US2061267A - Preparation of lead-sodiummagnesium alloys - Google Patents

Description

Patented Nov. 17, 193% UNITED STATES- [PATENT OFFICE PREPARATION or LEAD-SODIUM- ,MAGNESIUM .ALLoYs No Drawing.

Application November 16, 1934, Serial No. 753,301

4 Claims. (01. 15-161) This invention relates to the preparation of lead-sodium-magnesium alloys.

An alloy comprising 10% sodium, 89.95% to 89.00% lead and 0.05 to 1.00% magnesium is de- 5-v scribed in an application of F. B. Downing and L. S. Bake, Ser. No. 708,248 filed January 25, 1934. A process employing this alloy is described and claimed in an application of Downing and Bake, Ser. No. 613,260, filed May 24,

10 1932. .These applications of Downing and Bake 20 in discharging the still. If magnesium is present,

the'residual lead, after the distillation, tends to be finely divided andls easily discharged.

There are two general methods of preparing the ordinary lead-monosodium alloy. The first 25 method consists in placing the required amount of lead and sodium in a pot and applying heat thereto until the reaction takes place to form PbNa. The reaction of lead and sodium to form the lead-sodium alloy is exothermic. when this method is practiced, enough heat is liberated to raise the temperature of the alloy to from 500 to 670 C. At these high temperatures, there is a very strong tendency for the sodium to distill ofl and, if great care is not taken, the resulting 35 alloy will contain less than 10% sodium. This is a decidedly undesirable result as, if the amount of sodium varies as much as 0.1 to 0.2% below or above 10% the alloy will not produce the maximum yields of tetraethyl lead. Magnesium 40 has a melting point of about 651 C. Accords 'ingly, magnesium may be dissolved in the alloy by this method as the magnesium is soluble in the lead 'sodium' alloy at such high temperatures. However, such method involves the prob- 45 ileum of avoiding distillation of sodium from the 0y. I y

The second method of preparing lead-monosodium alloy, and the method which is more generally employed at the present time, consists 50 either in adding molten sodium to molten lead or molten lead to molten sodium at the desired rate with stirring in a pot jacketed with molten dipheny'l.- In.. this process, the rate of ,addition of one ingredient to the other may be so con- 55 trolled that the temperature within the pot does.

not exceed 400 C. At this temperature, there is little tendency for the sodium to distill ed. and, furthermore, such temperatures are necessary to prevent decomposition of the diphenyl. Diphenyl starts to decompose at about 400 C. but such decomposition does not becomeserious until temperatures of about 410 C. and above are reached. However, at the temperature of about 400 C., it was found that, when magnesium was added to the alloy, it did not go into solution in the alloy but remained floating on the surface of the molten alloy.

An object of the present invention is to provide a method for preparing lead-sodium-magnesium alloys such as are disclosed in the hereinbeiore identified applications of Downing and Bake. A further object is to provide a'method whereby such an alloy can-be prepared at temperatures not in excess of 400 6. Other objects are to advance the art. Still other objects ,will appear hereinafter.

These objects "may be accomplished in accordance with our invention which comprises fusing the magnesium with at least a major proportion of the lead to produce a le'ad-magnesium alloy which may be melted and added to the molten sodium or to which molten sodium may be added.

Our invention is based upon the discovery that lead-magnesium alloys decrease in their melting points with increasing amounts of magnesium until a minimum melting point of approximately 250 C. is reached, when the alloy contains about 3% of magnesium. When the percent of magnesium is increased above this point, the melting point gradually rises to 551.3 C. at 19.06% magnesium at which point only PbMgz is present. The melting point then decreases to 468 C. at approximately 35% magnesium and then increases gradually to 651 C.,

when pure magnesium is present. On the way up from the minimum of 250 (3., the melting point curve crosses the 400 C. line at approximately 8.7% magnesium. Accordingly, it is evi-= dent that, if any lead magnesium alloy containing up to 8.7% of magnesium is added to amoiten lead-sodium alloy at 400 0., fusion of the lead magnesium alloy will be efiected and a. homogeneous mixture of the magnesium will be obtained. 7

