Method of and device for producing light metal castings, in particular parts of magnesium or mangnesium alloys

Abstract

Production of light metal castings composed of magnesium or magnesium alloys, includes supplying a liquid metal first to a dosing chamber; pumping gas under pressure into the dosing chamber so as to press the liquid metal into a preliminarily evacuated mold nest; performing a production process within a system which is pressure-tightly closed from outside; performing heating of the liquid metal in a lower part of a melting device which adjoins a feed system; performing overheating of the liquid metal from a melting condition with a temperature of approximately 630° C. to a rigidification condition at a tool side to a lower region of a valve seat; and supplying and withdrawing a protective gas by a differential pressure system.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:  
     
         1 . A method of producing light metal castings composed of magnesium or magnesium alloys, comprising the steps of supplying a liquid metal first to a dosing chamber; pumping gas under pressure into the dosing chamber so as to press the liquid metal into a preliminarily evacuated mold nest; performing a production process within a system which is pressure-tightly closed from outside; performing heating of the liquid metal in a lower part of a melting device which adjoins a feed system; performing overheating of the liquid metal from a melting condition with a temperature of approximately 630° C. to a rigidification condition at a tool side to a lower region of a valve seat; and supplying and withdrawing a protective gas by a differential pressure system.  
     
     
         2 . A method as defined in claim  1 ; and further comprising performing, within the closed system a post-dosing of rigid light metal by a sluice device under an available pressure difference between outer atmosphere and an inner pressure in the melting device.  
     
     
         3 . A method as defined in claim  1 ; and further comprising supplying the light metal selectively in a liquid form through a metal supply conduit and/or as a rigid light metal through a sluice device.  
     
     
         4 . A method as defined in claim  1 ; and further comprising selecting a quantity of the light metal to be supplied as a multiple of a light metal quantity required for a light metal casting to be produced.  
     
     
         5 . A method as defined in claim  1 ; and further comprising rigidifiying the liquid light metal by a movement of a tool device away.  
     
     
         6 . A method as defined in claim  1 ; and further comprising supplying and withdrawing of the protective gas through a pressure intensifier, and compensating pressure losses by protective gas post-dosing.  
     
     
         7 . A method as defined in claim  1 ; and further comprising performing the rigidification of the light metal by lifting a casting retort and thereafter placing the casting retort on a tool device of a last workpiece to be treated.  
     
     
         8 . A device for producing light metal castings of magnesium or magnesium alloys, comprising a melting unit having a container; a metal supply conduit arranged in said container and extending outwardly in a pressure tight manner; a pre-melting oven; a check valve through which the liquid metal is supplied from said pre-melting oven; a differential pressure system with which said container of said melting unit is connected; and sluice means introduced into said container of said melting means in a pressure tight manner.  
     
     
         9 . A device as defined in  claim 8 , wherein said differential pressure system includes a pressure intensifier, and a protective gas-post-dosing means arranged after said pressure intensifier and compensating pressure losses.  
     
     
         10 . A device as defined in  claim 8 , wherein said differential pressure system includes a blow storage and a pump system associated with the latter.  
     
     
         11 . A device as defined in claim  1 ; and further comprising a casting retort which narrows in direction toward a feed system, said metal supply conduit being arranged in a pressure-tight manner in said casting retort and supplying a liquid metal from said pre-melting oven through said check valve, said casting retort being connected with a pressure intensifier, and said pressure intensifier being connected with a protective gas dosing means which compensate pressure losses, said sluice means being arranged in said casting retort in a pressure tight manner for supplying a rigid light metal; a valve control means for controlling the supply of the liquid metal and associated with a valve lock for performing a supply in a very short time.  
     
     
         12 . A device as defined in claim  8 ; and further comprising a system selected from the group consisting of a pneumatic system, a hydraulic system and both, and providing a valve control means, said valve control means being connected with a valve lock selected from the group consisting of a hydraulic valve lock, a pneumatic valve lock, and an electromechanical valve lock.  
     
     
         13 . A device as defined in claim  8 ; and further comprising means for rigidification of the liquid metal by a heat-insulating, cooled supply; and a heat-insulating layer locked between said melting device and a tool device.  
     
     
         14 . A device as defined in  claim 8 , wherein said check valve is located inside said container of said melting device.