34Cr2Ni2Mo鋼法蘭叉頭異常現象成因分析

34Cr2Ni2Mo鋼法蘭叉頭異常現象成因分析Cause Analysis on Abnormal Phenomenon of 34Cr2Ni2Mo Steel Flange Forks

某批34Cr2Ni2Mo鋼法蘭叉頭在調質處理后的機加工過程中，在軸承孔內靠近法蘭一面發現多條白色帶狀異常區域，通過低倍檢驗、化學成分分析、硬度試驗和金相檢驗等方法對其成因進行了分析。結果表明：在34Cr2Ni2Mo鋼法蘭叉頭鑄造過程中，由于20鋼內冷鐵支架固定不穩，澆鑄時受鋼液的沖刷作用坍塌堆積于鑄件內，并在隨后機加工過程中在軸承孔內靠近法蘭一面露出表面，從而形成異于基體的白色帶狀異常區域。

Multi white banded abnormal areas were found in the bearing hole close to the flange side of a batch of 34Cr2Ni2Mo steel flange forks in machining process after quenching and tempering, and the causes were analyzed by means of macro-etching test, chemical composition analysis, hardness test and metallographic examination. The results show in the casting process of 34Cr2Ni2Mo steel flange forks, due to fixing instability, the 20 steel internal chill frame collapsed and stored in the casting under the scouring action of molten steel. The 20 steel was exposed in the bearing hole close to the flange side in the following machining process, so white banded abnormal areas different from the matrix produced.