316L不锈钢激光焊接接头耐腐蚀性能研究

发布时间：2018-11-22 12:59

【摘要】：激光焊接半焊式板式换热器由于其可拆卸、耐腐蚀等独特的优点,在热交换行业,尤其在核电领域得到推广应用。但对激光焊接板片焊缝的耐腐蚀性能目前还缺乏系统的研究。为探求激光焊接接头的耐腐蚀性能,论文系统深入地研究了316L不锈钢高功率YAG激光惰性气体保护焊接焊缝的耐腐蚀行为。作为对比,又研究分析了YAG激光无气体保护焊接、CO_2激光气体保护焊接及激光冲击焊缝的耐腐蚀行为,为激光半焊式板式换热器在核电领域的安全可持续运行提供技术保障。论文以核电换热器常用的316L不锈钢材料为研究对象,以工业上通用的高功率YAG与CO_2激光为研究手段,采用金相显微镜、扫描电镜、X射线残余应力仪以及电化学工作站等设备对焊缝微观组织、晶粒尺寸、残余应力及接头耐腐蚀性能进行研究。研究结果表明:采用YAG激光气体保护焊接时,由于单位线能量和局部不均匀热输入量的影响,在激光功率1.5kW-2.0kW、焊接速度0.015m/s-0.035m/s区间,及激光功率3.0kW-3.5kW、焊接速度0.05m/s-0.08m/s区间形成较耐腐蚀接头,其耐腐蚀性达到母材的90%以上。无气体保护条件下,由于焊缝氧化的影响,与有气体保护相比,其组织均匀性下降,晶粒尺寸增大,残余应力变大,其焊缝区耐腐蚀能力下降约23%。采用CO_2激光焊接时,由于光束模式及激光波长影响,焊缝微观组织较粗大不均匀,残余应力大,其焊缝区耐腐蚀能力下降约16%。激光冲击接头后晶粒显著细化,形成厚度约100μm,应力值约-300至-120MPa的残余压应力层,激光冲击后焊缝耐腐蚀性能提高2-3倍。
[Abstract]:Laser welded semi-welded plate heat exchanger is widely used in heat exchange industry, especially in nuclear power industry, because of its unique advantages such as removable, corrosion resistance and so on. However, the corrosion resistance of laser welded plate welds is still lack of systematic research. In order to investigate the corrosion resistance of laser welded joints, the corrosion resistance of high power YAG laser inert gas welding welds of 316L stainless steel was studied in this paper. As a comparison, the corrosion resistance of YAG laser welding without gas protection, CO_2 laser gas shielded welding and laser impact welding are also studied and analyzed. It provides technical guarantee for the safe and sustainable operation of laser semi-welded plate heat exchanger in nuclear power field. In this paper, the 316L stainless steel materials commonly used in nuclear heat exchangers are used as the research objects, and the high power YAG and CO_2 lasers, which are commonly used in industry, are used as research means, metallographic microscope and scanning electron microscope (SEM) are used. The microstructure, grain size, residual stress and corrosion resistance of joints were studied by X-ray residual stress meter and electrochemical workstation. The results show that when YAG laser gas shielded welding is adopted, due to the influence of unit line energy and local inhomogeneous heat input, the laser power is 1.5kW-2.0kW, and the welding speed is 0.015m/s-0.035m/s. And laser power of 3.0kW-3.5kW, welding speed 0.05m/s-0.08m/s zone to form a corrosion resistant joint, its corrosion resistance to more than 90% of the base metal. Under the condition of no gas protection, the microstructure homogeneity decreases, the grain size increases, the residual stress increases, and the corrosion resistance of the weld zone decreases by about 23.3 due to the effect of weld oxidation. Due to the influence of beam mode and laser wavelength, the microstructure of the weld is coarse and uneven, and the residual stress is large, and the corrosion resistance of the weld is decreased by about 16%. The residual compressive stress layer with a thickness of about 100 渭 m and a stress value of -300 to-120MPa was formed after laser impact. The corrosion resistance of the weld was improved 2-3 times after laser impact.
【学位授予单位】：长春理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG457.11

【参考文献】