This paper presents the results of research which is part of studies carried out under the project POIG.01.01.02-00-015/09 "Advanced Materials and Technologies", one of the aims of which is to introduce new, environment-friendly, inorganic binders to the production of castings from non-ferrous metals. The paper presents the results of research on the management of waste moulding sands prepared according to the new technology, including their multiple reclamation and management of post-reclamation waste. Studies of multiple reclamation are a continuation of the preliminary research described earlier. The programme of the studies described in this paper also included validation of the results under industrial conditions.
Successful casting demands that during pouring of the foundry mould with molten metal the mould cavity suffers no deformation. This, in turn, demands the use of binding materials that can give the base sand adequate strength. The main bonding materials are clay binders. The foundry industry uses minerals rich in clay, such as kaolinite, halloysite, hydromica, montmorillonite, polygorskite, vermiculite and allophane. Due to their binding capacity, montmorillonites are the most interesting minerals of all the plastic clay rocks. The basic clay rock containing montmorillonite, used as a common binding material for traditional foundry sand mixtures, is bentonite. The domestic demand for raw bentonite materials is almost entirely satisfied by imports from Slovakia, Turkey, Italy, Germany and the Czech Republic, in order of import size. In Poland, the bentonite deposits occur in very small quantities. The exploitation of bentonites is carried out only in the Krzeniów deposit, where they constitute a mineral accompanying basalt. Much more common are bentonite clays containing in addition to smectites also a large amount of other clay minerals. The article presents the results of studies of the physico-chemical and mechanical properties of moulding sand mixtures containing pure bentonite, pure clay or hybrid bentonites which are a bentonite-clay mixture. Melting was also carried out to determine the effect of the type of binder on the surface quality of iron castings.
The results of own studies concerning the application of a new additive to the CO 2 -hardened sodium water glass foundry sands are presented. The new additive, which is a composition of aqueous solutions of modified polyalcohols, has been designated by the symbol "B" and is used as an agent improving the sand knocking out properties. The scope of studies included various mechanical and technological properties of foundry sand mixtures, such as permeability, friability, life cycle of cores and knocking out properties.Two types of water glass with different values of the silica modulus and density, designated as R145 and R150, were tested. Moulding sands used in the tests were made with the additive "B". For comparison, a reference sand mixture with water glass but without the additive "B" was also prepared.
One of the purposes of the application of chemically modified inorganic binders is to improve knocking out properties and the related reclamability with previously used in foundry inorganic binder (water glass), which allowing the use of ecological binders for casting nonferrous metals. Good knocking out properties of the sands is directly related to the waste sands reclamability, which is a necessary condition of effective waste management. Reclamation of moulding and core sands is a fundamental and effective way to manage waste on site at the foundry, in accordance with the Environmental Guidelines. Therefore, studies of reclamation of waste moulding and core sands with new types of inorganic binders (developed within the framework of the project) were carried out. These studies allowed to determine the degree of recovery of useful, material, what the reclaimed sand is, and the degree of its use in the production process. The article presents these results of investigation. They are a part of broader research programme executed under the project POIG.01.01.02-00-015/09 "Advanced materials and technologies".
The results of research on the possibility of using a gaseous medium (hot air) as a hardening agent for inorganic binders were discussed, and tests on the reclamation of waste moulding sands were carried out. The research programme also included the use of a modernized test stand for hardening of foundry sands with gaseous agents and a pilot plant for the sand reclamation. Cores made on the test stand were examined for the basic technological properties and were also used in moulds for the trial knocking out of castings. Two types of binders were tested, i.e. a modified water glass designated as Binder A and, for comparison, a reference material which was hydrated sodium silicate R145. The hardener for the sand mixtures was hot air (the dehydration of water glass). Trials of the sand reclamation were carried out in a laboratory pilot plant, installed and operating at the Foundry Research Institute. The obtained reclaim was added in different amounts to the sand mixtures subjected to technological tests. The next step included the manufacture of test moulds, pouring them with aluminium alloy, and knocking out of castings to test the collapsibility of moulds and cores.
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