US2212227A - High speed tool - Google Patents

Description

Aug. 20, 1940. R. P. DE VRIES HIGH SPEED TOOL Filed July 8, 1939 2 Sheets-Sheet l 2 5 4 7 Z60m/f /fvl/EN 70A A 7' TOQ/VEY Aus 20, 1940- l R. P. DE VRIES 2,212,227

HIGH SPEED TOOL ,f/ f /l///f AI77-@Avver- Patented Aug.'2o, reto! UNITED STATES 2,21z,z I

. PATENT OFFICE HIGH SPEED 'rooL RalphP. De Vries, `Menands, N. Y., assignor to Allegheny Ludlum Steel Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Application July 8, 1939, Serial No. 283,338

7 Claims.

superior to any other high speed tools formed of steel, of which I am aware, irrespective ofthe alloy content therein.

As a result of the making of many test melts of steel containing the usual elements found in 1high speed steels, including chromium, molybdenum, tungsten, vanadium. and cobalt, in various proportions, and particularly with varying proportions of tungsten and molybdenum, and the study of the life and eiiiciency of av large number of cutting tools made therefrom, I have discovered that by maintaining the' tungsten and molybdenum contents within comparatively narrow ranges, and within very limited proportionsl within these narrow ranges, it is possible to manufacture cutting tools having extraordinary and quite unexpected cutting properties.

In my copending application Serial No. 181,997, iiled December 27, 1937, I have also disclosed an alloy steel having very narrow ranges of tungsten and molybdenum which, if maintained in the specified proportions, form a composition from which high speed cutting tools having a very low alloy content and an unusually long life may be manufactured.

While the alloy described in the aforesaid copending application is quite superior to. other y high speed steels of which I am'aware, I have now discovered that by modifying the tungsten and molybdenum ranges therein disclosed and maintaining the total combined content of these elements withinv the very limited range of lfrom about 7.0% to about 12.0%, by weight, of the total composition, it is possible consistently to manufacture a high speed steel which when measured by the life and efficiency of cutting tools made therefrom, is several times better than the well known 18-'4-1 high speed steel.

In'order graphically. to indicate the'very unusual cutting properties of my steel and to indicate how critically narrow are the ranges and proportions of the tungsten and molybdenum.,

contents within which my present invention lies, reference may be had to the accompanying drawings in which- Flg. 1 is a graph showing how the average life of twenty-two different tools, divided into three groups, depending on the combined content of molybdenum and tungsten therein, varies With this combined content;

Fig. 2 is a graph showing how the life of a number of tools each having al low and substantially the same content, (2.75% by weight) of tungsten but with varying quantities of molybdenum, varies with the combined tungsten and molybdenum content at 4dieren-t Cutting speeds.

Fig. 3 is a graph showing how the life of a number of tools each having a tungsten content in excess of the molybdenum, varies with the combied tungsten and molybdenum content.

Fig. 4 is a graph showing how the lie of four different tools containing about 2%, by weight,

Vof cobalt and tested at three different cutting speeds varies with the combined content of tungsten and molybdenum;

Fig. 5 is a graph showing how the cutting life of three different tools when run at two diierent cutting speeds -varies with additions of cobalt above about 2%;

Fig. 6 is a graph showing how the cutting life of nine different tools, each having its tungstenv content about equal to its molybdenum content but having varying combined tungsten and molybdenum contents, varies with the total of the tungsten and molybdenum inthe steel; and

Eig. 7 is a graph similar to Fig. 6 but in which each tool was run at four diierent cutting speeds and the average inches cut for each toolsplotted.

Theessential elements of the steel from which my cutting tool is formed and the percentages, by weight, within which they are employed are as follows- Per cent Tcd20-,1.20 w 2.o 6.5 Mc 3.o '1.o cr 2.o 6.o v 0.50- 3.o Mo+W '1.o 12.0

has been substituted in whole or in part, and in various proportions, for the more expensive tungsten. Such tools,` while very much cheaper than the 18-4-1 tools, have only approached the 18-4-1 tools in cutting life and eiciency, and no tools containing comparatively low quantities of tungsten and molybdenum but having a cutting life and eiiiciency-from two to three 'times greater than 18-4-1 tools have every been proposed, so far as I am aware. sumption in regard to cutting life and eiiiciency seems to have been that these factors are increased in direct proportion to the tungsten and molybdenum employed, even when these elements are used in particular proportions as recommended by various investigators and patentees.

