The so-called steel leakage refers to the phenomenon that the solidification of the billet shell is not good or the billet shell is broken or leaked due to the action of other external forces, causing the internal molten steel to flow out during the continuous casting or the casting process. Steel leakage is one of the vicious accidents in continuous casting production. Serious steel leakage accident not only affects the normal production of the continuous casting machine and reduces the operating rate, but also damages the casting machine equipment and causes equipment damage.

 

Steel leakage accidents are divided into various forms due to the different time of occurrence and the location of the casting machine, and the reasons for their occurrence are also different, mainly divided into the following points:  

(1) Casting-on steel leakage: Casting started poorly and caused steel leakage.

(2) Suspended steel leakage: large corner cracks in the crystallizer, recessed corner pads or scratches on the copper plate, resulting in increased resistance to billet drawing in the crystallizer, which is prone to hang-up steel leakage.

(3) Cracked steel leakage: severe longitudinal cracks, corner cracks or cracking occurred in the mold shell, which caused steel leakage after exiting the mold. 

(4) Slag leakage: Because the mold slag or foreign objects are wrapped in the localized area of the solidified shell, the thickness of the billet shell is too thin, resulting in steel leakage.

(5) Steel leakage when cutting off the billet: when the drawing speed is too fast, the secondary cooling water is too weak, making the liquid phase cavity too long. After the billet is cut, the center liquid flows out.

(6) Bonded steel leakage: steel leakage caused by the casting billet sticking to the crystallizer wall and pulling off.

 

The statistics of a factory producing 5 million tons of slabs show that the proportion of various types of steel leakage: Casting-on 9.1%, slag inclusion 2.3%, bonding 54.5%, crack 22.7%, drum belly 4.6%, nozzle solidification steel 2.3%, other 4.5%.

 

What are the reasons for steel leakage during casting-on? How to prevent it?

The main reasons for steel leakage during casting-on are as follows:

(1) The cold material in the crystallizer is not placed well, and the ingot head is not plugged.

(2) Start early, start quickly, or increase too fast.

 

In order to prevent the leakage of steel during opening, adequate preparation and inspection should be made before opening. The key points should be noted:

(1) Check the ingot head compaction and cold material stacking situation;

(2) Check the alignment of the nozzle and crystallizer;

(3) Check whether the copper plate of the crystallizer has cold steel and whether the taper is appropriate;

(4) Check whether the second cooling nozzle is smooth and intact;

(5) Understand the fluidity of molten steel, the temperature of molten steel, the baking state of tundish and nozzle, and the quality of protective slag.

(6) The size of the injection flow and the residence time of the molten steel in the crystallizer should be determined according to the cross section of the slab.  

(7) The starting pulling speed is generally maintained at 0.5m / min, and the increase speed is slow (0.15m / min) to prevent the crystallizer liquid level from fluctuating too much.

 

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