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In this study, different melt treatment operations were evaluated and compared to end product's scrap rate using bifilm index (BI) method. Results clearly show that degassing with finer gas bubbles increases cleaning performance for the removal of any type of bifilms in the melt. BI method is a reliable and quick way to determine melt quality at any given time during casting process which is found to have a direct correlation with rejection rate. [ABSTRACT FROM AUTHOR]

In this work, commercially available Al-7Si alloy was used, and the microstructure was modified by the additions of AlSr15, AlTi5B1, and Al3B. Cylindrical samples were cast into a sand mold and the machinability of the alloys was characterized by means of surface roughness, chip morphology, and buildup edge of the chips. Tool life and surface finish can be improved by decreased chip size by lowering the energy required for machining. The surface finish is an indicator of the quality of the material during the machining process. Therefore, in addition, melt quality was measured by means of reduced pressure test and the calculation of the bifilm index was used to compare the melt quality with machinability. It was found that there is a good correlation between bifilm index and surface roughness of the machined parts. Thus, for a better surface finish, melt quality, which can be quantified by bifilm index, has to be high. AlSr15 modified alloy exhibits the lowest built-up edge with the lowest surface roughness, because strontium modification causes coarse silicon crystals to transform to fine fibrous structure, which enhances machinability. [ABSTRACT FROM AUTHOR]

Aluminium and its alloys have been widely used in the automotive industry for some time and A356 is one of the most popular aluminium alloys today in the sector. It contains approximately 7 wt.% Si and 0.3 wt.% Mg. Due to the defects that may be present in the cast parts, expected mechanical properties may not be reached and this alloy may perform in service under its potential. In a low pressure die casting, several precautions have to be taken in order to produce high quality and defect-free castings. Temperature of casting and the schemical composition of the melt is recorded continuously. Die temperature, pressure levels and their durations are optimized; degassing and fluxing operations are performed. Yet, regardless of the precautions, there could still be rejected parts. It is becoming clear that a good quality raw material is one of the most underrated points of the industry and that the starting material has a great effect on the final product and it should be taken in to account more seriously. Therefore, regarding the first rule of Campbell's 10 Rules of Casting, in this study, the quality of the starting material of supply chains for a wheel manufacturer was investigated. Chemical compositions were compared, fluidity tests, mechanical tests and bifilm indexes of these various sources and ingots were measured and a final quality index was proposed to create a reference for the quantification of quality of supplier's ingots. This new index was compared with the rejection rates. [ABSTRACT FROM AUTHOR]