SYSTEMS FOR CONTROLLING THE TIME OF SUBMERSION OF PARTS IN A QUENCHING LIQUID IN PERIODIC AND CONTINUOUS-PROCESSES

The susceptibility to crack resistance and warping and the uniformity of hardness distribution over the cross section of a part can be impro ved by controlling the direction and the degree of stirring of the coo ling liquid in quenching. In the initial stage of quenching the coolin g rate of the part should be high in order to obtain the requisite har denability. When the core of the steel part is cooled to the temperatu re of the start of martensitic transformation (M(s)), the cooling rate should be decreased. Stirring seems to be a principal method of affec ting the cooling rate in quenching and can be an ideal means if it is possible to change the stirring rate in correspondence with the requis ite conditions. At present, this can be achieved comparatively easily with the help of a computer-aided system for control of the time of su bmersion of parts in the quenching liquid (SCST). SCST are currently u sed by some plants in Korea The article concerns the principles and us e of SCST with the purpose of replacing oils by water-soluble polymer cooling liquids for quenching.