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.
In the article we were studing the impact of the remelting on transformations in Co-Cr-Mo prosthetics alloy. The TDA curves were analyzed, the microstructure was examined, the analysis of the chemical composition and hardness using the Brinell method was made. It was found that the obtained microstructure of the alloys that we studied do not differ significantly. In all four samples, microscopic images were similar to each other. The volume, size and distribution of the phases remain similar. Analysis of the chemical composition showed that all the samples fall within the compositions provided for the test alloy. Further to this the hardness of the samples, regardless of the number of remeltings did not show any significant fluctuations and remained within the error limit.After analyzing all the results, it can be concluded that the remeltings of the alloys should not have a significant impact on their properties. Secondarily melted alloys can be used for prosthetics works.
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.