Simulation Research On Optimization Of Related Process Parameters Of Continuous Casting Of Casting Billet

With the development of refining technology outside the furnace,the purity of molten steel has been greatly improved.In order to maintain the high cleanliness of the molten steel after the refining and prevent the molten steel from being contaminated by air,ladle slag,covering agent,and refractory materials in the subsequent continuous casting process,the molten steel in the continuous casting process needs to be protected and cast.In this study,the secondary oxidation of molten steel casting process must be strictly controlled in ultra-low-oxygen steel such as billet continuous casting bearing steel in a steel plant.A research method combining hydraulic simulation and numerical simulation is used to protect the casting from ladle to tundish.Related process parameters were optimized.1)In order to prevent the ladle molten steel swirling suction at the end of casting,the ladle slag entering the tundish to affect the cleanliness of the molten steel,and to reduce the amount of residual steel in the ladle,a study was carried out at the end of the ladle casting;The violent contact between the impact zone of the tundish and the covering agent or air caused secondary pollution of the molten steel.For the four-flow long-distance tundish,the shape structure of the turbulence controller and the turbulent kinetic energy,flow field and temperature of the liquid surface in the impact zone of the tundish were carried out.Research on the relationship between the field and the flow mode;3)In order to prevent the secondary oxidation of the"bare bright"of the tundish impact zone caused by the argon blowing of the ladle long nozzle,the ladle steel flow long nozzle protection casting argon blowing was carried out to achieve the criticality of the protection effect Research on the flow rate of argon gas and the reasonable insertion depth of the long nozzle of the large package;4)Industrial application optimization and verification of the research results.At the end of the ladle casting,the simulation results of the vortex control physical simulation experiments show that when the argon blowing control mode is used,the vortex height decreases with the increase of the Ar blowing flow,and the critical slag layer is caused by the interference of the turbulent flow formed by the argon flow on the vortex circulation.The blow-through height is increased,and the effect of using a single-hole Ar blowing to reduce the vortex height is slightly worse than the double-hole Ar blowing to reduce the vortex height.The average height of the double-hole argon blowing is 11%lower than the single-hole argon blowing,and the average through height is 9%lower;in order to achieve the effect of maximizing the reduction of the vortex height and preventing the blowing of ladle slag,there is an optimal argon blowing flow rate.The recommended flow rate for single-hole blowing Ar is 18.0 L/min(prototype value),corresponding to The spin height is 127.8mm,and the residual steel amount is 4.9t,which is 36.7%lower than when Ar is not blown;the recommended single-hole flow rate for double-hole blown Ar is 17.4L/min(prototype value),and the corresponding spin height is 120.9mm,The amount of residual steel is4.6t,which is 40.1%lower than when Ar is not blown.When the slag blocking ball(cone)control mode is adopted,if the slag blocking device can successfully fall into the nozzle position,the slag blocking ball(cone)changes the original The structural shape of the spout disturbs the flow field and the end of casting No through vortex will be formed,so as to achieve the purpose of eliminating the vortex,and also improve the metal yield;in addition,the diameter of the slag ball and the depth of the groove have little effect on the vortex control,but the smaller the diameter of the slag ball,the more The greater the number,the higher the hit rate(the probability of the slag ball blocking the water outlet).When the number of slag balls added is greater than or equal to 9,the hit rate can reach 100%,and the improved slag cone positioning input device is also It can ensure that the slag blocking cone hits 100%,achieves the effect of controlling the vortex,and prevents the molten steel from being oxidized twice.The results of mathematical simulation experiments of the tundish flow control device show that the octagonal turbulence controller has a moderate turbulent energy dissipation rate of 7.44×10^-2m²/s³,which balances the effect of the beam and the long-flow spacing tundish distant flow steel renewal.Contradictory relationship,there is no problem of"bright exposed"molten steel and oxygen absorption caused by excessive fluctuation of liquid level in the impact area of the tundish,and its erosion by the ladle injection flow is weak,and the floating rate of inclusions in the tundish is high(The numerical model is 96.1%and the water model is 94.1%),which significantly improves the cleanliness of the molten steel,and the results of the two simulation methods of physical simulation and numerical simulation are in good agreement,which mutually verify the accuracy of the simulation results of each other;The turbulence controller of the cavity structure has almost no effect on the starting height of the tundish at the end of casting.The starting and stopping height of the tundish still increases with the increase of the pulling speed.The cross section is 320mm×480mm,and the pulling speed is 0.4987m/min,The recommended minimum prototype operation level is201mm.The experimental results of the physical simulation experiment of the argon blowing protection in the long nozzle show that with the increase of the flow rate of argon blowing,the pressure in the long nozzle can be changed from negative pressure to positive pressure,and the stable value of the oxygen volume percentage concentration in the long nozzle tends to decrease.The exposed area of the impact zone of the bag is increased;when the argon blowing flow rate of the long nozzle is 45L/min,the pressure in the long nozzle is 30mm water column,and the oxygen concentration in the long nozzle is<0.5%,which can control the amount of oxygen and nitrogen in the molten steel to<1 The level of PPm,and the tundish impact area is not exposed and bright,this value is determined as the critical argon blowing flow of the long nozzle studied to achieve this protection level;under the condition of slightly greater than the critical argon blowing flow of the long nozzle(50L/min)With the increase of the insertion depth of the long nozzle,the liquid level fluctuation value that indirectly characterizes the exposed area of the slag surface in the impact zone of the tundish first weakens and then increases.There is an optimal insertion depth of the long nozzle,which is 260mm under design conditions.Under the condition of 260mm best long nozzle insertion depth,the liquid level in the impact zone of the tundish is relatively stable,the tundish covering agent is well covered,and there is no phenomenon of bare oxygen absorption and slag curling.The production site verification experiment included 54 sets of four-stream bearing steel,rolled into materials,and tested 57 batches and 342 test samples for inclusions.The statistics showed that all Ds inclusions were below 1.0,and the class B coarse system Inclusions are all grade 0,and class C inclusions are grade 0.No large non-metallic oxide inclusions caused by slag are found;the main substance of the nodules in the nozzle is Al₂Si O₃,and the secondary substance is Al₂O₃,indicating that the current use The high level of Si O₂in the tundish refractory composition is still a problem of secondary oxidation of molten steel.It is recommended that the content of Si O₂in the refractory should be strictly controlled when producing high-quality steel such as bearing steel;in the middle of the tundish pouring,20 consecutive furnace measurements The temperature of the 1#flow and 2#flow orifice all meet the target requirement of the temperature difference of the orifice in the tundish?5?(20furnaces).