CRITICAL HEAT-FLUX DENSITIES, QUENCHING INTENSITY AND HEAT EXTRACTION DYNAMICS DURING QUENCHING IN VAPORIZABLE LIQUIDS

摘要

Besides the cooling curve analysis of laboratory test specimens, the first critical heat-flux density (q{sub}(crl)) and the second critical heat-flux density (q{sub}(cr2)) can be used to characterize the quenching intensity in workshop practice. By using the Liscic/Nanmac quench probe it is possible to determine q{sub}(cr2) and then calculate q{sub}(crl). In this paper critical heat-flux densities have been determined when quenching this probe, having 50 mm Dia × 200 mm length in: oil, water, and a polymer solution of high concentration. The probe itself records the heat-flux density vs. time and vs. surface temperature during the whole quenching process, representing the heat extraction dynamics. After quenching cylindrical bars of 50 mm Dia, made of AISI 4140 steel and measuring hardness through the cross-section, it was found that the hardness distribution depends not only on the quenching intensity but primarily on the heat extraction dynamics.