Hard Teeth Face Gear, Transmission Gear

Applications:

Carburized and Hardened Gearing is used when optimum properties are required. High surface hardness, high case strength, favorable compressive residual stress in the hardened case, and suitable core properties based on selection of the appropriate carburizing grade of steel, result in the highest AGMA gear tooth ratings for contact stress, pitting resistance and root strength (bending).
Carburized Gear ratings are higher than the ratings for through hardened and other types of surface hardened gearing because of higher fatigue strength. Improved load distribution can be obtained by subsequent hard gear finishing. Conventional hard gear finishing (skiving and grinding) results in some sacrifice of beneficial compressive stress at the surface and substantially increases costs.
Carburized Gearing is used in enclosed gear units for general industrial use, high speed and aerospace precision gear units and also large open gearing for mill applications. Carburized Gearing is also used for improved wear resistance. Specified finish operations after hardening depend upon accuracy and contact requirements for all applications.
Carburizing technology is well established and the available equipment and controls make it a reliable process. Surface hardness, case depth, and core hardness can be specified to reasonably close tolerances, and the quality can be audited.
Some gearing does not lend itself to carburize hardening because of distortion. Gearing which distorts and cannot be straightened without cracking, rack gears, thin sections, complex shapes, parts not designed for finishing or where finishing is cost prohibitive, present manufacturing problems. Pressquenching after carburizing can be used to minimize distortion. Selected areas of gearing can be protected from carburizing (masked) to permit machining after hardening, or can be machined after carburizing and slow cooling before hardening.
Gearing beyond 80 inch (2032 mm) diameter is difficult to carburize due to the limited number of available furnaces for processing. Maximum size of carburize gearing is currently in the 120 inch (3048 mm) diameter range. Most of this large gearing requires tooth finishing (skiving and/or grinding) after carburizing and hardening.