Analysis of the Causes of Accidents Involving Porous Plug Bricks

The function of the porous plug seat brick is to protect the porous plug core; if abnormal cracking occurs during use, it not only fails to provide protection but can also lead to accidents in severe cases. Aside from issues regarding the quality of the brick itself, various factors in the steelmaking plant's operating environment can also affect the stability of the seat brick.

The design of the porous seat brick is unreasonable

The design of the gas-permeable seating brick is flawed, primarily regarding its physicochemical properties; an improper material mix results in poor thermal shock stability, leading to cracking, fracturing, and subsequent steel leakage. Addressing this issue requires adjusting the material composition to enhance thermal shock resistance; additionally, the appropriate inclusion of steel fibers can improve the brick's strength and stability to some extent.

Improper installation of the porous plug

A survey of major domestic steel manufacturers reveals that, when installing porous plug assemblies, most mount the seating block directly onto the steel shell, whereas a minority apply a layer of material between them. Kexin New Materials advocates for the latter approach. This is because, after prolonged use—subjected to high temperatures, impacts during lifting and transport, and shocks during ladle stripping—the bottom plate or steel backing plate of the ladle may deform or become uneven. If the seating block is installed directly onto such a surface, the contact between the block's base and the steel shell will be imperfect, leaving gaps. These gaps can lead to cracking at the base of the seating block and, consequently, steel breakouts. From a mechanical perspective, an uneven base creates an additional fulcrum; under the combined stress of molten steel's hydrostatic pressure and thermal shock, the seating block becomes highly susceptible to cracking. Therefore, we recommend leveling the steel shell surface with chrome-corundum castable when installing the seating block and promptly replacing any backing plates that show significant deformation.

Improper selection of castables

To facilitate the installation and removal of porous plug blocks, steel manufacturers typically leave a gap of 40–100 mm between the block and the ladle bottom bricks, subsequently filling it with castable material. We recommend using a high-quality, premium-grade corundum-based castable, which offers advantages such as excellent flowability and erosion resistance. If the filling material is of poor quality, it will erode too rapidly upon contact with molten steel, causing the porous plug block to become exposed or crack, thereby compromising the performance of the porous plug.

With the rapid advancement of steelmaking technology, secondary refining (ladle metallurgy) has become a crucial component of the steel production process, and the proper use of porous plugs is vital to ensuring safe operations.