Continuous Casting Process-11. Why is the nozzle blocked during pouring?

Continuous casting machine

In the continuous casting process, the tundish nozzle and the immersion nozzle are often blocked. The lighter ones need to burn oxygen, the more serious ones will interrupt the pouring and stop production. Clogged nozzles are often a headache for operators.

There are two reasons for the clogging of the nozzle:

One is that the nozzle froze to death. This is caused by the low temperature of the molten steel, the unbaked nozzles, and the condensation of the molten steel. Properly increase the temperature of molten steel and strengthen the baking of the tundish.

The second is that the deposits on the inner wall of the nozzle cause the nozzle to be narrow and even blocked, which is more serious when casting aluminum-killed steel.

The analysis of the nozzle blockage revealed that the main composition of the blockage was a mixture of glass phase and metallic iron with Al203 as the main body. The melting point of Al203 is as high as 2050C, and it exists as solid particles in molten steel. There are a large number of suspended Al203 inclusions in the molten steel, and there is a layer of molten glass on the inner wall of the nozzle. When the molten steel flows through the nozzle, solid Al203 is gradually deposited on the nozzle wall.

There are four sources of Al203 inclusions in molten steel:

One is the product of the reaction between aluminum in molten steel and the refractory material of the nozzle;

The second is the product of the reaction between oxygen in the air and aluminum in the steel;

The third is the deoxidation product of molten steel;

The fourth is the product formed when the temperature of molten steel decreases.

It can be said that the clogging of the nozzle is the result of the combined effect of the above four phenomena.

Therefore, it is very important to choose a product with a quality process. You can also leave your valuable comments, how can we avoid such problems?

E-mail: saleswn@hanrm.com

Daisy Zhai