Integral stopper rod is the core flow-control refractory in the continuous casting tundish. Alumina-carbon or magnesia-carbon grades resist thermal shock and erosion with a durable slag line. Argon-blowing structures and rod-head shapes are customized for stable multi-heat flow control.
| Al₂O₃ (Al2O3-C) | 40 – 55% |
|---|---|
| MgO (MgO-C) | ≥ 50% |
| C (carbon bond) | ≥ 15% |
| Bulk density | ≥ 2.40 g/cm³ |
| CCS | ≥ 25 MPa |
| Apparent porosity | ≤ 18% |
| Thermal shock (1100℃ water) | ≥ 5 次 |
Molten steel in the tundish flows into the mould through the upper nozzle. The stopper rod is mounted on the tundish cover with its head against the nozzle bowl. A servo mechanism lifts and lowers the rod, continuously adjusting the gap from fully closed to maximum opening, and thus the steel flow. The rod must stay free after long immersion: the body must not stick to steel, the head must not crack from thermal shock, and the slag line must not erode thin enough to break. Any failure means a casting interruption.
Mainstream stopper grades are Al2O3-C and MgO-C. Alumina-carbon rods use bauxite or corundum aggregate with graphite as the carbon source; excellent thermal shock resistance suits most plain and alloy steel casting and is the most widely used type. Magnesia-carbon rods resist basic slag better and suit aluminium-killed and calcium-treated steels or severe slag-line conditions. Both rely on a carbon-bonded network for conductivity and thermal shock resistance, so anti-oxidation treatment (glaze or coating) is an essential manufacturing step.
The rod-head profile defines the flow regulation curve. Some profiles give a gentle response at small openings for fine adjustment; others give a quick rise at larger openings for high casting speed. The design balances flow-control sensitivity against erosion resistance: too sharp a head regulates finely but wears fast; too blunt lasts longer but cannot stabilize small openings. Rod heads are therefore customized per casting practice - the source of stopper customization.
Modern casting widely uses argon-blown stoppers with an internal gas channel delivering argon to the nozzle area. Argon stirs the steel near the nozzle to prevent clogging, suppresses reoxidation and helps inclusion flotation. The channel must deliver a stable flow without leaking through the body - gas exits around the head into the nozzle. Channel sealing and anti-clogging are key manufacturing difficulties.
Four typical failure paths: thermal-shock cracking, mainly at start-up or during violent temperature swings, destroying sealing; slag-line erosion thinning the body with break risk; oxidation decarburization embrittling the carbon bond; and misalignment or nozzle mismatch causing head eccentric wear and poor closure. Standard practice: full preheating before casting, alignment during installation, controlled temperature swings, and regular checks on body thinning.
Henan Songrui New Refractory Materials Co., Ltd. customizes stopper grades and drawings for steel grades and caster types.
Check the failure location first. Slag-line erosion suggests higher MgO content or slag-line design; head cracking points to preheating practice and temperature swings; body embrittlement indicates oxidation protection or storage issues. Most life problems can be traced from failure location and casting records.
Not necessarily, but they must match. Head-to-bowl mating dimensions and material compatibility (e.g. carbon content and oxidation potential) affect flow stability and life. Use a matched material system within one sequence and keep mating-dimension records.
Flow control still works, but clogging and reoxidation risks rise without argon. Suitable for short sequences or low-demand casting; keep the argon system working and check channel throughput regularly.
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