Design Principles of Copper Tubes Inner Casing Shape of Continuous Casting and Rolling Machine Ingot Mould
Abstract: The molten metal is continuously poured into the ingot mould attached to the continuous casting and rolling machine (CCR) through copper tube. The inner cavity shape of copper tube has a great influence on the surface state, internal structure and performance of steel billet. Therefore, the inner cavity shape of copper tube is the key factor to determine the quality of CCR billet. Thus, in the design of inner cavity shape of copper tube for CCR billet machine, according to the flow state of molten steel in copper tube, the inner cavity structure of copper tube should be designed reasonably, so that the molten steel is evenly distributed in the copper tube, so as to ensure the surface of the billet is of good quality.
Keywords： Continuous Casting and Rolling Machine, Ingot Mould, Copper Tube, Inner Cavity Shape Design
1 Introduction
Continuous Casting and Rolling Machine (CCR) is a high efficient and advanced steel production equipment. In CCR process, the molten steel is continuously and vigorously poured into the ingot mould attached to the CCR through the copper tube. The shape of the copper tubes inner cavity has a great influence on the surface state, internal structure, quality and performance of the steel billets. Therefore, the inner cavity shape design of the copper tube is the key factor to determine the quality of the steel billets.
At present, in the design of the inner cavity shape of the CCRs ingot mould, most of the research focuses on investigating the hydraulic property of molten steel in the ingot mould, while the hydrodynamic property of molten steel in the copper tube was not taken into account. This is an important mistake. Therefore, it is necessary to conduct a systematic research on the design principle of the inner cavity shape of the copper tube for CCR ingot mould, so as to provide a scientific basis for actual design.
2 Literature Review
In recent years, research on the inner cavity shape design of copper tube for CCR ingot mould has been conducted from a variety of perspectives.
Koga (1988) research on the inner cavity shape design of copper tube for CCR ingot mould from the perspective of numerical simulation. Koga (1988) established the flow model of molten steel in copper tube and studied the influence of the inner cavity shape of copper tube on the flow state of molten steel. This research results that it’s important to maintain an optimal balance of the flow rate and wall shear stress in order to obtain better quality billet.
Wang et.al (2003) proposed a design theory based on the combination of hydraulic principle, practice and theory. This design theory focuses on how to control the flow pattern of molten steel in the copper tube so as to achieve uniform distribution of molten steel in the ingot mould and minimize the occurrence of shelling.
Qualey et.al (2003) conducted research on the inner cavity shape design of the copper tube for CCR ingot mould from the perspective of fluid mechanics. The research results show that the inner cavity shape design of the copper tube should rationally combine the resistance of the molten steel and the inertia force of the molten steel, so as to ensure that the flow of the molten steel is evenly and reasonably distributed in the ingot mould.
3 Design Principles
3.1 Flow Pattern of Molten Steel in Copper Tube
In order to reduce the effect of turbulence on the quality of billet, the flow pattern of molten steel in the copper tube should be gentle, uniform and steady. During the flow process, the molten steel should be evenly distributed in the ingot mould and there should be no dead angle and cavitation.
3.2 Optimal Balance between Flow Rate and Wall Shear Stress
In order to obtain better quality billet, it is necessary to maintain an optimal balance of the flow rate and wall shear stress in the copper tube. This can be done by adjusting the inner tangential angle and outer diameter of the copper tube.
3.3 Rational Combination of Resistance of Molten Steel and Inertia Force
The inner cavity shape design of copper tube should rationally combine the resistance of molten steel and the inertia force, so as todelay the deceleration and ward offturbulence at the stagnation point. This can be achieved by properly increasing the radius and the taper angle at the stagnation point.
4 Conclusions
In the design of inner cavity shape of copper tube for CCR ingot mould, the theoretical research mainly focuses on thehydraulic property of the molten steel in the ingot mould, while the hydrodynamic properties of the molten steel in the copper tube are often ignored. It is necessary to consider both the hydraulic and hydrodynamic properties during the design of inner cavity shape of the copper tube. Theinner cavity shape should be designed based on the flow state of molten steel in the copper tube, so that the molten steel is evenly and reasonably distributed in the ingot mould.The optimal balance of the flow rate and wall shear stress should be maintained, and the resistance of the molten steel and the inertia force should be combined reasonably in order to reduce the effect of turbulence on the quality of the billet.
