Moulding sands

Foundries consume considerable quantities of graphite the pattern is buried in moulding sand, the surface of which, after removal of the pattern, is coated with graphite often mixed with talc to provide a smooth surface and prevent the casting from sticking. 

Pouring molten metal into a green sand mould subjects the moulding-sand to considerable heat. This heat removes moisture from the sand and destroys the clay-bonded structure (and additives). If during pouring and cooling bentonite stays below the deactivation temperature, the lamellar structure is maintained as well its ability to swell and develop cohesion. The deactivition temperature varies with the bentonite type. 

In impact moulding, sand is fed under gravity into the flask and compacted by the instantaneous release of compressed air through a rapid acting valve. This process gives a high and uniform densification, particularly in the sand surrounding the pattern. 

The use of wet systems cause the production of a waste water flow. Which needs to be treated, a sludge fraction, which needs to be a disposed of. Some systems work without producing waste water. The sludge is thickened and, if it contains a sufficient amount of bentonite, is re-used in the moulding-sand cycle. 

Multiple use of treated waste water Multiple use of treated waste water needs to be considered, e.g. using process water from sand preparation in the moulding sand cycle or in slag granulation. The use of cooling water in wet scrubbing may also be considered Use of waste heat for the evaporation of waste water This technique can only be applied when waste heat is available on a continuous basis. A case-by-case evaluation is needed to evaluate its applicability and economic viability... 

The technique can be used for uncured coresand with organic binders. The regenerated sand may be re-used for core-making using the same binder type, after mixing with new sand. It may also be used, within certain limits, for the renewal of moulding-sand. 

Drews, B. (1996). Simultaneous mixing and cooling of moulding sand under vacuum". Casting Plant+Technology International. 2, pp. 4-10. 

Sand regeneration, recycling, re-use and disposal Since foundries make intensive use of sand as an inert primary material, the regeneration or re-use of this sand is an important point of consideration as part of its environmental performance. Various techniques are applied for regeneration of the sand (i.e. treatment and internal re-use as moulding sand), the selection of which depends on the binder type and the sand flow compostion. If sand is not regenerated, then external re-use may be considered in order to prevent the need for its disposal. Its application in various areas has been demonstrated. 

Moulding sand must be permeable, i.e. porous, to allow the escape of gases and steam strong enough to withstand the mass of molten metal resist high temperatures and have a grain size suited to the desired surface of the casting. 

Refractory bricks (7%). It is useful in refractory linings for furnaces and the kilns of the cement industry and in moulding sands in foundries because of its high melting point and relatively low cost. 

An external appearance of hollow bricks with a fraction of spent moulding sands does not differ from the normal production, only they are characterized by a higher compliance to over-heating in the stack middle part (black dye penetrations, blisters). 

J. Danko, R. Danko, and M. Lucarz, Processes and devices for reclamation of used moulding sands (Akapit, Krakow, 2007). 

Patent application No. P-389 371 valid from 23.10.2009.. .Method of processing and utilization of spent moulding sands . 

RESEARCH ON THE INFLUENCE OF MOULDING SAND WITH FURAN RESIN ON THE ENVIRONMENT... 

When moulding sands are prepared and moulds made of furan resin sands an emission of formaldehyde, phenol and fiirfuiyl alcohol is possible. However, when a polymerisation occurs at a room temperature, vapour pressures of these compounds are low. 

The list of harmful compounds emitted to the atmosphere during preparation and hardening furan resin moulding sands is given in Table I, while the comparison of this emission with phenol resin sands is shown in Table II. 

M. Holtzer, B. Grabowska, S. Zymankowska-Kumon et al., Harmfulness of moulding sands with bentonite and lustrous carbon carriers . Metallurgy 51 (4) (2012), 437-440. 

Research on the Influence of Moulding Sand with Furan Resin on the... 

Nonferrous smelting Copper slag, moulding sand... 

Automotive Moulding sand, paint shredder residue, used tires... 

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