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Si deoxidation and C deoxidation processes were compared

Two cold models were employed to simulate the formation of open-eyes in a gas stirred ladle. In the first model, water and silicon oils were employed to simulate liquid steel and slag respectively. In the second one, liquid Ga-In-Sn alloy was used to simulate liquid steel, while 12% hydrochloric acid simulated the top slag. The experimental results indicated that the gas flow rate, height of the lower liquid and height of the top liquid had a strong impact on the open-eye size. On the other hand, the viscosity of the top liquid and the interfacial tension between the two liquids had only little effect on the open-eye size. A semi-empirical model was developed to describe the size of open-eye as a function of the heights of the two liquids and the gas flow rate. The two sets of parameters obtained for the water and Ga-In-Sn models were very different. Industrial trials were also conducted to examine the applicability of the models. The model developed based on the Ga-In-Sn model could well predict the formation of an open-eye during ladle treatment. The model could be adopted by the industry to estimate the real gas flow rate by measuring the size of the open-eye online. On the other hand, the mathematical model based on water model experiments was unsatisfactory when applied to the industrial ladle process.

In the present study, the effect of gas flow rate on homogenization and inclusion removal in a gas stirred ladle was investigated. Both industrial trials and cold model experiments were conducted. CFD calculation was also carried out as an auxiliary tool. The mixing times predicted by CFD simulation agreed well with both the model experiments and industrial data. 99% mixing could be achieved in about 2–3 minutes. The increase of flow rate of inert gas would not improve the mixing substantially, while the mixing time decreased somewhat with the increase of gas flow rate. The water model study showed also that the gas flow rate had a negligible effect on the rate of inclusion removal. Both the experiments and CFD calculation strongly suggested that a low gas flow rate should be applied in the ladle treatment.

During continuous casting processes lubrication between mould and strand shell is very important for reaching and maintaining a good surface quality of both the as-cast strand and the finished product. The lubrication is influenced by the properties of the mould powder but also by the friction forces caused by the periodic movements of mould and the descending strand shell. In the present research measurements were carried out to investigate the friction forces during 150 mm sq. billet casting of different steel grades using mould powder or granules and submerged entry nozzles. The friction forces reached values up to 6 kN. Since friction forces are depending on upward and downward movements within the mould-strand-system, the evaluation of a rheogram shows the typical change of pressure and tension. Maximum friction forces arise during the positive strip time of the rising mould, introducing tensions and cracks in the as-cast strand. On the other hand lowest frictions forces are generated by the descending mould within the negative strip time leading to the healing of faults in the as-cast strand. These industrial experiments indicate a correlation between friction forces and surface quality of as-cast strands.Keywords: frictions forces, tension and pressure, mould, strand shell, positive and negative strip time, friction force Wing, surface quality, healing time, breakout, quality of the as-cast strand. the negative and positive strip time of the sinusoidal movement. Various research works [2-23] had been published about this topic. In this investigation intensive measurements were carried out to determine the friction forces at a billet caster with the strand size of 150 mm sq.