TL;DR
No argon stirring with the valve open means the bottom plug is blocked by solidified steel. Test the plug with a high-pressure purge before labeling it failed; blocked plugs often clear with a brief pressure pulse.
What you might see
- argon stirring flow indicator at zero with valve open
- steel bath not stirring visibly
- ladle chemistry not homogenizing as expected
- back pressure on the argon supply line high
Likely causes
Solidified steel blocking the plug porous element from the previous heat
Plug porous element worn out and sintered closed at end of service life
Argon supply pressure below the minimum required to penetrate the plug
Steel skull built up on the ladle bottom covering the plug opening
Required tools
- Argon pressure gauge
- High-pressure purge capability on the argon supply
- Ladle inspection stand
- LOTO kit for ladle cooling
Safety first
- Never approach the ladle bottom while the ladle holds molten steel. Molten steel contact is fatal.
- Only inspect the ladle bottom plug after the ladle is fully cooled and positioned in an inspection stand.
- Argon is an asphyxiant. Ensure adequate ventilation when working near high-volume argon purge operations.
Procedure
- 1
Verify the argon valve is fully open and the supply pressure is above the minimum specified for plug penetration.[1]
- 2
Apply a brief high-pressure purge pulse (if the ladle is positioned safely) to attempt to clear the blockage.[1]
- 3
If the plug does not clear, do not force excessive pressure that could damage the ladle bottom lining.
- 4
After the heat and ladle cooling to a safe temperature, inspect the plug porous element visually for steel penetration or total blockage.
Warning: Never inspect the ladle bottom plug until the ladle is fully cooled, drained of any steel, and positioned in a safe inspection stand. Contact with residual hot steel is fatal. - 5
If the porous element is blocked with solidified steel, assess whether the block can be drilled out or the plug must be replaced.
- 6
Replace the porous plug element at the ladle relining cycle. Do not attempt to continue heats without effective argon stirring, as steel chemistry will not homogenize.
Sources
Danieli Danieli LF Ladle Furnace / AOD / VOD general technical documentation, Danieli
General ladle furnace bottom plug operation and maintenance procedures (general)
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