| 摘要 |
<p>A method of low pressure die casting in which molten metal is forced upwardly from a furnace into a die through a riser tube extending below the level of the molten metal in the furnace by gas pressure applied to the surface of the metal. To avoid the formation of oxides in the metal, an inert gas, heavier than air, is introduced into the riser tube adjacent the die to fill the riser tube above the level of the metal in the furnace. On application of gas pressure to the molten metal in the furnace, as the metal rises in the tube, the inert gas expels out from the die cavity. After solidification of the metal in the die and removal of the gas pressure to the furnace, excess molten metal falls back by gravity into the furnace, the inert gas again filling the space above the metal in the tube to prevent ingress of air at the interface between the sprue orifice of the die and the riser tube. A low pressure die casting apparatus is disclosed which includes an apertured cap on the riser tube for engagement with the sprue orifice, the cap being provided with an inlet for an inert gas.</p> |
