Gear Tooling fixture processing tempering what issues need to pay attention to?

Gear processing wheel tempering changes the comprehensive mechanical properties of gears' material. The hardness after tempering is not high, generally around HBS200-240, and the hardness of the material before tempering is not much different, but the mechanical properties are excellent. At the same time, it can also ensure the quality of heat treatment, good toughness, and easy running together, which can compensate for manufacturing errors. So what aspects need to be noted when tempering gears Tooling fixture?

1. Gear processing in quenching is prone to quenching cracking, which will affect the use of gear performance or even scrap. In order to prevent quenching and cracking, measures should be taken to reduce quenching stress, such as cold quenching and the correct choice of quenching medium, and control of the cooling time. Quenching medium as far as possible to use water quenching can obtain a deeper hardened layer and satisfactory heart organization. When the water quenching is dangerous, only consider using oil quenching or water quenching and oil cooling measures. Cooling time is too long, but also may be too low temperature, so that the internal stress is too large, and the gear quenching crack, the available cooling time is selected to the heart of the cold to the MS point near (about 300 degrees Celsius) is appropriate. In practice, the heart temperature can not be measured, which needs to rely on the practical experience of the operator to determine.

2. Gear processing must be tempered promptly after quenching to prevent excessive stresses that can lead to gear cracking for tempering brittleness-sensitive gear material, tempering to oil cooling, and adding stress relief tempering. For hardened gear steel, such as 40CrNiMo, the use of salt bath heating, after quenching can not prematurely clean salt slag, otherwise due to the thermal stress of cooling during cleaning and internal stress generated by the transformation of internal subcooling austenite, causing cracking of gears.