Isothermal Heat Treated Nodular Iron with Austenitic-Bainitic Microstructure as Material for Gears

Author:  Jokipii M.Sc., Kalevi
Source:  Kymi Kymmene Engineering Santasalo-Transmission
Doc ID:  1977011
Year of Publication:  1977
Abstract:  
The use of nodular iron in the engineering industry is increasing rapidly. The tensile strengths of the most general grades of nodular iron standardized in different countries range from 400 to 800 Nmm-2. It is, however, feasible to improve the strength properties of these grades through heat treatment in the same manner as those of steels. The experiences the Karkkila Foundry of Kymi Kymmene Engineering has gained from the use of nodular iron in various applications have been favourable. Especially, the experiences gained by using nodular iron in gear wheels showed that the properties of nodular iron could be further developed. In collaboration with the Santasalo Factory, which belongs to the same concern as the Karkkile Foundry, and is know as a manufacturer of gear units, and intensive development of strong nodular iron grades was started. The goal was to improve both the static and dynamic strength properties, toughness and above all, the endurance limit for surface stress, which in many cases determines the transmitted power of the gear wheels. The research and development work resulted in the innovation of a new nodular iron grade KYMENITE-9805 for which a patent has now been granted in 5 countries (Belgium, the USA, Finland, Norway, the UK). A patent application has been filed in 13 countries.