US1508241A - Metal and its manufacture - Google Patents

Description

Patented Sept. 9, 1924.

I 1,508,241 PATENT oFFi-fcE.

AIJADAB PACZ, 0F CLEVELAND, OHIO, ASSIGNQR TO GENERAL ELECTRIC vCOMPANY,

' A CORPORATION OF NEW YORK.

I METAL AND ITS MANUFACTURE Kc Drawing. Original. application filed February 20, 1917, Serial No. 149,915. Divided and this application filed February 15, 1922. Serial No. 536,815.

' Serial No. 149,915, filed February 20, 1917.

The object of my invention is to produce tungsten metal which will retain to a much higher degree than heretofore its ori inal properties after being subjected to igh temperatures. In the case of incandescent lamp filaments, the high temperatures at which they are run have caused them to elongate and sag betweenv their supports.

This is especially noticeable in coiled file-- ments, and in gas filled lamps this tends to reduce the efficiency of the lamp on account N of the increased cooling efiect on the filament. By means of my invention the sa gin is substantially eliminated and o setting of the filament is substantially prevente during a normal or commercially useful'life of the lamp.

In the preferred form of my invention I bring into intimate association with tungsten a material which will have the desired influence upon the grain growth of the metal. -I precipitate, simultaneously, compounds from which the metal is to be directly reduced with the material or compound which is to accomplish the desired result. The material after precipitation will remain in intimate aSSOC15Lt1011 Wlth the metal even after the same has been reduced by the ordinary means, i. e., reducing gases. During the subsequent formation of the metal into in gots or bars, the material should be such that it will be removed as by volatilization. A material should be used which will have a fairly high volatilization point which is preferably somewhat lower than the sinter- 111% point of the metal.

onsidering my invention from the physical standpoint, the presence of the material hasan influence on the grain growth of the metal.- When the metal reaches the temperature. at which extensive grain growth would ordinarily take place, the

presence of this material intimately associatedwith the tungsten particles has al marked eiiect on the shape and size of the tungsten grains. The ingot of tungsten thus produced, whether it be due to the fact that the grains have not reached the equilibrium grain size or to other causes, is particularly susceptible to grain growth during subsequent heat treatments.

The probable reason. why filaments made according to my invention do not sag, is that the structure is comparatively coarse grained. The coarse grained filament produced by means of my invention does not ofiset so as to cut short the life of the lamp appreciably. i

- A-s hereinbefore stated, the material which is intimately incorporated with the metal should be such that itwill be volatilized out after the metal has reached the temperature of rapid grain growth. Tungsten above 1500 C. shows rapid grain growth, andI may use silica, or compounds containing it,

as the material, incorporated very intimately as heretofore explained. By the time the tungsten has reached the sinterin temperature the silica and the compoun s containing it are volatilized out.

In order to comply fully with the requirements of the patent statutes, I will now describe one method or process embodying my invention and also modifications thereof.

However, it is to be understood that the scope of my invention is. such that many changes and substitutions will readily suggest themselves to those skilled in the art, and, as indicated, in the a pended claims, are to be considered as forming part thereof.

A fusion of materials is first made which is quite similar to that disclosed in my Patent Number 1,299,017 issued April 1,

1919. '1400 grams of commercial tun tic,

acid, 620'grams commercial sodium car onate, 620 grams commercial potassiumlcarbonate, and 300 grams commercial sodium nitrate are mixed with water to a paste. I have found that half or more of the potassium carbonate may be replaced by sodium carbonate without affecting the results the object being to obtain a good fusion. his paste is dried on a hot late and fused with a torch for about fi een minutes, after which the fusion is dissolved in water, filtered and diluted to about six liters. Thiswe will term solution A.

A. mixture is then made of 180 grams-com mercial silicic acid, 820 grams commercial K C'O and 150 gramscommercial NaNO, with water to a paste which is dried and fused. The object is to produce a silicate which will be readily incorporated with'the tungstic acid in the subsequent portion of the process. An alkaline silicate such as produced by the specific example given is readily soluble and eflicacious for this purpose. The fusion is dissolved in water, filtered and diluted to 5 liters. This may be termed solution B.

