【作者】 步贤政；

【导师】 单平；

【作者基本信息】 天津大学 ， 材料加工工程， 2011， 博士

【摘要】 Inconel601镍基高温合金具有良好的机械性能和抗腐蚀性能,在钢铁冶金、能源电力、石油化工以及航空航天等领域有着广泛的应用。为了提高材料利用率、节约能源,目前这些应用领域的Inconel601镍基高温合金结构件正逐步从原来的“铸锻件”向“板焊件”发展,但采用传统的焊接工艺施焊时还存在大量的焊接问题。而由于激光焊接具有焊接熔深大、热输入小等优点,是镍基高温合金焊接的首选技术。本文结合实际工程应用,重点对Inconel601镍基高温合金的激光焊接工艺、焊接接头性能、接头的焊后固溶处理以及激光焊接质量的评定方法等问题进行了研究。首先,对Inconel601镍基高温合金的激光焊接工艺以及接头性能进行了研究。确定了3mm厚Inconel601固溶态板材全熔透型对接接头的激光焊接工艺边界曲线。讨论了该合金焊接接头的微观组织以及不同焊接线能量下的接头力学性能,并选取力学性能最优的一组焊接接头进行腐蚀试验。结果显示,在所确定的工艺曲线范围内,当焊接线能量处于333J/mm～400J/mm之间时焊接接头的力学性能最优;但是由于焊缝金属中“贫铬区”的出现使得该合金激光焊接接头金属存在较为明显的晶间腐蚀倾向,并且焊接接头的抗高温氧化性能与母材相比也略有降低。其次,讨论了焊后固溶处理对Inconel601激光焊接接头的影响。随着固溶处理温度的提高,激光焊接接头抗拉强度略有下降,延伸率呈现出先增大后减小的趋势。焊缝金属固溶处理后发生了再结晶现象,在1150℃固溶处理0.5h后可以得到了成分均匀、晶粒大小合适的等轴晶粒,同时焊接接头的晶间腐蚀倾向也随之消失,但固溶处理温度过高则会导致焊缝晶粒长大和晶间腐蚀的出现。此外,随着固溶处理温度的升高,焊接接头的抗高温氧化性能也略有提高。最后,研究了基于焊接声信号的激光焊接缺陷评定方法。构建了一套多通道激光焊接声信号采集系统,将容易采集、对传感器位置和方向不敏感的焊接声信号作为焊接缺陷的判别依据,采用FastICA的分析算法从多通道采集系统的采集信号中提取出有用的焊接声信号,并通过时频分析的方法实现了基于声信号的激光焊接过程中焊接穿孔缺陷识别。更多还原

【Abstract】 Because of the advantage of excellent mechanical properties and corrosion resistance, the Inconel601 nickel based superalloy has been widely applied in many fields, such as ferrous metallurgy, electric and energy industry, petrochemical industry and aerospace. In order to improve the material utilization and save energy, the Inconel601 structures are gradually developing from forging to welding, but there are a lot of welding problems when using traditional welding methods. Laser welding has become the first alternative for nickel based superalloy due to its advantage of deep penetration and small heat input. In order to meet the practical application, the laser welding procedure, properties of welded joint, solution treatment after welding and the welding quality have been investigated in this paper.At first, the laser welding procedure and joint properties have been researched. The boundary curve of full penetration laser welding of 3mm thick solution-annealed Inconel601 sheet was determined based on experiments. The microstructure and mechanical properties of the welded joint with different welding heat input was discussed, and a group of weld joints with optimal mechanical properties have been selected for corrosion test. Result shows, the welded joints have good mechanical properties when the welding heat input is between 333J/mm～400J/mm, but the laser welded joints of Inconel601 superalloy has a tendency of intergranular corrosion because of the“Cr depleted zone”in the weld metal, and the oxidation resistance of welded joints was slightly lower than base metal.Secondly, solution treatment after weld of Inconel601 superalloy was studied. As the solution temperature increased, the tensile strength of laser welded joints decreased slightly, and the elongation shows a tendency of first increased and then decreased. Recrystallization phenomena occurred in the weld metal after solution heat treatment, and the welded joint has homogeneous, equiaxed grains, while the intergranular corrosion tendency of welded joints was disappeared, but excessive high solution temperature would result in grain growth and the emergence of intergranular corrosion. In addition, the oxidation resistance of welded joints improved with the increase of the solution temperature. Finally, defect assessment methods of laser welding based on acoustic signals have been investigated. A multi-channel acoustic acquisition system for laser welding was been constructed. The easily captured acoustic signals which are not sensitive to the sensor’s position and orientation were used to distinguish the welding defects. The FastICA algorithm was used to extract useful welding acoustic signal from acquisition signals, and realized the laser welding perforation defect recognition based on acoustic signal through the time-frequency analysis method.更多还原