High Convection Quenching

The past few decades have brought quenching technology to a point where, in many cases, the quench has as much impact as heat treatment itself. Challenges associated with traditional (liquid) quenching have been well documented, yet they remain present in industry. Issues associated with quench uniformity and maintaining rapid quench rates present design challenges for engineers tasked with processing parts to achieve low distortion and desirable residual stress states. Several solutions to these problems already exist. For example, agitation of liquid quench media to limit non-uniform cooling. Another method known as intensive quenching uses a water and mineral salt solution combined with rapid recirculation or agitation to achieve higher than normal liquid quench cooling rates, although it remains unadopted on a wide scale.

High convection quenching (HCQ) is a term which can be defined broadly as a quenching process that uses sufficient convection (whether it be fluid quenchant or gas) to attain consistently high cooling rates up to and past the formation of martensite. It should be noted that this is not a specific operation or media used for quenching, but instead a term coined for a category of quenching techniques operating under the same principles. The present work combines finite element analysis (FEA) simulation with experimental results to explore the effectiveness of utilizing different methods for achieving HCQ. Specific addressed quench processing includes direct and interrupted quenching techniques. The overall goal is to tailor the microstructural composition to alter bulk-scale material properties such as hardness, toughness, and residual stress profile while tracking dimensional stability. The concepts are showcased on AISI 52100 and select low-to-medium carbon steels. While the properties and performance of these tests are material specific, the general trends and applications may extend beyond the scope of this project.