Spray quenching refers to a wide variety of quenching processes that involve heat removal facilitated by the impingement of a quenchant medium on a hot metal surface. This article provides information on the basic concepts of spray quenching, and discusses the most commonly used techniques in quench tank agitation to establish uniformity of the quenched part. Common techniques include quenchant stirring, quenchant circulation, and submerged jet/spray mixing. The article also describes the effect of quenching agitation and reviews heat-transfer characteristics of immersion quenching and spray quenching with water.

The role of a mixer/agitator in quenching applications is to control the mixing environment in order to meet the process criteria. This article provides the basic fundamentals of the sizing of agitators, tank geometry importance, and other considerations for the application of agitators in quench tanks. It also discusses the differing methods for the sizing and selection of agitators for quench tank applications.

Agitation is one of the most critical areas of quench system design. This article provides an overview of the impact of agitation on quench uniformity, followed by a general discussion of the selection and use of various types of agitators, including recirculation pumps, jet mixers, forced air (sparging), and impellers. A brief overview of heat-exchanger types and their selection criteria is also provided, along with simplified calculations for approximating heat-exchange requirements. The methods of selecting a quenchant are provided. Recommendations for system maintenance are also described. Much effort is placed on the proper design of the furnace for temperature and atmosphere uniformity, proper temperature control, and exact carbon potential. However, the design of the quench tank can have a drastic effect on the overall system performance, with proper design ensuring proper mechanical properties (hardness, strength, and fracture toughness) as well as distortion control.

Quenchant agitation can be obtained by circulating quenchant in a quench tank through pumps and impellers. The selection of the agitation method depends on the tank design, type and volume of the quenchant, part design, and the severity of quench required. This article describes flow measurement methods, temperature control, materials handling, and filtration processes during the agitation process. The maintenance of quenching installations is also discussed.

Induction heating for hardening of steels has advantages from the standpoint of quenching because parts are individually processed in a controlled manner. This article provides information on the effect of agitation, temperature, hardening, residual stresses, and quenching media, on quenching. It also describes various quenching methods for steel induction heat treating, namely, spray quenching, immersion quenching, self or mass quenching, and forced air quenching. The article also reviews quench system design and quenchants and their maintenance.

Flow visualization is an important characterization process to not only understand uniformity of the interfacial cooling mechanisms, but also to characterize the overall impact of agitation on the uniformity of the overall cooling process. This article focuses on thermal flow simulation and visualization in the quenching process. The study presents the effect of bubbling, boiling, and breaking the steam film on the heat-transfer coefficient during the agitated quenching process.

Quenching refers to the rapid cooling of metal from the solution treating temperature, typically between 465 and 565 deg C (870 and 1050 deg F) for aluminum alloys. This article provides an overview on the appropriate quenching process and factors used to determine suitable cooling rate. It describes the quench sensitivity and severity of alloys, quench mechanisms and the different types of quenchants used in immersion, spray, and fog quenching. The article provides a detailed description of the quench-factor analysis that mainly includes residual stress and distortion, which can be controlled by proper racking. It concludes with information on agitation and the quench tank system used in the quenching of aluminum alloys.

Quenching severity is agitation-dependent and therefore, magnitude and turbulence of fluid flow around a part in the quench zone are critically important relative to the uniformity of heat transfer throughout the quenching process. This article provides an overview of the measurement principles for different types of flow devices used in production quench tanks, namely, vane sensors, fluid-quench sensors, caterpillar quench-evaluation sensors, and thermal probes. Various methods of flow measurement in commercial quench tanks may be acceptable for adequate control to ensure a high-quality production process.

Molten salt, including nitrite/nitrate salts, is the quenching medium most commonly used in austempering and marquenching of ferrous materials. This article describes the use of molten salts in the quenching of ferrous materials. It provides information on the processing and operation of salt quenching including considerations of time, temperature, environment, and safety, as well as critical characteristics such as the composition of the quenchant, agitation, and water additions.