Research On Cylindrical Hollow Jet And Electrostatic Atomization Technology Of Spray Forming

The key process of spray forming is atomization which influences the microstructure of deposition. This thesis aims to improve the atomization quality by altering the properties of molten metal and changing the way of liquid. In spray forming, electrostatic interactions could reduce the surface tension of metal liquid. The ring way of liquid flow could make liquid membrane before the metal jet is not atomized once disturbance immediately broken. At the same time, the power of atomization increases air drag force and static repulsion, both of which comprehensively together could improve the quality of spray effectively.The whole device of hollow jet and electrostatic atomization was firstly pretreated, which included smelting furnace, generating device of ring-like metal liquid and charging device. The maximum temperature of melting furnace can rise up to 1400°C, that can meet 900°C of demand. Parts of a ring-like metal liquid generating device are connected by interference fit. The girth of 1.5mm consists of stream outlet and center core, and the stream outlet diameter is 10mm, the center core is 7mm. Designed charging device mainly uses inductive charging mode, one pole of high voltage DC power contacts with metal liquid through electrode bar, anode connects with plate electrodes, which can make the fog regions capacitors, induction charged atomization of molten metal in the region.Analysing the effects of electrostatic on spray forming in theory, which includes jet breaking length, surface tension of droplet and the size of liquid droplet. It also compares with ring-like metal and solid metal liquid charge. The results show that the length of electrically charged jet is 2-4mm shorter than uncharged under the same pressure. As the charging voltage increases, jet breaking length is narrow and the atomized droplet diameter decreases. The breaking length of jet and droplet diameter tend to be stable, when rises to 1.8kV. For industry pure aluminum, the surface tension of liquid droplets reduces 30% by static electricity, the ring-like metal liquid charge is 27mC~38mC bigger than the solid metal charge under the same charge voltage. According to the theoretical analysis, by the experiments of ordinary solid atomization, solid electrostatic spray and annular electrostatic spray, the experimental results and the theoretical analysis are basically the same. Through the analysis of the Al-Si deposition, it can be found that the deposition of the organization is loose, primary phase is skewed and hardness is lowest in no electricity condition. When atomization pressure is 0.8MPa, charging voltage is 1.0kV, the product's performance will improve. When atomization pressure is 0.8MPa, charging voltage is 1.0kV, girth wide is 1.5mm, the deposited organizations is tight, the size of primary Si significantly reduces, and the distribution is even. Product of micro-hardness also has the best performance, that can up to 60HV.