Research On Microstructure And Properties Of Aluminum Bronze Surfacing On Carbon Steel

Carbon steel is a commonly used structural material in industrial production.If copper alloys with corrosion resistance,wear resistance and high temperature resistance can be deposited on the surface of carbon steel,carbon steel can be used more widely and cost-effective.This topic uses self-made aluminum bronze welding wire and uses submerged arc automatic welding to surfacing aluminum bronze on the surface of carbon steel.By changing the welding current,welding speed,the effect of different surfacing welding processes on the macro morphology,microstructure and hardness of aluminum bronze is studied.The friction and wear tests were carried out on single-pass and multi-pass welding samples to study the wear performance of the surfacing layer in different working environments.The main test results are as follows:The aluminum bronze ingot is prepared by non-vacuum smelting,which is hot forged and hot rolled into a disk-shaped wire,and the disk-shaped wire is drawn into a welding wire.In order to select the drawing intermediate annealing process,use different temperatures and different cooling methods to anneal aluminum bronze: air-cooled and furnace-cooled annealed aluminum bronzes are composed of α phase,β phase and κ phase,the alpha phase content of furnace-cooled annealed aluminum bronze is significantly more than that of air-cooled annealing,and the plastic deformation capacity of aluminum bronze by furnace-cooled annealing is stronger than that of air-cooled annealing.With the increase of furnace-cooled annealing temperature,the elongation of aluminum bronze first increases and then decreases,The elongation reaches its peak at 750℃,reaching 21%.Finally,750℃×2h furnace cold annealing is used as the intermediate annealing process.A single-pass surfacing test was performed on the surface of Q345,and the single-pass surfacing layer and the substrate showed a good metallurgical bond,and no porosity appeared.Regarding the macroscopic morphology of the surfacing layer,as the surfacing current increases,the melting width,penetration depth,and total melting height of the single-pass surfacing layer also increase;the melting height first increases and then decreases.When the welding current is 350 A and the speed is 400mm/min,the dilution rate is the smallest,only 26%;the dilution rate increases greatly with the increase of the welding current,when the welding current rises to 550 A,the dilution rate reaches 54%.The single-pass welding surfacing layer is mainly composed of gray α phase and black κphase.The content of κ phase gradually increases with the increase of welding current.The structure of κ phase is mainly dendritic and dot-like.The hardness of the aluminum bronze single-pass surfacing layer increases with the increase of welding current.When the welding current is 550 A,the average hardness of the surfacing layer is the largest,reaching238.39 HV.When the welding current is small,the welding speed has little effect on the hardness of the surfacing layer;when the current is increased to 550 A,the surfacing layer hardness(average value of 288.39HV)with a welding speed of 400mm/min is obviously greater than that of 350mm/min.Layer(mean value 272.48HV).By studying the influence of welding process parameters on penetration cracks in the fusion zone,it is found that the size of penetration cracks can be effectively reduced by reducing the welding current and speeding up the welding speed;when the welding speed is 350mm/min and the welding current is 550 A,the maximum penetration crack length reaches 1120μm;When the welding speed is 400mm/min and the welding current is 400 A,the maximum penetration crack length is only 325μm.A multi-pass surfacing test was carried out on the surface of Q345.The structure of the aluminum bronze multi-pass surfacing layer was also composed of gray α phase and black κphase.The κ phase appeared in the shape of snowflakes near the surface of the surfacing layer.The peak hardness of the surfacing layer using the three-layer surfacing process was obtained at the weld,reaching 242.57 HV,and the hardness of the first surfacing layer to the third surfacing layer decreased successively,and the average values were 239 HV,187HV,and 179 HV respectively.The friction and wear test of the single-pass and multi-pass surfacing layers is carried out.When the load increases from 5N to 15 N,the average friction coefficient of the single-pass and multi-pass surfacing layers gradually decreases,the width of the wear scar,the amount of wear,and the wear scar line The roughness gradually increases.When the speed is increased from 200r/min to 400r/min,the friction pair will increase the grinding distance,and the surface wear will increase.A lot of heat will be generated on the surface of the wear scar and oxidative wear will appear.The test temperature rises from normal temperature to 300℃,and the surface of the wear scar is simultaneously oxidized wear and softened.The width and average friction coefficient of the single-pass surfacing layer gradually increase,and the amount of wear and line roughness first decrease and then increase;multi-pass stacking The average friction coefficient of the weld layer gradually increases with the increase in temperature,and the wear amount,line roughness and wear scar width first drop sharply and then rise slightly.