According to the current state of the art, wear and efficiency of worm gears can be calculated using ISO/TS 14521 [1] which is based on experimental investigations of the past decades. Concerning wear, the material properties of the typically softer worm wheel are major influence factors on the wear behaviour. Herein, the microstructure of the wheel material is only indirectly included in the calculation via the used alloy and the casting process. Previous work has shown that even with identical material composition and casting method, the microstructure is different depending on casting parameters and gear size. The consideration of the microstructure of bronze materials for worm gears is essential for the further development of a more precise wear calculation. The presented results in this paper are a further step towards the characterization of bronze materials for worm gears. For this purpose, material samples of 50 worm wheels from past research projects conducted are re-evaluated. The evaluation is carried out with regard to grain size according to ASTM E112-13 [2] and the δ—phase according to BDG 771 [3]. The investigated worm wheels consist almost exclusively of CuSn12Ni2, produced with the three casting processes, centrifugal casting (GZ), continuous casting (GC) and heat treated continuous casting (GCB). With the help of this database, confidence intervals are calculated to give a statement about the expected δ—phase and grain size for a gearbox size and casting process combination. Furthermore, a trend towards increasing average grain size with increasing outside diameter is determined.
