The main reason why the steel outlet of converter is perforated
The steel outlet of the converter is a material resistant channel of the converter. When the steel is discharged, the molten steel is injected into the ladle through the outlet. The schematic diagram is shown in figure 1.When the steel outlet brick part is damaged, the molten steel reaches the furnace shell area through the steel outlet brick, and the furnace shell steel plate at the connection of flange plate and furnace shell melts through, so that slag and steel flow out.After the occurrence of steel penetration, it is necessary to add the remaining molten steel into a large quantity of lime slag, the remaining molten steel in the furnace is poured into the ladle from the large furnace mouth to prevent the furnace shell from burning.Because there are no measures to prevent slag from coming out of the steel at the big furnace mouth, the slag steel comes out altogether, and the return of phosphorus from the slag is serious.
FIG. 1 schematic diagram of The converter steel tapping hole
After the steel outlet of the converter passes through the steel, check the outlet channel of the converter, and it can be seen that there is obvious melting loss of the steel outlet brick, and the location of the steel outlet (or steel leakage) is shown in figure 2.
FIG. 2 perforation and leakage of steel outlet
As can be seen from FIG. 2, the specific location of steel penetration is about 200mm to the west of the inner side of the steel outlet.There are some cracks in the whole refractory brick of the steel outlet, and steel leakage is caused by the molten steel passing through the cracks.The number of outlet through the steel occurs between 49 and 105 times.
According to the analysis of the above steel outlet piercing accident of converter, it is found that the main reasons for the steel outlet piercing are as follows:
1. Steel outlet Angle
The steel outlet Angle of converter is usually 0° ~ 15°.Most steel mills in China use 0 ° steel outlet design, xichang 200 tons converter USES 10 ° steel outlet design, 10 ° Angle design of the steel outlet is conducive to shorten the ladle car in the process of steel output, improve the steel output efficiency.However, in the process of converter steel output, the molten steel cannot freely fall in the vertical direction, and the molten steel tilting movement in the channel with an Angle of 10° is subjected to a force toward the back of the furnace, so the friction force of the steel output increases significantly, resulting in an increase in the force of the steel outlet.In the process of steel discharge, the vortex formed by the steel flow rotation will aggravate the erosion of the resistant material, and it is easy to cause a pit in the steel outlet channel.The Angle design of the steel outlet is difficult to be improved.
2, brick damage
The steel outlet brick is close to the inner part of the furnace.With the increase of smelting furnace, the resistant material of the converter body is gradually eroded, and the thickness of the brick is gradually reduced due to the erosion of the large surface behind the converter.In the middle and later period of converter operation, the thickness of the thinnest resistance material in the large surface of converter is only 300 ~ 400mm due to the long-term scouring of molten steel.At this time, the thickness of the brick in the steel outlet is only about 100mm.Under the external force impact of the steel outlet replacement, the brick is easy to crack, the anti-erosion ability of the brick becomes worse.In order to realize the long life of the furnace, the thickness of the steel mouth and the rear large surface was increased to 700 ~ 800mm by means of slag splashing, slag-hanging and patching. At this time, the base brick of the steel mouth of the converter was bonded slag splashing layer and patching material filling layer, and its anti-erosion ability was obviously lower than that of the base brick.
The damage of the block is the fundamental cause of the piercing of the outlet.There is a high risk of incomplete appearance and internal crack in the casing brick of damaged steel outlet.When maintenance is not up to speed, the high-temperature molten steel penetrates from the cracks in the block, and then the molten steel peroxidation occurs. The molten steel peroxidation in the cracks reacts with the magnesium-carbon brick, and the erosion speed will be faster, causing the block to loosen, perforate and damage, as shown in FIG. 3.
FIG. 3 fit of brick and steel outlet
3. Action of void water hammer
In the process of steel production, the bubbles adsorbed on the rough resistant surface float up when the steel is produced, which causes the molten steel to fill the opposite place where the bubbles rise up, resulting in the impact effect and the erosion of the refractory. This phenomenon is called void water hammer.The water hammer action of molten steel has a great influence on the penetration of the steel outlet. Once the penetration of the steel outlet occurs, the brick is basically in a damaged state, and the risk of further penetration will be significantly increased.
See FIG. 4 for the damage diagram of steel outlet sleeve brick.According to the anatomy of the steel outlet area after disassembling, a gap has been formed between the joint of flange and furnace shell and the steel outlet channel.After re-boring through the steel, it is filled with the knot material, rammed with the spray material, and finally used the spray fill to fill the mud and wet, so that the original burning leakage of the steel channel forms a dense knot layer here.But the knot layer is not as good as magnesia-carbon brick, the brick is still in fact full of holes, when the steel outlet furnace part of the brick cover maintenance is not good or the gap between the steel outlet and the brick, the gap part of the water hammer effect is significant, very easy to occur again steel leakage.
4. Irrigation technology and repair material quality
Tapping hole after the replacement, lining brick, tapping hole block and tapping hole of gap between the brick need repairing material filling, fire-proof material mixed with water through the spray gun, fill in the gaps, with sprinkler irrigation technology such as degree of rare stiff and injection Angle on crack filling has a great influence on the density degree, thus significantly influence on the use of tapping hole.
FIG. 4 schematic diagram of steel outlet through steel
The repair materials used for caulking are boiled and evaporated by water under the residual temperature of steelmaking converter (about >1000℃), and after a period of sintering, a dense sintering layer is formed to meet the needs of molten steel smelting and scouring.The MgO content in the resistant material and the anti-scour property of the sintered material also have obvious influence on the usage times of the steel outlet.