Parameter Optimization And Control Of Secondary Cooling Of Bloom Continuous Casting

The control of secondary cooling is a very important for continuous casting of billet and has significant effects on the billet quality.Many billet defects,such as:shape defect,inner defect,surface defect,etc.,origins from improper secondary cooling control.Also the secondary cooling affects the solidification rate and casting speed.Therefore,the fundamental study of secondary cooling is of importance for the billet continuous casting.The aim of the present paper is to solve the quality defects of continuous casting billet of No.l Steel-making plant,Xinjiang Bayi iron and steel company.Firstly,the comprehensive investigation on the inner crack cause of the billet continuous casting was carried out.Secondly,the numerical simulation of the billet continuous casting of steel HPB235 was performed and the effects of casting operation parameters(casting temperature,casting speed,secondary cooling water flow-rate)on the solidification process of steel HPB235 were investigated.Finally,the dynamic flow-rate of secondary cooling water was proposed and successfully employed in billet continuous casting.The main conclusions were listed as followings:(1)The statistics results show that the main causes of the billet inner crack of of No.l Steel-making plant,Xinjiang Bayi iron and steel company are the improper secondary cooling water flow rate and clogged nozzle.(2)The numerical results of the billet continuous casting of steel HPB235 show that when the casting speeds are 3.0m/min,3.3m/min and 3.6m/min,the solidification ends are respectively 17.6m,19.7m and 21.5m;when the superheats are 20?,30?and 40?,the solidification ends are respectively 17.6m,17.9m and 18.2m;when the secondary cooling water flow rate decreases from 1.81L/kg to 1.73L/kg,the strand surface temperature increase 30?,and the straightening temperature is higher than 900?,which can avoid the billet inner crack.(3)The dynamic flow-rate of secondary cooling water is proposed and successfully employed in billet continuous casting.The straightening temperature of billet continuous casting of HPB235 reaches 900? and the billet inner crack is improved.(4)After the application of the dynamic flow-rate of secondary cooling water,the inner billet quality is improved significantly.The ratio of the billet inner crack decreases from 18%to 6.7%,the average crack index decreases from 2.5 to 2,and the maximum crack index decreases from 3 to 2.5.