Centrifugal Casting Process Variables  and  Casting Quality

Once the particular process has been  established,  the main variables con‐trolling  casting  quality are speed of rotation, pouring  temperature,  pouring speed and mold  temperature.  Their individual significance can  be  briefly summarized:

Speed of Rolation‐The main factors influencing  speed  selection were dis‐cussed in detail. However,  the  governing factor in true centrifugal casting is  retention  of the bore shape against gravity while  still  avoiding longitudi‐nal tearing and stresses  during  the accelerated solidification of the molten  metal  against the mold face. Rotational speed also  exerts  a marked influ‐ence upon metal structure,  the  most common effect of increased speed being  to  promote grain refinement although this can also  be  brought about from turbulence induced by  instability  of the liquid mass at very low speeds. A  good  judgment is to use the highest speed of  rotation  possible without encountering hot tearing.

• Pouring Temperature‐Pouring temperature  exerts  a major influence on the mode of  solidification.  Low temperatures are associated  with  maxi‐mum grain refinement and with  equiaxed structures, while higher  tempera ‐tures promote columnar growth in  many  alloys; however, practical consid‐erations  limit  the available temperature range. The  pouring  temperature must be sufficiently high  to  ensure satisfactory metal flow and freedom  from  cold laps while still avoiding coarse  structures  and the increased risk of hot tearing  due  to excessive superheat