US1555956A - Melting and pouring magnesium - Google Patents

Description

Oct. 6, 19z5.- 1,555,956

' H. E. BAKKEN MELTING AND POURING MAGNESIUM Filed July 24, 1923 2 Sheets-Sheet l CLLbornqg.

Oct. 6, 1925. v

H. E. BAKKEN MELTING AND POURING MAGNESIUM 2 Shee ts-Sheot 2 Filed July 24', 1923 $6 5 g 4 lnuentor. B5 837%"- (1060 63 Patented Oct. 6, 1925.

UNITED STATES PATENT OFFICE.

HERMAN E. BAKKEN, OF NIAGARA FALLS, NEW YORK, ASSIGNOR TO AMERICAN MAG- NESIUM CORPORATION, OF NIAGARA FALLS, NEW YORK, A CORPORATION OF NEW YORK.

Application filed July 24, 1923. Serial No. 653,520.

To all whom it may concern.

Be it known that I, HERMAN E. BAKKEN, citizen of the United States, residing at Niagara. Falls, in the county of Niagara and State of New York, have invented certain new and useful Improvements in Melting and Pouring Magnesium, of which the following is a specification.

My invention relates to a method of melting and pouring magnesium and magnesium base alloys. Magnesium is exceedingly active chemically and at slightly above its melting point 651 C. will combine with both oxygen and nitrogen of the air. In melting and pouring magnesium and magnesium base alloys, it is necessary to 'providesome means to protect the metal from burning, otherwise the cast metal will have magnesium compounds included in it, which cause defects and weaknesses in the castings. In fact, failure to protect the molten metal may result in the complete oxidation of the magnesium before it can be cast.

It has been disclosed in a copending application of H. H. Osborne S. N. 597,380, that if a small quantity of glycerine is brought into contact with the metal in a closed receptacle during the melting and pouring operations, burning of the magnesium is largely obviated. In using the glycerine method, it has been the ractice to charge the furnace with the soli metal, add a few cubic centimeters of 'glycerine, cover the melting pot and raise the temperature. During the pouring or tapping, and whenever it is necessary to expose the interior of the pot to the open air, a few additional drops ofglycerine are added, so as to always keep the pot filled with glycerine yapor to exclude the air. 1

Glycerine bo'ls at approximately 290 degrees C. while magnesium melts at 651 degrees C. At the melting point o-f-magnesium the glycerine is in the form of a vapor. At such temperatures the glycerine breaks down, reacts with the magnesium, and carbon may be deposited, especially if a considerable amount of glycerine has been used. The rate of reaction of glycerine vapor and magnesium is, however, slow enough so that the gl cerine vapor exerts a marked protective e ect, and may be described as substantially inert. It is therefore obvious that it is advantageous to use as little glycerine as possible to accomplish the desired results.

While various types ofapparatus might be employed for carrying out this process, the one shown and described is merely illustrative of the principles -of the invention. This embodiment, however, has been found to be practical in construction andoperatioand efficient in use.

Description of figures:

Fig. 1 is a vertical section of the melting furnace;

Fig. 2 is an elevation;

Fig. 3 is a plan view, and 1 Fig. 4 is a section through the charging 10 e.

Referring to the drawings, 1 is a cast steel retort which is placed in an ordinary furnace shell 2, which may be heated by oil or in any other. suitable manner. The retort is closed at its top by a. cover 3, which consists of a steel plate provided with a series of slots 4 for engaging swing bolts 5, pivoted at 6 to flanges 7 carried by the retort, and having threaded ends 8 for engaging nuts 9 to securely clamp the cover in closed position. For making the cover gas tight, it is provided with a circular recess 10 engaging a complementary tongue on the retort, the

Fitted into the bottom of the retort is a metal valve seat 16 for engaging with the conical valve 17 carried by the valve rod 18. Secured to the lower end of the valve rod are paddles 19 for stirring the molten metal. The valve rod is made hollow and in operation a thermo-couple is placed therein. The valve rod passes through an aperture. 20 in the center of the cover, made tight by a suitable stufling box 21 and at its upper end is provided with a hand wheel 22 for rotating the paddles 19. For lifting the valve from its seat, a-lever arm 23, mounted on the red at its upper en The cover 3 is provided with a charging hole 25, a pipe cap 26 connected therewith, which is closed at its upper end by a cap 27 held in position by the clamping ring 28.

In the cover 3 is another hole adapted to be connected with a hand oil pump 30 for charging the pot with the necessary quantity of glycerine.

A pipe 31, welded to the retort is connected up to a suitable vacuum pump.

Operation.

The cover having-been placed on the retort and bolted down tight, the metal is charged into the furnace through the hole 25, which is then securely closed and the pot evacuated. Heat is then applied and the melting proceeds-in the usual manner. l Vhen amelt has been obtained, which can be indicated by the pyrometer placed in the valve rod and also by turning the paddles, in which case no resistance to solid materials is felt, the heat is cut ofi and the metal thoroughly stirred. Thereupon the vacuum line is closed; glycerine is gradually introduced into the retort by means of the hand pump until the v vacuum gage shows that the pressure within the pot is equal to atmospheric pressure, and for practical purposes an additional pressure of approximately one half inch of mercury is obtained by adding a few drops more of glycerine. The clamping screw cover is then removed from the bottom of the retort, a crucible placed underneath the furnace, the valve opened, and the metal flows into the crucible.

Although I have disclosed the melting operation as taking place under vacuum, it will be apparent that any suitable inert gas might be present in small amount, and while I have disclosed the pouring operation as taking place under the protection of glycerine, any similar substantially inert material might be substituted for glycerine.

I comprehend therefore in my invention,

1 the broad combination of melting the metal in the substantial absence of gases which would react with magnesium and thereafter protecting the molten metal with another suitable vaporizable fluid.

' protecting the molten metal by introducing glycerine-into the said container.

2. The process of treating ma-gnesiumand its alloys comprising melting the metal under vacuum in a container and during the pouring operation, protecting the molten metal by introducing a :substantially inert and vaporizable fluid into the said container.

3. The process of treating magnesium and its alloys comprising melting the metal under vacuum and thereafter breaking the vacuum by introducing glycerine into contact with the molten metal.

4. The process of treating magnesium and its alloys comprising melting the metal under vacuum, breaking the vacuum when ready to pour by introducing a small quantity of glycerine into contact with the molten metal and protecting the molten metal with glycerine during pouring.

5. The process of treating magnesium and its alloys comprising melting the metal under vacuum and thereafter protecting the molten metal by treating it with glycerine.

6. The process of treatingmagnesium and its alloys comprising melting the metal under vacuum, breaking the vacuum when ready to pour by introducing a substantially inert and vaporizable fluid into contact with the molten metal.

In testimony whereof I afiix my signature.

HERMAN E. BAKKEN.

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