| Continuous casting tube blank was the main blank form of seamless steel tube forming,and it had an important impact on the quality of steel tubes.The central defects,such as segregation and looseness in the continuous casting tube blank,tended to cause internal folds in the tube during the tube blank rolling process,which reduced the inner wall quality of the seamless steel pipe.The viscoplastic deformation in solidified end of the continuous casting billet,extrusing the molten steel enriched in the solute and welding the shrinkage and looseness,could effectively improve the core quality of the casting blank,and was an effective way to improve the overall quality of the continuous casting billet.However,at present,considering about the shape cross section of continuous casting tube blanks,there were few studies on the viscoplastic deformation of the solidification end in tube blank.In this paper,a ?500 continuous casting machine was set as the study object.The three-dimensional model of the solidification end reduction device of continuous casting tube blank was established by ABAQUS,and the rheological behavior of the solidification end position,liquid core deformation process in the continuous casting process,and reduction parameters were studied for the degree of healing of the tube blank defect.The main results are as follows:(1)According to the on-site process parameters of ?500 continuous casting machine,the solidification heat transfer model of continuous casting tube blank was established by Procast software.The solidification process of continuous casting tube blank was studied.The test results were compared and analyzed to verify the accuracy of the model.The exact position of the solidified end of the continuous casting tube blank was obtained by numerical simulation,and the effect of specific water volume,drawing speed and superheat on the solidification end position of the continuous casting tube blank was simulated.The simulation results showed that the limit was present in the casting speed of the continuous casting machine.When the drawing speed exceeded 0.43 m/min,the solidification end of the continuous casting tube blank appeared in the tensioning section of the continuous casting machine,and the continuous casting tube blank was prone to cracks.(2)Through the high temperature hot simulation compression experiment,the stress-strain curves of the material at high temperature were obtained,and the high temperature viscoplastic constitutive equation of the material was established,which provided the basis for the establishment of the solidification end reduction model of continuous casting billet.Using the formula,the elastic modulus of molten steel at 1400? was 8.608 GPa,and the elastic modulus was 5.728 GPa when the molten steel temperature was 1450? and above.Besides,the yield stress was 0.976 MPa when the molten steel temperature was 1400?.The yield stress at the time of 1450? was 0.962 MPa.(3)The liquid central reduction of continuous casting tube blank was deduced and calculated.The liquid central reduction of ?500 continuous casting tube blank was 82.52 mm2,and the total surface reduction of the pressing device was calculated to be 30 mm.The channel elongations were ?1=1.0545,?2=1.0422,and ?3=1.0298,and the inscribed circle diameters of the holes were 488.76 mm,478.70 mm,and 472.67 mm,respectively.(4)Using the established three-dimensional compression thermal coupling model of the solidification end of the continuous casting tube blank,the machining process of the solidification end reduction process of the continuous casting tube blank was simulated,and the stress field,strain field and tube blank deformation during the pressing process were simulated.The degree of uniformity and the flow behavior of the metal were studied.The maximum reduction efficiency at the wick of the tube was 33%,and the minimum reduction efficiency was 16.7%. |
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