While the heat treatment of steel plates was first limited to plates of medium thickness,the demand of the market has meanwhile extended to thick and particularly to very thin plates.The heat treatment of thick plates requires an adjustment of the mechanical system and the loading capacity of the rollers.For thin plates,however,significantly more work is required to achieve a uniform full hardening and sufficient flatness of the plates.The rollers and nozzles of the quench must be exactly aligned to each other as a non-uniform cooling of the plate upper- and lower side will lead to plate warping.More efforts are even required for gaining the defined mechanical properties of the plate.Thus the various nozzle zones of the quench must be individually controlled.Attention is to be paid to maintain a uniform cooling effect on the plate upper- and lower side,which is only possible within a small dynamic range due to the given characteristic of the nozzles.To meet these requirements,the quench device was further enhanced.Due to the very complex requirements to be fulfilled by the quench process in order to attain special mechanical features,recipes can only be developed by use of mathematical tools.These tools are based on TTT-diagrams and a numerical control for the cooling speed.Analyses of the heat transition of different nozzles depending on geometry,volume flow and inlet pressure help to adjust the water impact and the resulting heat transition.Mathematical models have also already been used to solve heat transition problems arisen in other fields of application,for example : the successful commissioning of an annealing plant for railway wheels.The mathematical models do not only allow developing recipes without scrap production,but also provide possibilities which could otherwise only be achieved by test runs during several years.