الفهرس 
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Abstract
Risers are used in the production of casting for the purpose of providing molten metal for the solidifying and shrinking castings requires, at a minimum that the riser solidify after the casting. The most important aluminum foundry alloys are based on the Al-Si system, especially the hypo – eutictic alloys with compositions ranging from 7 to 11 wt.% Silicon . In the present work blind riser of elliptical and spherical shapes were used in the casting of ”L” and ”T” sections of two different sizes.
The ratio between the casting modulus to the riser modulus was studied. William`s core was also used to study the effect of applying pressure on the quality of Al-Si alloy. The results showed that the position of the riser and the volume of riser influence significantly the soundness of the Al-Si casting.
The casting of ’L section with large size showed sound casting when blind elliptical riser is used , and when the pouring gate was placed beside the riser and relative modulus was 1.5. Also the proportion of feed metal available from the feeder which meets the modulus %C (coefficient related by riser type) was 9.7.
Sound casting for ’L’ section of small size was observed when the spherical riser with relative modulus 1.0 was used and %C was 8.4. Using the spherical riser in this case leads to save the material by 20%.
The casting of ’T’ section with large size showed sound casting when blind elliptical riser is placed either the riser was placed between the pouring gate and the casting , or beside the casting. On using the spherical riser sound casting , or beside the casting was obtained when the riser was placed between the pouring gate and the casting and relative modulus of the spherical riser was 1.6. Also the proportion of feed metal available from the feeder which meets the modulus 5C WAS 10.2 . The relative modulus of the spherical was 1.4. Also the proportion of the feed metal available from the feeder which meets the modulus %C was 13.889.
Sound casting for ’T’ section of small size was observed when the blind elliptical riser was used with relative modulus 1.3 was used and the %C was 3.764.