US2048706A

US2048706A - Method of making alloys

Info

Publication number: US2048706A
Application number: US753219A
Authority: US
Inventors: Pfanstichl Carl
Original assignee: PFANSTIEHL CHEMICAL Co
Current assignee: PFANSTIEHL CHEMICAL Co
Priority date: 1934-11-15
Filing date: 1934-11-15
Publication date: 1936-07-28
Anticipated expiration: 1953-07-28

Description

July 28, 1936- C. PFANSTIEHL METHOD OF MAKING ALLOYS Filed Nov. l5, 1934 6 Sheets-Sheet 1 July 28, 1936.` c:` PFANSTIEHL.

METHOD OE' MAKING ALLOYS Filed Nov. 15, 1934 6 Sheets-Sheet 2 July 28, 1936. c:` PFANSTIEHL METHOD OF MAKING ALLOYS 6 Sheets-Sheet I5 Filed Nov. 15, 1934 July 28, 1936. cA PFANSTIEHL 2,048,706

` METHOD OF MAKING ALLOYS Filed Nov. 15, 1954 6 Sheets-Sheet 4 Juli? 28, 1936. c. PFANSTIEHL 2,048,706

METHOD OF MAKING ALLOYS Filed Nov. l5, 1954 6 Sheets-Sheet 5 @@WM@ (fifi/@www www 1intestati July 2s, 193s UNITED STATES PATENTp FFICE 14 Claims. (Cl- 'J5-135) This inventionv relates to a method of producing tough alloys from alloys customarily fragile or brittle.

In my co-pending application Serial No. 753,220

iiled November 15, 1934, is described an alloy having the preferred composition of 35 to 50 parts cobalt, 30 to 40 parts chromium, 15 to 25 parts tungsten and- 3 to 5 parts of carbon. The percentage of tungsten carbides, chromium carbides and complex double carbides in this alloy is so great that when produced inthe ordinary manner the material has 'a mass of large' crystals which renderl it brittle. It has now been discovered, however, that this 'alloy may be prol5v duced in a tough form by rapidly cooling it to 25 Fig. l ls a broken elevation, partly in section,

of a vacuum furnace for fluxing of the alloy;

Fig. 2, a vertical section through a crucible, showing the method `of loading the ingredients of the alloy therein; v

30 Fig. 3'is a section along line 3 in Fig'. 1;

Fig. 4 shows abroken sectional elevation .of a `modified furnace provided with means for lowering the -cruciblef into a water-cooled area. for

j quick cooling of the alloy; 35 Fig. 5 is a sectional elevation .which is an exten- 4sion of the lower portion of Fig. 4;

Fig.`6 is a broken sectional elevation )of a furnace which .is provided with a chilled mold into which the alloy may be poured for shock cooling; 4o Fig. '1 is a section along the line 1 in rig. 6;

Fig; 8 is a similar section with a modified mold;

Fig. 9 is a brokensection'al elevation showing the furnace in Fig. 6 tilted to pour the alloy into themold;

45 Fig; 10 is a perspective view of a slugof alloy from the mold;l

I Fig. 11 is an elevation partly in section illus-- trating a magnet for weighing of the lalloy into measured charges; l 50 Fig. 12 is an elevation similar t0 Fig. 11 showing the discharge of the alloyinto, a smaller mold; l Fig. 13 is a sectional elevation of a lime button or mold for the production of small globules of the alloy; 55 Fig. 14 is a plan view, partly in section and partly broken away, of a furnace for the rapid fusion and rapid cooling oi globules of the alloy in the lime-molds;

Fig. 15 is a section elevation along the line I5 in Fig. 14;

Fig. 16 is a section View taken along the line lli-.J6 in Fig.- 14;

Fig. 17 is an end of the slide terminal block: and` Fig. 18 is a diagrammatic sketch of an appa- 10 ratus for welding the globules to a tip.

The invention will be described primarily in connection with the production of tough alloys of a cobalt type matrix, and rich in chromium or tungsten carbides. Alloys of this type, when pro- 15 l duced in the form of ne crystals, are extremely1 'hard, tough and inert. Nevertheless many of them are extremely sensitive to oxidation at temperatures near and above the melting point and it is therefore important that the fusion steps of 20 the process be carried out in the absence of oxygen.

