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研制了三种不同合金元素Nb加入量的药芯焊丝。采用金相显微镜和扫描电镜对其显微组织和断口形貌进行了观察,采用X射线衍射仪对其相结构进行了分析,采用图形分析软件对其奥氏体晶粒度进行了统计。结果表明,堆焊层金属的显微组织含有板条马氏体和少量铁素体;堆焊层金属的断口类型以韧脆性断口为主;合金元素Nb加入量为0.15%时,其显微组织最细小且分布最均匀,断口韧窝更加均匀、细小;加入合金元素Nb使奥氏体晶粒尺寸明显减小,由22.7μm减小到20.3μm;合金元素Nb细化奥氏体晶粒尺寸是细化堆焊层金属显微组织的主要原因。
Three kinds of flux-cored wire with different alloying element Nb additions were developed. The microstructure and fracture morphology were observed by optical microscopy and scanning electron microscopy. The phase structure of the microstructure was analyzed by X-ray diffractometer. The austenite grain size was calculated by the graphic analysis software. The results show that the microstructure of the surfacing layer contains lath martensite and a small amount of ferrite. The fracture type of the surfacing layer is dominated by ductile brittle fracture. When Nb is added as 0.15% The smallest and most uniform microstructure was obtained, and the fracture dimples were more uniform and smaller. The addition of alloying element Nb reduced the austenite grain size obviously from 22.7μm to 20.3μm. The alloying element Nb refined austenite grains Size is the main reason for refining the surfacing metal microstructure.