自由鍛造におけるインコネル718プロセスモデリング技術の開発

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INCOLEL alloy 718(IN718) has been used for important components such as gas turbine disk and jet engine shaft, and the amount of the usage are increasing. As for gas turbine disk, the demand of reliability has been getting stronger. One of the most effective methods to improve the reliability is grain refinement giving the increase of low fatigue strength and toghness. In order to refine the micro-structure of IN718, the only method is recrystarization at lower temperature in forging because of single-phase material. To obtain the forged components having fine micro-structure, forging temperature, strain and their distribution must be controled precisely. Process modelling using FE analysis is very effective to design optimal forging processes to obtain the target micro-structure and mechanical properties of the components. We have originally developed the digital engineering system named DAINUS composed of 4 prediction modules, which are (1)damage prediction module, (2)micro-structural prediction module, (3)die damege prediction module, (4)cavity consolidation prediction module. In this work, we have developed micro-structural prediction data base and system for IN718. Micro-structural prediction under multiple recrystallization and partial recrystallization condition is very difficult to obtain sufficient accuracy. Moreover the its system in incremental free forging is also difficult, because of the rapid increase and decrease of the temperature, strong strain distribution, occurrence of additional recrystallization by repeated forging during partial recrystallization. In this paper, to solve these problems we have developed new micro-structural prediction system of IN718 by the following approaches, (1)establishment of the precise recrystallization data base in wide temperature range, (2)establishment of the incremental method corresponding to rapid temperature and strain change, (3)development of new averaging method. By these new approaches, we could obtain enough prediction accuracy even in incremental forging of gas turbine disk.

自由鍛造におけるインコネル718プロセスモデリング技術の開発

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