The knowledge of the thermal boundary conditions helps to understand the heat transfer phenomena that takes place during heat treatment processes. Heat Transfer Coefficients (HTC) describe the heat exchange between the surface of an object and the surrounding medium. The Fireworks Algorithm (FWA) method was used on near-surface temperature-time cooling curve data obtained with the so-called Tensi multithermocouple 12.5 mm diameter x 45 mm Inconel 600 probe. The fitness function to be minimized by a Fireworks Algorithm (FWA) approach is defined by the deviation of the measured and calculated cooling curves. The FWA algorithm was parallelized and implemented on a Graphics Processing Unit architecture. This paper describes the FWA methodology used to compare and differentiate the potential quenching properties of a series of vegetable oils, including cottonseed, peanut, canola, coconut, palm, sunflower, corn, and soybean oil, versus a typical accelerated petroleum oil quenchant.

Many alternative ecofriendly quenchants have been developed to replace mineral oil such as vegetable oils, polymer quenchants, and nanofluids. Although vegetable oils show superior cooling performance to mineral oil, their use is limited due to high production costs and low thermal stability. In this study, used coconut oil was chemically treated and its cooling and heat transfer characteristics were compared with that of refined coconut oil and mineral oil. The thermophysical properties of chemically treated waste coconut oil were found to be higher than that of the other oils tested, and its wettability proved to be better as well. Quenching experiments using an Inconel 600 probe (as per ISO 9950 and ASTM D 6200 standards) showed that the vapor blanket stage was shorter for the chemically treated oil than either of the others. The treated waste oil was also found to have the highest average peak heat flux based on the solution to the inverse heat conduction problem.

Excessive distortion was observed in many small components made from 1080 steel that was neutral hardened following stamping. A study was then undertaken to determine how to reduce the distortion of the heat-treated parts while maintaining proper hardness and microstructure. A numerical simulation based on Simheat software was conducted to determine the effect of elevated temperature on the quenching oil used and its impact on distortion and microstructure. A second oil designed to operate at higher temperatures was also examined. Using Simheat software, the two oils were compared based on predicted distortion, hardness, and microstructure and the results were subsequently validated using empirical methods. It was concluded that a significant improvement in distortion could be achieved by using a different oil and higher quench temperatures.

In various studies, heat transfer coefficients (HTCs) have been used to characterize the relative ability of a quenching medium to harden steel. In this current work, HTCs are determined for a series of vegetable oils using a stochastic (particle swarm) optimization technique and cooling curves produced via Tensi probe measurements. The vegetable oils investigated include canola, coconut, corn, cottonseed, palm, peanut, soybean, and sunflower oil, and their quenching performance is compared with that of a typical petroleum oil quenchant.

In this investigation, the authors use a Tensi probe to obtain cooling curves for canola and palm oils and determine their heat transfer coefficient profiles. For comparison, the cooling curve of an accelerated petroleum oil quenchant is also presented. Canola oil exhibited minimal evidence of film boiling, while palm oil showed a pronounced film boiling behavior. This behavior suggests the presence of unrefined volatile by-products or subsequent degradation. The petroleum quenchant exhibited wetting front movement along the Tensi probe not observed with the vegetable oils.

Quench oil is susceptible to contamination from carbon deposits, dirt, water, and the byproducts of oxidation. This paper discusses the causes of contamination in quench oil and explains how they lead to reduced oil life, sludge accumulation, loss of production time, unplanned maintenance, variations in the quench curve, surface deposits, and rework costs associated with additional part cleaning. It describes the differences between parts quenched in clean and dirty oil and presents best practices for keeping quench oil clean by removing particulate and water over the course of its life.

In order to use quench oils over extended periods of time, it is necessary to understand how their properties and performance respond to heat and oxidation. This study investigates the effect of thermal and oxidative deterioration on dark and transparent quench oils. It describes the performance and property changes observed using accelerated testing methods and explains how quench oil behaviors in a laboratory setting compare with actual quench furnace usage.

