Keyword：Ladle, nozzle block
The ladle nozzle block in the steelmaking plant continuously produces cracks during use, which seriously affects the service life of the ladle and restricts on-site production. Adjustments were made in terms of the quality of the block itself, the construction and baking of castables around the block, the temperature drop during the ladle turnover process, and the operation of replacing the nozzle. Corrective measures were put forward for possible affecting links, and subsequent hidden dangers were gradually eliminated, and satisfactory results were achieved.
The ladle nozzle block in the steelmaking plant continuously produces cracks during use, which seriously affects the service life of the ladle and restricts on-site production. By comparing several nozzle seat bricks, adjustments were made in terms of the quality of the seat brick itself, the construction and baking of castables around the seat brick, the temperature drop during the ladle turnover process, and the operation of replacing the nozzle, and proposed rectification measures for the possible impact links, gradually eliminating subsequent hidden dangers , with satisfactory results.
The role of the steel ladle in the steelmaking plant is to transport the molten steel smelted in the converter to the continuous casting. On the turret of the continuous casting ladle, the 1500°C high-temperature molten steel flows out into the tundish through the nozzle and slide plate at the bottom of the ladle, and the billet transfer is suspended. Finally, it flows out from the tundish nozzle to the continuous casting and straightening, and the billet forming is completed. For the nozzle where the high-temperature molten steel flows out from the ladle, it needs to be placed inside the nozzle block. During the use of the ladle, the nozzle can be replaced online after 20-25 times of use. The nozzle block must be replaced when the ladle is repaired. Replace the nozzle block. The quality of the nozzle seat brick and the quality of the construction directly affect whether the ladle can operate normally. The quality problems of ladle nozzle seat bricks during operation usually include unstable materials, problems in knotting process control, inadequate baking, and defects in on-site construction and installation. This paper sorts out and solves the problems of the on-site nozzle block, and finally achieves satisfactory results, ensuring the normal operation of the ladle.
On-site situation of ladle use
The steelmaking plant uses a 150-ton ladle with double nozzles, and the nozzles are directly embedded in the seat brick. The seat brick is installed at the bottom of the ladle when the bottom magnesia-carbon brick is built. The service life is synchronized with the bottom of the ladle. The service life of the entire ladle is between 130-150 furnaces, and the schematic diagram of the overall refractory material of the ladle is shown in Figure 1 below;
The ladle nozzle is installed before the ladle is baked and put on the line. The sealing glue is applied to the outside of the nozzle, and the nozzle is embedded into the inside of the block by manual use of strong pressure, so that the block, the mortar and the nozzle are closely connected as a whole, increasing the overall strength. The specific installation diagram is shown in Figure 2 below. During the use of the block, the uppermost part of the block directly contacts the initial impact of the molten steel, and the continuous erosion and erosion of the molten steel flow out. The length of the block is getting shorter and shorter. The nozzle in the block It is the direct outflow channel of molten steel, which bears the impact and friction of high-temperature molten steel and the temperature difference change in the production process. The connection between him and the seat brick is sealed by the sealing glue between them.
From July to September, cracks in the nozzle block appeared one after another. It was found that the off-line treatment was carried out in time, and it was found that the steel was not penetrated through the cement channel between the nozzle and the block in time, which seriously restricted the on-site production rhythm. The cost of ladle is increased, and the production is in a passive situation. The following figure 3 shows the accident of Zizi steel sheathing caused by the crack of the seat brick, and figure 4 shows the crack of the seat brick observed online.
In view of the steel leakage accident between the channel of the seat brick and the nozzle caused by the crack of the seat brick, the quality of the nozzle, composition, quality of the seat brick, construction and other aspects are analyzed and tracked one by one. The reason can be ruled out if the nozzle is intact; Cracks are found, the analysis is mainly due to cracks in the seat brick, the integrity is incomplete, and the strength decreases. At the same time, the gap between the seat brick and the nozzle increases, and the molten steel penetrates into the gap of the cement, and the seat brick, cement and nozzle are integrated. The overall strength is destroyed, and the sealing cement cannot withstand the hot molten steel at high temperature, and is gradually corroded, resulting in steel seeding and steel leakage accidents.
Measures taken against steel breakout
As for the steel breakout accident caused by the cracks in the block bricks, the personnel of the steelmaking plant and the technical center combined with the manufacturer to analyze the reasons. On the one hand, the material of the block blocks was analyzed and adjusted by the manufacturer, and at the same time, the quality and quality were urgently dispatched from other domestic block block manufacturers. The company’s products with good reputation are tested, the situation is as follows:
1) The seat brick of manufacturer A was used on site, and after using it in the later stage (about 60 times), micro-cracks were found, and the upper part of the seat brick had obvious diameter expansion;
2) The seat brick of manufacturer B was offline, and there were many longitudinal micro-cracks, and the cracks were distributed at 90 degrees in the middle of the seat brick (from the ladle hot repair platform, the personnel facing the seat brick were used as a horizontal reference, and the cracks were not in the seat brick. the four corners of the ).
3) The ladle contractor analyzed the material of the seat brick, selected high-quality raw materials and carried out the formula operation step by step. decrease;
The measures taken for the installation and operation of block bricks are as follows:
The seat bricks are built together with the bottom of the package during installation. Before the seat bricks are installed and positioned, the steel structure at the bottom of the seat bricks is cleaned of impurities and filled, and the surrounding area is vibrated and filled with castables. Baking is carried out after the overall construction is completed. Baking, online, the specific schematic diagram is shown in the figure below:
1) Strictly control the water-cement ratio of the castable around the base brick, and control the moisture between 6-8%.
2) Castable construction: For the gap (30-100mm) between the seat brick and the bottom of the package, manual operation is used in the vibration process, and vibrating rods cannot be used to vibrate, so as to avoid excessive vibration force and aggregate sinking.
3) When replacing the nozzle online, check the cracks and erosion of the seat brick.
4) Frequently contact the dispatcher, and the time for the steel ladle to come off the assembly line exceeds 30 minutes, and a second baking should be carried out.
5) Strictly monitor the temperature when the ladle is baked, and designate a special record book to mainly record the temperature of each part (the bottom of the ladle, the wall of the ladle, the slag line, and the mouth of the ladle), and pay close attention to the exhaust at the nozzle of the ladle and the wall of the ladle during baking. situation.
The effect after transformation
Through the public relations of several aspects of the seat bricks for nearly two months, the cracks of the seat bricks have gradually decreased and disappeared, and the service life is also within the controllable range. The direction and effect of the transformation are better, the production accidents have been curbed, and the cost of refractory materials has been saved. .
The steelmaking ladle is an important tool for the transfer of molten steel in steelmaking. The quality of internal refractory materials and construction quality are directly related to the smooth operation and safety of production. For the daily management and deployment of steel ladles, technicians of each steel factory need to work according to their own requirements. To explore and summarize the working conditions, the above experience can be used for reference and promotion.