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WO1993017136A1 - Fusion et raffinage du magnesium et/ou d'alliages de magnesium sans utiliser de flux - Google Patents

Fusion et raffinage du magnesium et/ou d'alliages de magnesium sans utiliser de flux Download PDF

Info

Publication number
WO1993017136A1
WO1993017136A1 PCT/US1992/001401 US9201401W WO9317136A1 WO 1993017136 A1 WO1993017136 A1 WO 1993017136A1 US 9201401 W US9201401 W US 9201401W WO 9317136 A1 WO9317136 A1 WO 9317136A1
Authority
WO
WIPO (PCT)
Prior art keywords
magnesium
bath
scrap
molten
gas
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US1992/001401
Other languages
English (en)
Inventor
Vladimir Petrovich
William E. Ii Mercer
William G. Green
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Dow Chemical Co
Original Assignee
Dow Chemical Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Dow Chemical Co filed Critical Dow Chemical Co
Priority to PCT/US1992/001401 priority Critical patent/WO1993017136A1/fr
Publication of WO1993017136A1 publication Critical patent/WO1993017136A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
    • C22B9/05—Refining by treating with gases, e.g. gas flushing also refining by means of a material generating gas in situ
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B26/00—Obtaining alkali, alkaline earth metals or magnesium
    • C22B26/20—Obtaining alkaline earth metals or magnesium
    • C22B26/22—Obtaining magnesium

