Manufacture of hollow refractories — Hollow refractory bricks are commonly produced by which forming method?

Introduction:
Shaping methods for refractories include pressing, casting, and extrusion. Hollow bricks require continuous formation of uniform wall sections with internal voids, which strongly favors extrusion using a die configured to produce the desired hollow profile.

Given Data / Assumptions:

• Product: hollow refractory bricks/blocks.
• Requirement: continuous, uniform sections with controlled void geometry.
• Methods listed: slip casting, hand moulding, pressing, extrusion.

Concept / Approach:
Extrusion forces a plastic ceramic body through a die that shapes both external dimensions and internal cavities via mandrels, enabling efficient production of hollow sections (similar to structural clay tile). Slip casting suits complex, thin-walled shapes but is slower and not optimal for regular hollow bricks. Dry pressing is common for dense, solid shapes; creating continuous hollow cores is less practical. Hand moulding lacks precision and throughput.

Step-by-Step Solution:
Match shape to process: long, hollow, uniform → extrusion best.Assess alternatives: pressing and hand moulding are less suitable for continuous hollow cavities.Slip casting: viable for special shapes but inefficient for standard hollow bricks.

Verification / Alternative check:
Refractory production lines for hollow insulating bricks typically use auger extrusion with dies producing multi-hole sections.

Why Other Options Are Wrong:

• Slip casting: slow, mold-dependent; not economical for standard hollow bricks.
• Hand moulding: inconsistent quality.
• Pressing: optimized for solid shapes.

Common Pitfalls:
Overlooking the role of die design in forming internal voids; assuming pressing can easily create longitudinal hollows.

Final Answer:
Extrusion