Study On Solidification Process Of Super-huge Steel Ingot

Nowadays, steel ingots present the trendy to become super large-size with the advent of the large-scale major equipment forgings for the industries of electric power, metallurgy, shipping, petrifaction and so on, and the quality of ingot directly affects the quality of large-scale forging. Owing to the high cost of experimental study, numerical simulation has become an important way to improve ingot internal defects and optimize ingot design. In order to study the influence of riser heat preservation conditions and pouring way on the quality of large ingot, solidification process of large-scale ingot was studied by using computer simulation technology in the paper.The heating agent is always added to the riser after pouring so as to improve ingot quality. Based on the establishment of mathematical model with 0, 50, 100, 200, 300 and 500 heating agent thickness, the influence of the heating agent thickness on the large ingot solidification was studied in the paper, the results were obtained as follow:â‘ The solidification time is 23.7h without heating agent. As the heating agent thickness is added to 50, 100, 200, 300, 500, the solidification time is 26.2h, 28.4h, 30.2h, 31.1h, 31.1h successively. And the final solidified area moves to the riser, V-shaped shrinkage move up and V-shaped opening is getting bigger.â‘¡When the thickness is 300mmm, the size and distribution of the shrinkage no longer change even if the heating agent added is more. Adopting two-pouring method, nine kinds of pouring schemes were designed according to the interval time and the first pouring time. The results were obtained as follow:â‘ Keep the filling rate w1 is 66%, the effect of the interval time tm to the solidification process of ingot is studied in this paper. If the interval time tm is not more than 10h, one shrinkage cavity generates and gets into the ingot, and the shorter of the interval time the larger level of the shrinkage cavity gets into the ingot, which go against the ingot quality; if tm is more than 12h, two isolated liquid areas in the axis, one access to riser, the other access to the ingot, which greatly impact the quality of the ingot. if tm is 11h, one shrinkage cavity generates in the riser and the distance to the ingot surface is 63mm, and the solidification time is 38.4h. So if the interval time is properly controlled, the quality of the ingot can be promoted.â‘¡Keeping the interval time is 10h, the effect of the first pouring time to the ingot is studied. When the first pouring time is 20 minutes(filling rate w1=66%) , the shrinkage cavity generates deep into the ingot about 5mm, which affect the quality of the ingot; When the first pouring time is 22 minutes(filling rate w1=73%) , the shrinkage cavity generates at the place above the ingot about 145mm, which greatly improved the quality of the ingot; When the first pouring time is increased to 24 minutes(filling rate w1=79%) , the shrinkage cavity generates at the place above the ingot about 62mm, so increasing the first pouring time properly can greatly improve the quality of the ingot.â‘¢The preferred plan is the first pouring time of 20min (w1=66%) and the interval time of 10h. The solidification is 36h while using the plan and good quality ingot is got.Meanwhile, interface heat transfer characteristics between the cast and mould by experiment were studied in the paper. In the experiment, a set of test system was designed, the interface heat transfer coefficient was calculated with different gaps and interface temperature by adopting stead-state radial heat flux method combined with electrical measuring method. Meanwhile, interface heat transfer characteristics between the cast and mould by experiment were studied in the paper. In the experiment, a set of test system was designed, the interface heat transfer coefficient was calculated with different gaps and interface temperature by adopting stead-state radial heat flux method combined with electrical measuring method. The relationship between IHTC, gap, interface temperature at the cast and interface temperature difference is found out by means of data analysis and correlation analysis: The degree of the factors affecting the IHTC is in the following sequence: the gap, the interface temperature at the cast, the interface temperature difference, and IHTC varies inversely with gap and interface temperature difference, directly with interface temperature at the cast on the condition that two of the variables are certain. Theoretical analyses and experiments have proved that interface heat conduction and radiation heat transfer dominate, and heat convection is negligible because the air flow at the gap is laminar during the course of the heat transfer.