US1893144A - Alloy of high fusion point - Google Patents

Description

Jan. 3, 1933.

A. KROPF ALLOY OF HIGH FUSION POINT Original Filed Aug. 20, 1926 aamaq so y X 749 5O 6O 7O Patented Jan. 3, 1933 UNITED STATES PATENT OFFICE ALFRED KROPF, OF WETZLAR, GERMANY, ASSIGNOR TO STAHLWERQKE ROGHLING- BUDERUS A.-G., A STOCK CORPORATION ALLOY OF HIGH FUSION POINT Application filed August 20, 1926, Serial No. 130,562, and in Germany January 16, 1926. Renewed November 22, 1932.

My invention relates particularly to alloys of high fusing oint containing metals of a high fusing point as well as the method of producing the same.

The ob]ect of my invention is to provide alloys of the above character, and particularly alloys containing metals of high fusing point, as, for example, molybdenum, tantalum, tungsten and chromium, all of which are of a kindred nature in the periodical system of chemical elements, and are obtainable on a commercial scale at a comparatively low cost. Furthermore, the object of my inven tion is to provide a convenient and effective method for producing such alloys. A further object of my invention is to obtain alloys of this kind comprising three or more metals.

The alloys so obtained show remarkable characteristics in regard to stress, extreme hardness, toughness, indifference against high temperatures and resistance against abrasion. These alloys are, therefore, of the highest usefulness 1n machining, etc., as, for example, where extremely hard substances have to be machined. These alloys are entirely effective for this purpose, where other alloys fail, owing to the qualities of the alloys referred to above. The alloys made in accordance with my invention receive and retain a keen cutting edge and will withstand very strong pressures in use.

While my invention is capable of being carried out in many diiferent ways, for the purpose of illustration I shall describe only certain ways of carrying out the same hereinafter.

lin the accompanying drawing, I have shown in addition to Fig. 1, containing the diagram above referred to, apparatus for use in carrying out the operation as follows:

Fig. 2 shows a carbon tube furnace comprising a=graphite electrode 5=carbon tube a=collectingbar d=melting boat with casting mould;

Fig. 3 is a cross section of the same;

Fig. 4: shows a graphite crucible resistance furnace comprising a=graphite electrodes Z; crucible resistance Fig. 5 shows a melting boat with casting mould comprising Z=melting boat e=casting mould f pressed body of metal.

On account of its high melting point the alloy is produced-in a carbon tube furnace b or in a graphite crucible b, the latter acting as a resistance furnace. See Figs. 1 and 2. The melting process itself is carried out in a boat (Z, to which is adjoined the casting mould e, the two being of one piece (Fig. 3). The pulverutent mixture of the metals and oxides for producing the alloy is composed as follows:

Example J.l00 parts metallic tungsten, 60 parts metallic molybdenum (or the equivalent amount of dioxide). 5

It is more advantageous to use an equivalent quantity of the oxide of molybdenum instead of the metallic molybdenum.

Example 2.100. parts of metallic tungsten, 1030 parts of metallic molybdenum (or the equivalent dioxide), 20-50 parts of metallic tantalum.

Example 3-100 parts of metallic tungsten, 10-30 parts of metallic molybdenum (or the equivalent dioxide), 20-50 arts of metallic tantalum, 10 parts of meta lic chromium or cobalt.

The pulverulent mixture is divided in parts of 100 to 200 grams according to size and shape of the casting. They are filled into paper shells and pressed into suitable forms under high pressure. These forms are placed in the boatcZ and introduced in the'meltingzone of the furnace. As soon as the mixture melts it flows into the adjoining mould e, if the fur Race is arranged vertically. A??- is filled with metal, it is withdrawn from furnace, current having been. interruppreviously. the melting pros m1 is carried. out in a licrizont l carbon tub current is in s melt. Then e position, so ti we amine 50 c is more r the mould specific procedure for producing the alloy and the various eutectic oints. It is to be added, however, that the invention is intendhigh resistance against softening at high temperature appears preferable. These properties may be obtained, if the percentage of carbon is varied. This may be done by using varying percentages of mo ybdenum and tantalum. For example, a cutting alloy for the machining of extremely hard substances like manganese steel which cannot be machined by stellite nor high speed steel, must be very hard and highly refractory. The hardness is dependent upon the percentage of carbon in combination with tun sten and molybdenum in form of carbides. Kccording to the above, the percentage of carbon is controlled by molybdenum, but preferably by tantalum.

'lhe refractory qualities are inherent in the tungsten' The most preferable alloy has the following composition:

Garbon=2.5% Molybdenum=2025% Tantalum=1015% Tungsten=rest I This alloy is also remarkably adapted for the machining of hard rubber and fibre. lhe brittleness may be somewhat decreased-and to a certain extent the hardness -likewise--by lowering the molybdenum contents and raising the tantalum contents, e. g: p

c =l.5-2% c =i-i.5% Mo=l% Mo=% 'la =-20% TEL n% W =rest W =rest These are typical specimens how the alloy may be composed. There is furthermore the posibility of a widevariation accordin to the properties desired in the particular a loy. I only need vary the carbon contents, whichas stated previously-may be more readily at= tained by changing the tantalum contents than by changing the molybdenum contents.

When using tantalum, the regulation of carbon is done so-to-say automatically, the addition of tantalum furthering the formation of an eutectic alloy in a metallurgical way.

