Solidification Quality Control Of J80 Slab Ingot Electroslag Remelting Process

With the continuous development of naval ship technology,the performance requirements of steel for pressure shells of new generation ships are increasing.J80 steel is the secondgeneration pressure-resistant shell steel independently developed by China,and it is one of the highest strength ship steels in China.The traditional smelting process of J80 is as follows:vacuum treatment after electric furnace(or concerter)smelting,then casting to slabs.Although the cast slabs can meet the thickness requirements,the solidification quality is poor and the yield is low.The production of slabs by electroslag remelting can improve the crystalline structure of the slabs,increase the material yield,reduce the processing compression ratio,and save man-hours.After a field investigation of a single-electrode slab electroslag furnace in a domestic steel factory,it was found that:(1)The influences of process parameters such as voltage,filling ratio,and mold shape on the physical fields are not clear,and the relationship of the parameters with the shape of the molten metal pool is uncertain,during the on single electrode eleectroslag remelting the slab ingot.(2)The surface quality of slab ingots produced by electroslag remelting is poor,such as ripples,heavy skins,slag leakage,and steel leakage.Although the surface quality can be improved by manual grinding,it will waste a lot of manpower and material resources and reduce productivity.(3)After the electroslag remelting of J80 steel,the element content changes greatly,and some key elements fail to meet the composition requirements of the steel type.To solve the above problems,a three-dimensional dynamic mathematical model of the single electrode electroslag remelting slab ingot process was established based on the electromagnetic field equations,flow field equations,and energy equations.After the model established,this paper were mainly analyzed the distribution of physical fields and morphology of molten metal pool in detail.The calculation results showed that the potential drop during the electroslag remelting process mainly occured in the slag pool,and the maximum value of electric density,Joule heat and electromagnetic force appeared at the corner where the consumable electrode contacted the slag pool,and the minimum value appeared in the area where the top of the pool was in touch with the mold.Joule heat was mainly generated in the slag pool,and the heat generated by the slag pool was the heat source of the entire electroslag remelting system.The maximum value of the magnetic field intensity appears on the surface of the slag pool and the electroslag ingot,and the magnetic field intensity at the center axis was the smallest.As the remelting progresses,the potential distribution is basically unchanged,and the electric density,Joule heat,magnetic field strength,and electromagnetic force decrease slightly.The maximum value of the slag flow speed appeared below the consumable electrode.The maximum speed ranged at different times is 4.35 × 10-2?4.88 ×10-2 m/s.The maximum temperature range of the slag pool at different times was 2118?2122 K.As remelting progresses,the effect of forced cooling at the bottom of the mold on the temperature of the molten metal pool became smaller,the temperature gradient of the electroslag ingot gradually became smaller,the molten metal pool gradually became deeper,and the height of the cylindrical section of the molten metal pool increases.Based on the established mathematical model,the effects of different voltages,different filling ratios,and increased mold chamfer on the physical fields and the shape of the molten pool were studied.The results showed that as the voltage increases,the temperature of the slag pool and the molten metal pool increased,the height of the cylindrical section of the molten metal pool increased,and the molten metal pool became deeper.By increasing the filling ratio,the temperature distribution of the slag pool is more uniform,the height of the cylindrical section of the molten metal pool increases,the molten metal pool becomes shallower.After the mold was chamfered,compared with the non-chamfered mold,the temperature of the slag pool and the molten metal pool increased by 43 K,the height of the cylindrical section of the corner metal molten pool increased by 11 mm,and the maximum depth of the molten metal pool increased by 10 mm.According to the conclusions obtained from the simulation,the J80 slab ingots electroslag remelting production process at the industrial site was optimized to solve the problems of poor surface quality of the electroslag ingot during the process of slab ingots electroslag remelting.The content of each main element of the electroslag ingot produced after the process optimization is within the composition range required by the steel type,which fully meets the composition requirements of the steel type.The thickness of the slag skin is 1?2 mm,which avoids the phenomenon of slag leakage and steel leakage during the smelting process.The surface quality of the electroslag ingot is good,which improves the industrial production efficiency and reduces the production cost.