USRE21730E - Hard metal tool alloy - Google Patents

Description

netted Feb. 25, 1941 UNITED STATES 21,730 HARD METAL TOOL ALLOY Paul Schwarzkopf, Yonkers, N. Y., assignor to American Cutting Alloys, 1nd, New York, N. Y., a corporation oi. Delaware 1 No Drawing.

Original No. 2,170,432, dated August 22, 1939, Serial No. 155,919, July 27, 1937. Application for reissue August 6, 1940, Serial No. 351,638. -In Germany May 16, 1929 11 Claims.

This invention refers its hard mean tool ailloy and method of producing .the same.

This invention forms a continuation in part of my copending application Ser. #727,781, filed May 26, 1934, and of my copending application Ser. #743,717, filed September ,12, 1934, and issued into Patent #2,122,157, which were in turn copendingwith my application, Ser. #656,103, flied February 10, 1933, and issued into Patent #1,959,879, and my application Ser.. #625,042,

filed July 27, 1932, and issued into Patent No. 2,091,017, which were in turn copending with my application Ser. #452,132, flied May 13, 1930 and .I' of course do not claim herein anything which is subject matter 01' the claims in' my above mentioned earlier patents.

It is an object oi the invention to increase the hardness'of such hard metal tool alloys without impairing their toughness.

It is another object of theinvention to increase the resistance. of such hard metal tool alloys against mechanical wear andchemical efiects such as of the oxygen of the surrounding air, or

moisture, or a'oooling liquid such as water.

It is another object the invention to adjust the heat conductivity of the hard metal tool alloy without impairing its hardness or resistance against oxidation.

It isv still another object .of the invention to increase the speed at which hard alloys oi this kind can be used for cutting, drilling, milling, and othermachining purposes.

This and other objects of the invention will be more'clearly understood when tion proceeds.

Hard metal tool alloys of the type referred to have been made of tungsten carbide andauxiiiary metal taken substantially from the iron group; in amounts from about 3 to 20%. The tungsten carbide has been finely powdered and mixed with the auxiliary metal, and the The present invention particularly refers to a tool alloy comprising a consolidatedproduct con-,

taining the usual cementing auxiliary metal the specificametals of the group containing nickel, cobalt and iron and two carbides for instance of tungsten, i. e. an element 01' the sixth group of the periodical system), boron (i. e. an element oI-the third group of theperiodical system), titanium, i. e. an element of the fourth group of the periodical system), and vanadium" (i. e. an elenien-t of the fifth group of the periodical system) which are substantially or entirelycompounded by heating to a sufficient extent into crystalline solid solutions or homogeneous carbide crystal structures each of which contains atoms of two different selected elements capable to form such structures besides, 01' course, atoms of carbon required to form carbide with those selected elements.

Experiments have shown and science has given the rule that the hardness of solid solutions of elements isa function of their proportion, and that this function possesses a maximum. It is particularly advantageous to choose ior' use in the present invention carbides which form the above defined homogeneous carbide crystal structures, and to choose the range of their composition so that structures exhibiting the maximum hardness will \be produced which increase correspondingly the overall or average hardness of the v composition containing those structures.

Let me take the rules given by the science based on the investigations of Kurnakow and Zemczuznyin 'the"ZeitschIi1't iiir an'organische Chemie 1908, volume 60. p e 1, and 1910, volume 68, page 123, referred to in the standard book of Reinglass Chemische Technologie der Legierungen, second edition, pages 52, 53, and in the Metallund Legierungskunde" 01' Dr. M. v. Schwarz, Professor of the College at Munich, second edition (1929), page 49, in which the investigaitons of Kumakow are referredto and it maximum, which lies mostly at the simple atomic composition. If Schwarz-says atomic composition, it is to be considered that he mentions metals and not chemical compounds such as carbides. I! such compounds are to be taken, their instead 01' atoms" which exist only for the puremetals, molecules" are to be taken which in compounds are equivalent to the atoms of the pure metal. v

Furthermore, the science says, that the maximum does not always lie at simple atomic proportions. If one element materially exceeds-ano her element in hardness, then the maximum imately in a ratio to give the relatively greatest.

hardness, the higher ratio applying to the relatively harder carbide, if one of the composed carbides is essentially harder than the other. Lastly, if building up a curve of hardness of solid solutions depending on the content of therespective carbides, then the maximum of :the curve is flat and does not form a peak so that solid solutions of about the greatest hardness are practically obtained over a range of composition of about 5% to Let me take an alloy having 10% auxiliary metal and therefore 90% carbide. Let me further take that tungsten-carbide and titaniumcarbide are to be compounded'to form the hardest composition. Then we have to divide these 90% in the proportion of 603196, which means that we have to take about (by weight) titanium-carbide, about 70% tungsten-carbide and about 10% auxiliary metal.

