Microstructure, SDAS and Mechanical Properties of A356 alloy Castings Made in Sand and Granulated Blast Furnace Slag Moulds

Abstract

Investigations were carried out to ensure the granulated blast furnace (GBF) slag as an alternative mould material in foundry industry by assessing the cast products structure property correlations. Sodium silicate-CO2 process was adopted for preparing the moulds. Three types of moulds were made with slag, silica sand individually and combination of these two with 10% sodium silicate and 20 seconds CO2 gassing time. A356 alloy castings were performed on these newly developed slag moulds. The cast products were investigated for its metallography and mechanical properties. Results reveal that cast products with good surface finish and without any defects were produced. Faster heat transfers in slag moulds enabled the cast products with fine and refined grain structured; and also, lower Secondary Dendrite Arm Spacing (SDAS) values were observed than sand mould. Slag mould casting shows improved mechanical properties like hardness, compression, tensile and impact strength compared to sand mould castings. Two types of tensile fracture modes, namely cleavage pattern with flat surfaces representing Al−Si eutectic zone and the areas of broken Fe-rich intermetallic compounds which appear as flower-like morphology was observed in sand mould castings. In contrast, GBF slag mould castings exhibit majority in dimple fracture morphology with traces of cleavage fracture. Charpy impact fractured surfaces of sand mould castings shows both transgranular and intergranular fracture modes. Only intergranular fracture mode was noticed in both GBF slag and mixed mould castings.

Challenges and Future Prospective of Alternative Materials to Silica Sand for Green Sand Mould Casting: A Review

“…The high mould temperature of blast furnace slag mould indicates high thermal conductivity. Thus, secondary dendrite arm spacing in A356 alloy casting by silica sand mould and blast furnace slag mould is 42 and 31 lm, respectively [87,117]. Therefore, the hardness, impact, compressive, and tensile property of blast furnace slag mould casting is higher than silica sand mould [118].…”

A Study on the Suitability of Mahanadi Riverbed Sand as an Alternative to Silica Sand for Indian Foundry Industries

“…The new sources not only reduce the cost of casting products but also meet the scarcity of silica sand. Researchers and scientists are investigating the feasibility of industrial waste such as fly ash [4][5][6][7][8], ferrochrome slag [9,10], blast furnace slag [11][12][13][14], riverbed sand [15], and red mud [16] as an alternative to silica sand for sand mold casting process. On the other hand, some of the foundry industries are far away from the location where the silica sand having high SiO 2 content is available and they pay higher transportation costs, leading to an increase in the price of sand-casting products.…”