It is likewise of importance in' many instances that the metals themselves be in a very pure form. For the preferred high carbon alloy, the tungsten used is preferably pure wrought tungsten. and is preferably used in dense form rather 'than in powder. 'I'he carbon is preferably pure carbon, such as Aitcheson graphite electrodes.

vThe chromium is preferably pure electrolytic chromium depositedin small flakes and nodules having a thickness of .01 to .03 inch, and an average diameter of 11g to 1% inch.

The ingredients, in the desired proportions, may be mixed in a crucible, for example as illustrated ln-Flg. 2, in which I represents tungsten discs; 2, chromium flakes; 3, cobalt discs and the small particles 4 are the carbon, all of them contained `in the drucible 5.

Considerable diillculty is encountered in the selection of a. proper crucible, .but it has been foundrthat a good grade of magnesium oxide crucible is satisfactory.

In preparing the original melt of alloy-the crucible 5 is filledV as described, and is placed in a. 45

Vfurnace 6, as shown in Fig. 1. This furnace,

which is adapted to be evacuated, or to be supplied with an inert gas, comprises a. quartz cyl- 'inder 1 provided with a connection 8 leading to a vacuum pump. ll'he cylinder is set in a base 9 50 which is provided with a plate I0 cooled preferably by water-coollng. The crucible 5 sits in the furnace upon a support II and is provided with a graphite sleeve I2 which has a graphite cap I 3. This is likewise surrounded by a protecting crucible I4. A pyrex glass window I5 is provided at A graphite funnel 36 is provided at the mouth the top of .the furnace, and the various caps are 0f the mold. In' preparing the ingot or slug, the

provided with peep holes so that observations may crucible with its-contents is placed inside of the be made upon the alloy. furnace 63 and, after a vacuum has been drawn,

5 It is preferred to operate in a vacuum to avoid is fused by the heat of the electriclresistjance ele- 5 contamination and porosity of the alloy, and Jment 26. 'I-'he vacuum is preferably as lowas .05 after a proper vacuum has been reached in the to .1 mm. The fusion is continued for some furnace, preferably as low as .-1 mm., the ingreditime, and preferably the temperature ofthe molents are fused by lmeans of a high frequency inten metal is carried to a point sufficient to prom 'ductocoil lewhichis wrapped about the cylinder duce a uniform solution, for example, a tempera- 10 1 at the height of the cruc'ible. This coil is set ture high enough to dissolve all of the carbides. inhardasbestos supports l1 andis in the form of This may be from 200 to 500 degrees above the f -a flattened. copper tube I8, through which -coolmelting point. The 'temperature is maintained ing water circulates. 'I'he use of a high frelong enough to reach equilibrium. The melting l5 quenc'y Inductor coil causes violent stirring of the point of the ordinary alloy of this type is about 15 alloy, andis therefore much preferred` for this 2375 F., and the temperature is preferably carislnitial uxing. l Y -ried to about 2850 F. for the specific chromium, After the alloy has been melted and held at s tungsten. cobalt, high carbon alleys- After the temperature several hundred degrees above its temperature has reached the'desired point, the

zo melting point for a period long enough to free it furnace is lifted, and tilted to pOur-the alloy into 20 from volatile matter, during which time the gases the mold 3|, as shown in Fig. 9. Thismold in also remove other contaminating matter, the clect constitutes a water-cooled Chill, lined with current may be cut cfr and the alloy cooled. graphite. The alloy solidiies in about 2 or 3 sec- .Such'a' eatingperiod isv normally about 20 minonds in this mold, to form a slug or ingot 31 as t5 utes. When cooled in the furnace, however, shown in Fig. 10. When cooled in this manner 2.5 even thoughthe base and-roof of the furnace are the crystals of. the alloy 'are ner than in the water-cooled, the cooling is so slow that the crysoriginal Slug. tals of the alloy are relatively very large, and a After cooling, the ingot is removed and broken relatively brittle metal is produced. The crystals 11D into lille partielee- This may be readily "ae- :o are large enough so that on grinding or powdercompllshed by grinding in a Steel mortar With a 30 ingof the alloy, it is not certain that uniform steel pestle. The material is broken into small mixes will be obtained.' and it is therefore preparticles. The particles are then slfted. and it is ferred to remelt the alloy andcooi it in a small preferred to use those that pass a 30 mesh screen Vslug in order tov produce smaller crystals. and remain on a 100 mesh screen.