Let me take the carbide of vanadium, of the fifth group of the periodical system, and the carbide of tungsten, of the sixth group of the periodical system; Then the correct molecular proportion will be about 1:2, because tungstencarbide exceeds in hardness. Consequently the alloy will contain upon heat treatment of the constituents a homogeneous carbide crystal structure composed of about 76% tungsten-carbide and about 14% vanadium-carbide, corresponding to the molecular weight of 196 of tungstencarbide (WC) and 63 of vanadlan carbide (VC), if 10% auxiliary metal is present.

Let me take molybdenum-carbide and titanium-carbide. Titanium-carbide is exceedingly hard, at least considerably harder than molybdenum-carbide, and is furthermore very light. Consequently the optimum of hardnessisto be expected at a proportion of about 1:3. At 1:3 we have about 49.5 (that means less than 50%) molybdenum-carbide and 4 0.5% titanium-cab hide, it 10% auxiliary metal ispresent.

Let me take vanadium-carbide (carbide of the fifth group) and titanium-carbide (carbide of the fourth group). bide exceeds in .hardness vanadium-carbide, the molecular proportion is to be chosen at about 1:2 and consequently the hard metal will contain about 60% titanium-carbide and about vanadium-carbide in order to remain within the range of greatest hardness, if 10% auxiliary metalis present. I I

Let me take, as'last example, boron-carbide (of thethird group) and titanium-carbide (of the fourth group). Boron-carbide is known as oneof the hardest carbides. The boron-carbide is investigated as 360 with a molecular weight 'of '78. Taking that the hardness of both carbides is about the same, the homogeneous carbide crystal structure has to be madeof about equal proportions of the molecules, whichmeans in the proportion of about 78:60. Consequently such an alloy will contain about 50% boron-carbide-and about 40% titanium carbide, if 10% auxiliary metal is present. I

Hard metals of the above compositions. particularly exhibit high resistance againstbxida- Considering that titanium-can,

hardness is shifted in favour of the harderv tion at elevated temperatures, great hardness and relatively small specific weight.

In the examples given, 10% auxiliary metal is chosen only for the sake of uniformity. But the amount of auxiliary metal essentially of the iron group may vary between, about 3% and 22%. The amount may be smaller if heavy mixtures oi carbides are concerned and larger if lighter mixtures of carbides (e.. g. with titanium-carbide) are concerned.

As a consequence of the considerations presented, the following compositions exhibit the approximately hardest homogeneous carbide crystal structures or solid solutions: 10 to 20% vanadium-carbide, 85 to 65% tungsten-carbide, 5 to 20% auxiliary metal; to 10% titanium-carbide, 40, to 20% vanadium-carbide, 5 to 20% auxiliary metal; 3 to 50% titanium-carbide, to 40% boron-carbide, 5 to 20% auxiliary meta1; 15 to 25% titanium-carbide, 75 to 55% tungsten-carbide, 5 to 20% auxiliary metal.

Such solid solutions are cemented by auxiliary metals such as nickel, cobalt and iron singly or in suitable mixtures. Thereby the fine grain imparted to the powdered carbide is substantially maintained and a desirable toughness of the alloy or tool obtained.

For special purposes, e. g. for finest cuts or polishing mixtures of titanium-carbide and molybdenum-carbide in about equal proportions forming substantially homogeneous carbide crys- I tal structures or solid solutions and nickel upto 9% and 15% and chromium up to 1 and 2% as.

auxiliary metals has been proved advantageous.

But I have established good results also by forming substantially solid solutions of about 30 to 15% molybdenum-carbide (M020), of the sixth group, and about to 30% titanium-carbide (TiC) of the fourth group, adding hereto as auxiliary metals 8 to 15% nickel and 0 to 2% chromium. 'Within this range the optimum e. g. for

high speed work appeared to be at about Bio 10 nickel and up to l to 2% chromium.

Generally, according to this part of my invention compositions are usable which comprise substantial amounts of solid solutions or homogeneou's carbide crystal structures formed by heat treatment to 'sufiicient extent of one hard and refractory carbide of one element of the sixth group of the periodical system, and one hard and refractory carbide of one element of the fourth group of the periodical system, cemented by one or more auxiliary metals essentially, i. e. com

pletely or almost completely of the iron group.

