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Go-apic, greensand without organic additives for the production of iron castings

Three institutes, three foundries, one producer of raw materials and one supplier of foundry equipment worked together to create a bentonite bonded moulding sand system without addition of coal dust.

60-70% of ferrous casting word-wide is produced using bentonite bonded silica sand moulds. In principle an effective and environmental friendly way to create moulds. The binder “Bentonite” (clay) consists of ca. 70-90% Montmorillonite. This clay can be re-used in a cycle “sand system” and does not produce hazardous emissions.

To achieve clean / sand free casting surface, reduce casting failure tendency and promote mould breakdown during casting shake-out most foundries add coal dust in the bentonite bonded sand. Coal has some unique properties, but at a casting temperature of ca. ca. 1350°C it also is responsible for markable emissions e.g. carbon monoxide, benzene and dust.

Most foundries have automatic moulding lines, which produce up-to 400 moulds per hour. The bentonite based moulding sand is running in a cycle system that has to balance at a certain composition. All Go-Apic project steps are created to do maximum research and minimize risks before implement new materials and technology in the foundry.

S&B Industrial Minerals have tested many moulding materials properties of moulds not containing coal, but alternative materials. Their selected materials were further tested at the Danish Technological Institute by prototype casting. Based on these pre-investigations at Swedish Foundry Association casting were made in a cycle system without coal. This pilot-plant testing was the fundament for trials in production foundries.

Foundry trials using bentonite bonded sand without the addition of coal, but adding graphite treaded bentonite and zeolite, demonstrated; Casting produced in this coal free bentonite bonded sand show no abnormalities. More moulding sand remains on the casting surface and the return moulding sand has more lumps. Depending on the conditions during shake-out and casting shot blasting the technology can be implemented or partly by implemented. A reduction of hazardous emissions of 50% or more is achievable.

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S&B Industrial Minerals GmbH
Schmielenfeldstr. 78
45772 Marl
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