One of the most critical parts of the heat treatment process is the quenching operation, which is defined as rapid cooling of a work-piece by immersing it into a quenching media such as water, oil, or polymer. Quenching is carried out for altering and achieving the desired mechanical properties of industrial materials. Hardness, microstructure changes, and surface finish obtained are a few of the most sought objectives of quenching and these are greatly influenced by cooling time, cooling rate, quench media, etc. The cooling rate of quenchant must be sufficiently fast for phase transformation of the material, thus changing the microstructure. But, very fast quenching may result in distortions or crack formation on the material. Therefore it is very critical to have comprehension and control over the quenching process.
Normally a probe made up of Inconel 600 is used in a potable quenchometer to comparatively evaluate the cooling rate with different quenchants. The authors, in this study, have got fabricated specimens made up of two industrial-grade steel namely, SS 304 (less heat treatable) and EN 8 (more heat treatable) in addition to the standard Inconel Probe for determination of cooling rate thru' experiment. Experiments were performed with Servo-Quench 11 oil quenchant in accordance with ASTM standard. Cooling curves and cooling rates were used to determine microstructure changes and hardness achieved in the material by the inverse-iteration method. A software was used for modelling and simulations to generate quench outputs numerically. The experimental results were validated by the numerically simulated results.
The analysis shows that the quenching process is highly influenced by metallurgy, quenching medium, and HTC. Experimentally measured micro-structural changes and hardness achieved were observed and have been presented in this work. With the appropriate assumption of boundary conditions and thermal properties, the quench result can be simulated for other grades of steel.