,Any suitable known method may be used for the production of the solid solutions. The carbides can be suitably comminuted, mixed and heated up to about 1600 to 2000 C. for about 1 to 2 hours until homogeneous carbide crystal-structuresor solid solutions are formed in substantial amount. Then the selected auxiliary metal or metals are to be added in the desired quantity, the whole is to be intimately mixed and then to be sintered Zata temperature of about 1400 to 1600 C. If the carbide crystals are too coarse,

. then they are suitably pulverized and mixed with the auxiliarymetal andthen sintered. Before or while sinteringthe molding of the powder so ob- I tained takes place, preferably-under pressure of several atmospheres per square centimeter, up

to e. g. 50 and atmospheres and higher. 'It is also possible, to: mix oxides of the selected ele-' suitably pulverized carbon and to heat the mix- .ments, in finely divided form withadditions of thermore not to any method of consolidating such mixture to or in any shape adapted for the, use

intended, say as a tool element.

In particular the tool or hard metal composition according to my invention may be produced by mixing the carbides and auxiliary metal which are tobe contained in the tool alloy, in as finely divided a form as possible, shaping and pressing the mixture, if desired, and thereupon sintering one hand, with carbon in sufiicient amount so as.

to carbidize the elements or oxides, and, on the other hand, with the selected auxiliary metal, and

the mixture preferably powdered as finely. as possible, heated to sintering temperature for a suflicient period of time so that a tough and hard composition results containing the desired compounds, including at least substantial amounts of solid solutions or homogeneous carbide crystal structures as defined above, cemented by the aux -iliary metal. sintering-may be performed e. g. by

electrical induction heating, if desired, in vacuo.

An electric furnace can be employed for effecting the heating and sintering; the sintering may also be carried outby means of high ire.-

quency currents. In some cases particularly good results are obtained by carrying out the heating or sintering in a vacuum.

Electrical heating current may also be led through the body itself or around the body through the'mould.

The temperature of the body is to be elevated to about 1400 to 1600 C. and this heat-treatment to be continued for about one or several hours, or a major part of one hour, till the desired structure of the body is obtained.

In case, however, difiicult shapes of the body are to be produced not obtainable by usual moulds,

or in case sharp edges are desired, or angles difllcult to manufacture in such a way, so that the mechanical. working or finishing of the hard metal body is needed after sintering, then the following in ashort period of time, say 1 to 5 to minutes so that the particles are sufficiently fritted together to withstand mechanical treatment with out presenting, however, the hardness of a fully sintered body. Such a body is then subjected to finishing in any way and then the sintering at the same temperature is continued until the fully sintered body is achieved.

Another way consists in having admixed to the powders ready for preforming, glycerin,glycol or other alcohols, shaped this mixture and, if

desired, pressed and treated at elevated tempera" ture of about 100 to 200 C. but preferably below 180 C., then worked and finished this body of sufiicient cohesion whereupon the' sintering is possible without any furtherinterruption.

Generally, the body according to my invention is consolidated by using auxiliary metals of the kind'and in the amount as mentioned before and treating it at elevated temperature, e. g. in therange up to about 1400 to 1600 C. until the body of desired structure and qualityis obtained.

When I refer in the appended claims to carbide of elements selected from the third, fourth,

fifth and sixth group of the periodical system,

-I mean carbides adapted for use in hard tool elements, having a suitable hardness and not being dissolved by water or other liquid employed for cooling or similar purposes at operation temperatures. Such carbides are boron-carbide (belongingto the thirdgroup), titanium-carbide, (be-' longing to the fourth group), vanadium-carbide, columbium-cabide, tantalum-carbide (belonging to the fifth group), and tungsten-carbide, molybdenum-carbide (belonging to the sixth group).

When I refer in the appended claims to formation of solid solutions or homogeneous carbide crystal structures, as defined hereinbefore, in asubstantial amount of heat treatment, I mean 'a minimum amount of about 10% as disclosed in my co-pending application No. 743,717, filed September 12, 1934, and issued into Patent 2,122,157.

It is quite difficult to mention any minimum amounts of carbide to be present. Nevertheless, the minimum amount of carbide to, be present and forming part of a solid solution orhomogeneous carbide crystal structure, as defined hereinbefore, according to the invention, has to be substantial, and as a minimum about 1% by weight of the alloy. 4 r,

Tool alloys prepared according to the invention are, as a rule, not used for the production of the entire tool, but merely for the part of the tool which in practice is used directly for cutting, drilling, etc. and which is subject to wear.

From the above description it appears that the carbides to be cemented by auxiliary metal may either be compounded into solid solutions or homogeneous carbide crystal structures, .as defined hereinbefore, entirely. or in substantial amount before a substantial amount .of auxiliary metal is added, or the preferably extremely finely powdered carbides may be first mixed withthe auxiliary metal and sintered in such manner that extended sintering. It has been found that solid solutions or homogeneous carbide crystal structures, as defined hereinbefore, resist recrystallization to a large extent. Thereby finest grain of carbides present in the alloy including homogeneous carbide crystal structures or solid solutions are retained, and a tough and very efficient,

clean cutting material is obtained.

