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What is Nozzle X?

2025.9.25

Nozzle X, often simply called “casting sand” or “opening material,” is a refractory granular material specifically used in the sliding gate system between the ladle (the container holding molten steel) and the tundish.

Its primary placement is inside the upper nozzle (fixed at the bottom of the ladle) and the cavity above it. When the ladle needs to pour molten steel into the tundish, the sliding gate mechanism opens the steel flow channel. The opening material flows out first, utilizing its unique physical and chemical properties to “guide” a clear path for the subsequent flow of molten steel.

Simply put, it is a key functional material in modern continuous casting processes that ensures the ladle can open for casting safely, controllably, and smoothly.

2. Primary Functions

1. Automatic Casting Start: This is the core function. The opening material guides the molten steel to flow out automatically from the ladle nozzle, avoiding dangerous operations like oxygen lancing to open the nozzle, thereby improving operational safety and automation.

2. Preventing Steel Solidification: During the waiting period before casting, molten steel in contact with the inner wall of the upper nozzle rapidly cools and solidifies, forming a “cold steel” plug. The opening material fills the nozzle, isolating the molten steel from direct contact with the refractory material of the nozzle, effectively preventing the formation of such plugs.

3. Protecting Nozzle Refractory Material: High-quality opening material can reduce erosion and wash on the nozzle’s inner wall, extending the nozzle’s service life.

3. How It Works

The automatic casting start function relies on its unique property of “sintering at low temperatures, melting at high temperatures.”

1. Filling and Preheating Stage: Before the ladle receives molten steel, dry opening material is filled into the upper nozzle and the well block cavity above it. After the ladle receives the hot molten steel, the opening material is heated.

2. Sintered Layer Formation Stage: The surface layer of the opening material (about 10-30mm) near the nozzle wall and in contact with the molten steel at the bottom sinters at relatively low temperatures (around 1100°C – 1400°C) to form a domed shell with a certain strength. This sintered layer is crucial. It acts like a small cap, capable of withstanding the static pressure of the liquid steel above, temporarily “holding back” the steel and preventing automatic leakage.

3. Casting Start Stage: When casting is required, the operator opens the sliding gate. The lower slide plate moves away, opening the nozzle channel.

At this point, the loose, unsintered opening material below the sintered shell flows out first.

The sintered shell loses its underlying support and is **crushed or melted through** under the static pressure of the molten steel.

The molten steel then flows smoothly through the channel created by the outflowing opening material, achieving automatic casting start.

4. Key Performance Requirements

1.  **Good Sinterability:** Ability to form a sintered layer with moderate strength within a specific temperature range. This is the core requirement for successful automatic casting start.

2.  **Appropriate Fluidity:** Dry and loose, able to fill all corners of the nozzle smoothly without leaving voids.

3.  **High Refractoriness:** Able to withstand prolonged contact with high-temperature molten steel without completely melting.

4.  **Chemical Stability:** Does not undergo harmful chemical reactions with the molten steel or nozzle refractory materials.

5.  **Low Moisture Content:** Must be kept dry (typically required <0.5%). Otherwise, moisture encountering hot molten steel can vaporize instantly, causing a dangerous steel splash explosion.

5. Usage Methods and Precautions

1.  **Filling:** After ladle preheating and before it is positioned to receive molten steel, a specified amount of opening material is filled into the upper nozzle using specialized tools.

2.  **Filling Amount:** Must be sufficient to ensure a thick enough sintered layer forms. Typically, it fills the upper nozzle and forms a small cone above it.

3.  **Dry Storage:** Must be stored in a dry environment, containers should be opened just before use, and damp material must never be used.

4.  **Compatibility with Steel Grade:** Different steel grades have different temperatures and compositions, requiring the selection of the appropriate type of opening material. For example, high-manganese steel must use chromite-based sand.

• Summary

Although a small consumable, ladle tundish opening material is an indispensable “key link” in modern continuous casting steelmaking. Its performance directly affects the smooth operation, safety, steel quality, and production efficiency of the casting process. By carefully formulating its composition and controlling its sintering properties, a near-100% automatic casting start rate can be ensured, providing a solid foundation for efficient and automated steel production.