5 Y Fig- 4 `represents an optional furnace 6e pro- After crushing and screening to pass a 30 mesh 35 -vlded with a -mov'able bottnm 'I9 mounted on 'and to be caught upon a 100 mesh screen, asmall screw. shaft- 20 and adaptedto be lowered by amount of the powdered alloy is put into a mold turning of the crank 2|. In this manner the for 11e-fusing. It has been Afound that the powder crucible 5 may be lowered with the molten alloy is slightly magnetic. and an accurate and speedy within the Steel cylinder 22 and directly within way of measuring the same into` the molds may 40 the areaof the water-:cooling coil 23. with this be had by the use of a. magnet. A form of magnet apparatus it is possible to 'procure much more 38 is shown in Fig. 11, and comprises a ine soft rapidicooling of the alloy, and to produce crystals iron wire 39 somewhat smaller than a pencil lead of such a size thaton grinding they will give a inserted'in a bakelite cylinder 40 and surrounded 5 substantially unito by copper -wire winding 4l. By dippingthis mag- ;45

It is preferred, however, with the present app'nhet into the pewdena rlleaellredA Charge may be ratas, to remlelt the high carbide hllcysnnd freeze picked up, and the amount of. the charge may be Y them in the form of thinner slugszif metal, It is varied by adjus'tment of the current through the appreciated that -by proper mechanical developcell". Y'

ace 6 may be provided with-means The charge is then carried and dropped into a 50 whereby7 the allo'y could be poured directly into a :mold 42 Preparatori t0 further fuSiQnf The mold mold. This may be 'done withfthc present fm. preferably consists of a lime button having a cennace but 'it is preferred to use a second heating tral depression 43, as shown in Fig.- 13. This treatment in a vacuum furnace 53 of he type lime is preferably a specially treated lime which i. Showh Fig.'6. This furnace in genera] cci-1rehas been hcated'for a considerable period after 55 spends 1-,0 that shcwninpig 1', but it is provided the removal of all carbon dioxide at a tempera- .with a metal shield 24 about a graphite shield 25 ture considerably above the normal calcining 'and is heated by/an electric-resistance element temperature The lime-thus Produced has un 26 within the furnace. Preferably the resistance usuel prepertles'ef Stability in air as well as preel'ement is of tungsten or molybdenum, and' 1s. ducing a-stronger mold. In loading the powdered 60 Wound about an Alun'dum tube 21 1n which the alloy into the lime molds, it is preferred to dust crucible s is set. The bese za and top 2s of the it lightly with powderk of the Same lime- This lful-nece are preferably watel-.cooled and the top prevents sticking to the mold, which otherwise is'provided with a pyrex window 30. Immedimay 00cm in Some instaincesately above and to one side of the crucible and Afte loading the charge into thaboat 01 mold- 65 inclined with rcspct' thereto is the mold con.. the latteris placed in the electric furnace,

`tainer 3| which comprises a seamless steel tube This flll'lleA comprises an air-@tight jacket 45 3-2 having a watel--cccled end plate 33 into which provided with an inlet 49 for the introduction of `is screwed a graphite mold 34; As' shown .in Fig. pure hydrogen sas, and also provided with seam` 7 the mold is Shaped to provide a central opening Y less steel tubes 46, 41 `and 43 about y, inch squareA 70 of small cross section.v Normally the slug of alloyfor the introduction and ejection of molds. The

should be not more than 54, inch in and furnace is provided at the top and at the bottom the preferred dimensions are xgl; x3 inches. with water-cooled plates v5I) and 5|, respectively.

In Fig. 8 is. showna pper; mold 35 lined with The side walls 45 of thejacket are preferably of graphite 34. l seamless steel tubing. 1 v C n 75

Copper terminals

52 and 53 .are provided in the furnace, the bottom plate I being drilled to permit the necessary connections, and to permit water-cooling of the terminals. Cooling pipes are indicated at 54. Two tungsten strips 55 and 56, one about 1% inch above the other, connect the two terminals. These strips are normally about .025 inch in thickness, by 1A of an inch wide, vby 2*/8 inches long. Directly above the lower strip 55 is.provided a water-cooled copper block 51. The furnace is as a whole construcd so that when removed from the tungsten filament 55 the molds will be subjected to as much cooling action as possible, to the end thatrthe alloy will be cooled in the shortest possible length of time.

