Citation: Lucarz, M.; Garbacz- Klempka, A.; Dro ˙ zy ´ nski, D.; Skrzy ´ nski, M.; Kostrzewa, K. Mechanical Reclamation of Spent Moulding Sand on Chromite Sand Matrix; Removal of Alkali-Phenolic Binder. Materials 2023, 16, 2919. https://doi.org/10.3390/ ma16072919 Academic Editor: Feng Qiu Received: 15 February 2023 Revised: 29 March 2023 Accepted: 1 April 2023 Published: 6 April 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). materials Article Mechanical Reclamation of Spent Moulding Sand on Chromite Sand Matrix; Removal of Alkali-Phenolic Binder Mariusz Lucarz 1 , Aldona Garbacz-Klempka 1, * , Dariusz Dro ˙ zy ´ nski 1 , Mateusz Skrzy ´ nski 1 and Krzysztof Kostrzewa 2 1 Faculty of Foundry Engineering, AGH University of Science and Technology, Reymonta 23 St., 30-059 Krakow, Poland 2 Huta Malapanew Sp. z o.o., 1 Kolejowa, 46-040 Ozimek, Poland * Correspondence: agarbacz@agh.edu.pl; Tel.: +48-12-617-27-74 Abstract: The foundry industry generates large amounts of waste when casting metal into sand moulds. An important issue is the activities that are related to the re-recovery of the grain matrix (the main component of the moulding sand) for realising subsequent technological cycles. This process is particularly important in the case of the expensive chromite matrix that is necessary for use in manganese steel casting. The effects of the reclamation treatments of spent alkali-phenolic binder sand were evaluated by scanning electron microscopy with EDS, analysing the chemical composition in micro areas and proving the loss of binder on the surfaces of the matrix grains. Tests were also performed using the main criteria for evaluating a reclaimed organic binder: sieve analysis and ignition loss. A thermogravimetric analysis study was performed to assess the change in the chromite character of the grain matrix under the influence of temperature. The effects of the reclamation measures were verified by making moulding compounds on a matrix of reclaimed sand and a mixture of reclaimed and fresh sand. The tests and analyses that were carried out indicated the direction of an effective method for reclaiming used alkali-phenolic binder masses and the extent of the proportion of the regenerate in moulding sand in order to maintain the relevant technological parameters of the moulding sand. Keywords: foundry engineering; mechanical reclaim; chromite sand; moulding sand properties; scanning electron microscopy; thermal analysis 1. Introduction The production of steel castings that use the alkali-phenolic Alphaset process of mould- ing sand preparation has been recognised as the most convenient and environmentally friendly casting process and has become the standard in England [1]. The benefits of the alkali-phenolic process are a significant improvement in casting quality and a reduction in the costs that are associated with casting cleaning. At the same time, the total amount of gaseous substances given off when a mould is flooded with liquid metal is significantly lower than with other organic resins [2]. The tensile strength of a moulding compound that is prepared on a matrix of new sand using alkali-phenolic technology is generally lower than that of other organic resins [3]. However, the tensile strength is sufficient for meeting the requirements of core and mould technology in most applications while improving the surface quality of the casting [4]. The main advantage of the alkali-phenolic process is the two-stage setting—an initial setting at the ambient temperature, and an essential setting from the temperature of the liquid casting melt. The initial strength that is obtained is sufficient for carrying out the technological procedures that are associated with the casting mould. The alkali-phenolic resin (which is not fully bonded) exhibits thermoplastic properties; this compensates for the resulting thermal expansion of the grain matrix during the pouring of the mould with liquid metal, eliminating mould cracking and the possible Materials 2023, 16, 2919. https://doi.org/10.3390/ma16072919 https://www.mdpi.com/journal/materials