Modelling the As-cast Structure in Large Stell Casting

An industrial steel casting might easily weigh from several tons up to one hundred. They are produced either discontinuously as large ingots or continuously by forming slabs or billets. All these products reveal a certain as-cast structure which can be classified as columnar dendritic, equiaxed dendritic, or of mixed type. Due to the large tonnage, the castings may take days or weeks to solidify; several transport and accompanying redistribution phenomena can happen during this time, e.g. by crystal motion and melt convection. Understanding these phenomena is one of our key interest.

Our research has the potential to optimize the casting parameters by controlling the as-cast structure and minimizing the macrosegregation in industry castings (ingots and continuous casting of steel, DC casting of non-ferrous alloys). It may aid industry to design new solidification processes (e.g. semi-continuous casting of steel). It will also be important as it allows an integration into industry 4.0 as an important part of the virtual/intelligent manufacturing.

The primary aims and objectives of this research topic are:

  • To understand the formation of the as-cast structure of steel castings that are manufactured at an industrial scale;
  • To develop a numerical model for the mixed columnar-equiaxed solidification considering columnar-to-equiaxed-transition (CET) and macrosegregation;
  • To model the electromagnetic stirring during continuous casting, and its effect on the as-cast structure (crystal fragmentation);
  • To apply the numerical model to aid industry to optimize the casting processes (ingot, continuous casting);
  • To apply the numerical model to aid industry to design a new casting process (semi-continuous casting);
  • To further evaluate the numerical model by comparing the modelling results with laboratory experiments and plant trials.

Examples of recent achievements are given in Fig. 1. Further details on that topic can be found in

  • M. Wu, A. Ludwig, A. Kharicha: “Simulation of as-cast steel ingot, a review”, Steel Res. Int. 89 (2018) 1700037.
  • Y. Zheng, M. Wu, A. Kharicha, A. Ludwig: “Incorporation of fragmentation into a volume average solidification model”, Modell. Simul. Mater. Sci. Eng.26 (2018) 015004.
  • A. Ludwig, M. Wu, A. Kharicha: ”On Macrosegregation”, Metall. Mater. Trans. A46 (2015) 4854-67.
  • M. Wu, A. Ludwig, A. Kharicha: “A four phase model for the macrosegregation and shrinkage cavity during solidification of steel ingot”, Appl. Math. Modelling41 (2017) 102-20.
  • M. Wu, Y. Zheng, A. Kharicha, A. Ludwig: “Numerical analysis of as-cast structure, macrosegregation and shrinkage cavity in steel ingots: case study of a 36 tons’ ingot”, 7th Int. Conf. on Mod. & Simul. of Metall. Processes in Steelmaking (STEELSIM2017), Qingdao, China, 129-32.
  • Y. Zheng, M. Wu, A. Kharicha, A. Ludwig: “Concept of semi-continuous casting (SCC) for large steel strand: a numerical study ”, China Symposium on Sustainable Steelmaking Technology, Oct. 24-26, 2018, Tianjin, China, Proceedings in electric device:  355-357.
  • J. Li, M. Wu, A. Kharicha, A. Ludwig: “The predication of macrosegregation in a 2.45 tons’ steel ingot with a mixed columnar-equiaxed three phases model”, Int. J. Heat and Mass Transfer72 (2014) 668-79.

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