Numerical Simulation Of Flat Ingot Solidification Process And Technical Parameters Inquiry In Water-Cooling Mold

With the development of machinery, chemicals, and electric power industry, there is a increasing demand of special plate, and the requirements of quality are more stringent. The raw material of special plate production includes mold flat ingot, forging billet and continuous casting slap. Using forging billet as the raw material for special plate production has many shortcomings, such as large investment, high energy consumption and low metal utilization. Continuous casting slap is also restricted to single weight and compression ratio. Therefore, mold casting has an important position in the production of large flat which are used to as raw material of special steel ingot.Water-cooling mold casting has the advantages of large cooling intensity, fast solidification rate and high production efficiency, so it brought to the attention of many steel enterprises in recently years. Many steel enterprises build water-cooling mold casting facility to product flat ingot, such as Nanjing Iron and Steel Company, Yingkou medium-sized plat Company. But from the beginning of design to now, due to lack of casting, solidification process control systems theory for its technical support, has yet to achieve continuous and stable production.In this paper, we take the water-cooling flat plate ingot produced by a domestic enterprise as the prototype. Explore the new technology of produce large flat slap using of water-cooling mold casting and soft reduction in continuous casting slab. Study on the solidification process of water-cooling mold casting, to find out the rule of gap form and growth and the influence of gap on solidification process, for provides a theoretical basis for soft press to vanish air gap in the solidification process. Study the advancing of solid-liquid interface to provide a theoretical basis for soft reduction in the last period of solidification process. And study the influence of soft reduction on flat ingot’s central shrinkage cavity. In this paper, we also put a study on the technical parameter.In this paper, we simulation study the filling and solidification process of water-cooling mold casting flat ingot of size 2300mm×2000mm×500mm, the findings are as follows:(1) When the casting speed is too small, the filling process is very gentle and the level rise is very steady, but will generate shunt phenomenon at the down sprue resulting gas involved in liquid steel; when the casting speed is too fast, although the elimination of shunting, but will cause spattering of molten steel and bring slag to liquid steel in filling process. So the most suitable casting speed is 0.7 m/s in the range of this simulation condition.(2) With the increasing of pouring temperature, the columnar grains become more and more flourishing, and the shrinkage cavity depth is increased. Therefore, in the premise of successfully pouring, the pouring temperature should be reduced as far as possible, so the pouring temperature of 1530℃ is appropriate.(3) When the water-cooling intensity of mold walls and chassis is the same, bridging phenomenon will occur in the final period of solidification, bring about porosity and shrinkage cavity in the center of ingot. Increasing the differences of water-cooling intensity between mold walls and chassis is conducive to eliminate shrinkage phenomenon in the center of ingot. Decreased water-cooling intensity form the bottom of mold walls to the top is also conducive to eliminate shrinkage phenomenon in the center of ingot.(4) At the start of solidification, an air gap begins to form between the ingot solidified shell and the mold within a very short period of time, the gap width reaches 0.2mm to 0.5mm after solidification of 75s to 100s, started to exert an significantly influence on solidification process of heat transfer. The rate of temperature drop at surface node significantly reduced since the form of gap. At the end of the ingot solidification, the air gap width on the narrow surface is relatively large when compare with broadside, and there is some difference between the two narrow surfaces on air gap width, the air gap width on the surface closed to sprue is 12mm to 20mm, and the air gap width on the surface closed to sprue is 4mm to 13mm. The air gap width on the broadside surface is relatively small, the maximum air gap width is about 6.5mm. After the air gap form between the ingot solidified shell and the mold, the time of ingot completely solidified is extend by about 50%.(5) It is useful to eliminate the porosity and shrinkage phenomenon in the center of ingot by take soft reduction on the surface of ingot. Under the simulated conditions of this paper, the soft reduction displacement of 4 mm is more appropriate.