Steel teeming practice: the slide gates in teeming ladles used for pouring steel into ingot moulds are typically lined with which refractory material?

Introduction / Context:
Teeming ladles deliver molten steel through controlled slide gates. The plates and nozzle regions experience severe thermal shock, erosion, and chemical attack by steel and slags. Correct refractory selection is essential to minimize wear and ensure consistent casting performance.

Given Data / Assumptions:

• Slide gate components require high hot strength, corrosion resistance to basic slags, and thermal-shock tolerance.
• Impregnation (e.g., with phenolic/bakelite) can reduce permeability and enhance durability.

Concept / Approach:
Periclase (MgO) is a basic refractory with good resistance to basic steelmaking slags and high-temperature strength. Fused magnesia offers dense, high-purity microstructures. Phenolic (bakelite) impregnation of shaped parts reduces open porosity, improving erosion resistance and thermal-shock performance. While alumina–graphite systems are common today, the classic exam reference for this question highlights bakelite-impregnated or fused periclase for slide gate lining in teeming service.

Step-by-Step Solution:
Identify service conditions: high temperature + basic slag exposure + thermal cycling.Match chemistry: basic refractory (MgO) is compatible with basic slags.Add impregnation to reduce permeability and spalling.Select “Bakelite-impregnated or fused periclase (magnesia).”

Verification / Alternative check:
Steelmaking literature documents magnesia-based shapes (often with carbon or resin impregnation) in slide gate/nozzle systems, aligning with the stated option.

Why Other Options Are Wrong:

• Silica/semi-silica/fireclay: acidic/neutral linings more vulnerable to basic slags.
• Standard graphite only: excellent thermal shock, but chemical/oxidation limits and design specifics make pure graphite alone atypical as the sole lining material in this location.

Common Pitfalls:
Ignoring slag chemistry when picking slide gate materials; focusing only on thermal shock without considering corrosion and infiltration.

Final Answer:
Bakelite-impregnated or fused periclase (magnesia)