Answer:
The disadvantages of slow casting rate in the production of metal by casting are:
1. Solidification of metal may start even before the mould is completely filled which may produce defects like misruns and shrinkage capacity as shown in the attachment.
So slow casting rate will produce incomplete and partial casting
2. Slow casting rate will produce casting which have a coarse grain structure which in turn affects the strength of the casting adversely.
3.It causes higher production time for production of casting which in turn increase high labour cost per casting.