| H-beam is a kind of economic cross-section profile,which is widely used in infrastructure construction fields such as bridge construction,high-rise buildings,and ocean engineering.Hot-rolled H-beams are mainly produced by beam blank.Due to the complex section of the beam blank(12 faces and 12 corners),the solidification in the mold is extremely uneven,and it is easy to produce cracks on the surface and under the skin of the strand.This is a key problem in the production of beam blank continuous casting.For this reason,in the present research is based on the actual mold structure and continuous casting production process of a domestic steel plant,a three-dimensional thermal/mechanical coupling analysis finite element calculation model of the beam blank and the mold copper plate as the overall simulation object and the dynamic filling of the mold flux film and the air gap between the two interfaces were established by using the method of numerical simulation,the temperature field of solidified shell in the mold and the evolution law of thermal behavior such as the distribution of mold slag film and air gap in the interface,as well as mechanical evolution law of dynamic deformation and shrinkage of blank shell under typical beam blank continuous casting conditions were studied and analyzed.On this basis,the process parameters such as casting speed and molten steel superheat on the thermo/mechanical effects of the above-mentioned beam blank in the mold solidification process were analyzed and discussed.The main conclusions are as follows:(1)Under the typical beam blank continuous casting process of the steel plant,the interface mold flux film is mainly filled in the form of solid flux;the thickness of the mold flux film at the Flange inner and outer corners and the Flange Tip of the inner and outer arc wide surfaces of the strand is relatively thick,the thickness of t the Flange Tip is the thickest,and the thickness at the exit of the mold is about 1.86 mm and 1.78 mm.The thickness of the mold flux film at the web,Fillet and Flange slope is thinner and the distribution is more homogeneous;during the solidification process of the beam blank in the mold,affected by the deformation of the shell and the above-mentioned dynamic filling of the mold flux film,the air gap of the wide surface of the shell is mainly distributed in the inner and outer corners of the Flange,and near about 10 mm from the inner and outer corners of the Flange Tip,the thickness gradually increases as the shell moving downward,reaches the maximum value at the exit of the mold,and the thickest at the outer corner of the Flange,the thickness is about 0.936 mm and 0.905 mm;there is basically no air gap at the web,Fillet,Flange slope and Tip,the thickness of the mold flux film at the corners of the narrow surface of the inner and outer arcs of the strand and the off-corner area is thicker,and the thickness of the off-corner area at 410 mm and 460 mm below the meniscus and 4 mm and 8 mm away from the corner reaches the maximum,about 0.89 mm and 0.85 mm;the thickness of the mold flux film in the circumferential direction of the mold increases first and then becomes smaller along the center of the narrow surface of the shell.The air gap initially appeared in the corner area 290 mm below the meniscus,and concentrated in the corner area of 0～50 mm;the air gap continues to grow in the narrow area,and the thickness of the corner area of the shell at the exit of the mold reaches the maximum value of about 0.443 mm and 0.44 mm.(2)Based on the effects of the above-mentioned mold powder film dynamic filling and air gap,under the typical beam blank continuous casting process,the Flange Tip,inner and outer corners of the inner and outer arcs of the strand,as well as the narrow-faced corners and the off-corner area have large fluctuations in the interface heat flow,web,Fillet,Flange slope and the center area of the narrow surface have slight fluctuations;the temperature of the Flange inner and outer corners of the inner and outer arc wide surfaces of the shell decreases rapidly and then gradually slows down;the temperature at the Flange Tip at the exit of the mold is the highest,about 1499K and 1506K;the narrow surface of the inner and outer arcs of the shell,the concentrated area of the ’hot spot’ of the strand surface temperature along the circumference of the mold appears in the off-corner area,the temperature of this area at the exit of the crystallizer is 332.3K and 327.1K higher than the corresponding center;the temperature changes at the Flange Tip,inner and outer corners of the copper plate of the crystallizer are severe,and the temperature in these areas in the lower part of the crystallizer is relatively low,while the temperature changes in the remaining parts are relatively gentle.(3)The surface of the shell in the mold is always subjected to tensile stress,while the solidification front bears the action of compressive stress,and the stress gradually increases as the shell moving downword;due to the thermal shrinkage of the initial solidified shell,the inner and outer corners of the Flange and the narrow corners begin to separate from the mold copper plate.As the shell descends,the Flange Tip begin to shrink due to the heat shrinkage of the inner and outer corners,and the interface distance continues to increase until the distance at the exit of the mold reaches the maximum value,and the wide/narrow surface taper of the mold copper plate is insufficiently compensated;the beam blank is prone to surface longitudinal cracks and corner internal cracks.(4)Other process parameters remain unchanged,and the wide/narrow surface of the beam blank(except the center of the Flange Tip)is moved downward,and the thickness of the solid flux layer and the air gap becomes thinner;the thickness of the liquid flux layer in the center of the Flange Tip increases with the increase of the casting speed in the middle and upper part of the mold,and is distributed in the opposite trend in the middle and lower parts of the mold;the interface heat flow increases with the increase of thecasting speed,and has a certain regularity;the temperature of the inner corner center and outer corner center of the Flange shows an upward trend with the increase of the casting speed;the temperature of the starting point and the end point of the outer corner of the Flange and the corner area of the narrow surface showed an upward trend in the upper part of the mold with the increase of the casting speed,and the surface temperature of the strand at the lower part of the mold was the maximum at a casting speed of 1.2 m/min;the temperature at the Flange Tip increases with the increase of the casting speed in the range of 0～345 mm from the meniscus.In the range of 345～720 mm below the meniscus,the surface temperature of the strand shows an opposite trend distribution;Except for the Flange Tip,increasing the superheat of the molten steel will intensify the growth of the air gap in the contraction part of the beam blank.The thickness of the solid flux layer at the interface is distributed in the opposite trend,and the position where the liquid flux is completely solidified moves upward;the interface heat flow and the temperature of the shell during the initial solidification stage increased slightly with the increase of the degree of superheat,and both showed opposite trends as the shell descended.The thickness of the solid flux layer and the liquid flux layer at the Flange Tip decreases as the superheat increases,and the interface heat flow is distributed in the opposite trend. |
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