Determination of the Geometry of Ingots with Minimal Development of Defects in the Axial Zone and Their Application for the Production of Round Bars with Diameters Greater Than 300 MM

Abstract

On the basis of the data of computer simulation, we perform the analysis of the influence of the geometry of ingots and the procedure of their thermal insulation on the specific features of their solidification and the development of shrinkage defects. A 2⁷ complete factorial matrix of the experiment was designed and realized for the description of the dependence of the diameter of axial sponginess on the values of geometric, thermal, and engineering parameters of the molds and the melt. We establish the relationship reflecting the influence of each factor on the development of shrinkage defects. On the basis of the results of processing of the data of simulations, we determined the geometric and technological parameters of a 7.0-ton ingot. The pilot-production testing of the designed 7.0-ton ingot shows that its application makes it possible to increase the directedness of the process of solidification due to the 1.3-fold decrease in the rate of propagation of the solid phase in the horizontal direction, which improves the process of feeding of the axial zones of the ingot with head melt. The choice of the most efficient heat-insulating materials makes it possible to increase the thermal power of the head by 20.8%, which guarantees the possibility of efficient replenishment of shrinkage in the axial zone of the ingot. The realization of the procedure of directional solidification in combination with a more effective thermal insulation of the head makes it possible to reduce the development of shrinkage defects in the ingot and in the rolled bars produced from this ingot. The analysis of the quality of 320 mm rolled bars produced from the 7.0-ton ingot shows that its application makes it possible to reduce the level of rejection based on the ultrasound control, while the ingot-to-product yield increases by 2.0%.