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Analysis on longitudinal crack of continuous casting billet by technical department and its countermeasures
Mar 20, 2018

The causes and characteristics of longitudinal cracks in continuous casting billet the longitudinal crack on the surface of continuous casting slab is the crack on the surface of continuous casting slab along the direction of the billet, mainly including the longitudinal crack of the face and the longitudinal crack of the corner. The longitudinal crack in the slab is more than the central position of the wide surface, the square billet occurs at the edges and corners more. Surface longitudinal cracks directly affect billet quality. After observation, it is found that the longitudinal crack has the following characteristics:

(1) compared with the crack-free part, the crack zone has thin and equiaxed crystal structure. 

(2) The thinner the quench layer, the greater the crack depth. 

The main cause of longitudinal crack is the uneven thickness of the primary billet shell due to the uneven cooling strength in the mold, the stress concentration in the thin shell of the billet, and the crack when the stress exceeds the tensile strength of the billet shell. 

Second, how to prevent the continuous casting billet longitudinal cracks to prevent continuous casting slab longitudinal cracks is the key to the meniscus surface of the birth shell uniformity, to this end should take measures: 

(1) The mold using a reasonable taper, and the best cavity shape of the copper tube or copper, as far as possible to make the mold heat flux uniformity. 

(2) Selection of protective slag with good performance. 

(3) The outlet inclination and insertion depth of the immersed nozzle should be suitable, the installation should be correct, and the flushing of the casting billet shell should be reduced, and the growth uniformity will be made. 

(4) Determining the reasonable pouring temperature and the casting speed according to the cast steel.

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