The most common probe used for cooling curve analysis of quenchants is a 12.5 mm diameter x 60 mm Inconel 600 cylindrical probe with a Type K thermocouple inserted into the geometric center. The time-temperature cooling curve is obtained at this position and is the basis for national and international standards including ASTM D6200, D6482, D6549, ISO 9950 and others. However, greater insight into the quenching process would be possible if a better profile were available for the uniformity and wetting kinematics of the quenching process. An alternative probe design, proposed by Prof. H.M. Tensi and his colleagues, utilizes a cylindrical 15 mm diameter x 45 mm flat-bottom shape with four thermocouples. One thermocouple is inserted to the geometric center of the probe at 22.5 mm from the bottom. The remaining three thermocouples are located 2 mm below the surface of the probe at 2 mm, at 15 mm, and at 30 mm from the bottom. This alternative probe design was used to characterize the usual centerline cooling curve properties as well as rewetting properties of two vegetable oils, palm oil and canola oil, a commercial fast petroleum oil quenchant, and a conventional petroleum oil quenchant. The probe construction, use, and quenching characterization results are reviewed in this paper.

Because quench oil deterioration varies depending on the operating conditions, maintaining constant performance is difficult. Various defective phenomena occur in response to changes in the quench oil degradation. In this paper, we will examine how the oil condition, cooling performance, brightness and carbide growth are effected by various defective phenomena such as oil oxidation, thermal decomposition etc. In doing so we would like to introduce important points in managing and setting operating conditions to optimize the performance of quench oils.

It is well known that petroleum oil base stocks possess a number of limitations, such as being non-renewable, but even more importantly, they are considered relatively toxic with limited biodegradability. One class of base stock that is renewable with excellent biodegradability characteristics and that is generally, but not always, non-toxic is animal and seed oils. The quenching performance of many different animal and vegetable oil compositions has been reported in the literature. However, as a class, they suffer from generally poor thermal oxidative stability, even when containing oxidation inhibitors, when compared to quenchants derived from petroleum oil. This factor limits their potential commercial utility. One method of addressing this problem is to chemically modify the vegetable oil to produce increased resistance to thermal-oxidative degradation. This work discusses the physical properties and quenching performance of epoxidized soybean oil-based formulations and the resulting metallurgical properties, hardness, and microstructures obtained. These results have not been reported previously.

Although petroleum oils continue to be the dominant type of base stock for the formulation of vaporizable quenchants, there is increasing pressure to identify an alternative. Petroleum oils are not a renewable base stock, and they possess generally poor toxicity and biodegradability properties. Currently, the most often cited alternative base stocks are those based on seed oils since they are renewable and are readily biodegradable, and usually non-toxic. However, they suffer a critically important deficiency in that they are also typically much less stable to thermal-oxidative degradation than petroleum oils. Various studies have addressed the effect of vegetable oil structure on oxidation and on the use of oxidation inhibitors to provide the necessary stabilization. However, most of these reports do not address the relative effects of specific antioxidant structures on inhibiting oxidation and on quenching performance. This paper describes the use of certain antioxidant structures on inhibition of thermal-oxidation and on the effect of the presence of antioxidants on quenching performance.

Vegetable oils, especially soybean oil, exhibit substantially poorer thermal-oxidative stability than commercially available petroleum oil quenchant formulations. Therefore, to achieve any commercially interesting performance vegetable oils must be stabilized by the addition of antioxidant inhibitors. This work describes the ability of two commercially available antioxidants, Irganox L 57 and Irganox L 109 to stabilize soybean oil against thermal-oxidative degradation. In addition, the effect of antioxidant stabilization on quenching performance was evaluated by determining the profile of heat transfer coefficient variation throughout the quenching process at different times after being subjected to an accelerated thermal-oxidation ageing test. The results of this work are discussed here.