Combined Effects of Copper and Tin at Intermediate Level of Manganese on the Structure and Properties of As-Cast Nodular Graphite Cast Iron

Abstract

Copper, manganese and tin are commonly used as pearlite promoter elements in cast irons. A number of studies have been aimed at quantitatively evaluate the effect of each of these elements, individually or at given levels of the others. As a matter of fact, while tin may be necessary for achieving a fully pearlitic matrix, it is known that when in excess it is detrimental for mechanical properties. As the pearlite promoting effect of each of those elements is totally different, it is of real interest to know the optimum combination of them for a given cooling rate. The present report is a first part of a work dedicated at characterizing the best alloying levels in terms of room temperature mechanical properties of as-cast pearlitic materials.Keywords: pearlitic nodular cast irons, copper, manganese, tin, room temperature mechanical properties IntrodutionCast irons are mostly used in as-cast state to avoid costly heat-treatments that would also impair some of their mechanical properties such as fatigue resistance. In several cases, the desired matrix may be either fully ferritic or fully pearlitic. The aim of this work was to find if an optimal combination of manganese, copper and tin could be defined as regards room temperature (RT) mechanical properties of nodular graphite iron (SGI) when a fully pearlitic matrix is looked for in the as-cast state. It appeared of interest to first perform a literature review of available information on the effect of these pearlite promoter elements on microstructure. A series of castings have then been achieved for selected compositions. Microstructure and mechanical properties of these castings are presented and compared to literature data. Literature reviewObtaining fully pearlitic matrix in as-cast complex components made of SGI needs resorting to alloying additions. Amongst other elements, the effect of manganese, copper and tin as pearlite promoters is well known though there are very few works available for really quantifying it. Furthermore, the published reports deal with at most interaction between two of these elements, tin and copper in the work by Levin et al. In all these works, the alloys contained 3.60-3.75 wt.% carbon and more or less 2.4 wt.% silicon. However, the casting conditions in these various works differed and as the cooling rate has a definite effect on the pearlite and ferrite amounts the results from these studies could be only partly compared.

Microstructure of As-cast Ferritic-pearlitic Nodular Cast Irons

“…27) showed that the same kind of behavior as seen for copper in Fig. 9 exists for tin with a critical amount at about 0.05 wt.%.…”

Effect of Tin on the Phase Transformations of Cast Irons

“…This effect on the eutectic temperature is so small that it would hardly be observed experimentally, as seen with the results by Lacaze et al [2] who reported that Sn addition showed either an increase or a decrease of the eutectic plateau temperature as recorded by thermal analysis. The calculated decrease is however in agreement with results reported by Kanno et al [19] The most important information expected from the above description concerns the eutectoid transformation.…”

“…However, it is recognized that addition of these two elements is generally not sufficient to get a fully pearlitic matrix [1] and it is usual to add some tin or some antimony to this aim. Previous work has shown that a tin equivalent Sneq could be defined as [2,3] :…”

Improvements in Wear and Corrosion Resistance of Ti-W-Alloyed Gray Cast Iron by Tailoring Its Microstructural Properties

“…This resulted in an enhancement of the tensile strength by 4.62%, yield strength by 10%, and Brinell hardness by 13.14% compared to un-alloyed Sample B-1 [60]. The addition of Ti and W is reported to elevate the pearlite contents in the microstructure, enhancing the mechanical properties and reducing the graphite flake aspect ratio [61,62]. Further increasing the Ti and W content to 0.762 wt.% and 0.785 wt.%, respectively, Sample B-3 demonstrated an 8.38% increase in tensile strength, 19.23% increase in yield strength, and 27.69% increase in Brinell hardness compared to Sample B-1.…”