Centre segregation is the main reason for cup fracture during drawing of high carbon wire rod. Therefore, producing continuously cast billets with very low centre segregation is an important objective. The soft reduction technology is considered to be an effective method to minimize centre segregation. In order to clarify the effectiveness of soft reduction on internal quality of high carbon steel billets, soft reduction was applied in a laboratory casting machine while the solid fraction in the core area of billets was varied. A coupled temperature/displacement Finite Element model was developed to calculate the solid fraction with the commercial software ABAQUS. Centre segregation, centre porosity, homogeneity of elements and equiaxed crystal zone were obviously improved by applying soft reduction, especially when the solid fraction was about 0.9.

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The high temperature properties of steels depend on the solidification parameters and the formation parameters of manganese sulphide precipitates. Therefore, the occurrence of MnS precipitations in relation to primary and secondary microstructures was studied for different steel grades with a primary delta-ferritic solidification or a primary austenitic solidification. The liquidus and solidus temperatures as well as the by-transformation temperature were calculated thermodynamically and measured by a DTA analysis in order to describe the solidification and transformation temperature range. The MnS formation temperature was calculated thermodynamically and compared to the results of SEM/EDX investigations on fracture surfaces of hot tensile specimens torn at different temperatures after in situ melting and controlled solidification. A special focus of these investigations was the location of MnS precipitates in relation to the primary and secondary grain boundaries. To explain the results, calculations were carried out taking into account the supersaturation of manganese and sulphur during the solidification in residual melt on the primary grain boundaries.

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Thixoforming is a new manufacturing technology which has been widely investigated for aluminium alloys. The thixoformability of steel and especially the impact of different pre-processing is subject of this paper. For the thixoforming process it is of special interest to obtain the required fraction liquid content between 20 and 40 %, a globulitic microstructure and low process temperatures. Therefore, steel primary material from three different processing routes was compared. The primary materials are rolled bars, laboratory cast billets and laboratory cast billets with liquid core reduction. The melting behaviour of the different materials was investigated by using Differential Thermal Analysis (DTA). Furthermore the materials were reheated into the solid-liquid range and quenched to monitor the development of the microstructure. No significant differences between the three different pre-processing routes could be determined with regard to thixoforming. Thus it seems possible to start thixoforming with as-cast primary material.