LNG用镍基合金焊条熔敷金属的组织与性能

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。

Microstructure and properties of deposited metal for nickel-based electrodes used for LNG

For domestic LNG tank with nickel-based low-temperature electrode,it was difficult to satisfy the re-quirements of both strength and toughness simultaneously.The microstructures of three kinds of deposited metal by self-made ENiCrMo-6 electrodes were observed by metallographic microscopes and scanning electron micro-scopes.The mechanical properties of joints were tested by hardness,impact and tensile tests.The results show that the weld metal is mainly composed of austenite and precipitates.The low melting eutectic exists in grain boundaries which is easy to form intergranular crack and reduce the tensile,impact and bending properties of de-posited metal.With increase of the alloy content,the strength and hardness of the weld metal are improved when plasticity and toughness decrease to a certain extent.Moderate of Nb content is beneficial for hindering crack prop-agation which improves low temperature toughness.The new developed nickel-based electrode can meet the re-quirements for the key components of LNG equipment.