Key Takeaways
- 1A tundish is the vessel between the ladle and the mould in continuous casting, and it isn't lined with just one material, it has multiple distinct layers, each doing a different job.
- 2The permanent lining protects the steel shell of the tundish and stays in place across many casting sequences, while the working lining is the layer that actually touches the molten steel and gets renewed far more often.
- 3Tundish spraying mass is a fast, sprayed-on way to apply or refresh the working lining, chosen when speed of application and even coverage matter as much as final lining performance.
- 4Getting the working lining wrong, or skipping proper maintenance of it, shows up directly in steel cleanliness, since it's the one layer in constant contact with the metal throughout the sequence.
- 5Because the working lining is consumed and replaced on a cycle tied to casting sequences, choosing a spray mass actually rated for that duty, not just "high temperature" generically, is what determines how many sequences you get before problems start.
What Are the Different Refractory Zones in a Tundish?
A tundish, the vessel that sits between the ladle and the mould in continuous casting, has at least two distinct refractory zones doing entirely different jobs: a permanent lining that protects the steel shell across many campaigns, and a working lining that's in direct contact with molten steel and renewed on a cycle tied to casting sequences. Treating "tundish refractory" as one product, rather than two zones with different duty cycles, is a common source of confusion when specifying materials or planning turnaround time between sequences.
Quick answer: The permanent lining sits against the tundish's steel shell and is changed infrequently. The working lining is the layer actually touching molten steel, renewed far more often, and can be applied by board, dry-vibe, trowel or spraying. Tundish spraying mass (our TRLlite-87/75 grade: MgO 70-75%, sinters at 750°C, max service 1650°C) is one working-lining application method, chosen specifically when speed and even coverage across an irregular tundish shape matter.
Permanent Lining vs Working Lining: Different Jobs, Different Materials
| Zone | Job | Change frequency |
|---|---|---|
| Permanent lining | Protects the steel shell from the working lining's own installation and service heat | Many casting campaigns |
| Working lining | Direct molten steel contact, governs steel cleanliness | Tied to casting sequence, renewed far more often |
The permanent lining isn't in metal contact under normal operation, its job is thermal and mechanical protection of the shell itself. The working lining is what actually determines steel cleanliness, since it's the one surface in constant contact with the metal for the full duration of every sequence. Specifying the permanent lining to a high standard while treating the working lining as an afterthought, or the reverse, misses that these two zones are solving different problems.
What Is Tundish Spraying Mass and When Is It the Right Application Method?
| Property | TRLlite-87/75 |
|---|---|
| MgO | 70-75% |
| Fe₂O₃ | 4-7% |
| SiO₂ | 14-18% |
| Bulk density, dried 110°C | ≤1850 kg/m³ |
| Bulk density, fired 1525°C/3h | ≤1900 kg/m³ |
| Sintering temperature | 750°C |
| Max service temperature | 1650°C |
Spraying mass is chosen as a working-lining application method when speed of application and even coverage across an irregular tundish shape matter as much as the lining's final performance. Spraying can cover a tundish's working-lining area faster than board installation or trowel application, which translates directly into shorter turnaround time between casting sequences. The chemistry itself, an MgO-based, iron-oxide and silica-bearing mix, is formulated to sinter at a workable 750°C so the sprayed layer bonds into a coherent lining before it sees molten steel, while still holding up to a 1650°C max service temperature during casting.
SAPL Supply for Tundish Refractories
Why this matters: a tundish working lining specified by "high temperature rating" alone, without matching chemistry and application method to your steel grade and turnaround schedule, is a common reason for inconsistent steel cleanliness between sequences on the same caster.
Shanker Agencies supplies tundish spraying mass for continuous casting working linings. Tell us your tundish capacity, steel grade and turnaround time between sequences, and our engineering team will confirm the right working-lining application method and grade.
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Frequently Asked Questions
What are the different refractory zones in a tundish?
A tundish has at least two distinct refractory zones doing different jobs. The permanent lining sits against the steel shell and protects it across many casting campaigns, changed infrequently. The working lining is the layer in direct contact with molten steel, renewed on a cycle tied to casting sequences since it's the layer actually consumed by metal contact and erosion. Confusing the specification of one for the other is a common cause of unexpected tundish lining failure.
What is tundish spraying mass and when is it used instead of other working lining methods?
Tundish spraying mass is a working lining material applied by spraying rather than by board, dry-vibe, or trowel application. It's chosen when speed of application and even coverage across an irregular tundish shape matter, spraying can cover a tundish faster than boards or trowel application, which matters directly for turnaround time between casting sequences.
What is a typical spray mass chemistry and service temperature?
Our TRLlite-87/75 grade is MgO-based (MgO 70-75%, Fe₂O₃ 4-7%, SiO₂ 14-18%), sinters at 750°C and is rated to a maximum service temperature of 1650°C. The sintering temperature matters separately from the max service temperature, it's the temperature at which the sprayed layer bonds into a coherent working lining before it sees molten steel.
Does the working lining need replacing after every casting sequence?
This depends on sequence length, steel grade and tundish design rather than a fixed rule, some working linings are refreshed between every sequence, others hold up for multiple sequences before a full respray or reline is needed. What's consistent is that the working lining is the layer expected to wear on a defined cycle, unlike the permanent lining behind it, which is not expected to need attention on anything like the same schedule.
Can the wrong spray mass chemistry affect steel cleanliness?
Yes, directly. The working lining is the one refractory surface in constant contact with the molten steel throughout the sequence, so its erosion resistance and inertness toward the specific steel grade being cast has a direct bearing on inclusion pickup and steel cleanliness. Specifying by "high temperature rating" alone, without matching chemistry to the steel grade, is a common gap.
How is tundish spraying mass different from a tundish board?
Both can serve the working lining role, but installation method and turnaround differ. Board is a preformed, rigid lining component installed by placement, while spray mass is applied wet or semi-wet by spraying equipment. The choice between them typically comes down to tundish geometry, turnaround time available, and site equipment, rather than one being universally better than the other.