Durango Bizkaia, Spain
Durango Bizkaia, Spain
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Sertucha J.,AZTERLAN | Larranaga P.,AZTERLAN | Lacaze J.,Toulouse 1 University Capitole | Insausti M.,University of the Basque Country
International Journal of Metalcasting | Year: 2010

Copper is known as a pearlite promoter in cast iron and has been used as such for a long time, most often together with low amounts of manganese. Literature data, however, has shown that these two elements act differently on the ferritic and pearlitic transformations. In order to provide more insight in the role of this element on the solid-state transformation of spheroidal graphite (SG) cast iron, this paper investigates the effect of adding copper in small step increments, from 0.11 to 1 wt. % Cu, to SG irons containing about 0.15 wt. % Mn. The characteristic temperatures for the stable and metastable eutectoid transformations as recorded during cooling after solidification in standard cups and after austenitizing are presented together with microstructure information. It is found that a copper content of about 0.6 wt. % is the upper limit over which only small amounts of ferrite could be obtained except at very low cooling rates. This is tentatively related to the lowering of the temperature for ferrite and the associated decreased kinetics for austenite decomposition in the stable system. Copyright © 2010 American Foundry Society.

Valle N.,Center De Recherche Public Gabriel Lippmann | Theuwissen K.,ENSIACET | Sertucha J.,AZTERLAN | Lacaze J.,ENSIACET
IOP Conference Series: Materials Science and Engineering | Year: 2011

Five spheroidal graphite cast irons were investigated, a usual ferritic grade and four pearlitic alloys containing Cu and doped with Sb, Sn and Ti. These alloys were remelted in a graphite crucible, leading to volatilization of the magnesium added for spheroidization and to carbon saturation of the liquid. The alloys were then cooled down and maintained at a temperature above the eutectic temperature. During this step, primary graphite could develop showing various features depending on the doping elements added. The largest effects were that of Ti which greatly reduces graphite nucleation and growth, and that of Sb which leads to rounded agglomerates instead of lamellar graphite. The samples have been investigated with secondary ion mass spectrometry to enlighten distribution of elements in primary graphite. SIMS analysis showed almost even distribution of elements, including Mg and Al (from the inoculant) in the ferritic grade, while uneven distribution was evident in all doped alloys. Investigations are going on to clarify if the uneven distribution is associated with structural defects in the graphite precipitates.

Asenjo I.,AZTERLAN | Lacaze J.,ENSIACET | Larranaga P.,AZTERLAN | Mendez S.,AZTERLAN | And 2 more authors.
Key Engineering Materials | Year: 2011

Parameters that affect chunky graphite formation in heavy-section castings have been studied in previous works which showed that inoculation and cerium addition both increase the tendency for this degenerate graphite. This suggested that laboratory study on chunky graphite formation could be performed on small castings by over-treating the melt. Though the role of silicon was not ascertained, it appeared of potential interest to also investigate its effect in relation with the carbon equivalent of the iron and the nucleation potential of the melt. Keel-blocks were thus cast using Ce or Ce-Mg treated melts, with increased silicon content (up to 4.0 wt.%) and inoculation rate as compared to usual practice. It was observed that chunky graphite systematically appeared in more or less extended areas centred on the upper part of the keel-blocks. The as-cast microstructure (graphite shape and distribution) has then been studied in relation to melt composition and additions (Ce treatment and inoculation) in both affected and non-affected areas. Finally, microanalysis of oxides and other minor phases showed them to be similar to those appearing in heavy-section castings. It may then be concluded that chunky graphite appears in light-section castings in the same way than in heavy-section castings when using over-treated melts.

Serrallach J.,INFUN | Lacaze J.,ENSIACET | Sertucha J.,AZTERLAN | Suarez R.,AZTERLAN | Monzon A.,INFUN
Key Engineering Materials | Year: 2011

There is a continuous demand for low-cost nodular cast irons with improved mechanical properties, this being an industrial requirement both for pearlitic as well as for ferritic grades. Developments in pearlitic nodular irons should lead to alloys with higher and higher strength while retaining some ductility in the as-cast state so as to respond to demands related to castings for high power automotive engines in competition with steel castings and ADI. According to these aims, several alloying elements have been selected and added separately or combined to standard commercial nodular cast irons. In all cases, only low-level additions were made and their effects on the microstructure and mechanical properties at room temperature have been characterized and are discussed. A statistical analysis has been performed on the data obtained that accounts for changes in alloying additions as well as for variations in process parameters.

Sertucha J.,AZTERLAN | Lacaze J.,ENSIACET | Serrallach J.,INFUN S.A. | Suarez R.,AZTERLAN | Osuna F.,INFUN S.A.
Materials Science and Technology | Year: 2012

The development of low temperature applications for ferritic nodular cast irons calls for improved materials in the as cast state, e.g. for off-shore windmills components. Within this line of work, a series of 68 castings were prepared with the same casting procedure and slight changes in composition. The tensile properties at room temperature, as well as the impact energy for rupture at room temperature, 220°C and 240°C, were measured. Outputs from multivariate analysis performed on the data are then discussed and compared to literature results, putting emphasis on the properties of the ferritic matrix. © 2012 Institute of Materials, Minerals and Mining.

