Effect of Normalized Microstructure in Alloy Steel on the Performance of Planetary Gear Set of Automatic Transmission

970972

02/24/1997

Event
SAE International Congress and Exposition
Authors Abstract
Content
The banded microstructure of pearlite and ferrite in normalized alloy steel is susceptible to thermal distortion during carburizing process due to its unidirectional orientation parallel to rolling direction. The planetary gears with material of banded microstructure have been experienced in high thermal distortion during carburizing and quenching process and result in uneven surface hardness and effective case depth at the inside of pinion gear after honing. These defects played failure initiation site roles in durability test during development of new automatic transmission. The galling between the contacting components in severe lubricating system was the main failure mechanism. Double normalizing at 920 °C was designed to resolve the banded microstructure of normalized alloy steel. The microstructure and grain size of the double heated steel became equiaxed and fine due to homogenizing and recrystallization through double heat treatment. The thermal distortion and subsequent surface properties at the inside of pinion gear were also improved. Finally the durability of the planetary gear set at maximum speed test is enhanced by 2.91 times.
Meta TagsDetails
DOI
https://doi.org/10.4271/970972
Pages
13
Citation
Jung, S., Ahn, S., Kim, H., and Kim, Y., "Effect of Normalized Microstructure in Alloy Steel on the Performance of Planetary Gear Set of Automatic Transmission," SAE Technical Paper 970972, 1997, https://doi.org/10.4271/970972.
Additional Details
Publisher
Published
Feb 24, 1997
Product Code
970972
Content Type
Technical Paper
Language
English