Cr5Mo/A302异质焊接接头C扩散及其对高温蠕变寿命的影响  

CARBON DIFFUSION AND ITS EFFECT ON HIGH TEMPERATURE CREEP LIFE OF Cr5Mo/A302DISSIMILAR WELDED JOINT

作　　者：姜勇[1] 张佐[1] 巩建鸣[1] 

机构地区：[1]南京工业大学机械与动力工程学院,南京211816

出　　处：《金属学报》2015年第4期393-399,共7页Acta Metallurgica Sinica

基　　金：国家自然科学基金资助项目10172046~~

摘　　要：基于时效处理实验、微观硬度测量和Fick第二定律,对Cr5Mo/A302异质焊接接头的C扩散行为进行研究,随后对已存在200μm脱碳层的异质焊接接头和没有脱碳层的焊态接头进行持久实验,研究了脱碳层在不同应力水平下对接头寿命的影响.结果表明,随时效时间的延长,增、脱碳现象加剧,增、脱碳层的宽度变化均遵循抛物线型规律,实验测量结果与Fick第二定律拟合结果基本一致.预先形成的脱碳层在高应力条件下,可以成倍降低接头持久高温寿命,导致接头发生提前断裂,但是随着应力水平不断降低,断裂时间不断提高,预先形成的C扩散对接头持久寿命的影响程度不断下降,当应力降低到接头抗拉强度的36%以下后,其影响可以忽略.建立了C扩散影响因子S与应力的关系,并确定了已存在脱碳层对高温持久寿命不产生影响的临界应力值.Based on the consideration of economy and being easy to construct on site, Cr5Mo/A302 dissimi- lar welded joints are widely used in elevated temperature applications such as coal-fired power station, nuclear plant and petrochemical industry. Because of the difference in carbide forming elements on both sides of welded joint fusion line, carbon diffusion will happen in service progress and induce premature invalidation. The calcula- tion methods of carbon diffusion and its harm to creep life of dissimilar welded joints have been investigated in the past decades. Theoretically, at a certain temperature, creep damage mechanism changes according to stress levels. However, the previous works paid little attention on the effect of carbon diffusion to creep life at different stress levels and few studies have been done focusing on relationships among carbon diffusion degree, stress level and creep life. In this work, carbon diffusion behavior of Cr5Mo/A302 dissimilar welded joint was first studied by em- ploying aging treatment test, micro-hardness measurement and Fick＇s second law. Subsequently, creep tests were performed to investigate the effect of 200 μm wide decarburized zone on the joint creep life at different stress lev- els. The results showed that carbon diffusion in Cr5Mo/A302 dissimilar welded joints became serious with the in-crease of aging treatment time. The widths of carbon rich zone and decarburized zone were both consistent with the parabola distribution law and could be simulated by Fick＇s second law. The decarburised zone, which formed in the process of aging, reduced the creep life of the joint greatly at high stress levels. However, with the decline of test- ing load, its effect became much smaller. When the stress level dropped to about 36% of the yield stress, its effect was negligible. Meanwhile, the relationship of stress and carbon diffusion impact factor S was established to deter- mine the critical value of the stress below which the decarburised zone .would not affect the high-tempera

关 键 词：Cr5Mo/A302异质焊接接头 C扩散 C扩散影响因子S 

分 类 号：TG457.11[金属学及工艺—焊接] TG113.3