Steel plant term for a ladle that opens and flows freely when its slide gate is first opened at the caster, because the well filler sand, usually chromite-based, stayed loose instead of sintering. A ladle that fails to free open has to be lanced with oxygen, which delays the cast, oxidizes the steel and damages refractories. Free-opening rate, ideally close to 100 percent, is tracked daily.
Free open rate dropped to 96 percent this week, check the well sand and how long ladles are sitting full.
A ladle that sits full too long sinters its well sand, so holding time matters as much as the sand itself.
Also heard as
- free opening
- self-opening
- free-open rate
Related terms
Slide gate
Valve of sliding refractory plates under a ladle or tundish that controls the flow of molten steel.
Skull
Layer of solidified metal and slag left stuck to a ladle, converter or furnace lining after emptying.
Taphole
Opening through a furnace wall or bottom through which molten metal and slag are drained.