Study On Laser Cladding Repair Technology Of Roll

Rolls are prone to damage due to the combined effect of heat and force in the service process.It is urgent to repair and remanufacturing them to save cost,energy and resources.Laser cladding technology has the advantages of high forming quality,small heat affected range,diverse processing materials and high degree of automation.It has significant advantages in the repair and remanufacturing of failed rolls.At present,the research of laser cladding repairing roller is mostly based on powder,but the lateral wire feeding laser cladding technology has the advantages of stable cladding process,high utilization rate of wire,low price of wire and simple structure.In this paper,the lateral wire feeding laser cladding repair of 45 steel roll surface is studied.The specific research contents are as follows:In order to obtain a wide process window,the wire feeding process was optimized firstly.The influence of wire feeding process on the forming quality was studied by using HB-YD405A(Q)flux-cored wire as cladding material through single factor experiment.The results show that : The wire feeding process will change the proportion of heat distribution,which will seriously affect the stability of the test process and the quality of the cladding layer.The morphology of the cladding layer obtained by pre-wire feeding is better,and the cladding process is stable and the processing window is wide.When the wire feeding angle is 45°,the wire is not easy to bend and is excessively continuous with the molten pool.The cladding process is stable,and the quality and morphology of the cladding layer are the best.When the filament spacing is 1mm,the cladding process is stable,and the quality and morphology of the cladding layer are good.When the wire spacing is too large,the wire is easy to deviate from the molten pool and laser beam,resulting in the interruption of the cladding process;When the distance between filaments is too small,it is easy to form large droplets at the end of the filament,resulting in more defects in the morphology of the cladding layer.The effect of process parameters on the quality of single-pass cladding layer was studied by orthogonal experiment,and a set of optimal process parameters combination was obtained by multi-objective optimization of process parameters through grey correlation analysis method : laser power 2200 W,scanning speed 4.5mm/s,wire feeding speed 45 mm/s.Then the effect of overlap ratio on the forming quality of cladding layer was studied by multi-pass laser cladding test,and the interlayer spacing was selected.The experimental results show that the optimal overlap ratio under the optimal process parameters combination is 30 %.The cladding layer has good morphology and no obvious defects.The interlayer spacing is 2 mm.The microstructure of the cladding layer is mainly martensite,the top is equiaxed crystal,and the remelted area between the two layers is mostly columnar crystal.The transverse and longitudinal microhardness of the cross section of the cladding layer changes periodically,and the surface hardness is about 550 HV.The effect of resistance heat on machining efficiency and cladding layer quality was studied.Through laser beam and resistance heat composite deposition test,it was found that the resistance heat generated by heating current preheats the wire,reduces the dependence on laser power,effectively reduces the defects of the cladding layer,broadens the process window,and improves the cladding efficiency and stability of the cladding process.