| Spray forming is a new material preparation technology. Not only can overcome traditional casting process's shortages such as coarse grains, segregation serious, but also can markedly improve powder metallurgy's inadequacy complex processes, easy oxidation, with controlling the metallic melts from liquid to solid solidification process. It is a kind of very promising technology.In spray forming process, the liquid metal atomization is the key process to the quality of the production; so atomization technology is the most important technology in spray forming. At present during all the injection forming atomization technology, liquid metal flows from liquid pipe with solid forms. And has no reports about the research on liquid metal flows out with hollow form, the hollow outflow form may make atomization droplet size smaller in the same atomization conditions. On the foundation of current spray forming atomization technology, I design the devices which can generate cylindrical hollow jet and d the research on the annular jet flow fields. This thesis lays the foundation of hollow jet atomization technology in Spray forming.First on the foundation of original experiment equipment, design a crucible which can generate hollow jet, composed with crucible part, core part and flow components. Crucible is filled with liquid metal and plays the role as heat preservation in trials. Core part is made of the core and positioning dish composition, and core has straight type solid core, pour tapered solid core and hollow steel core. It can compose with the bottom of the crucible as a circular seam. Positioning plate fixed core, guarantee export concentric with a core, forming concentric girth. Funnel shaped export's angle is between 70～90°. Core and export over surplus cooperate to crucible.According to the actual experiment equipments establish two-dimensional geometry model, simulate Flow field's distribution under the condition of single-phase flow and two-phase flow. Single-phase flow simulation show straight form core and pour tapered core make a little effect to metal jet, due to the density of liquid metal, viscosity and surface tension are relatively large. Large inlet velocity can get larger backflow area and lower negative pressure, also be used to the flow of liquid metal. The two-phase flow field simulation shows that the hollow core of atmospheric connectivity can produce hollow cylindrical liquid jet flow, when the hollow-core is pressurized by 0.03MPa of flow, annular jet increases.On the foundation of numerical simulation results, do hollow jet experiment in several different kinds of process conditions. These conclusions are basically as the same as the experiment. Use hollow tubes core, filled with 0.03MPa nitrogen can get good hollow jet. |