- About 250 cubic centimeters of solution B is added to 3 liters of solution A. The whole solution is then boiled with steam and poured into a boiling solution containing about 1500 cubic centimeters of HCL and 1500 cubic centimeters of H 0, preferably through a funnel. The precipitate is allowed to settle, the liquid decanted, and the precipitate separated by filtration. The precipitate is then washed with hot H O until the filtrate becomes milky. The precipitate is then dried. and ignited in a quartz dish. It is reduced in hydrogen in boats, each boat containin about 100 grams. The metal thus produced may be termed metal A. I a

The metal A may be pressed up and sintered to produce tungsten slugs which may be drawn into filaments having the non-sag and other characteristics hereinbefore described. I prefer, however, in order to obtain greater uniformity of product to continue the operation as follows:

About 1200 grams of metal A are mixed with about 1200 grams of the oxide from which metal A was reduced, the mixing be ing very intimate and being performed referably in a tumbling mill. The mixture is then reduced as before although 150 gram charges may be here used. The metal thus produced may be termed metal B. It is then sieved, pressed into ingots, sintered 'and formed in the usual way as set forth in the Coolidge Patent 1,082,933.

As a modification ofthe above described process, solution B may be added directly to the fusion from which solution A is made. This is preferably done by utilizing the proper proportion as heretofore stated of solution B in making the paste which is dried and fused and dissolved to form solution A.

' Another modification would be to utilize combinations of WO and oxides of tantalum, for example Ta O or of niobium, for example Nb O or,as before indicated, of these oxides of tantalum'or niobium per se. F or this purpose, instead of sodium potass1um silicates, otassium tantalates'or niobates may be a ded to the solution of tungstates. (Sol. A.) y The metal obtained from the first method above described I have called 218, a purely arbitrary name. I have produced a metal difierin in appearance and physical characteristics from 218 metal by' adding a sg lgtion of adcid to chemically ure evaporlzlng, rymg, 1gn1t1ng an reducing. The metal thus produced; when made mto wire is not superior to 218 in nonsagging 0r non-offsetting characteristics, but a combination of this method with that for producing 218 in which the W0 from the latter is mixed with that from the former produces a metal which I term- Z and which is eflicacious in the production of nonsagging and non-offsetting filaments .To produce this metal one method wh ch I have practiced is to mix 1 kilogramfof the tungstic oxide from which metal A is reduced in the 218 rocess with a. solution of 12.5 grams fused meters of water. This mixture is evaporated, dried, ignited and reduced. The resulting metal is blacker than 218, flows more readily and possesses at least one-third larger. volume than 218 although reduced under exactly the same conditions;

The tungsten ingots produced accordlng to my invention have usually fine gra1ns, as for example, between 2500 and 6500 grams per square-millimeter. In the case of the 218-- ingots analyseshave shown that the percenta e of non-metallic material is below two-tent s of one per cent and in man cases below one-tenth and even one-twentiet ofone per cent.-

When the tun sten metal produced any of the met ods above described 15 made into a filamentary body, the method described in the -Coolid e Patent No. 1,082,933 for drawing or ot erwise working down the ingots is practiced. Wherethe wire is to be used at high temperatures such as in incandescent electric lamps it should. be given a preliminary heat treatment or' aging. This helps to secure the non-sag characteristics of the wire made accordin to my invention. One procedure follow with ood results with the ordina 110-115 volt amps was to run at 30 V0 ts for 2 minutes and then at steps of 5' volts each for two minutes, up to volts. After this the.

wire was run at 115% voltage for 15 minutes.

The tests show that substantially all of the sagging occurs during the aging of the at I claim as new and deslre to secure by Letters Patent of the United States, is

'1. The method of producing substantially" non-sagging and non-offsetting tungsten filaments which includes reducing an intimate mixture of finely d1vided tungsten and a compound or compounds contaimng oxide of tantalum or niobium or both and thereafter sinteriug a compacted body of said mixture.

2. The method of producing substantially non-sag iiig and non-offsetting tungsten filaments w ich includes producing an intimate mixture of finely divided tungsten and a. compound or compounds containing oxide of tantalum or niobium or both, sintering e compacted body of said mixture to form an ingot and thereafter working the said ingot to filamentary form.

3.- The method of producing substantially non-sagging end non-ofisetting tungsten file.-

'ments which includes the incorporation with finely divided tungsten of an oxide of tentelum or niobium or both derived from potassium tantalate or niobate or both, sintering e compacted body of said mixture to A i at PACZ.

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