Study on Low-Cycle Fatigue Property of 316 Stainless Steel at Room Temperature and 350℃
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摘要: 采用MTS材料试验机研究作为反应堆结构材料的316奥氏体不锈钢母材在350℃和室温,以及焊缝在室温,±0.3%1.5%应变幅的低周疲劳性能试验,并采用扫描电镜对试验后样品进行了断口分析。研究结果表明,316不锈钢疲劳性能较好,室温下疲劳寿命高出350℃同一应变幅的30%50%以上,且母材的疲劳寿命显著高出焊缝同一应变幅的一倍以上。随应变幅的增加,材料疲劳寿命相应下降,峰值应力增加。室温下母材和焊缝均呈现出随循环周次增加、峰值随应力逐渐下降的规律。母材在高温下,随应变幅的增加,逐渐由循环硬化过渡到饱和行为。低周疲劳试验后,断口表面可观察到裂纹源和疲劳条带。随应变幅增加,疲劳条带间距增大,且同一应变幅下,焊缝的间距大于母材,高温的疲劳间距大于室温,与疲劳试验结果相吻合。Abstract: Low cycle fatigue property of 316 stainless steel was investigated at room temperature(RT,both base material and weld bead) and 350℃(base material) under a strain amplitude(SA) range from ±0.3% to ±1.5%,and fracture morphology of representative samples was observed by scanning electron microscope(SEM).The results showed that,316 stainless steel had an excellent fatigue property.Compared with 350℃,the fatigue life was 30%-50% longer at RT in the same SA,while the fatigue life of the base material was twice than that of the weld bead in the same SA.The decreasing of the fatigue life and the rising of the peak stress coincides with the increasing of the SA.The peak stress has a corresponding drop with the rising of cycles at RT,both base material and weld bead;however,the cyclic hardening turned into cyclic saturation,resulting from the increasing of the SA at 350℃.The fatigue crack source and striation was found at the surface of the samples by SEM,the striation gap became longer in accordance with the rising of SA,and in the same SA,the striation gap of weld bead was longer than that of base material,while that of 350℃ was longer than RT,which matched the fatigue experimental results.
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Key words:
- 316 stainless steel /
- Low cycle fatigue /
- Base material /
- Weld bead
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