Reserch On Process,microstructure And Properties Of Overlaying Monel400 On The Surface Of Q345R Low Alloy Stell

Monel400 was widely used in chemical industry for methane chloride equipment,in order to improve the quality and efficiency of Monel400 surfacing in the methane chloride core equipment,to Ensure the core equipment normal operation in strict service conditions and avoid the economic loss caused by frequent shuts down situation due to equipment problems.Therefore,it was important and meaningful to find out reasonable methods of surfacing Monel400 on the surface of low alloy steel Q345 R,to detect the relevant properties of its surfacing joint,to ensure the quality of surfacing and meet the requirements of equipments.In this thesis,three methods of overlaying Monel 400 on Q345 R surface were designed,they were CMT cold metal transition,electrode arc welding and manual TIG surfacing.After test,the parameters of CMT surfacing were optimized,and the best technological parameters were determined: the welding current of transition layer was 146 A,the welding voltage was 15.5V.The corrosion resistance surfacing parameters were as follows: the welding current of transition layer was 116 A,the welding voltage was 12.7V.electrode arc welding and manual TIG surfacing were surfacing in accordance with the mature process parameters.CMT cold metal transition,electrode arc welding and manual TIG surfacing could form smooth surfacing surface with reasonable parameters.This thesis mainly analyzed the quality of CMT cold metal transition,electrode arc welding and manual TIG surfacing by surface penetration test,metallographic analysis,composition analysis,dilution rate analysis,corrosion resistance analysis,shear strength analysis and bending test analysis.Through the analysis,it was found that CMT cold metal transition,electrode arc welding and manual TIG surfacing met the standard requirements.After PT test showed no surface defects.Metallographic examination of the surfacing layer was carried out by metallographic microscope,the results showed that the surfacing layer was austenitic.The main components of the surfacing layer were two elements Ni and Cu by SEM.The dilution rate of CMT overlay was calculated and the corrosion resistance of the overlay was better.Through shear strength test,the shear strength was 413 MPa,385MPa and 347 MP respectively.After 180°bending test,there was no crack in the overlay.Three surfacing methods could getting Monel400 overlay with stable quality.The quality of CMT surfacing layer is better than that of electrode arc welding surfacing and manual TIG surfacing.CMT surfacing was carried out based on the first few chapters analysis,stress heat treatment is eliminated after welding and the stress condition was also analyzed.The test of Stress tester with indentation strain method proved that the residual stress produced by surfacing could be eliminated obviously after welding heat treatment,so that the surfacing layer could be better quality and can be well applied on chemical equipment under service condition.