The decarbonization of steel production processes will lead to the increased use of scrap - including low-grade scrap - in the future. In addition to the more difficult control of some residuals in electric arc furnace steelmaking, tramp elements could also lead to problems in the manufacturing processes. In continuous casting, tramp elements such as Cu and Sn may cause network cracking and the so-called Cueq is still the most common indicator for surface defect susceptibility. This study addresses the experimental simulation of surface defect formation and the role of Cu, Sn, and Ni for the temperatures 900 and 1100 °C. Its goal is to define an optimized operational window for continuous casting. Experiments were conducted utilizing the in-situ material characterization by bending (IMC-B) test which characterizes the crack sensitivity of steel after controlled solidification and subsequent cooling under an adjustable water vapor atmosphere. The tests were performed on medium carbon steel with varying but moderate concentrations of Cu, Sn, and Ni. Results indicate that the simultaneous presence of Cu and Sn leads to a notable increase in the occurrence of surface cracks. This is attributable to the formation of partially liquid phases in the area of the grain boundaries due to selective oxidation. However, the introduction of Ni into the alloy composition demonstrates a substantial improvement in crack mitigation. This finding emphasizes the importance of carefully managed tramp element content, particularly Cu and Sn in the continuous casting process to minimize crack formation during straightening but also indicates a strong influence of thermal history and bending temperatures.