Research On Forging Forming Technology For Gear-Shaft In Yaw System Of Wind Turbine

There were some problems and defects,due to the unique shape characteristics and use requirements of large wind turbine shaft parts,in the production of wind power output shaft by using the traditional free forging technology of continuous upsetting and stretching: more forging fires,low production efficiency,difficult to guarantee the appearance quality of forgings and large machining allowance,the continuity of metal fiber in the transition part of forgings is damaged,which seriously affected the mechanical properties of the gear shaft and reduces the fatigue strength and service life of the gear-shaft.With the development of the "going out" strategy of China's wind power industry,higher requirements were put forward for the stability of the performance and manufacturing cost of the important internal parts of wind turbines.Therefore,it was of great engineering application value to study the forming process of shaft forgings to ensure the actual production with high material utilization and stable quality.In this paper,an gear-shaft forging in yaw system of horizontal axis wind turbine made of 18 Cr Ni Mo7-6 structural steel was taken as the research object.The formability of forgings,the die structure,the optimization of billet and billet making have been studied.The main research work has the following points:(1)Based on a series of shortcomings of traditional free forging technology of continuous upsetting and stretching in the production of shaft forgings,a two-dimensional forging diagram of "free forging + die forging" composite forging was designed,and a new process of "free forging + die forging" composite forging was proposed.The gross to net ratio of forgings decreased from 1.34 to 1.21,the weight was reduced by 48 kg.Based on the new process,the round bar specification and the initial billet size were determined,which provided the data basis for the numerical simulation analysis of the subsequent billet making process and the die forging process;(2)In view of the problems of oxide skin cleaning and material overflow at the end of forging in the process of die forging,the integral type die structure,splicing type die structure and combined type die structure were proposed.Based on the results of numerical simulation,the advantages and disadvantages of the above three kinds of die structures were analyzed,and the combined die structure scheme was finally determined,which can effectively solve the problems of forging end overflow and oxide scale cleaning;(3)The effects of anvil parameters on drawing efficiency,anvil stress and maximum energy required in chamfering and rolling process were studied.The results show that using the inclined arc anvil with slope,the elongation of the billet was 14%larger than that of the common inclined arc anvil,the maximum tensile stress of the anvil was reduced by 24%,while the difference of the maximum compressive stress and the maximum energy required for forming was not obvious.Comprehensively considering,l=100 mm,?=20° inclined arc anvil was selected,and the chamfering times was 11,the rolling method was 45° X 8,which can meet the requirements of dimensional accuracy.At the same time,the rod diameter at 455 mm was more than260mm;(4)The numerical simulation optimized process was verified by the actual trial production,and the test results show that the forging appearance size meets the design requirements,and all physical and chemical testing indexes were qualified.