Selection of basic refractories for steelmaking: Magnesite (MgO) bricks are best suited for lining those furnace zones which primarily need which performance characteristic?

Introduction / Context:
In steelmaking and non-ferrous metallurgy, slag chemistry dictates refractory choice. Basic refractories like magnesite (MgO) and dolomite are selected where basic oxide slags are present. Knowing the primary advantage of MgO bricks helps avoid premature lining failures.

Given Data / Assumptions:

• Material: magnesite brick (basic refractory).
• Service environment: contact with basic slags rich in CaO and MgO.
• Goal: identify the chief benefit that motivates choosing MgO.

Concept / Approach:
Refractory “basicity” should match slag basicity to minimize chemical dissolution. Magnesite bricks have excellent resistance to attack by basic slags and are therefore preferred in basic oxygen furnaces, EAF slags, and cement kilns with basic conditions. While MgO bricks can handle high temperatures, their standout attribute is chemical compatibility with basic slags.

Step-by-Step Solution:
Match slag chemistry to refractory chemistry: basic with basic.Identify magnesite's forte: chemical resistance against basic slags.Select the option highlighting resistance to basic slag.

Verification / Alternative check:
Industry practice places MgO linings in converter slags; silica or high-alumina bricks would be rapidly corroded by CaO-rich slags.

Why Other Options Are Wrong:

• Thermal cycling resistance: not the primary reason for MgO selection.
• High mechanical load: many refractories can handle load; chemistry is the key differentiator here.
• None of these: incorrect, as basic slag resistance is central.

Common Pitfalls:

• Overvaluing generic “strength” over chemical compatibility with slag.
• Using acidic refractories in basic environments, leading to rapid wear.

Final Answer:
resistance to corrosive basic slag