The selection of the ladle nozzle is a key link in the continuous casting process, directly affecting the control of molten steel flow, the quality of the cast product and production efficiency. The following are the main points for selecting a ladle nozzle:
1. Steel type characteristics and process requirements
Steel type composition:
Low carbon steel/ordinary carbon steel: usually an ordinary aluminium-carbon nozzle is used.
High-oxygen steel (e.g. stainless steel, high-manganese steel): A zirconium carbide (ZrO₂-C) or calcium-treated nozzle with strong oxidation resistance is required to prevent Al₂O₃ blockage.
Titanium/rare earth steel: A magnesium or composite material nozzle with good erosion resistance is selected to avoid reacting with molten steel.
Pouring temperature: A material with high temperature resistance (e.g. high-purity zirconia) is required for high-temperature steel.
2. Nozzle material selection
Aluminum carbide (Al₂O₃-C):
Suitable for most plain carbon steels, low cost, but average erosion resistance.
Zirconium carbide (ZrO₂-C):
High temperature resistance, strong erosion resistance, suitable for high oxygen steel and long cycle casting.
Magnesium carbide (MgO-C):
Used for high alkalinity steel grades (such as calcium treated steel), good slag erosion resistance.
Composite material (e.g. zirconium inside, aluminum outside):
Balances cost and performance, with the inner layer resisting erosion and the outer layer resisting thermal shock.
3. Tuyere structure design
Aperture and shape:
The diameter is selected based on the ladle capacity and pouring speed (typically φ30-80mm). A large aperture is suitable for high-drawing-speed continuous casting.
A flared outlet can reduce turbulence and prevent slag entrainment.
Quick-change vs. fixed:
Quick-change nozzle: reduces changeover time when multiple furnaces are used, but requires a special mechanism.
Fixed nozzle: used in billet casting, simple structure but requires regular replacement.
Anti-blockage design:
argon blowing nozzle (prevents Al₂O₃ deposition), coating treatment or special texture on the inner wall.
4. Continuous casting process parameters
Pouring speed: A high pulling speed requires a large flow nozzle to avoid insufficient molten steel supply.
Protective pouring:
Long nozzles need to be combined with argon sealing to prevent secondary oxidation.
Tundish type:
The symmetrical arrangement of nozzles is required for a two-stream tundish to ensure balanced flow.
5. Thermodynamic and mechanical properties
Thermal shock resistance: The material needs to withstand the impact of molten steel and sudden temperature changes (e.g. preheating to above 1000°C).
Resistance to erosion: Particular attention should be paid to erosion at the slag line (the material can be locally reinforced).
Mechanical strength: Cracking due to installation or thermal stress should be avoided.
6. Economy and maintenance
Life cycle costs: Zirconium nozzles are expensive but have a long lifespan.
Ease of replacement: A quick-change system reduces downtime and is suitable for efficient production.
