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目前国产LNG用镍基低温焊条存在的主要问题是无法同时满足强韧性要求。采用金相显微镜和扫描电镜对自主生产的3种ENiCrMo-6焊条熔敷金属的显微组织进行观察,应用硬度、冲击和拉伸试验对接头力学性能进行测试分析。结果表明:焊缝金属主要由奥氏体以及析出物构成,晶界间存在的低熔点共晶物,易形成沿晶裂纹,降低熔敷金属的拉伸、冲击和弯曲性能。随着合金含量的升高,强度和硬度总体呈上升趋势,对塑性和韧性有所损害,Nb的碳化物析出对裂纹扩展具有阻碍作用,有利于提高韧性。新研制的镍基焊条满足LNG设备对焊缝金属的性能要求。
At present, the main problem of nickel-based low-temperature welding electrodes for domestic LNG is that they can not meet the requirements of toughness at the same time. The metallographic microstructure of 3 types of ENiCrMo-6 electrode deposited by ourselves was observed by optical microscope and scanning electron microscope. The mechanical properties of the joint were tested by hardness, impact and tensile test. The results show that the weld metal mainly consists of austenite and precipitates. The low melting point eutectic between the grain boundaries easily forms intergranular cracks and reduces the tensile, impact and flexural properties of the deposited metal. With the increase of the alloy content, the strength and hardness generally show an upward trend, which impairs the ductility and toughness. The precipitation of Nb carbides hinders the crack growth and helps to improve the toughness. Newly developed nickel-based welding rod to meet the LNG equipment performance requirements of the weld metal.