engleski

Selection of Optimal Conditions for Immersion Quenching

Quenching steel parts by immersing them in liquid quenchants is still the most used method for hardening carbon and low alloyed structural and tool-steels. The achieved hardness, residual stresses and distortion of a workpiece depend on the selection of the quenchant, the phenomena of nonlinear heat transfer and on used cooling parameters. The non- steady heat transfer at liquid quenchants, because of film-boiling, nucleate-boiling and convection stages, is the main reason why the cooling rate depends on temperature. In most cases the actual cooling rate does not completely fit to the required transformation of microstructural phases in steel, depending on its hardenability and the chosen point of the workpiece’s cross-section. By application of the automatic control of specified process parameters it is possible in some conditions to regulate the cooling rate and adjust the heat transfer coefficient to the required cooling of the workpiece. The present work explains the theoretical principles of the automatic control at immersion quenching.

steel quenching; controlled heat extraction; heat transfer coefficient; cooling curve

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