论文部分内容阅读
本文对在3.5％的氯化钠溶液中进行抗应力腐蚀开裂(SCC)试验的Hy-130钢焊缝金属的单边缺口悬臂梁试样进行了断口组织和显微组织分析。焊件是使用标准焊条和具有基体金属成分的焊条通过钨极气体保护焊(GTA)、气体保护金属极电弧焊(GMA)和惰性气体保护金属极电弧焊(SMA)工艺制备的。其中某些试样以焊接状态进行试验,而其它试样在试验前进行了热处理。本研究的目的在于,使断口形貌和相应的显微组织与各种焊接状态及热处理状态的焊缝金属的抗应力腐蚀开裂性能相关连。研究发现用细小焊珠低熔敷速率的钨极气体保护焊(GTA)焊接工艺焊制的焊件具有最高的抗应力腐蚀开裂性能。因为这种焊接工艺使熔敷状态的焊接金属再加热,因此产生了一种均匀而晶粒细化的回火状态的显微组织,它主要因显微孔穴聚集而引起断裂。气体保护和惰性气体保护金属极电弧焊焊件中均产生粗晶粒的不均匀的显微组织。用这两种工艺焊制的试样均产生解理断裂。对钨极气体保护焊焊件进行热处理而故意使显微组织晶粒粗化,结果导致晶间断裂和抗应力腐蚀开裂性能的显著降低。另一方面,对钨极气体保护焊件进行热处理使显微组织晶粒细化,结果导致由于显微孔穴聚集而产生的断裂并改进了抗应力腐蚀开裂性能。焊接金属中主要合金元素含量的有限变化对抗应力腐蚀开裂没有明显的影响。
In this paper, uni-notch notched Izod specimens of Hy-130 steel weld metal subjected to stress corrosion cracking (SCC) test in 3.5% sodium chloride solution were analyzed by fracture microstructure and microstructure. Weldments are made using standard electrode and electrode with base metal composition by GTA, GMA and Inert Gas Metal Arc Welding (SMA) processes. Some of the specimens were tested in the as-welded condition, while the other specimens were heat-treated prior to the test. The purpose of this study was to correlate the fracture morphology and the corresponding microstructure to the stress corrosion cracking resistance of the weld metal in various weld and heat treated conditions. It has been found that the weldment produced by GTA welding with a small weld bead with a low deposition rate has the highest resistance to SCC. Because this welding process reheats the weld metal in the as-deposited state, a uniform, grain-refined tempering microstructure is created that breaks primarily due to the aggregation of the micropores. Non-uniform microstructures of coarse grains are produced in both gas shield and inert gas shielded metal arc welding. Samples welded with both processes produced cleavage fractures. Heat treatment of the tungsten-arc-gas-shielded weldment intentionally roughens the microstructural grains, resulting in a significant decrease in intergranular fracture and stress corrosion cracking resistance. On the other hand, the heat treatment of the tungsten-arc gas-shielded weldment causes the grain refinement of the microstructure, resulting in the fracture due to the accumulation of the micropores and the improvement of the stress corrosion cracking resistance. The limited variation of the main alloying element content in the weld metal has no significant effect on stress corrosion cracking.