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Metal Casting Technologies : March 2011
FEATURE STORY ● Sand fusion over casting is expected to be minimum compared to some sand moulds containing binder such as sodium silicate, so cleaning of casting is easier ● Sand mixing/mulling are not needed and sand control is irrelevant ● No sand reclamation needed. Sand is reusable, so sand disposal problem is also minimised ● Moisture/binder related casting defects are eliminated ● No pollution in the moulding/core making shop and pouring area arising out of binder. It is true particularly for organic chemical binders ● No parting line defects such as mismatch /fins ● No chances of sand drop and sand inclusion during filling of mould ● Close tolerance casting, hence machining cost is minimised/eliminated ● All metals can be cast by SMMC process. For iron and steel casting low carbon steel sheet , for Al casting pure Al sheet and for Cu alloy casting Cu/brass sheet are to be used ● Possibility of producing bi-metallic casting with a wear/corrosion -- resistant outer layer of different alloy Disadvantages/limitations The following disadvantages and limitations are associated with the SMMC process: ● Feasible only for mass production, where sheet metal mould in parts can be produced with sheet metal working machines (Press)and dies ● Suitable for small and medium size castings only ● Only those shape of castings are possible that can be moulded by assembly of worked sheet metal ● Complete filling of mould with liquid metal is possible only in presence of proper venting ● Overall high installation cost associated with making and assembly of sheet metal mould ● Risk of mould collapse similar to LFC process, since no binder in sand mould ● Lack of fusion of sheet metal mould with body of casting ● The process appears to be economic only when the machining cost of casting is very high Conclusion A new casting process has been demonstrated successfully, that uses a sheet metal mould having shape and dimensions similar to those of the casting to be produced, surrounded by loose unbounded sand in a mould box. The process has several advantages over conventional casting processes. However one problem of non-fusion of sheet metal with the casting was observed that needs to be solved. Acknowledgement The author is thankful to M/s. Leader Valves, Jalandhar for providing casting facility of this work. ■ Figure 4. Photograph of gland casting Figure 5. Photograph of sectioned sample from gland casting showing separation of sheet metal from casting due to incomplete fusion A NEW CASTING PROCESS HAS BEEN DEMONSTRATED SUCCESSFULLY, THAT USES A SHEET METAL MOULD HAVING SHAPE AND DIMENSIONS SIMILAR TO THOSE OF THE CASTING TO BE PRODUCED, SURROUNDED BY LOOSE UNBOUNDED SAND IN A MOULD BOX. References M. D. Lawrence, C. W. Ramsay and D. R. Askeland, AFS Transactions, Vol.106 (1998) p.349 S. Bennett, T. Moody, A. Vrieze, M. Jackson, D. R. Askeland and C. W. Ramsay, AFS Transactions, Vol.108 (2000) p.795 K. Kim and K. Lee, J. Mater. Sci. Technol., Vol.21 (2005) p.681 N. Gupta, P. C. Maity, S. Choudhury and Santosh Kumar, Indian Foundry Journal, Vol.54 (2008) p.36. METAL Casting Technologies March 2011 25