| With the rapid development of supercritical units and ultra-supercritical units,As a hightemperature heat-resistant material that can improve the efficiency of thermal power generating units,it has become a research hotspot,especially TP91 heat-resistant steel.TP91 is the key material for the transition of the main steam parameters of the generator set from 566? to 593 ?,however,in the traditional continuous casting process,TP91 which is due to lack of feeding ability is prone to have the defects,such as center cracks,loose,serious segregation and other defects,which bring negative effects on the product quality.So it is urgent to solve the defects in order to improve the application of TP91.This project uses different electromagnetic stirring methods to improve the defects in the continuous casting billet of TP91.First,the distribution of magnetic induction intensity in electromagnetic stirrer under different electromagnetic stirring modes is measured and analyzed,and the effects of different electromagnetic stirring methods on the feeding behavior during solidification is investigated by simulation experiments of low temperature alloy.Finally,combining the characteristics of TP91,the experiment of different electromagnetic stirring modes are carried out in the laboratory,focusing on study the effects of different electromagnetic stirring methods on central crack,loose,serious segregation and solidification structure,the main contents are as follows:(1)At 350A/12Hz stirred parameters,the radial magnetic induction intensity changes slightly in R-EMS,and the axial magnetic induction decreases from the center to the sides,the magnetic induction intensity at the center is 0.11 T;magnetic induction intensity decreases rapidly with increasing distance in the direction perpendicular to the agitator in V-EMS,its maximum value is 0.23 T,and the magnetic induction intensity decreases from the center to both sides in the vertical direction.(2)The conclusions of low temperature alloy experiments show:during the solidification process,V-EMS makes the slope of the metal solidified shell larger,the stirring depth is deeper,the feeding capacity is enhanced,and the position of the liquid core is shifted away from the side of the agitator.R-EMS makes the slope of the metal solidified shell small,slope,the stirring depth is shallowand the position of the liquid core is unchanged.The above phenomenon helps to analyze the influence of different electromagnetic stirring methods on the flow of metal liquid flow.(3)Based on result of simulation experiments,comparison of the effects of different electromagnetic stirring methods on the feeding capacity(u/D)of TP91:(u/D)V-EMS>(u/D)R,EMS.(4)Comparison of the effects of different electromagnetic stirring methods on macrostructure of TP91:the macrostructure of TP91 is dominated by columnar dendrites without EMS,the rate od center equiaxed grain is only 5%,the ratio of equiaxed grain is increased to about 78%with R-EMS,but the ratio of equiaxed grain is further increased to 85%.It can be seen that the ratio of equiaxed grain is englarged effectively by V-EMS.(5)Comparison of the effects of different electromagnetic stirring methods and times on equiaxed grain of TP91:without EMS the average size is 160 ?m;when the initial stirring time is 90 s and 150 s,,the average size with R-EMS is 95 ?m and 85 ?m;but with V-EMS,the average size is only 70 ?m and 90 ?m.(6)V-EMS can create an upward electromagnetic force by using travelling magnetic field,generate the longitudinal loop convection,which makes better mixing the upper liquid steel with higher temperature and lower liquid steel with lower temperature,then reduce the segregation of C and Cr,and improve the quality of the slab. |
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