Mendez S.,AZTERLAN | Lopez D.,AZTERLAN | Asenjo I.,AZTERLAN | Larranaga P.,AZTERLAN | Lacaze J.,ENSIACET
ISIJ International | Year: 2011

Chunky graphite is a particular form of graphite degeneracy that appears in the centre of large iron castings, with a well-defined transition from the outer unaffected area and the inner affected one. All previous works that looked for macrosegration to explain the phenomenon concluded that there are no significant composition differences between the inner and outer parts of such castings. This was challenged again because the analytical methods generally used for chemical analysis are not efficient for low-level elements. Accordingly, an ICP-MS procedure has been developed and validated to replace the usual ICP-OES method. Together with the usual methods for analysis of C, S and Si, this ICP-MS procedure has been applied to characterize chemical heterogeneities in a large block with chunky graphite in its centre, and to a standard part for comparison. It could be concluded that no macrosegregation has built up during the solidification process of the block investigated, i.e. that chunky graphite appearance is not related to any composition changes at the scale of the cast parts, in particular of elements known to affect graphite shape such as Ce, Mg, Sb, S,⋯. © 2011 ISIJ.

Niklas A.,Azterlan | Abaunza U.,Azterlan | Fernandez-Calvo A.I.,Azterlan | Lacaze J.,ENSIACET | Suarez R.,Azterlan
China Foundry | Year: 2011

Thermal analysis technique has been used for a long time, in both ferrous and nonferrous industries for evaluating the metallurgical quality of the liquid metal before casting. However, obtaining a proper microstructure in a standard cup does not ensure that the microstructure is correct in real parts which may solidify at very different cooling rates. For this study, alloy A356 with different metal quality in terms of modification and grain refinement was tested. Different cooling rates were obtained by using cylindrical test samples with various diameters cast in sand and metallic moulds. The correlation between microstructure features such as grain size, modification rate and secondary dendrite arm spacing (SDAS) measured in the standard thermal analysis cup with those obtained in the cylindrical test parts has been investigated. Thus, knowing the thermal modulus and the mould type it is possible to establish the required grain size and modification rate in the standard cup in order to get a desired structure in a real part. Corrective actions can then be taken in order to improve the metallurgical quality before casting the part.

Fernandez-Calvo A.I.,AZTERLAN | Niklas A.,AZTERLAN | Lacaze J.,ENSIACET
Materials Science Forum | Year: 2010

Both thermal analysis (TA) and differential thermal analysis (DTA) have been used since long to evaluate latent heat release and solid fraction evolution during solidification of metallic alloys. TA makes use of cooling curves recorded under "natural" cooling while DTA consists in recording the temperature difference between the sample temperature and an inert reference during a controlled cooling, i.e. at imposed constant cooling rate. In both cases, the solid fraction evolution is deduced from a calculation of the latent heat release as estimated by means of a heat transfer model. This paper provides a comparison of such evaluations performed on one Al-Si alloy. © (2010) Trans Tech Publications.

Lacaze J.,ENSIACET | Armendariz S.,S.A. Pol. Sansinenea Erreka | Larranaga P.,AZTERLAN | Asenjo I.,AZTERLAN | And 2 more authors.
Materials Science Forum | Year: 2010

The influence of post-inoculation and of cerium and antimony additions on the solidification process and on the formation of chunky graphite in ductile iron heavy-section parts have been studied previously in the case of near-eutectic alloys. It appeared of interest to complement these works by analysing the effect of carbon equivalent on graphite degeneracy. In the present work, hypo-, hyper- and near-eutectic melts have been cast in large blocks and standard cups. Analysis of the corresponding cooling curves recorded during solidification as well as microstructure observations on these casts have been carried out. A clear effect of carbon equivalent as promoter of chunky graphite formation is observed. The results have been added to the set of data already available and various correlations are discussed. © (2010) Trans Tech Publications.

Helber J.H.,B B H | Zarrabeitia G.,AZTERLAN
71st World Foundry Congress: Advanced Sustainable Foundry, WFC 2014 | Year: 2014

Carbon footprint analysis (CFA) is a sophisticated environmental method to evaluate the impact of the whole life-cycle of a product on our climate - starting with the raw materials and ending with their disposal or re-use. This may prove a challenge for foundries in this field in the future. Today CFA already is applied to some consumer products like cars or the propellers of large shipping vessels. There it is used as proof that a specific product and its production are environmentally advantageous in comparison to other alternatives of manufacturing, product, and consumption. CFA is not yet compulsory for cast parts as semifinished products. But the example of the ship's propeller demonstrates that it may be introduced, especially if the CO2 reduction programmes in the EU countries should not show the desired results. Therefore the authors regard it useful to present a view on future trends, which some may regard as a "worst case scenario" while others take it for the useful strategic information that it is intended to be. Based on actually available (but hard to come by) data and methods an introduction shall be given to this relatively young and very complex topic.

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