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.
维普
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