The terminal 53 is slidably mounted on the block V530 in order to provide for expansion of Y the heating elements. The spring 65 tends to movethe terminal with the expansion of the tungsten strips and holds the strips straight. The exible copper strips 64 provide the electric connection tothe terminal.

Before `putting the furnace into operation a stream of hydrogen gas is admitted throughthe tube vil! and the furnace completely cleared of all oxygen. The hydrogen usedshould be of extreme purity, and it isadvisable to treat even the best hydrogen on the market to remove all traces" of Awater and oxygen therefrom. The hydrogen leaves the furnace through the openings 46, d1 and 48, through which a gentle current of the gas is maintained.

The loadeaiime boats of ablyinserted in the arm 41 which is heated by a resistance coil 58 about the tube. It is preferred to raise the temperature to about 200 C.'to expel all oxygen fromthe molds. Y They are then pushed through the'arm 41 intothe tube 45, and then by a small wire (not shown) operating through a small hole in the end of the tube 46 on to the tungsten lament 55. The tube 66 extends almost to the lament 55, and the hydrogen inlet preferably enters this tube` a short distance from its inner end. In this manner a currentof hydrogen is maintained across the filament in the direction of passage of the molds, through the furnace, so that any material volatilized on the filament will not settle on or condense on the incoming alloy.. In passing to and from Ithe filament the mcolds pass along the watercooled copper slide 59 set upon the water-cooled copper block 51.' .'I'he alloy is thus kept well below fusion up to the time that itis pushed on to the lament and is immediately frozen upon leaving the'same. v

vThe filaments are heated continuously and the buttons are left on the, lower one for about 5 to 15 seconds. As soon as the powdered alloy melts, it spheroids itself by surface tension, and maintains `this spheroidal' shape thereafter. The heating is continued for about 5 to 15 seconds,

during which time the temperature may be car.

riedseveral hundred degrees above the melting point of the alloy, in order to produce a uniform alloy.

In heating the furnace a preferred current is 850 amperes with one volt. With. this current a hotspot about 1/2 inch.. long is produced in the center of the filaments, in the center of which the lmold sits. l A

After the alloy is thoroughly fused, the lime button is pushed off the tungsten lament on'to the copper runway 59 where it is almost instantly frozen.,A The size of the spheroid is such that the freezing will occur in an extremely short time,

, crystals.

buttons -are preferand preferably should -take place in about one second;or less. It is` therefore preferred that the diameter of the spheroid be of the order of 115th of an inch or less in the case of high carbide alloys. When produced in this manner the alloy is tough, extremely hard and resistant, and

is particularly valuable for use in pen-points.

The structure may be further altered by at tachlng the spheroidto av metal base, for instance as described in my Patent 2,005,752, issued June 25, 1935, and then fusing and welding the spheroid to the base in^an inert atmosphere. Cooling is somewhat more rapid under this condition, and there ls a tendency to produce ner 'I'he nal welding operation in some instances of high carbide alloys is preferably conducted so that the spheroid remains fused for 2 to 3 seconds. In some instances this produces a ner crystal structure than where it is instantly fused and then instantly solidified.A 'I'his is preferred for an alloy composed of 46.7% cobalt, 30.8% chromium, 19.2% tungsten, and 3.3% carbon.

The diagrammatic welding step is illustrated in Fig. 18 showing a tipped base 50 to which a spheroid 6I has been tacked. The spheroid may then be welded to the base by operation of the arc 62 in an inert atmosphere.

Apparently owing to the large proportion of carbides, the alloy is lsomewhat resistant to weldweld.

A preferred method of coating the spheroid is to mix a small proportion of gold with the pow der before fusing in the furnace 45. For some. -reason, not yet fully understood, the gold is expelled from the alloy and substantially all oi' it coats the exterior oi' the spheroid. Gold may be added to the finished spheroid in the same manner, and will coat it by surface tension, but the former method ispreferred.

A gold plated ball of this type welds readily to a pen-nib. Sufficient gold is applied to produce a coating from .001 to .005 inch thick. The gold may be, for example, from 14 to 24 karat gold, as desired. As an example, 18 karat gold containing to 15% silver and 10 to 15% copper may be employed. A gold coated spheroid should not bemaintained at fusion temperature more than a few seconds, inasmuch as if left more than a minute the gold is likely to evaporate. Other metals not alloying easily with the alloy may be used.