What I claim is: b a

1. A tough cemented hard metal sintered by heat treatment and consisting substantially or auxiliary metal selected essentially from the iron group in amounts from about 3% to 22% and two carbides of elements selected from the third,

fourth, fifth and sixth group of the periodical system, said carbides containing together substantially more than 2.6% carbon and being present in finely divided state, said carbides heat treated to form solid solutions insubstantial amount.

2. A cemented hard metalcomposition sintered'byheat treatment into a hard and tough body for tool elements and other working appliances, consisting substantially of auxiliary in amounts of about 3% to 22% and finely divided hard carbide crystal structures formed by heat treatment from carbon and two different elements other than carbon belonging to different groups of the periodical system and selected from the third to sixth group thereof, substantial amounts of said structures homogeneously containing atoms of said two selected elements in addition to carbon atoms.

4. A tough cemented hard metal composition sintered by heat treatment, for tool elements and other working appliances, consisting substantially of auxiliary metal essentially of the iron, group in amounts of about 3% to 22% and finely divided hard carbide crystal structures formed by heat treatment from carbon and two elements selected from the group consisting of boron, titanium, vanadium, columbium, tantalum, tungsten, substantial amounts of said structures homogeneously containing atoms of said two selected elements in addition to carbon atoms soas to increase the average hardness of the composition.

5. A cemented hard metal composition sintered by heat treatment into a hard and tough body for tool elements and other working appliances, consisting substantially of two hard 40 carbides of elements of the fifth group of the periodical system, these carbides being selected and admixed in proportions adapted to yield and heat treated to form approximately hardestsolid solutions in substantial amounts, and auxiliary 45 metal taken essentially from the iron group in amounts from about 3% to 22%.

6. Acemented hard metal composition sintered by heat treatment into a hard and tough body for tool elements and other working appliances,

50 consisting substantially of a hard carbide of an element of the third group and of a hard carbide of an element of the sixth group of the periodical system, these carbides being present in substantial amounts in proportions adapted to form 55 approximately hardest homogeneous carbide crystal structures containing'atoms of said two elements in addition to carbon atoms and auxiliary metal essentially of the iron group in amounts from about 3% to 22%, said carbide 60 crystal structures formed. by heat treatment in substantial amount.

7. A tough cemented hard metal composition sintered by heat treatment, for tool elements and other working appliances, consisting substantially of two hard carbides of different elements belonging to different groups of the periodical system and selected from the third, fourth, fifth, and sixth group thereof, and auxiliary metal essentially of the iron group in amounts of about 3% to 22%, the minimum amount of a selected carbide to be 1%, said carbides being present in 'finely divided state and heat treated to form in substantial amount homogeneous carbide crystal structures containing atoms of said selected two elements in addition to carbon atoms.

8. A tough cemented hard metal composition sintered by heat treatment, for tool elements and other working appliances, consisting substantially of auxiliary metal essentially of the iron group in amounts from about 3% to about 22%, and two hard carbides of elements selected from the group consisting of titanium, tantalum, columbium, and tungsten, the minimum amount of a selected carbide to be 1%, said carbides present in finely divided state and heat treated to form in substantial amount homogeneous-carbide crystalstructures containing atoms of said selected two elements in addition to carbon atoms.

9. A tough cemented hard metal composition sintered by heat treatment, for tool elements and other working appliances, consisting substantially of auxiliary metal essentially of.the iron group in amounts of about 3% to 22% and finely divided hard carbide crystalstructures formed by heat treatment from carbon, titanium and tung sten, substantial amounts of said structures homogeneously containing atoms of titanium and tungsten in addition to carbon atoms.

10. A tough cemented hard metal composition sintered by heat treatment, for tool elements and other working appliances, consisting substantially of two hard carbides of diflerent elements belonging to different groups of the periodical system and selected from the third, fourth, fifth and sixth group thereof, and auxiliary metal essentially of the iron group in amounts of about 3% to 22%, the minimum amount of a selected carbide to be 1%, said carbides being present in finely divided state and heat treated to form in substantial amount homogeneous carbide crystal structures containing atoms of said selected two elements in addition to carbon atoms and to increase the average hardness of the composition.

11. A'tough cemented hard metal composition sintered by heat treatment, for tool elements and other working appliances, consisting substantially of two hard carbides of different elements belonging to difierent groups of the periodical system and selected from the third, fourth, fifth and sixth group thereof, and auxiliary metal essentially of the iron group in amounts ofabout 3% to 22%, the minimum amount of a selected carbide to be 1%, said carbides being present in as finely divided a state as possible and heat treated to form in substantial amount homogeneous carbide crystal structures containing atoms of said selected two elements in addition to carbon atoms and to increase the average hardness of the composition.

' PAUL SCHWARZKOPF.

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