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Metal Casting Technologies : September 2006
70 No Bake processes are so well understood both in terms of the wide range of binders on the market, it is possible to say without contradiction that all types of castings lend themselves to these processes. This includes high quality aluminium castings, such as those used in the aerospace and military sectors, where no wall deformation is acceptable (casting wall thickness 2-2.5mm). These results are universally available to No Bake users (eg Agusta Foundry - Italy, Ferrari Foundry - Italy, Ussel, Angelino). There are castings whose large size means the use of moulding boxes (flasks) is unavoidable, where any reference to "alternatives" to chemically bonded sand verges on the ridiculous. Heavy castings for earth moving machinery (flaskless moulds 3000 x 1800 x 1200/1200) such as those moulded by Harrison Steel (see plant and casting photos). What other process is more competitive than No Bake? How would the majority of the mineral wear parts industry (Magotteaux, Norcast, ME Global) manage without chemically bonded moulding? Once the decision has been made to go down the No Bake route, then the only problem is which process to chose. Amongst the binders, sodium silicate, alkaline phenolic, furan, phenol urethane all are in wide use and whose characteristics are perfectly understood: in addition the characteristics of the sand to be used (chemical & physical) need to be taken into account, not to mention other numerous variables, all of which influence the process quality of the castings. Once all these are considered, then the choice of binder can be made with confidence. To be more specific, sodium silicate ester hardened is successfully used for ferrous castings including wear parts, marine diesel piston rings; furane is the universal binder for cast iron both grey and SG and also wear parts and carbon steel, but not light alloys; phenolic urethane has a large niche amongst aluminium and magnesium founders, not to mention steel; alkaline phenolic, ester hardened, has a faithful following among steel founders for whom high reclaimabilty is a low priority. 3D drawing of a complete moulding line The casting for the plastic injection industry Produced at Chen Hsong - China The huge No-Bake flaskless moulds produced at Harrison Steel - USA www.metals.rala.com.au ADVERTISING PROMOTION