Air vent valve for a die-casting mould

点击翻译按钮获取中文摘要

High-pressure die-casting is a process used to make a wide range of metal components, in which liquid metal is injected under high pressure into a steel mould, where it freezes very rapidly upon contact with the walls. Air in the mould cavity must be vented during metal injection or it becomes trapped in the metal part, creating pores that may require the piece to be scrapped. In practice a valve is mounted at the exit of the air passage, actuated using either an electric, pneumatic, or hydraulic system, that allows air to vent and then shuts in time to prevent molten metal from discharging through it. The University of Toronto will collaborate with Bholster Technologies to develop a valve to permit air from die casting moulds to vent during the injection phase while preventing liquid metal from escaping. We plan to do this by using the momentum of the fast moving liquid metal to impinge on the valve and shut it off before the melt can escape from the valve exhaust. The vent valve consists of two portions, one half positioned in the moving die and the other half in the stationary die. A passageway is machined in the die cavity to allow trapped air to escape through the vent valve. A spring holds the valve piston open. When the fast moving molten metal fills the mould cavity the air in it is forced through the open valve and exits though the valve exhaust. When the melt arrives it is directed by the contours of the valve body to impinge on the spring-loaded piston. The high momentum of the liquid metal forces the piston to close while simultaneously steering the melt away from the valve opening, thus preventing liquid metal from flowing through the valve exit. Experiments will be done with the valve using water as the working fluid and a high-speed video camera used to observe the path of water flow through the valve. We propose to study how the liquid momentum affects valve movement and how sensitive the valve response time is to changes in the liquid flow rate