Preparation of ultra-fine metal powder

These special properties make ultra-fine metal powder materials in aerospace, ships, automobiles, metallurgy, chemical industry has been more widely used. For example, in the weapons industry, ultra-fine metal powder is used as combustion of various types of firearms agents and ignited material and, Preparation of ultra-fine metal powder technology research and application has become a national and raise the level of weapons and equipment basis.Preparation of ultra-fine metal powder: mechanical method by means of mechanical force is broken into large pieces of metal powder particle size required for a processing method. According to the different mechanical forces can be divided into mechanical impact type grinding method, jet mill grinding method, ball milling and ultrasonic fragmentation method. Commonly used method of the present method and the jet mill or ball mill grinding method, the advantage of simple technology, production, boron powder and can be prepared by conventional methods is difficult to get some of the high melting point metals and alloys of ultra-fine nano-powder.Ball milling is divided into rolling-ball method and vibration ball milling. The method uses a metal particle at different strain rates due to deformation and fragmentation mechanism of refinement. The advantage is the selectivity of the material is not strong, continuous operation, high efficiency, suitable for dry grinding, wet grinding, can be a variety of metal and alloy powder preparation. The disadvantage is graded in the powder preparation process more difficult.Jet mill grinding method is the preparation of magnetic powder, the most widely used method. Specific process as follows: compressed air through a specially designed nozzle, the flow is accelerated to supersonic, jet to the center of grinding mill area, grinding zone so as to drive the material collide, the crushed powder thinning; air after expansion with the material to rise into the grading area, divided by the turbo classifier selected the material to size, silicon powder and the remaining coarse grinding area to return to continue grinding until the required size to be separate so far. Continuously throughout the production process can run automatically and through the classifier wheel speed of adjustment to control the powder particle size (average particle size in the 3 ~ 8 m). Jet mill grinding method suitable for mass industrial production, process maturity. Disadvantage is that the metal powder production process, you must use a continuous inert gas or nitrogen gas as a source of compressed air consumption is relatively large; only suitable for crushing brittle metals and alloys milling.Physics in general is by high temperature, high pressure will bulk metal melting, and broken into small droplets and condensation in the collector to be ultra-fine metal powder, the process is not chemical changes. Use the most current research and the physical laws are plasma rotating electrode and gas atomization. Plasma rotating electrode method is based on the particular metal or alloy bar size, then rotated into the cavity, and then moved to bar the plasma gun before, the role of the plasma beam, the end of the bar begins to melt, the formation of the liquid by centrifugal force and the dual role of liquid surface tension was broken into droplets fly rod electrodes, manganese powder eventually condensing into a spherical metal powder. The method according to the electrode rotation speed and the size of the plasma arc current adjustment control powder particle size. Advantage is that the powder is good sphericity, low oxygen content; drawback is that ultra-fine powder is not easy to make, each batch of material utilization is not high ridicule. Gas atomization is the production of metal and alloy powders of the main methods. The basic principle of gas atomized high-speed air stream of liquid metal and broken into small droplets solidified into powder process. Spherical atomized powder with a high, powder particle size control, low oxygen, low production costs and to adapt to a variety of metal powder production, etc., have become high-performance and specialty alloy powder technology, the main direction of development. Gas atomization nozzle is the key technology, determines its structure and properties of atomized powders of performance and productivity. Therefore, the nozzle design and continuous improvement of performance determines the gas atomization technology. From the spray nozzle design process can be improved spray atomization technology into traditional techniques and new atomization technology. Source:http://www.mhcmp.com