Experimental investigation of temperature-dependent interfacial heat transfer mechanism with spray quenching for 22MnB5 steel

The mechanical properties of heat treatable high strength 22MnB5 steel will become much more excellent after high pressure spray quenching through controlling process parameters. The contact between hot parts and fluid medium is a complex two-phase flow quenching process, which can affect the microstructure and mechanical properties directly. A main objective of this paper is to investigate the influence factors on temperature-dependent interfacial heat transfer coefficient (T-IHTC) law during spray quenching process for 22MnB5 high strength steel. The impact of flow field and boiling stages were analyzed based on single-point spray experimental platform. The Beck's non-linear estimation method was used to calculate the fluid-solid contact T-IHTC between blank and fluid medium. The influence of different process factors, including injection air and water pressure, spray height, initial quenching temperature and oxide layer, were discussed. The results showed that the peak of T-IHTC appears in nucleate boiling stage, the T-IHTC correlates highly with injection pressure by a positive power function, and inverse correlation with the initial quenching temperature and the spray height. In addition, surface oxide layer also has a significant impact on T-IHTC, which impedes the contact between steel and fluid medium, leads to the weakening of heat transfer efficiency.