行星架锻件端面及销孔内亮斑原因分析

Analysis of Causes of Bright Spots on End Face and in Pin Hole of Forging for Planet Carrier

在大功率风电机组锻件中,42CrMo4行星架销孔端面及销孔精加工过程中出现了大量的亮斑,通过对行星架锻件本体亮斑及附近基体进行成分、硬度检测,结合锻后正火冒口余料、锻件本体正火+回火态试环及锻件本体调质试环的高、低倍检测,对亮斑的形成进行了全流程分析。研究结果显示,钢锭在凝固结晶过程中,由于冷却速度缓慢,导致了斑点偏析的产生。这些斑点区域与基体区域由于成分不同,因此在调质淬火处理时,二者的相对冷速也不同,以致二者硬度差值较大,车削过程中在硬度较高的斑点偏析区域形成亮斑。在分析的基础上,通过热处理实验证实,行星架性能检测不理想并非亮斑存在导致,且亮斑组织为预期理想组织。

For the forging of large megawatt wind turbine generation set,many bright spots appear on the end face and in the pin hole of 42CrMo4 planet carrier during the finishing process.In this paper,the forming reason of the bright spots is analyzed in the whole process after the chemical composition and hardness tests of the bright spots and nearby matrix of the forging for planet carrier,in combination with the high and low magnification inspection of the residual materials of normalized riser after forging,normalized + tempered test ring of forging body and quenched and tempered test ring of forging body.The research results show that in the process of solidification and crystallization,the spot segregation was caused due to slow cooling of ingot.After quenching and tempering treatment,the large difference of hardness between spot area and matrix area was caused due to different chemical composition and different relative cooling speed of these two areas.In the process of turning,bright spots were formed in the spot segregation area with higher hardness.Moreover,it has been proved after heat treatment test on the basis of analysis that the unsatisfactory properties of planet carrier are not caused by the bright spots and the microstructure of bright spots is good as expected.