Casting defects · pouring

Cold shut casting defect

A cold shut is a seam where two streams of metal met but did not fuse. It reads like a crack, but the cause is temperature and filling, not stress.

By Versatile Equipments Pvt Ltd · equipment manufacturer & calibration provider · updated 2026-07-15

What it is

A cold shut is a linear discontinuity with smooth, rounded edges, formed where two fronts of metal met without fusing - each had cooled and skinned over before they touched. It often appears where flows converge on the far side of a core or at the last area to fill.

Cold shut, crack or misrun?

A crack (hot tear or cold crack) has ragged edges and comes from contraction stress; a cold shut has rounded edges and comes from cold, late-meeting metal. A misrun is the same cause taken further - the metal did not just fail to fuse, it failed to fill. Cold shut and misrun usually share a fix.

Root causes

• Low pouring temperature. Metal skins over before the fronts meet.
• Slow or interrupted pouring. Hesitation lets the leading front chill.
• Thin sections and long flow paths. Metal loses heat before it fuses.
• Gating that splits the stream so two cold fronts converge.

Prevention checklist

• Pour hot enough and fast enough for the section; hold pouring temperature under control.
• Gate to fill thin sections first and to avoid two fronts meeting cold.
• Reduce flow length to thin features; add ingates where the last-to-fill area needs hotter metal.
• Keep pouring steady - no hesitation once started.
• Track cold shuts by part and location; a recurring seam usually names a filling problem in the method.

Frequently asked questions