Solidification Behavior Of Electroslag Remelting Hollow Ingot Based On Multi-field Coupling

In recent years,China is speeding up the development of advanced manufacturing industry,moving China from a "big manufacturing country" to a "strong manufacturing country".This also makes the demand for the output and quality of special steel in our country higher and higher.Especially with the rapid growth of the demand for large-scale tubes in the fields of petroleum refining furnace tubes,thermal power and other energy sources,hollow ingots as important raw materials for forgings,the market demand will become larger and larger.Electroslag remelting is an effective way to produce hollow ingots in industry.It inherits the advantages of Electroslag Metallurgy and continuous casting.It is a high efficiency,high quality and energy saving production technology.Electroslag remelting hollow ingot technology is usually carried out in high temperature and high current environment.Usually,it can not rely entirely on experiments to measure its temperature field and flow field.Therefore,the solidification behavior of electroslag remelting hollow ingot is studied by numerical simulation method,which provides theoretical basis for on-site process.In this paper,a mathematical model of electroslag remelting hollow ingot including the coupled electromagnetic field,flow field and temperature field is established.The electromagnetics field,fluid flow and temperature field in a laboratory scale electroslag remelting hollow ingot(inner and outer mould size is 300/100 mm)are solved by the commercial software FLUNET.The model was validated against the experiment of the production of Mnl8Cr18N hollow ingot.Besides,the electromagnetic field,flow field,temperature distribution,droplet behavior and solidification characters during the electroslag remelting Mn18Cr18N hollow ingotwere systematically analyzed.Then,the model was employed to optimize the process parameters of electroslag remelting Inconel 625 alloy hollow ingot.The effects of different process parameters such as slag height,electrode arrangement and melt rate on the remelting process have been analyzed in detail including the electromagnetic field,fluid flow and temperature field.Finally,the optimized process parameters were determined with the model to guide the production of electroslag remelting Inconel 625 alloy hollow ingot.By comparing the calculated metal pool profile with the experimental result,it is found that the calculated metal pool profile agrees well with the experiment result.The uneven distribution of electrodes results in uneven distribution of electromagnetic field,flow field and temperature field in the electroslag remelting process.The formation,departure and dripping of metal droplets through the slag were observed and the fundamental formation of droplets were also obtained.The total time of droplet melting is 1.01 seconds.The radius,temperature and velocity of droplet passing through the slag-metal interface are 5.1 mm,2019 K and 0.42 m·s-1,respectively.The residence time in the slag pool is 0.29s.The simulation results are in good agreement with the calculated values.The optimized processparameters for the production of electroslag remelting Inconel 625 alloy hollow ingot are as follows:the depth of slag pool is 90 mm;the arrangement of eight electrodes is adopted;and the melting rate is 2.33 kg·min-1.Under these conditions,the shape of molten pool,the height of liquid head and local solidification time are appropriate,which can ensure the surface and interior quality of ingot simutaneously.