Based on the intermediate cracks in continuous casting Q235B steel 230 mm slab produced by LD-Ar route

a series of analyses the macroscopic and microscopic characteristics in intermediat cracks are done by optical microscope

SEM and EDS. The results show that irregular arc of segments and low precision of roll gap as well as misalignment of the supporting rollers are the outer causes of forming and extending in intermediate cracks

and coarse grains and serious element segregations such as manganese

sulfur and complex inclusion compound accumuleted at the crack band are the inner causes of producing intermediate cracks. With the process measures including control segments arc ≤ ±0.3 mm

roll gap ≤ ±0.5 mm

secondary cooling water ratio 0.50 L/kg

[S] ≤0.030%

[Mn]/[S]≥15

it is available to decrease and avoid the occurrence of the cracks. As a result

the quality of the slab center quality is enhanced.