Detailed explanation of ladle slag retention and steel tapping technology

Overview of converter slag blocking and steel-tapping technology

Ladle slag-blocking steelmaking technology, as an efficient and economical smelting method, achieves outstanding metallurgical results by precisely controlling the slag volume at the ladle bottom. This approach significantly reduces phosphorus reabsorption from slag while lowering deoxidizing aluminum consumption, thereby cutting converter smelting costs. With continuous technological advancement, this technique has evolved from simple slag-blocking balls to more sophisticated solutions such as slag-blocking plugs and automatic slag-blocking systems with sliding nozzles.

Application of slag balls

At the end of the converter tapping process, a robotic arm precisely places a slag stopper ball above the taphole. Once the slag stopper ball lands at the taphole, it effectively blocks the molten slag from entering the ladle. The interior of this slag stopper ball is typically composed of a cast iron block, with an outer layer of refractory clay, such as a high-aluminum or magnesium castable, having a density of approximately 4.2-4.5 g/cm³. By using slag stoppers, the slag retention efficiency can reach approximately 60%, and the alloy yield is maintained at around 85%. At the same time, the slag thickness below the ladle is controlled within the range of 80-120 mm.

Pneumatic slag blocking technology

Pneumatic slag blocking technology uses infrared technology to monitor the difference in radiation emitted by molten steel and slag within the infrared frequency range. Once slag formation is detected, the system issues an alarm and activates the slag blocking device, mechanically sealing the taphole while simultaneously injecting high-pressure gas to prevent slag from flowing out. Pneumatic slag blocking achieves a slag blocking efficiency of 60-70%, maintaining an alloy yield of approximately 90%, and controlling the slag thickness in the ladle to within a range of 70-100 mm.

Sliding gate slag blocking technology

The sliding gate slag retaining technology for converter tapping holes is similar in principle to the sliding gate flow control system for ladle tapping holes. This technology utilizes a sliding gate slag retaining device installed on the outside of the converter tapping hole. Using a hydraulic drive system and an automatic slag retaining detection system, it automatically opens and closes the tapping hole, achieving low-slag or even slag-free tapping. This technology can reduce ladle slag thickness to below 40 mm, or even to below 30 mm.

Slag plug technology

The slag stopper features a hemispherical shape with a threaded steel bar running vertically through its center. Its lower section is encased in refractory material to serve as a guide rod, while the upper section is secured by a clamping device. During the final stages of ladle tapping, a robotic arm gently inserts the guide rod portion of the slag stopper into the tapping hole, allowing its hemispherical section to float lightly on the interface between molten steel and slag. As molten steel gradually flows out, the hemispherical section seals the tapping hole at the precise moment, effectively preventing slag from entering the ladle. Notably, the ingeniously designed flow channels on the hemispherical body not only suppress vortex formation and slag entrainment in the molten steel but also ensure residual steel flows smoothly through these channels into the ladle, thereby enhancing molten steel recovery. By employing slag stopper technology, slag blocking efficiency can exceed 90%, alloy recovery rates can surpass 95%, and ladle slag thickness can be controlled within the range of 40-70mm.