Abstract
Numerical simulations based on a conjugate heat transfer solver have been carried out to analyze various gas quenching configurations involving a helical gear streamed by an air flow at atmospheric pressure in a gas quenching chamber. In order to optimize the heat transfer coefficient distribution at key positions on the specimen, configurations involving layers of gears and flow ducts comprising single to multiple gears have been simulated and compared to standard batch configurations in gas quenching. Measurements have been performed covering the local heat transfer for single gears and batch of gears. The homogeneity of the heat transfer coefficient is improved when setting up a minimal distance between the gears (batch density) and when introducing flow ducts increasing the blocking grade around the gears. An offset between layers of the batch as well as flow channels around the gears plays a significant role in increasing the intensity and the homogeneity of the heat transfer in gas quenching process.
Highlights
IntroductionIn order to achieve a sufficient hardness distribution (corresponding to a martensitic microstructure) or shape quality [1], specific heat treatment processes are applied in the manufacturing process of parts
In the automotive industry, in order to achieve a sufficient hardness distribution or shape quality [1], specific heat treatment processes are applied in the manufacturing process of parts
Gas quenching has been developed over the past years as an environmentally and economically friendly solution to replace conventional liquid or salt-based quenching [2]
Summary
In order to achieve a sufficient hardness distribution (corresponding to a martensitic microstructure) or shape quality [1], specific heat treatment processes are applied in the manufacturing process of parts. In comparison to quenching techniques using liquids, the impact of the gas flow on the heat transfer between the quenching gas and the element to be quenched is of major importance [9]. This influence can be scaled according to the dimension of the system: at the micro scale, the solid workpiece is streamed by a complex gas flow depending on the structure of the batch (meso scale) comprising many layers of workpieces as well as racks creating a pressure drop to the incoming flow. Where c2 is a factor related to the quenching chamber geometry
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