CMT Surfacing Process And Deformation Control Of Boiler Water Wall

When garbage burning boiler burns rubbish,it will release a large number of HCl,HF,SO2 and other corrosive gases.These corrosive gases are more serious corrosion to water wall tubes.Thermal spraying methods commonly used in coal-fired boilers can no longer meet the protection needs.The protective layer can be obtained by surfacing.The protective effect of surfacing depends on the dilution rate of the surfacing layer.The lower the dilution rate,the better the protective effect.In this thesis,the CMT surfacing technology of water wall and the deformation control of surfacing welding are studied Respectively ER50-6,304 and Inconel625 wire surfacing to optimize the welding process,the deformation law of surfacing welding was analyzed,and the deformation control measures were adopted.The results showUsing 304 stainless steel wire surfacing boiler water wall process parameters are:20G steel pipe process parameters for surfacing current 170A,voltage 13.9V,surfacing speed 2mm/s,pendulum width 7mm,two ends residence time 0.1 s,frequency is 1.1 Hz,amount of overlap 1mm;The welding parameters of steel pipe and fin joint are surfacing current 180A,voltage 13.9V,surfacing speed 2mm/s,pendulum width 5mm,two ends residence time 0.5s,frequency is 1.7Hz;The welding parameters on the fins surfacing current 180A.voltage 13.9V,surfacing speed 2mm/s,pendulum width 5mm,the frequency 1.1 Hz,and two ends residence time of the two welds the left is 0.5s,right is 0.2s and each side are 0.3s.The protective gas of all weld surfacing is pure AR gas and the flow rate is 18L/min.The joint between steel pipe and fins is surfaced,and then surfacing the fins.Finally,the steel pipe with symmetrical surfacing sequence surfacing pipe.304 stainless steel wire and Inconel625 wire surfacing,two kinds of welding wire after melting the fluidity is similar.With the same surfacing parameters,the surfacing weld is similar to the welding forming.Therefore,304 stainless steel wire surfacing water wall parameters can be directly used in Inconel625 wire surfacing welded water wall.The surfacing layer obtained by Inconel625 welding wire surfacing is well combined with the matrix metallurgy,and the shear strength minimum value is 330MPa.Weld surfacing dilution rate is very low,almost zero.There is hardly any transition from the matrix to the surfacing layer.The hardness of the surfacing layer is between 230?310HV,the hardness of the substrate is between 140?190HV,and the hardness of the surfacing layer is higher than that of the base material.Hardness distribution on both sides of the fusion line are relatively uniform.There is surfacing deformation in the surfacing of boiler water wall,which will be flexural to the surfacing layer.The deflection and axial shrinkage deformation of the water wall is larger when the water wall is not restrained.Rigidly fixed welding method,although not completely eliminate distortion,deformation when compared with non-binding,significantly reduced the welding deformation.By simulating the method of rigid fixation of the two ends of the boiler water wall,it is proved that this kind of rigid fixation method can effectively reduce the transverse shrinkage of the water wall.However,this kind of fixation method is not obvious to the longitudinal shrinkage and deformation reduction of water wall.