Among common refractory types, which brick typically has the lowest firing temperature window (about 1250–1400°C) during manufacture?

Introduction:
Refractory manufacturing requires firing the green body to develop desired phases and strength. Different chemistries need different peak firing temperatures. Knowing these ranges helps in cost estimation and quality control.

Given Data / Assumptions:

• Fireclay: alumino-silicate composition.
• Silica, magnesite, and direct-bonded basic bricks typically demand higher firing temperatures to achieve strong bonding.
• Target window named: 1250–1400°C.

Concept / Approach:
Fireclay bodies sinter effectively at lower temperatures than pure silica or basic (MgO-rich) systems. Direct-bonded basic bricks especially require higher temperatures to develop direct periclase or spinel bonding.

Step-by-Step Solution:
Compare typical firing windows: fireclay ~1250–1400°C.Silica bricks often >1400–1500°C to stabilize cristobalite/tridymite bonding.Magnesite/basic bricks require still higher temperatures.Hence the minimum window given corresponds to fireclay.

Verification / Alternative check:
Manufacturers’ datasheets and handbooks align with these firing ranges for standard grades.

Why Other Options Are Wrong:

• Direct-bonded basic/magnesite/silica: need higher peak temperatures to densify properly.
• Chromite often fired higher than fireclay for adequate bonding.

Common Pitfalls:
Confusing service temperature capability with firing temperature; basic bricks may work at higher service temperatures but also require hotter firing during manufacture.

Final Answer:
Fireclay brick