US 5,632,881 AGranted

Measuring magnesium concentrations in molten metal alloys

AssigneeHughes Aircraft Company

InventorsStephen A. Gabelich, John McHardy

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Abstract

A simple robust sensor probe for determining the magnesium concentration in molten metal alloys in real-time. The probe provides needed process control information in molten metal technologies and has particular application to processes for removing magnesium impurities from scrap aluminum. The probe employs a specially constructed electrochemical concentration cell adapted for repeated immersions into vessels containing molten metal alloys. Specifically, the probe comprises two electrodes, both inert to a molten salt layer, to the molten metal (aluminum), and to magnesium. One electrode comprises an inverted molybdenum cup, a magnesium reference material, and a fibrous ceramic wick, e.g., yttrium oxide, for retaining molten salt therein in contact with the magnesium reference material when the sensor probe is first inserted into the molten salt layer and then into the molten aluminum layer. A readout between the two electrodes provides a measure of the electromotive force and thus a measure of the concentration of magnesium in molten aluminum during demagging of the molten aluminum.

Claims15

Dependent claims

A sensor for real-time detecting and monitoring magnesium concentration in molten aluminum covered with a molten salt solution, said sensor probe comprising:

(a) first and second electrodes chemically inert with respect to molten magnesium and to molten aluminum, each electrode having two ends, with one end of each electrode provided with an electrical connection and the other end of each electrode adapted for immersion into said molten aluminum;
(b) readout means connected to each said electrical connection of each said electrode for detecting a change in electromotive potential between said other ends of each said electrode;
(c) said first electrode comprising an outer housing having a top and a bottom, a magnesium reference material, a support cup located within said outer housing and being open at one end for containing said magnesium reference material, and a first fibrous ceramic wick comprising yttrium oxide, wherein said first fibrous ceramic wick is positioned at said open end of said support cup in contact with said magnesium reference material to thereby retain said magnesium reference material in said support cup, said open end of said support cup comprising said other end of said first electrode and being adapted for receiving said molten salt solution therein whereby said molten salt solution becomes trapped in said first fibrous ceramic wick, said sensor probe adapted to provide an electrochemical cell comprising
[Mg(l)].vertline..vertline.[MgCl.sub.2 CaCl.sub.2 (l)].vertline..vertline.[Mg in Al(l)],
where "l" refers to liquid.

2 more elements

A method of measuring magnesium concentration in molten aluminum during a process for reducing magnesium content in said molten aluminum, said process including forming a molten salt layer on said molten aluminum and passing a current through an anode immersed in said molten aluminum and a cathode immersed in said molten salt layer so as to ionize and collect said magnesium from said molten aluminum, said method comprising;

(a) providing a sensor probe comprising
(1) first and second electrodes chemically inert with respect to molten magnesium and to molten aluminum, each electrode having two ends, with one end of each electrode provided with an electrical connection and the other end of each electrode adapted for immersion into said molten aluminum;
(2) readout means connected to each said electrical connection of each said electrode for detecting a change in electromotive potential between said other ends of each said electrode;
(3) said first electrode comprising an outer housing having a top and a bottom, a magnesium reference material, a support cup located within said outer housing and being open at one end for containing said magnesium reference material, and a first fibrous ceramic wick comprising yttrium oxide, wherein said first fibrous ceramic wick is positioned at said open end of said support cup in contact with said magnesium reference material to thereby retain said magnesium reference material in said support cup, said open end of said support cup comprising said other end of said first electrode and being adapted for receiving said molten salt therein, said sensor probe adapted to provide an electrochemical cell comprising
[Mg(l)].vertline..vertline.[MgCl.sub.2 CaCl.sub.2 (l)].vertline..vertline.[Mg in Al (l)],
where "l" refers to liquid;
(b) first immersing said sensor probe into said molten salt layer to wet said first fibrous ceramic wick with said molten salt wherein said molten salt remains trapped in said first wick;
(c) then immersing said sensor probe into said molten aluminum layer to contact said molten salt in said first fibrous ceramic wick with said molten aluminum;
and
(d) measuring change in potential as a function of time, said change in potential related to said magnesium concentration.

7 more elements

Dependencies are inferred from the claim text.