Modelling of induction heat treatment in a manufacturing chain

Abstract: Due to increased competitiveness in the aerospace industry, deeper knowledge of the manufacturing process is needed. It is, for example, known that the microstructure is important for the performance of the components. In order to make a cost effective prediction of a product's final shape and mechanical properties, modelling of the various processes in a manufacturing chain is of interest. The finite element method is the best and most common tool used for this purpose. The main route for manufacturing of structural components in aero engines are either forging, casting or fabrication. During these steps, manufacturing defects such as cracks or voids can occur. Repair welding is then necessary. However, welding changes the microstructure of the material. In order to restore the microstructure, and reduce welding residual stresses an heat treatment of the component is necessary. The heat treatment is usually performed by placing the component in a furnace, i.e. a global heat treatment, although it is only a local region that needs to be restored. One method to perform a local heat treatment is by induction heating. The possibility to replace global heat treatment with local using induction heating has been evaluated in the project, both numerically using the finite element method as well as with validation experiments. Finite element models has also been used in order to simulate induction heating in the manufacturing process chain of stainless steel tubes. The aim of this work has been to simulate a process chain consisting of repair welding and local heat treatment with induction heating. It is then possible to predict deformations as well the residual stress state and the change in microstructure. For this has a material model been developed. It is a dislocation density based flow stress model in which precipitate hardening for alloy 718 is taken into account.

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