In carrying out my invention, I have dis covered, that the very high carbon content of the well-known tungsten-carbon alloy m y be advantageo'usly reduced by adding molybby themselves provide alloys for any ratio of proportions of the same, that is to say, from 1 to 99% of molybdenum with 99 to 1% of tungsten. However by the addition of carbon thereto it will be found, that for each percentage of carbon only one alloy with a fixed ratio of tungsten to molybdenum is possible which will have a minimum melting point. The tungsten-carbon alloy which has a minimum melting point itself contains about 4.5 to 5% carbon. However, when certain quantities of molybdenum are added in the production of this tungsten-carbon alloy, the saturation of the same with carbon takes place at a lower percentage of carbon than in the case of the pure tungsten-carbon alloy, provided certain conditions are followed while melting, such as: keeping temperatures as low as possible, i. e. not materially exceeding the melting point of the alloy; preventing the action of the carbon of moulds on alloy by using indifi'erent gases in the furnace, and by shortening the meltin process as much as possible. The alloy thus obtained has a structure resulting from the absence of free carbon with the qualities above referred to, such as extreme hardness, toughness, etc. If the percentageof' molybdenum is raised or lowered, the percentage of saturation of the same with carbon varies accordingly, also the toughness and hardness of the alloy. lln these alloys the molybdenum content should preferably not be under 20%, tungsten from about 5 to 75%, carbon from 0.5 to 4%. For example, an alloy made in. this way may be comprisedof- I Per cent Molybdenum to Tungsten to Carbon 115 to 2.5

formation of alloys having a minimum melt point and in addition controls the saturation of the alloy w1th carbon. Consequently the addition of tantalum forms an easy method for regulating the amount of the carbon content. Tantalum, at its fusing point, does not form carbides and, accordingly, this quality enables this metal to be used conveniently for diluting the carbon in the alloy. Only by a reliable and easymethod of this kind for regulating the carbon content, may these extremely hard alloys be made practical for the roduction of cutting tools inasmuch as,

as a ove referred to,'pure tungsten carbide 1,aea,144

is too brittle for such purposes owing to its extremely high carbon content lln preparing the alloys made in accordance with my invention, the melting of the metals is conducted as above explained in the presence of abundant carbon in order to insure the formation of carbides or alloys containing carbon which have a much lower fusing point thanv the pure metals, molybdenum and tungsten. If, however, the metals are in excess of the percentage necessary to form carbides containing a maximum of carbon, an alloy of lower carbon content is formed which has a lower fusing point. For example, such an alloy may be made by adding from 5 to 80% tungsten to from 60 to 20% of molybdenum having a carbon content of from 0.5 to 4%, and the carbon content may then be regulated by adding tungsten carbides, as, for example, from 20 to 50% of tungsten carbide containing 5% of carbon therein, or by the addition of other suitable carbonizing medium. If desired, certain quantities of tantalum may then be dissolved in this mixture without forming tantalumcarbides. Even though the fusing point of tantalum is above the fusing point oi? this alloy, the tantalum is readily dissolved therein. This is also true in the case of the alloy, molybdenum, tungsten and carbon, which melts at. a lower temperature than the metals therein. Such an alloy may, for example, be comprised of the following:

, Percent Tantalum 1 to 20 Molybdenum 10 to 40 Tungsten 40 to 65 Carbon l to As pointed out above, if desired, the whole or part of the molybdenum or the tungsten may be substituted by tantalum, according to the hardness and heat resistance desired. The hardness is increased with the increase of the tantalum content. However, a molybdenum tantalum carbon alloy, though very homogeneous, is more brittle and more afi'ected by high temperatures than the tantalum molybdenum tungsten carbon alloy.

Furthermore, the alloys of the above character are further improved in hardness and toughness by the addition of from 0.5% to 25% of the metals of the iron group, that is to say, chromium, nickel, cobalt, manganese, etc, or of the group, vanadium, titanium, zirconium, silicon, etc. Such addition may be of from 0.5% to'25% of one of these metals or two or several of them, the total quantity added, whether being of one or several of the metals, amounting to from 0.5 to 25%.

A base alloy of still a lower fusing point may be obtained by using a chromium tantalum base with the ratios of the tantalum and chromium varying according to the purpose desired, and to which there may be added the necessary amount of pure tungsten carbide or a tungsten molybdenum carbon alloy. The amount of chromium may be increased up to 40 0, while the tantalum and tungsten or moly denum may make up the remainder in the relative proportions mentioned in the examples given above. Such an alloy may, for example, be comprised of- Percent Chromium It to 40 Tantalum; 1 to 4.0 Tungsten 60 to 10 Molybdenum 30150 5 Carbon d to 0th -While l have described my invention above in detail, 1 wish it to be understood, that many chan es may be made therein without departing :rrom the spirit of the same.

1 claim:

1'. An alloy of high fusing point containing from 1 to 2.5% of carbon, l0 to 65% of tungsten, 10 to 40% molybdenum and 1 to 20% oi tantalum.

*2. An alloy of the character described, containing 2 to 2.5% carbon, 40 to 65% tungsten, 15 to 25% molybdenum and 5 to 15% tantalum.

in testimony that I claim the foregoing, l have hereunto set my hand this lth day of Aug, 1926.

KROPF.

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