X80/2205双金属复合管CMT/TIG管端堆焊组织及性能

Microstructures and properties of CMT and TIG surfacing layers at X 80/2205 bimetal mechanical lined pipe end

采用冷金属过渡(CMT)和钨极氩弧(TIG)堆焊工艺对X80/2205双金属复合管管端进行堆焊,研究堆焊速度对堆焊层形貌、组织形态及其比例的影响,从而确定合理的CMT堆焊工艺,并对比分析CMT和TIG堆焊层的组织和性能。结果表明:随着焊速增加,CMT堆焊层焊道宽度变窄,高度降低,由于CMT堆焊层Σ3 CSL晶界比例高于TIG堆焊,CMT堆焊层韧性较高;堆焊层与X80钢交界处存在浮凸的脆硬组织,该组织为具有BCC晶体结构的马氏体,其晶粒细小且多为大角度晶界,导致交界处硬度突变;TIG耐蚀层中铁素体与奥氏体比例为37∶63,CMT铁素体与奥氏体比例为54∶46;CMT堆焊层的耐点蚀性能优于TIG堆焊层和2205内衬层,从焊接效率、耐蚀性考虑,CMT更适合于复合管的管端堆焊。

The cold metal transfer(CMT)and tungsten inert gas welding(TIG)surfacing processes were used to surfacing the X80/2205 bimetal mechanical lined pipe ends,and the effect of surfacing speed on the morphology,microstructures and proportion of surfacing layers were studied in order to determine a reasonable CMT surfacing process.On the other hand,the microstructures and properties of CMT and TIG surfacing layers were compared and analyzed.The results show that both the width and the height of welded bead decrease with the increase of the welding speed.The toughness of CMT surfacing layer is higher than that of TIG surfacing layer because theΣ3 CSL grain boundary ratio of CMT surfacing layer is higher than that of TIG surfacing layer.It is found that there is an embossed brittle-hard structure at the junction between the surfacing layer and the X80 steel.This brittle-hard structure is martensite with the BCC crystal structure,the fine grain size and much large-angle grain boundaries,resulting in sudden changes in hardness at the junction between the surfacing layer and the X80 steel.The ratio of ferrite to austenite in the TIG corrosion resistant layer is 37∶63,and that in the CMT corrosion resistant layer is 54∶46.The pitting corrosion resistance of CMT surfacing layer is better than that of the TIG surfacing layer and the 2205 lining layer.Considering the welding efficiency and the corrosion resistance,the CMT surfacing process is more suitable for surfacing welding of composite pipe ends.