The present invention is particularly applicable to amethod of spheroiding high melting point metafis-that is, with a melting point over- Moreover, not only are the crystals made ilner, but their amount.- may be decreased. For example, in tungsten, cobalt, chromium carbidev alloys. thematrix may be supersaturated with carbides' in "solid solution, dueto the sudden cooling, thus: reducing the amount present in segregated crystals.

This supersaturation may be of particular importance where the alloy has to be heated above its melting point to dissolve all theI carbides.

Moreover, the supersaturated matrix may be chemically and physically better thanA the normal matrix.

In some instances it may be possible so to supersaturate the matrix that a uniform homogeneous` metal will be produced. When the alloy is fused in hydrogen, it should not be maintained in fused state for a long period, or gas may be absorbed.'

The foregoing detaileddescription is given for earness of understanding only; and no unnecessary limitations shouldL/be understood therefrom, but the appended claimsl should be construedas broadly as. permissible in view of the -prior art.

What I regard as new and desire to secure by Letters Patent, is: l 1. The method of treating an alloy having the approximate composition cobalt to 50 parts, chromium .30 to 40 parts, tungsten 15 to 25 parts. and carbon 3 to 5 parts; which comprises fusing .the alloy and freezing it, the freezing being accomplished in @time ofthe order of 3 seconds.

, granulating the resulting solid, heating a small portion of the resulting material to a tempera- -um furnace.

Y the-fusion and cooling tureseveral. hundred `freezing it in a time 2. The method as which the fusion and cooling are carried out in an inert atmosphere.-

3. Themethod aslset forth in claim 1, in which are carried out in an inand in which the alloy is pridegrees above fusion. and of the order of one second.

'ertatmosphera marily produced thenmelting them in a high frequency vacu- 4. The method of producing a tough alloy `having the :approximate composition cobalt 35 l`to 50 parts, chromium 30 to 40 parts, tungsten 15, to 25 parts, and carbon 3 to 5 parts, which comprises fusing the alloy and freezing it. the freezing being accomplished in a `time* of the above fusion, freezing itin a tim-'offthe' set 'forth' in claim 1, in.

by mixing the ingredients and` granulating the resultingv .the area of contact being small, maf.'

lng it by heat supplied substantially entirely through the alloy, and then suddenly freezing it in a time of the order o f Ik second.

.5. The method as set forth in claim 4, in which the base is a sold base and alloy is lightLv coated with gold prior to the weldingoperation.

6. The method as set forth in claim 4, in which a small amount of gold is mixed with the gran.- ulated alloy, whereby on fusion a thin gold coating is produced on the resulting spheroid.

7. The vmethod of producing coated tungstenchromium-cobalt-carbon alloy spheroids which comprises mixing gold with alloy, and fusing the mixture'in a portion small enough to spheroid itself by surface tension, and solidifying the spheroid, whereby the gold is substantially repelled to the surface, and produces a lmii'orm coating thereon. h 8. In the production of alloys having the approximate lcomposition cobalt 35 to 50 chromium 3o to 40 parts, tungsten 15 to 25 parts, and carbon 3 to 5 parts, in which a series of l open molds containing' granulated alloy are placed in line. approaching a heating-element whereon the alloy is fused, the,step of maintaining a current of inert gas across the molds adjacent to the heating element, in the direction of the heating element, whereby the granulated material is kept free from matter volaiilized upon the heating element.

30 9. The method of forming a corrosion resistant quantity to pro '351 perature at which the materlaL'will form a rspheroid' by surface sulting spheroid from such. temperature in a @time of the order of one second or less.

10. The methodes set forth in vclairii 9 in which the temperature is several the fusion point.

base while depending therefrom.

12. The method as set forth in claim- 9 in which the fusion is carried out in an inert atmosphere.

the alloy has the approximate composition cobaltv35-50 parts, chromium 30to 40parts; tungstcn15 to 25 parts, and carbon 3 to 5 parts.

um-tungsten-'carbon alloys. which com- "iixelting small quantities of the material Ithemilspheioidonravlime surface.

"'14: The-step in spheroids or come,

tension, and freezing the rel himdred ldegrees above 11. The method as iet forth m claim s in which the spheroid is re-fused and frozen to a metallic 13. The method as set forth in claim 'l in which f5 CARL PFANSTIEHL.