The Elliptical Shape of the Continuous Cast Round Billet
Continuous casting is one of the key advances in steel production. The technology involves pouring liquid steel from a furnace into a special vessel, where a cylindrical mold moves along its length and pulls the steel in a continuous strand. The liquid steel quickly solidifies, forming a circular cross-section that is then cut into ingots of the desired length.
Due to the mechanical and thermo-mechanical rigidity of the process, there is often some imperfection in the shape of the resulting round billet. The imperfections may manifest as ovality, which is a variation from a true round cross-section. This ovality is typically due to the movement of the molds in the vessel, which causes a deformation of the round billet during its formation.
The typical method of controlling ovality in round billets is to increase the speed of the moving molds and apply an external passivating force to assist in controlling the shape during solidification. While this method is proven to be effective in producing round billets, it can be expensive to implement.
An innovative alternative is to adjust the shape of the round billet by using an elliptical tray instead of a cylindrical one. The elliptical tray is designed to be slightly longer than a cylindrical one in order to encourage a more uniform solidification of the steel.
The elliptical tray, made of a specifically formulated ceramic material, is inserted between the continuous casting machine and the molds in order to adjust the shape of the circular billet. As the round billet moves along the elliptical tray, the deformations on its cross-sectional area reduce significantly.
The resulting shape is a highly consistent ellipsoidal form. This shape has been proven to offer an enhanced mechanical and thermo-mechanical stability that is superior to the cured round shape. As a result, the round billet has a significantly reduced ovality and improved strength.
The elliptical tray eliminates the need for an external passivating force, as it helps control the shape of the billet without any additional cost. In addition, the use of an appropriate core material for the tray enables a rapid solidification process, which helps minimize ovality even further.
The implementation of an elliptical tray for the production of round billets is a cost effective solution that offers improved mechanical and thermo-mechanical stability without having to increase the speed of the molds. This technology provides a means for suppressing ovality in the round billet and reducing the risk of fatigue failure in applications where the round billet is used.
