The capacity of a refractory to take fast heating or cooling without cracking. It improves with low thermal expansion, high conductivity, a network of controlled microcracks and additions such as graphite, silicon carbide or andalusite. It is tested by repeated water or air quench cycles, or by measuring strength retained after cycling. Ladles, kiln furniture, burner blocks and anything fired in short cycles depend on it.
Burner blocks crack every restart, we need a grade with better thermal shock resistance, not more strength.
Strength and thermal shock resistance often pull in opposite directions; the densest, strongest grade is rarely the one that survives fast cycling.
Also heard as
- spalling resistance
- TSR
Related terms
Spalling
Cracking off of pieces or layers from the hot face of a refractory lining.
Silicon carbide
Hard, highly conductive refractory used where abrasion, thermal shock and heat transfer all matter.
Magnesia-carbon brick
Resin-bonded brick of magnesia and graphite, the workhorse lining of BOFs, electric arc furnaces and ladle slag lines.
Grog
Pre-fired clay or crushed brick added as aggregate to cut shrinkage and cracking in refractory bodies.