Design Chemical Composition And Study On Heat Treatment Method Of The Main Shaft Of Wind Power Generator

The main shaft of wind power generator is a key part in the wind power generator unit, and its market will be very huge under the condition that the whole world is paying great attention on developing the wind power. Regarding the developing trend of our national industry, the target of this study is "to realize batch production with a possibly low cost, and to build a high efficiency production line of main shaft of wind power generator", which shall be very meaningful to social and economic developments.Vestas Company in Denmark, as the inductor of global wind power generator, its 42CrMo4 V80/V90 main shaft has very high requirements in world market for its integrated mechanical properties, especially for excellence impact property and fatigue strength. Therefore, to realize the batch production of Vestas 42CrMo4 V80/V90 main shaft becomes the specific goal of this study. The main purposes are as follows:①To reduce production cost, the forging processing was performed on a relatively smaller scale hydraulic press, typed 31.5 MN, by Using normal B.C ingot.②To improve fibrous continuity of the main shaft, reduce machining allowance of it, and depress production cost, a new forging process, characterized as using a forming die, was adapted.③Under a precondition of normal melting and forging process, high technological requirements should be satisfied, and a stable production line of main shaft realized by designing reasonable chemical composition and using effective heat treatment method.The result of the study shows:①The way to design chemical composition of 42CrMo4 is based on controlling composition to a normal level of raw materials but increasing Ni% to 0.60-0.80%. Meanwhile, the content of P and S, which is very adverse to impact property, will be strictly controlled.②If the EF melting and LF refining method are used as melting technology, then P% and S% can be controlled to a low level, based on that, even use B.C for casting, the total amount of harmful elements will not evidently be increased in actual chemical composition. With the above melting process, UT and MT requirements can be fulfilled, and the required chemical composition to achieve good mechanical properties can be realized.③The forming die in forming flange of forging process can dramatically decrease machining allowance and increase fibrous continuity of the main shaft, which can not only reduce production cost, but also can improve the integrated quality of main shaft as well.④Using water quenching oil cooling as quenching process to instead of oil cooling, the impact property of main shaft was remarkably improved, furthermore, it is proved to be the necessary way of quenching and cooling to meet the mechanical properties of main shaft for wind power generator⑤By adjusting chemical composition of 42CrMo4, adopting vacuum melting+B.C and combining die forming together with water quenching oil cooling as the integrated manufacture technology, a reasonable technology route of manufacturing the main shafts was obtained in No. 2 Heavy Machine Manufacture Company in China and the low cost batch production of main shaft for wind power generator can be fulfilled, and the factors of the performance of the shafts have reached an advanced level of world wide as well.