AGMA 92FTM1-1992 pdf free.Experimental Characterization of Surface Durability of Materials for Worm Gears.
The analysis made of the two rollers tested on the simulator (chill casting and centrifugal) had two aims. The first was to observe the structure of the three different types of bronze to try and predict their behavior tO fatigue and the second was to interpret the structural effects of fatigue due to the surface pressure. These different analysis were made at the ECAM Metallurgy Laboratory under the supervision of Mr P. COUVRAT.
3.2 Structural observations of the different types of bronzes
SAND CAST
In this case the cooling of the bronze during its solidification is slow. The process of solidification starts by the formation of SSa germs’ followed by their growth. A heterogeneous structure formed of dentrites is then obtained. Between these dentrites, the remaining liquid provides the eutectoid component.
The first tests made on this grade did not produce conclusive results. In fact the rolling track did not stabilize and had a tendency toy the whole width of the roller in a very short lime, even when the roller was submitted to light loads.
Fig. 5: Structure of the bronze
IJEI2P CHILL CAST BRONZE
Castings in metallic moulds have a quicker cooling process those in sand casting with germination and dendrite formation. The grains obtained are of greater dimension and have little homogeneous structure. On the other hand a greater quantity of eutectoid a —6 is observed between the SSa grains. It is the hard and fragile eutectoid that gives the mechanical characteristics of the material. The fatigue tests have not caused any special problems for this grade.
UEI2P CENTRIFUGAL CAST BRONZE
The casting by centrifugation allows an even quicker cooling rate than the two previous techniques. The quantity of eutectoid a-6 is thus greater. The grain obtained is more compact and much smaller. Due to these observations we can consider that this type of bronze has good mechanical characteristics. This type of bronze has the greatest hardness of SSa gram (see the hardness chart in paragraph 2.4).AGMA 92FTM1 pdf free download.