Pouring Metal Defects
The likely defects in this category are
Mis-runs and
Cold shuts.
A mis-run is caused when the metal is unable to fill the mould cavity completely and thus leaves unfilled cavities. A mis-run results when the metal is too cold to flow to the extremities of the mould cavity before freezing. Long, thin sections are subject to this defect and should be avoided in casting design.
A cold shut is caused when two streams while meeting in the mould cavity, do not fuse together properly thus forming a discontinuity in the casting. When the molten metal is poured into the mould cavity through more-than-one gate, multiple liquid fronts will have to flow together and become one solid. If the flowing metal fronts are too cool, they may not flow together, but will leave a seam in the part. Such a seam is called a cold shut, and can be prevented by assuring sufficient superheat in the poured metal and thick enough walls in the casting design.
The mis-run and cold shut defects are caused either by a lower fluidity of the mould or when the section thickness of the casting is very small. Fluidity can be improved by changing the composition of the metal and by increasing the pouring temperature of the metal.
The likely defects in this category are
Mis-runs and
Cold shuts.
A mis-run is caused when the metal is unable to fill the mould cavity completely and thus leaves unfilled cavities. A mis-run results when the metal is too cold to flow to the extremities of the mould cavity before freezing. Long, thin sections are subject to this defect and should be avoided in casting design.
A cold shut is caused when two streams while meeting in the mould cavity, do not fuse together properly thus forming a discontinuity in the casting. When the molten metal is poured into the mould cavity through more-than-one gate, multiple liquid fronts will have to flow together and become one solid. If the flowing metal fronts are too cool, they may not flow together, but will leave a seam in the part. Such a seam is called a cold shut, and can be prevented by assuring sufficient superheat in the poured metal and thick enough walls in the casting design.
The mis-run and cold shut defects are caused either by a lower fluidity of the mould or when the section thickness of the casting is very small. Fluidity can be improved by changing the composition of the metal and by increasing the pouring temperature of the metal.
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