Refractoriness/fusion point classification: ‘‘Superduty’’ refractories fall in which fusion temperature range (°C)?

Introduction / Context:
Duty classifications (medium, high, superduty) help users quickly match refractories to service temperatures. ‘‘Superduty’’ indicates the highest class among common siliceous/aluminosilicate refractories, associated with very high softening/fusion behavior under standard tests such as PCE/Seger cones.

Given Data / Assumptions:

• PCE cone > 33 aligns with ‘‘superduty’’ class.
• Equivalent temperatures are approximate but standardized for comparison.
• We pick the range that correctly represents superduty behavior.

Concept / Approach:
Superduty refractories exhibit fusion points exceeding about 1730°C, allowing duty in severe, continuous high-temperature operations. Options with lower ranges correspond to lower duty classes and do not meet superduty thresholds, while a blanket ‘‘> 2000°C’’ is too restrictive for the class definition.

Step-by-Step Solution:

Verification / Alternative check:
Correlation tables used in refractory datasheets confirm that superduty aligns with temperatures above 1730°C.

Why Other Options Are Wrong:

• 1520–1630 and 1630–1670°C: Too low for superduty.
• > 2000°C: Exceeds typical superduty threshold; applies only to elite oxide refractories.

Common Pitfalls:
Equating ‘‘superduty’’ with absolute highest melting oxides; the term is specific to established PCE-based classes.

Final Answer:
> 1730