 3.8% Cu, there are still ferrite precipitations near the compacted graphite. The effect of copper on the
hardness of cast iron and the pearlite microhardness was given. This stems from the high propensity to direct ferritization of this type of
cast iron. It has been shown copper increases the hardness of compacted graphite iron both due to its pearlite forming action as well as
because of the increase in the pearlite microhardness (up to approx. 3% Cu). The conducted studies have shown copper increases the
hardness of the compacted graphite iron approximately by 35 HB per 1% Cu.
This article presents the methodology for exploratory analysis of data from microstructural studies of compacted graphite iron to gain
knowledge about the factors favouring the formation of ausferrite. The studies led to the development of rules to evaluate the content of
ausferrite based on the chemical composition. Data mining methods have been used to generate regression models such as boosted trees,
random forest, and piecewise regression models. The development of a stepwise regression modelling process on the iteratively limited
sets enabled, on the one hand, the improvement of forecasting precision and, on the other, acquisition of deeper knowledge about the
ausferrite formation. Repeated examination of the significance of the effect of various factors in different regression models has allowed
identification of the most important variables influencing the ausferrite content in different ranges of the parameters variability.