Size effect in cast-in insertion process

Abstract

In the cast-in insertion process, the thermal conditions necessary for good bonding have been estimated by volume ratio. However, even with the same volume ratio, the bonding state varies with the size of the insert and the casting as well as with the location of the insert in the casting. Estimates of the effects of these geometrical conditions are useful to improve ease and reliability of this process. This study performed solidification analysis together with experiments to explain the size effect in cast-in insertion, and the results are discussed and compared. The model used in the study is a hollow cylindrical ductile iron casting and a mild steel ring insert located at the bottom of the cylinder. The standard size is about 80mm in diameter and height, and the scale was varied from 0.33 to 3 times the standard size for three volume ratios, 20, 25, and 30. The periods where the insert is in contact with liquidus melt (liquidus period) obtained by calculations were compared as the thermal condition. The calculations showed that, the liquid contact time is longer for larger sizes until about twice the standard size, but that it then decreases rapidly with even larger sizes. This is because the thick solidified layer formed by the large cooling effect of the insert does not remelt. Large size is not always advantageous to good bonding, and it is necessary to choose volume ratios suitable to the size of a casting.

Keywords:

• Cast-in insertion
• bonding
• size effect
• solidification analysis
• finite different method