Based on the results of dilatometric investigations, parameters of standard single-step and multi-step (or non-isothermal) ADI heat treatment were optimised. The optimisation was based on analysis of the heat treatment processes simulated under laboratory conditions and used correlation between volume changes accompanying the decomposition of an ausferritic structure at 400-650°C and the amount of α acicular ferrite and γs (C) high-carbon austenite, the proportions of which determine the mechanical properties of alloys.
Optimisation of the complex heat treatment of nodular cast iron predicts mechanical properties of ADI, impossible to obtain through the standard, single-step heat treatment.
The results of mechanical tests have not confirmed the expectations; very good mechanical properties Rm and A5 obtained by multi-step and non-isothermal treatments, were also obtained by standard heat treatment with appropriately selected parameters.
Keywords: ADI, ausferrite, thermal analysis, quenching dilatometer,
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Mariusz Holtzer, Angelika Kmita, Agnieszka Roczniak
Among various sands with organic binders, moulding sands with furan resins belong to the group most widely applied in the manufacture of castings from ferrous alloys. This is due to a number of undisputable advantages offered by these sands, although they are not free from certain drawbacks, which ultimately can result in casting defects. The main disadvantage of furan resin sands is the fact that the binder contains nitrogen, sulphur and phosphorus, and all these elements are transferred in the course of casting from sand to metal. Additionally, producers of furan resins are forced to reduce the free furfuryl alcohol content to <25 wt. %, due to its toxic properties. Special attention deserves the presence of sulphur in moulding sand when castings are made from the cast iron with nodular or vermicular graphite. Then, as very often occurs, the effect of degradation of these two graphite forms take the shape of flake graphite. The study shows how to calculate the amount of sulphur introduced into the moulding sand together with binder, related to the acid catalyst composition (most often, its main components are various organic sulphonic acids). It is expected that the results will be useful in the selection of an optimum catalyst for a given type of furan resin.
Keywords: furan resin, sulphur, degradation of graphite forms, moulding sands,
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The article presents the results of preliminary studies on the possible application of innovative activation treatments of inorganic binders during the reclamation of waste water glass moulding sands hardened by conventional drying. The test moulding mixture based on silica sand and selected sodium water glass in grade 145 was subjected to the following processing steps: mixing of components, compaction, drying at 100°C for hardening, cooling, thermal loading of mould up to a temperature of 800°C, cooling to ambient temperature, knocking out, and dry or wet mechanical reclamation to restore the sand mixture binding properties. Several waste sand processing techniques were chosen; they use, among other things, various surface phenomena usually accompanying the mechanical reclamation combined with dedusting of the thermally reacted binder separated from the base silica sand grains. Studies also covered possible use of some elements of the wet reclamation process to rehydrate the thermally reacted binder. To check the effectiveness of the proposed methods of activation, after their implementation, selected strength parameters were measured. Studies disclosed, moreover, the importance of the type of device used for the activation and dust removal during the preliminary reclamation of moulding sand. The possibility of restoring partially the binder ability to bond the waste and properly processed moulding sand containing sodium silicate has been confirmed, providing physical methods which are applied for its hardening. The results of conducted tests, including examination of the surface of sand grains in the reclaimed mixture, allowed selecting the best method that can be used for the waste moulding sand treatment in an innovative process of the periodical sand rebonding. The results of tests highlight the possibility to use an eco-innovative method of rebonding the moulding sands with inorganic binders hardened by physical means and make them an alternative technology for the traditional system sands.
Keywords: moulding sand, water glass, drying, hardening, reclamation,
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Irena Izdebska-Szanda, Michał Angrecki, Aleksander Palma
The article presents the results of tests and studies carried out within the framework of statutory activities on various additives to moulding sands based on water-soluble inorganic binders for ablative knocking out of castings. As a result of technological research and bench tests, the composition of moulding sand providing high quality castings and easy knocking out of moulds combined with ablative cooling was selected. The developed moulding sand composition produces moulds which not only possess the required high strength but are also susceptible to the destructive effect of a cooling medium (water). The results of conducted experiments are satisfactory and raise hope as to further possible use of this method in the industry.
Keywords: ablation, mould destruction, water-soluble binders,
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Patrycja Turalska, Natalia Sobczak, Artur Kudyba, Rafał Nowak, Marta Homa, Aleksandra Siewiorek, Łukasz Boroń, Adam Klasik
The studies of the drop-size effect on the wetting kinetics of the nickel substrate by lead-free solder were performed by the sessile drop method in a vacuum at a temperature of 260°C.
In this work, Sn-based alloy SAC305 (Ag - 3.0 wt. %, Cu - 0.5 wt. %) and polished nickel substrate (99.8%) were used. During the wettability tests, a separate heating of the couple of materials to a test temperature was performed by placing a sample of SAC305 alloy in a graphite capillary above the nickel substrate. After reaching the test temperature, the SAC305 drop was squeezed from the capillary and deposited on the Ni substrate. After 30 seconds, the second drop was squeezed and deposited on the first one, thereby increasing the volume of the drop twice. The process was repeated 9 times every 30 seconds reaching a 10 times larger drop volume, compared to the first drop.
After wettability tests, the solidified drop/substrate couple was cooled, cut and subjected to a shear test and structural analysis by optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy analysis.
Wettability studies have not shown a significant difference between the values of the contact angle obtained for each drop produced by subsequent adding of nine drops despite their different size of ten drops produced on the substrate, their contact angle values formed after 30 second contact time were similar showing θ = 35 ±2°. High repeatability of the measured contact angle value θ demonstrates not only physical homogeneity of the substrate surface but it presents a lack of size effect over a range of SAC305 drop volume used in this study.
The obtained results demonstrate the suitability of the sessile drop method for surface quality evaluation, particularly for quality tests of thin technological layers or coatings used in joining dissimilar materials.
Keywords: wetting kinetics, contact angle, lead-free soldering, SAC305, nickel, drop-size effect,
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