Physical Modeling Of The Molten Steel Flow In A Slab Continuous Casting Mold With Argon Injection

The flow field of molten steel plays an important role on the inclusion removal, slag entrapment and formation of solidification shell. It is an effective method to improve the flow field of molten steel in the mold by optimizing the operating parameters and structure of submerged entry nozzle (SEN), which can improve the slab quality remarkably.According to the slab mold of Tangshan Jianlong Steelmaking Plant, a physical model with 0.6:1 scales to the plototype was established to study the flow behavior of molten steel in the slab mold based on the similarity criteria theory. The effect of the operating parameters (flow rate of gas injection through SEN, immersion depth of SEN and casting speed) and structure parameters of SEN (port angle and shape)on the flow field, surface fluctuation and slag entrapment was investigated, and optimization of process parameters and structure of SEN was made based on the experimental results, so as to control the flow pattern of molten steel in the mold, reduce the entrapment of mould powder in the practical production, and therefore improve the superficial and internal quality of the slab.The research results of physical modeling show that the affecting extent of gas injection flowrate on the surface of mold is different for different surface positions of the mold, the bigger influence on the mold surface can be observed near the nozzle area. With the increase of gas flowrate, the surface fluctuation became severe, and the probability of powder entrapment and surface exposure increased. But the penetration depth of flowing stream decreased, which is favorable for the inclusion floatation and formation of solidification shell. With the increase of the immersion depth of SEN, the surface fluctuation became weaken, and the slag entrapment and surface exposure decreased. But the penetration depth increased and inclusion floatation becomes difficult. With the increase of casting speed, the surface fluctuation became severe and slag entrapment increased. Increasing the port angle of SEN will increase the range of the upward flow in the mold and the penetration depth of flowing stream, which is unfavorable for the inclusion floatation. For the mold of (500mm-700mm)×180mm at Tangshan Jianlong Steelmaking Plant, the optimum parameters have be obtained. When the casting speed is more than 0.8m·min-1, the 15°square SEN should be proposed, the optimum gas flow is 6L-min-1 and the optimum immersion depth of the SEN was 200mm.