Twin-roll casting is an energy-efficient technology for the magnesium strip production consisting of casting and rolling combined in one process step. Producing magnesium strips in an adequate quality-price ratio requires the application of material flow cost accounting to identify hidden improvement potentials. In the following, a material flow cost accounting analysis is carried out for the twin-roll casting process of AZ31 twin-roll-cast strips. Based on the findings, inefficient process steps of the twin-roll casting process are to be revealed, and actions for cost reduction from the point of a stable process management are to be assessed. Overall, an economic process and efficient material consumption can be designed for twin-roll casting considering the strip property development.

Introduction
Value for money is an important criterion for the acceptance of magnesium components by Original Equipment Manufacturers for an industrial application. Beside external business process optimization in the context of supply chain quality individual process steps need to be further improved to achieve the required quality-price ratio [1]. Especially in case of the twin-roll casting technology for the production of magnesium strips [2] the detection of saving potentials is considerable challenging. Compared with other production routes it is an economic and resource-saving procedure combining casting and rolling in one process step [3, 4].To realize additional cost savings, hidden material and energy inefficiencies need to be detected deriving measures for improvement. Supporting transparency of material and energy consumptions and its environmental and financial consequences material flow cost accounting is a useful tool to identify concealed inefficiencies [5, 6]. Therefore, the objective of this paper is to carry out a material flow cost accounting analysis for the twin-roll casting of magnesium AZ31 twin-roll-cast strips at the pilot plant of the Institute of Metal Forming at the TU Bergakademie Freiberg [7]. For this purpose, the twin-roll casting process is initially briefly described. Building on this, the material flow cost accounting analysis is conducted enabling a detailed view of all material and energy flows during twin-roll casting via material flow models. In the next step, the identified energy and material flows are illustrated as Sankey diagram proportional to their mass and energy content. To identify weak points, cost drivers and optimization potentials a material flow cost matrix was developed, whose results will be evaluated in this paper. Based on the technology’s limitations appropriate improvement actions are proposed for further research.