| Electroslag remelting?ESR?is a secondary refining method of further refining of steel or alloy on the basis of primary refining.The ingot formed by remelting is dense,uniform in composition and high in purity.With the development of the technology and society,the standard of ESR product's cleanliness and performance become higher and higher.The properties of steel are mainly determined by the chemical composition and structure of the steel.And nonmetallic inclusions would seriously affect the structure of the steel matrix.Therefore,the study of the movement of inclusions in the remelting process is of great significance to the removal of inclusions.Based on the results of the domestic and foreign researches,a transient three-dimensional coupled mathematical model of the electroslag remelting process is developed.The electromagnetic field,two-phase flow and heat transfer are included.Based on the physical fields,the Euler-Lagrange approach is invoked to describe motion trajectories of the inclusions.The effect of electromagnetic pressure force on the movement of inclusions is also included.And the effects of the applied current and inclusion diameter on the removal rate are clarified.Meanwhile,the effect of different current intensity on the electrode oxidation was simulated,the distribution of FeO in the slag and the rate of FeO formation were obtained.The main conclusions are as follow:?1?A large proportion of inclusions are captured in the region of the top surface and the slag/mold wall,while a small quantity of inclusions are still suspend in the slag.Few inclusions can pass through the slag/metal interface to enter the ingot.?2?The removal ratio of large inclusions is greater than that of small inclusions.When the current is 1200A,the proportion of the 1?m trapped inclusions is90.49%,while the removal ratio of 10?m inclusions is 99.28%.;the removal ratio of inclusions increases from 91.40%to 99.80%while the current is 1500A;the percentage of the captured inclusions increases from 94.55%to 99.99%while the current is 1800A.?3?The total removal ratio of inclusions with five diameters all rises while the current increases from 1200A to 1800A.Compared with the total removal ratio,the captured ratio of the top surface of slag has the same trend with it.The proportion of free inclusions in slag falls with the increase of the current.The percentage of trapped inclusions in slag/mold wall is influenced by both the current and diameters of inclusions.?4?As the electrode melts,iron oxide skin produced on the surface of the electrode enters into the slag pool and then moves down to the slag/metal interface.Then it changes direction and moves upward,which coincides with the counterclockwise eddy in the middle part of the slag pool.Then it fills the whole slag pool area gradually.The FeO which flows upward moves clockwise at the slag/mold wall,and moves downward along the side wall of the mold,which is the same as the clockwise vortex trajectory in flow field at slag/mold wall.?5?In the early stage of remelting process,the concentration of FeO in the slag pool was higher than that in the slag/mold wall.With the diffusion of FeO in the slag,the FeO concentration basically reached the same level.But because of the water cooling and solidification,the concentration of FeO in the slag pool is slightly higher than that in the metal.Compared with the simulated results of the current intensity increasing from 1500A to 1800A and increasing from 1200A to 1500A.When the current increases to 1800A,and the increase rate of FeO per unit area was faster.When the current intensity is the same,the increase of FeO per unit area is slower in the early stage,and the speed increases rapidly after 8min.When the current intensity is 1800A,the growth rate of FeO per unit area is the largest.?6?The quality of the final FeO in slag increases with the rise of the current intensity.When the current intensity increases from 1200A to 1800A,the mass of FeO increases from 23.56×10-2g to 24.64×10-2g increasing by 4.58%. |
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