Gear cracking of pitch reducer for wind power generation

Pitch reducer is widely used in wind power generation system. Its working characteristics are frequent start and stop of intermittent work, large transmission torque and high transmission ratio. The production process of pitch reducer gear used by a wind energy limited company is as follows: blanking → annealing → turning → hobbing → Tongling → carburizing → quenching → grinding → finished products. The accuracy of the gear is 6-7, the speed of the pinion and blade shaft changes from 6.7 to 10.1 R / min, and the gears and bearings in the pitch gearbox are lubricated with mobilshcxmp320 gear oil. In addition to the annual inspection and regular greasing of the grease lubrication system, the pitch reducer does not need maintenance, and oil samples are taken every 5 years.

It is required that the service life of pinion and shaft can reach 20 a when the impact energy akv2 ≥ 27 J at – 20 ℃. A pitch reducer gear (with the specification of φ 98 × 65, 20CrMnTi) was used in a wind farm in Liaoning Province. After 1 year, the gear teeth cracked and cracked, and other gears matched with it also had similar phenomenon (as shown in Fig. 1).

According to the gear manufacturer’s report on gear tooth breakage, this phenomenon is not found in other wind farms of the same batch, and maintenance personnel reflect that the wind power in this wind farm is relatively large. Therefore, when the external load is large, the reliability of the product decreases. In this paper, the gear was inspected, the failure reason was analyzed, and the improvement suggestions of heat treatment were put forward.

The gear failure of pitch reducer is caused by the quality defect of carburizing and quenching heat treatment process. The content of retained austenite in carburized and quenched layer can be reduced by adopting secondary quenching method and tempering in time, and increasing cryogenic treatment process, so as to obtain ideal carburizing and quenching structure.

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