糊状区渗氮对Cr10Mn9Ni0.7合金氮含量及凝固相变过程的影响

Effect of Nitriding in Mushy Zone on the Nitrogen Content and Solidification Transformation of Cr10Mn9Ni0.7 Alloy

研究了糊状区保温对Cr10Mn9Ni0.7合金凝固过程和氮含量及相变过程的影响。结果表明,随着糊状区保温时间的延长,铸锭中的氮含量逐渐升高,同时铸锭中的气孔率逐渐降低。当氮气压力为0.1 MPa时,氮含量由0.17%升高到0.23%,而气孔率则从1.86%降至1.37%;当氮气压力为0.4 MPa时,氮含量由0.29%升高到0.37%,而气孔率从1.41%降至1.06%。糊状区保温的增氮机制可归结为:在糊状区保温会促进包晶反应进程,使更多的铁素体转变为奥氏体;同时糊状区保温能够提高残留液相中的氮含量,进而提高"通道状"奥氏体中的氮含量。糊状区保温能够消除铁素体阱,从而降低气孔率。

The effect of nitriding of Cr10Mn9Ni0.7 alloy in mushy zone on solidification,nitrogen content and phase transformation was investigated.The results showed that the nitrogen content raised with nitriding time,and the occurrence of gas pore defects was reduced.When the nitrogen pressure was 0.1 MPa,nitrogen content increased from 0.17%to 0.23%,while the porosity declined from 1.86%to 1.37%.When the nitrogen pressure was 0.4 MPa,nitrogen content increased from 0.29%to 0.37%,while the porosity declined from 1.41%to 1.06%.The mechanism of the nitrogen content improvement by nitriding in mushy zone can be ascribed to the facilitation of peritectic reaction and diffusion of nitrogen from liquid into austenite.The increase of the nitrogen content of channel like austenite in the residual liquid is another reason for the nitrogen content improvement.Melt holding in mushy zone can avoid the“ferritic trap”,and thus reduce the occurrence of the gas pore defects.