应力控制条件下奥氏体不锈钢的低周疲劳性能

STUDY ON LOW CYCLE FATIGUE PROPERTY OF AUSTENITIC STAINLESS STEEL UNDER STRESS-CONTROLLED CONDITION

以JIS SUS 304和SUS 304N为实验材料,在应力控制条件下研究了两种奥氏体不锈钢的低周疲劳性能.结果表明:（1）在低应力区（σa<430 MPa）,SUS 304N的疲劳寿命高于SUS 304的疲劳寿命;但在高应力区（σa>430 MPa）,静强度较高的SUS 304N的疲劳寿命反而低于SUS 304的疲劳寿命.（2）SUS 304中疲劳微裂纹萌生的循环次数比远小于SUS 304N.在低应力区,SUS 304中的疲劳微裂纹萌生后。其扩展速率大于SUS 304N;但在高应力区,SUS 304中的疲劳微裂纹萌生后,其扩展速率小于SUS 304N,使它在高应力区的疲劳寿命超过了SUS 304N.（3）添加氮元素后.奥氏体组织的稳定性得到提高.疲劳实验过程中SUS 304发生了显著的应变诱发马氏体转变,而SUS 304N基本未发生此现象.

Tension-compression fatigue test has been performed under stress-controlled condition to investigate the low cycle fatigue behavior of austenitic stainless steels of SUS 304, and SUS 304N which is strengthened by increasing nitrogen content. The main results obtained are as follows: (1) The fatigue life of SUS 304N is shorter than that of SUS 304 in the region of high stress amplitudes (sigma(a) >430 MPa) unexpectedly, although the fatigue life of SUS 304N is longer than that of SUS 304 in the region of low stress amplitudes (sigma(a) < 430 MPa). (2) The cyclic ratio for fatigue crack initiation of SUS 304 is much smaller than that of SUS 304N. The fatigue crack propagating rate in SUS 304 is faster than that in SUS 304N in the region of low stress amplitudes. However, the fatigue crack propagating rate in SUS 304 is slower than that in SUS 304N in the region of high stress amplitudes. (3) Austenite becomes more stable with nitrogen content increasing. Remarkable austenite-martensite transformation occurs in SUS 304 during fatigue test, on the other hand, almost no austenite-martensite transformation occurs in SUS 304N.