Physical Modelling Of 125t Ladle Furnace Refining Process

A quality requirement of steel users pushes forward the development of refining technology.As an important means of refining technology,with its simple equipment,applicability,reliability,easy operation and flexible,low cost,gas-stirred ladle is widely used.Argon refining liquid steel can not only rapidly becomes uniform composition and temperature but can also play a role in purifying the liquid steel.Gas-stirred ladle plays a decisive role in the whole refining process.Therefore,a physical modelling system was set up from the similarity theory for the bottom blowing argon process in a 125t ladle furnace to study the refining process of LF.The physical model experiment was performed in 1:5 scales to investigate the influence of gas flow rate on the mixing time,flow field,and the inclusion removal rate.The effect of viscosity of slag on the exposed surface and slag entrainment was studied.The main conclusions were shown as follows:(1)The mixing time decreases with the increasing gas blowing rate,but shows a non-linear relationship.Before the gas blowing rate reaches 250 Nl/min,the mixing time sharply decreases with the increasing of the gas blowing rate.When the gas blowing rate is between 250 Nl/min to 1500 Nl/min,the mixing time slowly drops due to the rising of the blowing rate.However,there displays no change in the mixing time when the gas blowing time increases after the blowing rate is greater than 1500 Nl/min.The results indicates that the most proper gas blowing rate should be set as 250 Nl/min for the uniform mixing in the LF refining process.(2)The alloy input position is at the upper part of the gas blowing hole,and a slightly better mixing efficiency displays than the input position in the upper hole in the ladle,but the efficiency difference between the two positions is not significant.(3)Slag entrainment takes place at two positions,one of which is around the slag eye and the other is located at the junction of two slag eyes,and the frequency for the slag entrapment is higher at the later position.The slag entrainment becomes serious with the increasing of the gas blowing rate,and when the viscosity increases,the slag entrainment frequency drops.(4)The experiment of the removal of inclusions in the ladle furnace showed that the removal of inclusions mainly occurred in the first 4 minutes after blowing.During the first 0?-2min the speed of removing inclusions was the fastest,the maximum removal rate achieved about 35%.Until blowing to the seventh 4min,the removal rate was all below 3%.Extending the blowing time did little effect.The optimal bottom argon blowing volume was 60 Nl/min and the maximum removal rate was 84%in this subject.