Question

Which one of the following casting defects is caused due to the supply of the molten metal through two gates?

• A. Cold shut
• B. Rat tail
• C. Pin hole
• D. Shift

Hint:

Associate casting defects with their root causes: "Cold" in cold shut refers to the metal streams being too cold to fuse. "Gas" defects (like pin holes, blow holes) are from trapped gases. "Sand" defects (like rat tails, scabs) are from mold sand issues. "Shape" defects (like shift, mismatch) are from mold alignment problems.

Answer 1

The Correct Option is A

Mechanism of Cold Shut:
A cold shut is a physical discontinuity (a seam or crack) created when two streams of liquid metal flow from different directions (often via multiple gates) and meet within the mold cavity. If the metal is too cold, or if there is excessive surface oxidation, the two fronts will touch but fail to fuse together into a solid bond. Analysis of Alternatives:

• Rat tail: This is a surface defect caused by the expansion of the sand. It is related to mold properties, not gating flow meeting points.
• Pin hole: These are tiny gas bubbles caused by hydrogen or moisture. This is a metallurgical/gas solubility issue.
• Shift: This is a dimensional defect caused by the misalignment of the cope and drag flasks.

Therefore, only Cold Shut is directly related to the intersection of two metal flow streams.