Investigation On Preparation Of Spherical Fine Metal Powders By Centrifugal Atomization Based On Mono-Sized Droplets

Currently,metal powders are as an important industrial raw material;the demand for this material has dramatically increased for use in additive manufacturing,thermal spraying,surface mount technology,metal injection molding,braze welding and electronic packaging.The development of powders with small particle size,narrow size distribution,high sphericity,without satellite powders is needed to satisfy the growing requirements for the accuracy and quality of products,especially in additive manufacturing fields.Although powders prepared by traditional atomization methods have entered the stage of large-scale production,problems still remain in the particle size,size distribution,powder morphology and sphericity.At present,the preparation of spherical fine metal powders in our country has a small capacity and most of the high quality fine spherical powders rely on imports.Therefore,it has important significance to explore a new efficient technology for the preparation of microspherical metal powders.In this study,a novel technology for the preparation of spherical fine metal powders by Centrifugal Atomization based on Mono-Sized Droplets is developed by our team which combines pulsated orifice ejection method with centrifugal atomization.In this method,the mono-sized droplets were prepared by pulsated orifice ejected system,and then the droplets were atomized by centrifugal atomization.Fine Sn63Pb3,Sn0.3AgCu powders were prepared by this method.The effects of different disk diameter,melt temperature,rotation speed,heated treatment on rotation disk and different disk materials Cu,Ni,304 steel on the powder size and particle size distribution,powder morphology,the impurity content and the melting point of powder were studied,the difference between the experimental value and the theoretical value of particle size was analyzed,and the disintegration mode of liquid film in atomization process was discussed.The main conclusions obtained were:(1)The powders with smooth surface,small size,narrow size distribution,high sphericity,and without satellite powders can be prepared by centrifugal atomization based on mono-sized droplets method.(2)Technological parameters have important effects on the preparation of powders: The size distribution of powders prepared by this method exhibits normal bimodal distribution,the powder size decreased with the increase of the disk diameter,melt temperature and rotation speed.The smallest average size of the powders is 18.5?m,and the parameters applied inpreparation of the smallest average size of powders are: the disk diameter is 15 mm,the melt temperature is 573 K,the rotation speed is 48000 r/min.The theoretical value of powders is higher than the calculated value,and the maximum is 54%.(3)The liquid film on the rotation disk tend to thin and the average particle size of powders can be refined by heating the rotation disk.The better the wettability between the rotation disk and the metal material,the smaller the average particle size of the powders obtained,and the theoretical value of powders is higher than the experimental value,the smallest average particle size of the powders is 24.0 ?m prepared by copper rotation disk.(4)The content of impurity in powders under different disk materials varies greatly,the content of copper impurity in powders prepared by copper disk is up to 100 times,and the impurity is not introduced as the powders prepared under nickel disk and stainless steel disk.(5)The mode of liquid disintegration in this method is related to the wettability between the rotation disk and the metal material,the copper rotation disk shows direct droplets disintegration,the nickel rotation disk shows film disintegration,the 304 steel rotation disk did not show liquid disintegration.