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采用示波冲击法测定了9Ni钢冲击过程中裂纹萌生、扩展等阶段所消耗的能量,并通过测定钢中回转奥氏体含量,研究了冲击断裂过程中回转奥氏体的作用机制。结果表明:随着回转奥氏体含量的增加,裂纹形核功不断上升,但趋势减缓,而裂纹扩展功则先快速上升后又大幅下降,峰值与回转奥氏体稳定性的峰值重合,表明稳定性差的回转奥氏体会导致扩展功大幅下降。由于裂纹形核功随回转奥氏体稳定性的变化相对平缓,扩展功的变化则更为剧烈,因此提高回转奥氏体稳定性进而增加扩展功是改善9Ni钢低温韧性的有效手段。
The energy consumed by crack initiation and propagation in 9Ni steel during impacting was measured by oscillometric method. The mechanism of austenite transformation during impact fracture was studied by measuring the austenite content in steel. The results show that with the increase of the content of austenite, the crack nucleation work increases continuously, but the trend slows down. However, the work of crack propagation first increases rapidly and then drops sharply, and the peak value coincides with the peak value of the stability of revolving austenite. Poor stability of the rotary austenite will lead to a substantial decline in the expansion work. Because the crack nucleation work is relatively smooth with the change of the stability of the rotary austenite, the change of the work of extension is more severe. Therefore, improving the stability of the rotary austenite and increasing the work of extension are effective measures to improve the low temperature toughness of 9Ni steel.