TREATMENT OF LIQUID METAL

• US 3,753,690 A
• Filed: 09/10/1970
• Issued: 08/21/1973
• Est. Priority Date: 09/12/1969
• Status: Expired due to Term

• Current Assignee: Edward Frederick Emley, Malcolm Victor Brant
• Original Assignee: Edward Frederick Emley, Malcolm Victor Brant
• Inventors: Emley, Edward Frederick, Brant, Malcolm Victor
• Primary Examiner(s): Rutledge, L. Dewayne
• Assistant Examiner(s): Rosenberg, Peter D.
• Application Number:
  US05/071,112
• Time in Patent Office: 1,076 Days
• Field of Search: 75/67,68,93,94 148/23,26 210/10,69
• US Class Current: 75/412
• CPC Class Codes: C22B 21/066 Treatment of circulating aluminium, e.g. by filtration C22B21/068 takes precedence
• CPC Class Codes: C22C 1/02 by melting C22C1/1036 takes precedence

Abstract

A process for removing non-metallic constituents in molten metal, particularly aluminium and its alloys. In one treatment the metal is flowed through a multiplicity of flux-lined channels which are conveniently provided by a bed of flux-coated granules of a size such that the channels are large enough not to become clogged during use. In another treatment the metal is degassed by continuously passing it through a containing vessel while passing a substantially inert gas such as nitrogen therethrough under a flux cover; this can be followed by passing the metal through the flux-lined channels.

Claims

2. A process in accordance with claim 1, wherein a layer of said molten flux is maintained on the surface of said molten metal, and nitrogen is passed through said molten metal to degas said molten metal.

3. A process in accordance with claim 1, wherein said coarse refractory granules are Al2O3 balls of 3/8 in. minimum size.

4. A process in accordance with claim 1, further comprising flowing said molten metal through a second bed of substantially uncoated coarse refractory granules.

5. A process for removing non-metallic constituents including hydrogen and solid particles from liquid aluminum and its alloys in a continuous manner which comprises flowing such liquid metal at a temperature up to 800*C. through a containing vessel, maintaining a molten salt flux layer on the surface of metal in the containing vessel, simultaneously passing a substantially inert gas into the liquid metal, and thereafter flowing the liquid metal through a bed of coarse refractory granules substantially of a size to be retained on a 3/8 in. aperture screen, said bed being submerged beneath the surface of the molten metal, the inert gas being passed into the container and into the liquid metal in such a manner as to create vigorous turbulence whereby a coating of said molten salt flux is produced and maintained on at least some of said granules, said salt flux being selected from mixtures of salts which are molten at said temperature and which salts are selected from the group consisting of chlorides and fluorides of alkali and alkaline earth metals and magnesium.

6. A process in accordance with claim 5, wherein said containing vessel Is divided by a baffle wall to provide a substantially U-shaped vessel in which the direction of liquid metal flow is down a first leg of the U and up a second leg of the U, wherein said process comprises passing said inert gas upwardly through the liquid metal in said first leg with said molten salt layer being maintained on the surface of the liquid metal in said first leg.

7. A process in accordance with claim 5, wherein said substantially inert gas is nitrogen.

8. A process in accordance with claim 5, wherein said bed of coarse refractory granules is located in a second vessel downstream from said containing vessel.

9. A process in accordance with claim 5 for additionally removing sodium metal from the liquid aluminium, wherein said flux contains at least 5 percent by weight of MgCl2 and is substantially free of the fluoride and complex fluorides of sodium.

10. A process for removing solid non-metallic constituents from molten aluminum and its alloys in a continuous manner which comprises continuously flowing the molten metal at a temperature up to 800*C. through a containing vessel, maintaining a molten salt flux layer on the surface of molten metal in the containing vessel, continuously creating vigorous turbulence in the molten metal in contact with the molten flux within the containing vessel;

and thereafter continuously flowing the molten metal having some molten flux entrained therein through a flux trap comprising a bed of coarse refractory granules substantially of a size to be retained on a 3/8 in. aperture screen, said bed being submerged beneath the surface of the molten metal, whereby at least some of said granules become coated with said molten salt flux, said salt flux being selected from mixtures of salts which are molten at said temperature and which salts are selected from the group consisting of chlorides and fluorides of alkali and alkaline earth metals and magnesium.

11. A process in accordance with claim 10 for removing hydrogen and solid particles wherein the residence time of said molten metal in said containing vessel is at least 1 1/2 min., said vigorous turbulence is created by passing a substantially inert gas into said molten metal at a rate sufficient to provide at least 10 cu. ft. of inert gas per ton of molten metal.

12. A process in accordance with claim 11, wherein said molten flux layer is provided in an amount of at least 1 lb. of flux for each 100 sq. in. of surface area of said molten metal and wherein said flux is substantially free of oxides, oxysalts, fluorosilicates and volatile halides.

13. A process in accordance with claim 12, wherein said gas is nitrogen.

14. A process in accordance with claim 11, wherein said flux trap further comprises a layer of fluoride.