Price application and effect of magnesia carbon brick for refractory preform used in ladle mouth

At present, the price of MgO-C Bricks in domestic steel plants generally adopts the cladding masonry method: after the cladding bricks are completed, MgO-C Bricks are wholesale filled with castables at the distance of 150~200mm between the upper surface of the cladding bricks and the steel ladle shell, and the flange ring is auxiliary welded to protect the built cladding bricks. However, the ladle mouth material will fall off in the process of use, which will affect the use of the ladle. Each time the wholesale ladle of steel magnesia carbon bricks is off-line for minor repair or overhaul, the ladle mouth needs to be repaired, and the damaged flange ring needs to be re welded, which will directly affect the operation of the ladle, with more flange consumption and increased use of castables. Through experimental research, the ladle mouth prefabricated parts are designed. After installation and use, the utilization rate of ladle mouth can be improved, the erosion of ladle edge can be reduced, the repair work of ladle shell flange ring can be reduced, and the cost can be saved.

1. Fabrication and installation of preform for cladding

(1) Preparation before production: fix the mold according to the designed size of the prefabricated part drawing (see Figure 1), and lubricate the mold to facilitate demoulding.

(2) Mixing: according to the provisions of the ingredients list, weigh various raw materials, pour the materials into the mixer, and add the materials according to the principle of particle first, then fine powder, and finally admixture; Explosion proof fibers shall be spread evenly and shall not be put in clusters; Dry mixing for 2~3min, then wet mixing for 12~15min, and the amount of water added shall be controlled at 4.2%~4.6% (W).

(3) Molding: pour the mixed material into about 1/3 of the mold, turn on the vibrating rod, slowly rotate along the mold core in the mold, and continuously add the material at the same time. When the material is full, vibrate it with the vibrating rod, and then carefully flatten it with a trowel until there is a water film on the surface.

(4) Film removal: semi finished products shall be cured at ≥ 15 ℃ for 1 day in spring and autumn. If the temperature is higher than 25 ℃, they can be demoulded after 9 hours. Care shall be taken during demoulding to avoid damage to the outer edge and the mold core.

(5) Drying: qualified semi-finished products shall be dried at 110 ℃ for 24h. According to the construction requirements of the scheme, the installation shall be carried out in a steel plant. Attention shall be paid to the details during the installation process. Before the masonry of the full repair package, the flange ring of the steel ladle shell shall be assembled as required, and the flange surface shall be flat. When installing the prefabricated parts of the ladle mouth, attention shall be paid to the door closing and installation construction. After the prefabricated parts are installed, the ladle shall be built according to the masonry procedure. Finally, the castables shall be tamped between the prefabricated parts and the ladle bricks to make the prefabricated parts and the ladle bricks firmly combined. Then, the prefabricated parts shall be baked and put into normal use. After baking, the prefabricated parts are very stable, and the prefabricated parts and the ladle bricks shall be closely combined.

2. Use effect

After 68 furnace runs, it will be taken offline. From the offline package, it can be seen that the prefabricated parts have less erosion and no peeling, providing good protection for the sealing bricks, and there is no looseness in the sealing bricks; The sealing area filled with castable during the same period is prone to detachment during use and needs to be repaired at any time, resulting in severe peeling of the sealing bricks. The steel ladle uses the second furnace service, which uses prefabricated components. After removing the magnesium carbon bricks from the ladle, the bricks are directly laid, without the need for repairing the flange and prefabricated components at the ladle mouth. After baking, the ladle can be directly put into use; After the completion of masonry, the steel ladle that does not use prefabricated components needs to be re welded to the mouth and the mouth area needs to be re poured before it can be put into use.

This time, a total of 3 furnace runs were used for the use of prefabricated components at the mouth of the package, with a total of 210 steelmaking cycles. The oxidation depth of each run was about 60mm, and the residual thickness after removal was 1/2 of the design thickness, meeting the design requirements. It can be seen that the use of prefabricated components has improved the utilization rate of the steel ladle mouth, from pouring the ladle mouth once per furnace to installing it once in 3-4 furnaces, and can be disassembled and replaced at any time during the process. This not only reduces the welding work of flange rings, but also saves material and labor costs for steel mills; Moreover, it reduces the usage of ladle pouring materials and effectively protects the ladle opening bricks, making the ladle stable in use, meeting the requirements of the steel factory regulations, and achieving good contracting benefits.