Continuous Casting Defects

Continuous casting transforms liquid steel into solid slabs, blooms, or billets at remarkable speed — a typical slab caster processes 100–300 tonnes per hour. But the solidification process is complex: liquid steel contracts on solidification, heat must be extracted uniformly from a moving strand, and the strand must support its own weight through the support rolls while still partially liquid inside. Any disruption to this precisely balanced process produces defects that may render the product unsaleable, require expensive surface conditioning, or — in the worst case — cause a catastrophic breakout.

Understanding casting defects is essential for both caster operators and downstream processors: hot rolling can worsen some defects (opening surface cracks into seams) or reveal internal defects that were invisible in the cast strand. Automotive and energy customers increasingly require process capability data and defect tracking from caster to finished product.

Continuous casting defects fall into four broad categories: surface defects (visible after casting or after rolling), subsurface defects (just below the skin, revealed by pickling or grinding), internal defects (porosity, segregation, cracks in the strand interior), and shape defects (rhomboidity, bulging, laps). Each category has characteristic causes and specific process levers for prevention.