Definitions

  • This invention relates to melting and refining of magnesium and/or magnesium alloys and more particularly, this invention relates to melting and refining of scrap magnesium and/or magnesium alloys.
  • the fluxing agents are a mixture of various chloride salts used for the protection of molten metal and of the removal of oxides and other non-metallic inclusions (NMI).
  • NMI non-metallic inclusions
  • the sludge being more dense than the melt, settles to the bottom of the crucible thereby enabling the now refined ⁇ ielt to be separated from the sludge.
  • the separated, refined magnesium can then be cast directly into ingots.
  • One flux which has been commercially used to refine magnesium and its alloys contains approximately 40 weight percent (wt. % ) magnesium chloride, 55 wt. % potassium chloride and 5 wt. % calcium fluoride and will be referred to hereunder as M-130 flux.
  • the use of the fluxes has its disadvantages however. For example, some of the flux can remain in the cast metal causing flux inclusions and adversely affecting corrosion resistant properties of magnesium and its alloys. Also, the sludge produced by fluxing creates a disposal problem and entraps a quantity of metal resulting in an accumulated melt loss. The flux also creates an environmental problem by generating HCl, which can further corrode the equipment. In addition, the use of flux adds cost to the process of refining.
  • the present invention is directed to a process for fluxless melting and refining of magnesium or ,- magnesium alloys including contacting a bath of molten magnesium or magnesium alloy with an inert gas, such as argon, sufficient to purify and remove nonmetallic inclusions present in the molten magnesium or magnesium alloy.
  • an inert gas such as argon
  • Figure 1 is a schematic view showing a molten metal bath and a sparging apparatus for the process of M r the present invention.
  • Figure 2 is a graph showing the effect of argon on the number of NMI in a bath of molten magnesium alloy.
  • the process of the present invention is used for the refinement of magnesium or magnesium alloy melts for removing or decreasing the number of non-metallic
  • Non ⁇ metallic inclusions include oxides present in the melt. NMI's in the melt will increase in direct proportion to the surface area of the ingot or parts
  • NMI non-magnetic inorganic styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-S-S-S-S-S-S-S-S-S-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-st
  • the process of the present invention involves fluxless melting of magnesium or its alloy whereby floating of impurities to the top 10 of such melt is accomplished by inert gas sparging and skimming dross formed on the top of the melt.
  • the melt may be filtered to further reduce the NMI.
  • Any magnesium or magnesium base alloy may be used in the present invention.
  • those containing various amounts of Al, Zn, Mn, rare earth metals, Zr, Ag, I, Th, and the like can be used.
  • Alloys of magnesium such as AZ91, EZ33, ZK60, AM 60 and other
  • the present invention is advantageously used in obtaining a scrap-derived ingot product because a greater number of NMI are usually found in melting of scrap. For example, die cast scrap
  • scrap 30 resulting from die casting operations may be the source of scrap metal.
  • This scrap is usually dirty and oily which adds to the problem of separating the oxides from the melt.
  • fluxless melting of die cast scrap is that such process provides remelting
  • Any gas inert or slightly reactive to magnesium and magnesium base alloys may be used in the present invention such as Ar, air, N 2 , He, C0 2 , Cl 2 , SF 6 BF 3 and HCl.
  • argon gas is used in the present invention to minimize melt loss.
  • the process of the present invention may be carried out in any melting and casting operation using conventional equipment with one or more pots or crucibles.
  • crucible 10 containing a molten magnesium 11.
  • a sparger tube 12 with holes 12a is immersed into the bath of melt 11.
  • a container 13 supplies a gas through flow meter 14 and the flow is controlled with valves 15 and 16.
  • the gas is bubbled through the bath of melt and the bubbles 17 carrying the impurities float to the top surface of the melt forming a layer of dross 20.
  • the gas thereafter escapes into the atmosphere.
  • the resultant dross formed at the top of the melt can then be skimmed off in familiar fashion.
  • FIG. 1 While in Figure 1 there is shown a sparger tube 12 for bubbling the gas through the melt, it is understood that any other conventional method of bubbling the gas through the melt can be used, for example, centrifugal pumps or other diffussion devices or dispersion tubes and pumps.
  • argon gas is the preferred gas used in the present invention for bubbling through the melt.
  • the bubbling of argon gas through the melt is herein referred to as "argonization.”
  • the present invention will herein be described with the use of argon gas.
  • Figure 2 is a graphical illustration of one embodiment of a scrap melting process and the effect of
  • a magnesium or magnesium alloy scrap is preferably degreased by any environmentally accepted method, for example, by washing in a solvent
  • Degreasing helps keep the subsequent melt cleaner of non-metallic inclusions and dissolved gasses and reduces smoke and soot within the melting
  • Non-degreased "oily" scrap produces copious quantities of black, sooty smoke during meltdown and adds large amounts of dissolved gas (which is presumed to be hydrogen) in the melt. Washing or degreasing the scrap, for example, in CHLOROTHENE ® prior to melting
  • the scrap is then preheated thoroughly prior to melting to as high as practical above the boiling point of water. It is desired to assure that all moisture on 35 the scrap is driven off from the scrap because of the well known violent reaction of magnesium with water.
  • the scrap is preheated to a temperature of at least 150 degrees centigrade (° C) and more preferably to a temperature of from about 200° C to about 300° C.
  • scrap is charged into a crucible for melting.
  • the scrap can be charged directly into a pot opened to the atmosphere or the scrap can be charged into the pot through a chamber positioned above a covered pot.
  • the charging of the scrap could be carried out by conventional mechanical means.
  • the chamber prevents the contact of the pot atmosphere directly with air above the pot during changing operation so as to minimize protective atmosphere losses. It is advantageous to minimize protective atmosphere losses to minimize the cost of the scrap melting process.
  • the protective atmosphere used in the pot may be conventional protective atmosphere known in the art to prevent burning of the molten metal.
  • one of such protective atmospheres in the pot preferably is kept to a 0.4% to 0.5% SF 6 concentration.
  • the atmosphere may contain any concentration of C0 2 to air ratio. If AZ91 is used, for example, and AZ91 contains at least about 6 ppm of beryllium, there will be no burning problem during melting and holding of the scrap in the pot at a pot temperature of up to about 800° C.
  • the scrap is stirred in the pot with conventional mechanical stirring means to the point of appearance of a "gentle" vortex in the melt until all the scrap is molten.
  • the pot temperature is controlled to a temperature of from about 630° C to about 750° C.
  • the stirring action in the pot helps to even the temperature gradients from top to bottom within the pot and helps to increase the melting rate of the scrap.
  • the dross which forms on the top of the melt is removed from the top by skimming with any conventional mechanical means such as a surface skimmer.
  • manganese may be alloyed, by conventional methods, into the melt, if desired, at about 630° C to about 750° C. to decrease the iron content of the melt and produce a high purity magnesium alloy.
  • the melt can be transferred to a casting pot or a transfer ladle by pumping through a transfer line or tilting or any other means commonly used in foundry operations.
  • the melt may be pumped through a suitable filter to remove non-metallic inclusions from the melt.
  • a suitable filter for example, any conventional filter suited for a particular pot geometry and capacity may be used such as a Johnson screen filter with 0.045 inch openings and 31% open area.
  • the filter further removes NMI and may be used before the argonization step or after the argonization step.
  • an ample screen surface area to pot volume ratio is used.
  • the static screen to weight ratio is 0.07 in ⁇ /lb. or for an estimated throughput of 1.5 lb/sec. (5400 lbs/hr) the casting capacity ratio is 0.04 in 2 /lb.
  • the melt is pumped into molds or die cast machines to form ingots or castings.
  • the molten material may be cast into ingots such as DOWLOK ® 10 (trademark of The Dow Chemical Company) or any other desired casting shape.
  • a selected number of ingots are fractured using an air-hydraulically operated ram. For example, 112 ingots (1800 lbs.) is selected and fractured. The ingots may be fractured, for example, in half.
  • the fresh fractures are visually 0 examined for non-metallic inclusions (NMI) using a stereo microscope at 10X and 45X magnification.
  • the number of visually detectable particles, i.e. NMI are counted for the total fracture surface area. A value expressed in number of NMI per square inch of total 5 surface area of fracture is obtained for each ingot and averaged.
  • the counted non-metallic inclusions are sorted into the following three groups:
  • the procedure for 45X magnification is to count the number of NMI in the field of view of the stereo microscope in 5 random passes from the left edge to the right edge.
  • a Bausch and Lomb stereo binocular microscope with fluorescent flat incident light may be used.
  • the field of view at 45X is 0.01 square inch.
  • the numbers are averaged per pass and multiplied by 100 to express it as the number of NMI per square Inch.
  • the same procedure for the 45X magnification is carried out except that the field of view is 0.2 square inch and the multiplying factor is 5.
  • For particle size determination a standard grading in the ocular is used. No filters are used on the lenses.
  • Figure 1 illustrates a system similar to that used to carry out the present example.
  • a 3/4 inch steel tube sparger was connected to an argon cylinder and placed in a molten bath of AZ91 magnesium alloy with one end of the sparger placed to the bottom of a stainless steel pot about 56 inches In height and 34 inches inside diameter.
  • the sparging time was about 25 minutes and the flow rate was about 25 standard cubic feet per hour (SCFH) at 5 pounds per square inch (psi) line pressure.
  • the sparger submerged in the melt in the pot was moved in the pot to about four general areas of the pot during argon bubbling ("argonization").
  • the argon consumption during the 25 minute "argonization” at 25 SCFH was 1.5 lb for the pot which contained , about 3000 lbs of AZ91.
  • the number of NMI/in 2 was lowered as shown in the Table below.
  • the argonization temperature was approximately 700° C plus or minus 10° C.
  • Sample 2 was cast from the same melt that Sample 1 was obtained, but after argonization.
  • Sample 3 was cast from the melt from which Sample 2 was obtained.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Manufacture And Refinement Of Metals (AREA)

