The Study Of Radiation Heat Transfer Characteristics For Solid Slag Film Based On The Slag Film Heat Flux Simulator

As the auxiliary materials of steelmaking,continuous casting mold flux has significant effect on the continuous casting process and strand quality.Heat transfer control is the key function of the mold flux for guarantee the strand quality.However,during the continuous casting of 304 stainless steel,due to its composition and different solidification characteristics,volume shrinkage and stress produced by slab will be increase,which can lead to slab dent and cracks.To eliminate the surface quality problem such as longitudinal crack and dent,it is very important to come ture the slow cooling between the shell and mold wall.With the slow cooling realizing,the thermal resistance will be increase,which can make the green shell be thinning.The organizational stress and thermal stress distribution will be more homogeneous and the stress concentration is not easy to produce,which can eliminate the surface quality problem such as longitudinal crack and dent.There are two way to realize slow cooling,one is to reduce the conduction heat transfer and the other is to reduce the radiation heat transfer.Reducing conduction heat transfer is realized by improving the basicity.Due to the low freezing point of 304 stainless steel,submerged nozzle open up to guarantee the effect of slag melting.To avoid slag entrapment,the viscosity of 304 stainless steel mold flux should not be too low and the basicity of 304 stainless steel mold flux should not be too high.So it is impossible to increase the basicity to reduce the conduction heat transfer.Reducing the radiation heat transfer is the only way to make the slow cooling come ture.There are two ideas for design mold flux aim at realizing slow cooling.?1?Transition metal oxides is added to the mold flux.?2?To make the dispersity of bubble in solid slag of mold flux be increase.In this paper,the radiation heat transfer calculation model with the conduction and radiation under steady state is established.The effect of MnO?FeO?TiO₂ and the distribution of bubble on radiation heat transfer?the effect of carbonate and sulfate on the distribution of bubble are researched by this model,which can find a more effective way to control the radiation heat transfer.The main contents of this paper are as follows:?1?The effect of carbonate and sulfate on the distribution of bubble1)The adding of Na2CO₃ and Li2CO₃ can increase the bubble density of the solid slag and decrease the size of bubble.The ability of generating CO₂ for Li2CO₃ and SiO₂ is better than Na2CO₃ and SiO₂.2)As the bubble clarifying agent,the bubble density of the solid slag decreases gradually with the increase of the sulfate content,the size of bubble increases gradually with the increase of the sulfate content.?2?The effect of transition metal oxides and the distribution of bubble on optical properties1)The adding of FeO?MnO?TiO₂ can decrease the transmittance of the solid slag film.2)The transmittance decreases gradually with the increase of the bubble density of the solid slag film.?3?The effect of transition metal oxides and the distribution of bubble on radiation heat transfer1)The ability to reduce the radiation heat transfer is :TiO₂>Fe O>MnO,The ability to reduce the integrated heat transfer is: TiO₂>Fe O>MnO.Both are consistent.2)The radiation heat transfer and integrated heat transfer decreases gradually with the increase of the bubble density of the solid slag.?4?The effect of optical properties of solid slag film on the temperature distribution1)The temperature of the solid slag film increases with increase of the distance from the probe.Because of the radiation heat transfer,the temperature of the flux flim is not a liner change along with the the change of distance from the probe,temperature gradient decreaces gradually with the increase of the distance.The bigger the absorption of solid slag film is,the greater the relationship between slag film temperature and the change of distance deviates from the linear relationship.When transition metal oxides are added in mold flux,the cold temperature of solid slag film is 655-762?,the temperature of the solid liquid interface is close to 1200?.As for mold flux containing bubbles,the cold temperature of solid slag film is 631-844?,the temperature of the solid liquid interface is close to 1200?.2)The absorptivity of the solid slag film increases gradually with the adding of FeO?MnO?TiO₂ and increase of the bubble density of the solid slag.The relationship between slag film temperature and the change of distance deviating from the linear relationship is greater and temperature gradient decreaces gradually with the increase of the distance.Due to the solid liquid interface of mold flux is adjacent,the cold temperature of solid slag film is higher.It is easier to realize slow cooling between the shell and mold wall,which can increase the quality of casting billet.?5?The effect of optical properties of solid slag film on radiation heat transferThe radiation heat transfer through solid slag film is associated with T2/?1-R?.The radiation heat transfer increases gradually with the increase of the T2/?1-R?.