Analysis of problems and improvement measures in the use of steel ladle

Analysis of problems and improvement measures in the use of steel ladle, let's understand together below.

01. Poor corrosion resistance at the bottom of the ladle

Corrosion of refractory materials can be divided into physical erosion and chemical erosion. Physical erosion refers to the erosion of refractory materials by impact and other mechanical actions, while chemical erosion refers to the erosion of refractory materials by changes in temperature and stress fields under high temperature loads. The bottom of the ladle is mainly subject to physical erosion. In use, the corrosion resistance and impact resistance of the bottom working layer of the ladle are poor. Under the impact and erosion of high-temperature molten steel, a large area of refractory material falls off, with a delamination thickness of 100mm~150mm. The delamination sites are mostly concentrated at the collision position of the molten steel, which poses a great danger to the safe use of the ladle.

1.1 The breathable bricks of the ladle and the age of the ladle are not synchronized

Narrow slit breathable bricks are widely used as bottom blowing components in steelmaking processes due to their wide range of gas supply regulation and good erosion resistance. However, the performance of bottom blown permeable bricks directly affects the effectiveness and usage of ladle bottom blowing. During the entire bottom blowing process of the ladle, it often occurs that the bottom blowing cannot be carried out, the air permeability is small, and the air permeability is poor, which forces the ladle to be taken offline and affects the age of the ladle, resulting in the asynchronous service life of the permeable bricks and the ladle.

1.2 The invalidity of the bottom line of the ladle is too late

Due to the lack of specialized equipment for measuring the bottom of the package, the erosion of the package bottom (package bottom, package wall, breathable brick, water outlet seat brick) is determined by the hot repair skateboard worker based on experience and the weight of the empty package. Due to the different levels of thermal repair workers, the situation of each ladle is different, and when the ladle is in a hot state and the thermal repair worker is burning it, it is often difficult to observe, resulting in incorrect judgments and premature or delayed stopping of the ladle. Stopping the ladle too early can affect its lifespan; If the ladle stops too late, there is a risk of ladle accidents.

02. Improvement measures

2.1 Improvement of the repair process for the bottom of the ladle

Before improvement, in the impact zone of the bottom of the casting material package, the casting material (high aluminum material) trembled or poured, and it was 100mm higher than the bottom of the package, forming a sloping shape. Due to the long-term cleaning and erosion of molten steel during use, the impact zone is prone to forming pits and thin bottoms, filling the risk of accidents.

After improvement, the repair form of using a bottom impact zone prediction machine to punch prefabricated impact blocks replaces the original inclined high aluminum material. The prefabricated component is magnesia carbon with a stamping strength of 1700N. Construction plan: After pouring 300mm of castable at the bottom of the package, fix the prefabricated impact and embed it into the bottom impact zone. Then pour 300mm thick castable and use a vibrating rod to firmly vibrate the surrounding area. After the construction was completed, the prefabricated blocks in the impact zone were 150mm higher than the bottom of the package. The comparison of the effects before and after the improvement of the steel package bottom repair process is shown in Figure 2.

2.2 Improvement of Breathable Bricks

When the permeability of breathable bricks is poor and their service life is not synchronized with the bottom of the package, the following measures should be taken. （1） Increase the number of slits in breathable bricks from 20 to 36; 2) Increase the slit width of the breathable brick from 0.13mm to 0.20mm; 3) Change the material of the existing breathable brick core from corundum to chrome corundum. By improving the cutting and material technology of breathable bricks, the breathability and service life of breathable bricks have been enhanced. Through joint research with breathable brick manufacturers, physical and chemical indicators of breathable brick cores have been developed as the basis for regular inspections. The specific physical and chemical indicators are shown in Table 1.

2.3 Timely improvement of the prohibition of castables

Add measuring tape to measure the thickness of the bottom and permeable bricks, reducing the error of empirical judgment. In response to the phenomenon of delayed use of castables, reasonable bottom measuring equipment (fireproof boards and measuring scales) should be set up to reduce or eliminate the phenomenon of using the ladle too quickly or too slowly, eliminate the impact on production, and make it safe and reasonable to stop using the ladle, achieving the optimal state of stopping the ladle. The inspection method for the condition of the ladle before and after increasing the measurement size is shown in Figure 3.

Technical solution: For castables with a package age of 70 furnaces or special circumstances, duty personnel must be organized to conduct the lowest measurement of the bottom of the package and the lowest point of the two breathable bricks. Before measurement, the waste steel slag attached to the bottom of the bag and two breathable bricks must be cleaned with a large oxygen tube (ignition is prohibited), and nitrogen gas should be connected to blow back while removing the breathable bricks.

Standard: Package bottom 300mm, breathable brick 250mm, package wall 130mm, cover with package (without edge) 46.5t. Size: The package bottom is designed to be 2700mm long, and the breathable brick is measured to be 2750mm long.

03. Improvement effect

1) The measure of embedding the convex block into the bottom of the package can alleviate the phenomenon of steel cleaning and erosion resistance of the castable during use.

2) The corrosion resistance of breathable bricks has been greatly improved, and the air permeability meets the requirements of converter bottom blowing. The service life can be synchronized with the age of the package.

3) Comparing the residual thickness measurement data of the ladle before and after using the measuring device, it was found that the residual thickness of the ladle after using the measuring device better met the requirements of the bottom line standard of the castable (bottom thickness of 28020mm, thickness of the permeable brick 16020mm), and the ladle stopped too quickly!

4) The overall age of the pouring ladle has increased from an average of around 80 heats in the past to an average of over 100 heats now, with the highest age reaching 125 heats.

The above introduction is the analysis of problems and improvement measures in the use of steel ladle. If you need to learn more, please feel free to contact us at any time!