Definition and appearance
The vibration mark is convex, the billet surface is wrinkled, slag is sticky, there are tiny cracks under the skin, and in severe cases, there is a lap phenomenon. There are horizontal folding marks on the billet surface, and in severe cases, there are horizontal cracks.
Causes and hazards
(1) The suspension inside the crystallizer causes the solidified shell to tear. Due to the strong cooling of the crystallizer, the molten steel leaked at the tearing point immediately solidifies on the surface to form folding marks.
(2) Improper crystallizer vibration parameters.
(3) The crystallizer is poorly lubricated, and the billet shell is bonded to the copper wall.
(4) The arc of the crystallizer outlet and the secondary cooling section is poor.
The valley part under the vibration mark is distributed with a large number of microscopic cracks. The cracks are oxidized at high temperature to form iron oxide inclusions. This results in the inability to weld the cracks during the rolling process, and scarring and block falling appear on the rolled material.
Prevention and elimination methods
(1) Reduce the negative slip rate and optimize the crystallizer vibration parameters.
(2) Adjust the physical and chemical properties of the mold protection slag, improve lubrication, and reduce the mechanical force between the ingot and the mold.
(3) Strictly align the mold outlet with the secondary cooling section.
