Optimization of internal quality improvement of continuous casting billets containing V steel
In order to solve the problem of internal cracking of vanadium-containing steel in the continuous casting process,the solidification process analysis,organization prediction and surface temperature control of HRB500E re-bar steel were carried out by using thermodynamic calculations,solidification organization simulation and the method of second-cooling water distribution control.It was found that the thermodynamic precipitation temperature of V(C,N)in the rebar steel was 1118 ℃ and the maximum precipitation amount was 0.06 wt％,which indicated that vana-dium had the dual raction of precipitation strengthening and solid solution strengthening;the organization analysis of the as-cast billet showed that when vanadium was increased from 0 wt％to 0.089 wt％,the grain radius was re-duced by 2 times,the number of grains was increased by 2.8 times,and the central equiaxial crystal was increased by 2.2％.It shows that the addition of vanadium can refine the grain,improve the organizational properties and gain metallurgical properties;at the same time,it is found that the reason for cracks and other defects is mainly due to the unreasonable water distribution of the second cold,resulting in the surface of the billet return temperature is too large.Based on this,a corresponding optimization of secondary cooling water distribution process has been pro-posed,along with the introduction of a three-section program for 2.9 m length of secondary cooling process,and ul-timately designed a 1.4-2.7 m/min pulling rate of the water table,the surface of the billet return temperature was below 100 ℃ and the return temperature met the metallurgical guidelines.Industrial production has proved that the internal quality of billet has been greatly improved by the optimization of water distribution in the secondary cooling.
vanadium-containing steelcontinuous casting billetinternal crackingsecondary cooling water distri-butionoptimization
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