We have found that lead-magnesium alloys having a melting point up to about 500 C. may be melted andthen added to molten sodium or a molten lead-sodium alloy and such leadmagnesium alloy will dissolve in the sodium. e

lead-sodium alloy and form a homogeneous mixture therewith. According to the broader ashave melting points below 500 C. and fall within the broader aspects of our invention. However, it will generally be desirable to use leadmagnesium alloys containing not more than 8.7%

' of magnesium as these alloys will melt at temsium and 89.95% lead.

peratures not higher than about 400 C. and

hence are more convenient to employ. Furthermore, magnesium,up' to approximately is very soluble in lead at the molten temperature of 327 C. Therefore, a homogeneous mixture of magnesium in the desired amount of lead-sodium alloy can be obtained by first dissolving the required amount ofmagnesium in the molten lead before adding to thesodium or before adding the'sodium to the molten lead-magnesium alloy. This latterfmethod appears to be the simplest and most practical and is the preferred method of practicing our invention;

In order to more clearly illustrate our invention and the preferred modes of carrying the same into efiect, the following examples are given:

' Example 1 1000 lbs. of molten sodium were gradually Example 2 The same process employed in Example 1 was followed except that only 7000 lbs. of lead were employedand 2000 lbs. of the lead-magnesium alloy was added thereto. The resulting product contained sodium, 89% lead and l% magnesium. r-

Example 3 1000 lbs. of molten sodium was added to 8985.7 lbs. of molten lead at 400 C; The resulting leadsodium alloy was maintained at 400 C. while 14.3 lbs. of a lead-magnesium alloy containing magnesium was added thereto. The resulting alloy contained 10% sodium, 0.05%

Example 4 'A mixture of 1000 lbs. of sodium and amis of lead was prepared and maintained at a tem- 35% sodium, 1%

magnesium and 89% lead.

magneing' 10% of maghesiump- The product contained 10% Example 5 5 lbs. of magnesium were dissolved in 8995 lbs. of lead at 327 C. The moltenlead-magnesium alloy was then added to 1000 lbs. of molten sodium with stirring- The resulting product-contained 10% 89.95% lead.

Example 6 100 lbs. of magnesium were dissolved in 8900 lbs. of lead at 327- C. To this was added 1000 lbs. of molten sodium with stirring and without permitting the temperature to rise above 400 C. The resulting product contained 10% sodium, 1% magnesium, and 89% lead.

While we have disclosed the preferred embodiments of our invention, it will be readily apparent to those skilled in the art that many va riations and modifications may be made therein without. departing'from the spirit thereof. Ac-

cordingly, the scope 'of our invention is to be limited solely by the appended claims, construed as broadly as'is permissible in view art.

We claim: 1. The process of preparing an alloy comprising 10% sodium, 89.95% to 89.00% lead and of the prior I sodium, 0.05% magnesium and 0.05% to 1.00% magnesium which comprises fusing the magnesium with suflicient molten lead to produce a mixture melting below 500 C. and then fusing the mixture with 'suflicient sodium and lead to produce the alloy, the magnesium being fused with the lead at temperatures below the melting point of the magnesium and the lead-magnesium mixture being fused with the sodium at temperatures below 500 C. and above the melting point ofsaid mixture.

2. The process of-preparing an alloy comprising 10% sodium, 89.95% .to 89.00% lead and 0.05% l to 1.00% magnesium which comprises fusing the magnesium with at least 90% of the *5 molten lead and then fusing the mixture with suiiicient sodium and lead to produce the alloy,

the magnesium being fused with the lead at temperatures below the melting point of the magnesium and the lead-magnesium mixture being fused with the sodium at temperatures below 500 C. and above the melting point of said mixture.

3. The process of preparing an alloy comprising 10% sodium, 09.95% to 89.00% lead and 0.05% to 1.00% magnesium which comprises fusing the magnesium with the molten lead and then fusing the mixture with the sodium, the magnesium being fused with the lead attemperatures below the melting point of the magnesium and the lead-magnesium mixture being fused with the" sodium at temperatures below 500 C. and above the melting point of said mixture.

4. The method of preparing an alloy comprissodium, 89.95% to 89.00% lead and 0.05% to 1.00% magnesium which comprises fusing the magnesium with the lead at about 327 C. and then adding the sodium while maintainin the temperature to below about 400 C.

FREDERICK BAXTER DOWNING LOUIS SAMUELv BAKE. ALFRED PARLIELEE.