Abstract

L'invention concerne un procédé de fusion et de raffinage de magnésium ou d'alliages de magnésium sans utiliser de flux. Ledit procédé consiste à asperger un bain de magnésium ou d'alliage de magnésium le gaz inerte tel que l'argon en quantité suffisante pour purifier le magnésium ou l'alliage de magnésium en fusion et enlever les inclusions non métalliques.
PCT/US1992/001401 1992-02-21 1992-02-21 Fusion et raffinage du magnesium et/ou d'alliages de magnesium sans utiliser de flux Ceased WO1993017136A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/US1992/001401 WO1993017136A1 (fr) 1992-02-21 1992-02-21 Fusion et raffinage du magnesium et/ou d'alliages de magnesium sans utiliser de flux

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1992/001401 WO1993017136A1 (fr) 1992-02-21 1992-02-21 Fusion et raffinage du magnesium et/ou d'alliages de magnesium sans utiliser de flux

Publications (1)

Publication Number Publication Date
WO1993017136A1 true WO1993017136A1 (fr) 1993-09-02

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WO (1) WO1993017136A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6632641B1 (en) 1999-10-08 2003-10-14 Metrigen, Inc. Method and apparatus for performing large numbers of reactions using array assembly with releasable primers
CN103667835A (zh) * 2012-09-24 2014-03-26 天津德盛镁科技发展有限公司 一种镁合金光谱高纯标准物质的制备方法
CN108842064A (zh) * 2018-07-12 2018-11-20 五台云海镁业有限公司 一种高纯镁及其生产工艺
CN113308614A (zh) * 2021-05-21 2021-08-27 贵州安吉航空精密铸造有限责任公司 一种zm6合金精炼方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4021026A (en) * 1974-12-23 1977-05-03 Union Carbide Corporation Protection for externally heated cast iron vessel used to contain a reactive molten metal
US4203581A (en) * 1979-03-30 1980-05-20 Union Carbide Corporation Apparatus for refining molten aluminum
US4327901A (en) * 1980-03-10 1982-05-04 Kaiser George S Melt and hold furnace for non-ferrous metals

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4021026A (en) * 1974-12-23 1977-05-03 Union Carbide Corporation Protection for externally heated cast iron vessel used to contain a reactive molten metal
US4203581A (en) * 1979-03-30 1980-05-20 Union Carbide Corporation Apparatus for refining molten aluminum
US4327901A (en) * 1980-03-10 1982-05-04 Kaiser George S Melt and hold furnace for non-ferrous metals

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6632641B1 (en) 1999-10-08 2003-10-14 Metrigen, Inc. Method and apparatus for performing large numbers of reactions using array assembly with releasable primers
CN103667835A (zh) * 2012-09-24 2014-03-26 天津德盛镁科技发展有限公司 一种镁合金光谱高纯标准物质的制备方法
CN108842064A (zh) * 2018-07-12 2018-11-20 五台云海镁业有限公司 一种高纯镁及其生产工艺
CN113308614A (zh) * 2021-05-21 2021-08-27 贵州安吉航空精密铸造有限责任公司 一种zm6合金精炼方法

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