Forming pressure: machine moulding (dry pressing) of a dry refractory mix typically requires compaction pressures of the order of how many kg/cm²?

Introduction / Context:
Dry pressing is a common forming method for refractories and ceramics where little or no water is added. Achieving sufficient green density and strength demands very high uniaxial compaction pressures, especially with fine powders and minimal plasticizers.

Given Data / Assumptions:

• Dry, granular/powder mix with minimal moisture.
• Uniaxial or isostatic pressing context in refractory manufacture.
• Typical industrial equipment capabilities.

Concept / Approach:
Green density scales with applied pressure, particle size distribution, and binder content. For dry pressing, pressures are often in the range of hundreds to over a thousand kg/cm² to achieve target densities before firing. In many textbook and exam references, “of the order of 1000 kg/cm²” is quoted for machine moulding of dry refractory mixes.

Step-by-Step Solution:
Recall standard pressure ranges for dry pressing: high hundreds to ~1000+ kg/cm².Select the closest order-of-magnitude figure among the options.Choose 1000 kg/cm² as the representative pressure.

Verification / Alternative check:
Process handbooks cite pressures from 700 to 1500 kg/cm² for dense shapes and tiles; isostatic pressing can achieve even higher equivalent compaction.

Why Other Options Are Wrong:

• 10 or 100: far too low for dry pressed refractories.
• 500: sometimes used, but the commonly taught representative “order of” value is ~1000.
• 2500: above typical machine-moulding norms and closer to specialized isostatic/ultra-high-pressure methods.

Common Pitfalls:
Confusing wet (plastic) forming pressures with dry pressing; underestimating pressure needed for low-moisture compaction.

Final Answer:
1000