US1657693A - Protecting molten magnesium - Google Patents

Description

Patented Jan.- 31, 1928,

.U'NlTE-D sTA1. ES"

inseam mus, NEW YORK, ,assrenoa 'ro AMERICAN mom H, osnomvn, on

MAGNESIUM CORPORAIKI'H, OF NIAGARA FALLS, NEW YORK, ACORPOBATION OF imw YORK.

Jlo Drawing.

8 above its melting point, 651 de s 0.,wi1l

combine with both oxygen an nitrogen of the air. .-In melting and casting magnesium and high magnesium alloys,it is necessary to vide some means to protect the -metal m l I 10 grom burning, otherwise the cast metal will have magnesium compounds occluded in it;

which cause'defects and weaknesses ill/the castings. -In fact, failure ,to rotect the metal. from burningmay result in the complete consumption of the magnesium before.

it can be-cast; g For attaining the. desired end, I have discovered that if a small quantity of glycerine, preferably anhydrous, is brought into contact with the molten metal in a closed receptacle, that burning of the magnesium is obviated and that no deleterious products areformed; resultingfrom decompositlon of the lycerine so that-the finished castings are free from imperfections with a consequent improvement in their physical pro 8113165 The lycerine maybe added at t e beginning o the melt and it may be added from time to time as the melting proceeds. In practice, however, there is a covei on the pot and while it is not gas-tight, it might be called circulation tight, that is to say, It prevents the ready escape of the vapors which may be formed by the breakmg down of the liquid or vaporized lycerlne.

In starting a melt, the c arge of magnesium containing metal having been placed in the furnace, a few cubic centimeters of as nearly anhydrous'glycerine as posslble are added, all openings are covered with rather close fitting covers, and the heat is turned.

on. 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 of glycerine are added so as to always keep the pot filled with glycerine vapor and to exclude the air.

The theory upon which glycerine acts to v prevent oxidation of the molten metal in a follows:

Glycerine boils at approximately 290 declosed receptacle may be explained in part as grees C. while magnesium melts at 651 dernornc'rme v uom'nn maermsm'm.

Applicatlon fllcd october a7, 1922; Serial No. 597,880.

grees C. Accordingly, when the metal is molten, the glycerine or product thereof will be n the form ofa vapor and is effective because it excludes the air and at the same time, it does notvquickly react with the molten' magnesium. .The specific gravity of the vapor of glycerine at the melting point of the metal 1s comparatively high and for that reason it does not escape easily from a fairly well closed up vessel. tity of glycerine is brought into contact with the: molten metal, the volume of the vapor is many times the volume of the initial liquid material. Theglycerine vapor originates in the lower portion of the gas space which is over the metal and the tendency accordingly is to gradually but continuously forceout sium does not undergo any appreciable loss.

Ths is probably the condition during the early stages of melting when the temperature is still fairly low. As the temperature rises, the glycerine vapor begins to form.

other compounds which also afford protection to the molten metal but not combining with it. Ultimately there is, of course, a complete decomposition of the glycerine or at least an escape of it from the pot which is the practical reason why a small quantity is intermittently added during the melting operation. As the temperature of the metal approaches its melting point, glycerine bemg an organic substance is fairly easily changed into other compounds when its vapor is brought to such an elevated temperature. The strong reducing action of the magnesium probably promotes the decompos1 ion.

When a small quan-' Glycerine is a trihydric alcohol having the en glycerine va- "of molten magnesium or its alloys as would otherwise be freely exposed to. the air, such as surfaces in the melting crucible or pouring stream; and as the continuation of this stream surface, the surfaces of the. molten metal in the openings of the-mold where it is freely exposed to the air. 0

I claim:

1. The method of protecting molten magnesium and magneslum alloys comprising bringing in contact with the molten metal,

products resulting from-the heating of glycerine above the melting point of said metal.

2. The method of protecting molten magnesium and magnesium alloys comprising treating the molten metal in .a closed receptacle from time to time with a relatively small quantity of glycerine.

3. The method of protecting molten magnesium comprising treating the molten magnesium in a closed receptacle with a rela:

tively small quantity of glycerine and providing a vent in the said receptacle to permit escape of the displaced gases.

4. A method of protecting molten maging during melting and pouring, comprising bringing in contact with the surface of the metal in a closed receptacle, :1 material having a boiling point which is relatively high but lower than the melting point of the metal, the said material in a gaseous condition serving to prevent burnin of the metal, without itself reacting excessively with the molten metal, the specific gravity of the said material in a gaseous condition bein relatively highfiwhereby it does not rea 11y escape from the closed receptacle.

4 6. Method of protecting molten magnesium and magnesium alloys against burning at surfaces freely exposed to the air, comprising bringing in contact with such surface of the molten metal a material having a boiling point between about 290 C. and

650 C., which will react only slowly with the molten metal and which will produce a vapor heavier than air.

In testimony whereof I afiix my signature.

HAROLD H. OSBORNE.