Unexpected temperature losses in the secondary metallurgy are compensated at the company Hüttenwerke Krupp Mannesmann (HKM) via aluminothermic heating. This process is conducted in a ladle degasser which is equipped with an oxygen-blowing lance. Intention and task of this master thesis is the development of a mathematical model for the calculation of the required amount of aluminium, oxygen, lime and FeSi. Based on this model the required temperature increase after a defined time span shall be achieved whereas the change of the chemical composition of the steel is kept to a minimum. For the development of the model 124 aluminothermically reheated melts are evaluated. The operational sequences during aluminothermic heating, the measured temperature increase and the change of the chemical composition of the steel are described. The interaction between aluminium and silicon regarding the measured temperature increase and the oxygen utilization are examined via multiple linear regressions. The achieved temperature increase based on the oxygen input and the oxidation of elements is also determined. In addition slag samples were taken to evaluate the influence of metallurgical reactions in the slag for the oxidation of the elements. The maximum attainable temperature increase by oxidizing aluminium and silicon for 100 % thermal efficiency is calculated. Facilities for reheating in the secondary metallurgy and operating results are presented. The influence of aluminothermic heating on steel cleanliness and desulfurization is explained.