Quality Control of Refractory Bricks in Steelmaking

Original Language: French

The Challenge

Steelmaking refractories operate under brutal conditions: extreme temperatures, chemical attack from molten metal and slag, and repeated thermal cycling. For years, sonic testing had been used reactively—detecting cracks after thermal shock damage occurred. But the real value lay in understanding what the elastic modulus measurement could reveal about a brick before it went into service.

The question was whether modulus readings could predict other physical properties, enabling rapid non-destructive screening to replace slow destructive testing.

The Solution

Petit’s comprehensive study at Sollac tested refractory batches from three different suppliers, building distribution histograms and searching for linear correlations between elastic modulus and other physical characteristics.

The physics supports this approach: elastic modulus corresponds to the initial slope of the stress-strain curve—a fundamental property that integrates information about porosity, grain bonding, and microstructure. Sonic methods measure this property more easily and accurately than static mechanical tests, either through continuous vibration at variable frequency or through impulse excitation.

Results

The research established clear correlations between modulus readings and the physical properties that determine service performance. Production batches showed characteristic distributions, enabling statistical quality control through rapid sonic measurement.

For steelmakers, sonic testing evolved from a damage-detection tool to a predictive screening method. It complements traditional inspections for standard applications and becomes essential for critical components where reliable service performance is non-negotiable. A brick’s modulus reading now provides meaningful quality information before installation rather than damage evidence after failure.