My investigations quite clearly establish that The general aswhilefthis may be true in respect of tools having a life and cutting eciency approaching or even approximating an 18-4-1 tool there are, nevertheless, very narrow ranges of tungsten and molybdenum withinwhich, if the total percentage of tungsten and molybdenum is maintained within verynarrow limits, the curve of tool life and cutting emciency rises to heights `far transcending the life-efficiency curve of the 18T-.4 1 tools.

In Table ,1 below I have set forth anumber of steels containing vtungsten and molybdenum in various quantities and relative proportions, ac-

4aus

cording/to the analyses thereof set forth in Table 2, ,and which are divided into three groups according to the total combined percentage of the tungsten and molybdenum in the steel. In the/first group are all steels having a combined percentage of tungsten and molybdenum less than 9%; in the second group, those steels having a combined percentage of tungsten and mo- /lybdenum between 9% and 10%; and in the third group,those having a. combined percentage of 10% or more. At the bottom of Table 1 is the average of the (W-i-Mo) in each group, and the average of the number of inches cut'by each tool before failure. All tools were identical in size and shape, subjected to the same heat treatment, and tested under identical conditions at a cutting speed of 85 surface feet per minute (85 S. F. M.).

ciency of varying quantities of molybdenum with a low and substantially constant quantity of tungsten, a series of steels of the analyses shown in Table 3 below were melted.

TABLE 3 oms111- Molyb 'rungvana- Melt No bon hmme con denum sten dium 77 4. 19 65 6.15 2. 70 1. .s2 4. 08 67 5. 53 2. so 1. .73 4.19 .63 5.11 -ass 1. 82 3. 88 63 6. 92 2. 34 1. .80 4.17 .66 6.60 2.72 1. .77 3. 72 .75 8. a2 2. s3 1. .s1 3. ce .61 s. 12 2. es 1.

In all these steels tungsten was melted at 2.75% and the molybdenum was varied so as to give a range of (W-l-Mo) varying from 8% to 11.15%.

Fig. 2 comprises three graphs showing the lifeeilciency curves of tools made from these steels when tested at 67 S. F. M., 70 S. F. M. and 80 S. as compared with an 18-4-1 tool These curves show that the maximum life-efficiency of the tools with low tungsten is attained when the (W-i-Mo) percentage is between about 8.25% and 9.50% although the general trend of the curves,

especially at the higher speeds, indicates that creditable performance superior to 18-4-1 tools is attained with a (W-i-Mo) of from about 7.0% to slightly over 11 TABLE 1 W+Mo=(7.50% to 9%) W+Mo=(9% to 10%) W+Mo=(10% and greater) Melt N o. W-l-Mo Inches cut Melt No. W-i-Mo Inches cut Melt No. W-i-Mo Inches cut T-609 8. 48 7, 900 T-602 9. 54 A 8, 450 T-614 l0. 33 6, 600

T-611 8. 48 13, 150 T-607 9. 4l 13, 650 T-627 10. 70 10, 000

T617 8. 54 A14, 900 T-616 l 9. 40 10, 350 T-633 10. 04 4, 050

T-664 8. 10 10, 400 T-643 9. 44 5, 400 T-647 10. 31 6, 100

Average--- 1o. 2s 524 'TABLE 2 Analyses of melts shoum in Table -1 Silicon Tung- Vanasten Oar- Melt No. bon

Fig. 1 is a graph in which the average inchescut by each group is plotted as a function of the average (W-i-Mo) of each group, and indicates how the average life-eilicency of the tool decreasesf as the average (-W-i-Mo) increases In order to determine the eie'ct on the life-em- In order topdetermine the effect ofincreasing the tungstenlcontent to points above the molybdenum content, the series of steels shown in Table 4 below were melted, tools made therefrom and tested.

TABLE 4 Chrom- Molyb Tung- Vana- Tool No. Carbon um enum Sten dium Sillcon The life-emciency curve of these tools is plotted vin Fig. v3, and, for comparative purposes the average lie-eiciency of 18-4-1 tools under the same test-conditions is also Iplotted as a horizontal line.

Here, the maximum of performance is clearly limited to those tools in which the total tungsten and molybdenum content combined is between.

between about 8.5% and 11.25%.

All of my steels have the advantage thatthey may'be hardened from very high temperatures in the range of 2275 F. to 2325 F. In fact the,

life-efficiency curves (shown in the drawings) are all based on .a hardening temperature of 2325 F.

with a reheating to 1025 F. The hardness of these tools is at a maximum when the tungsten and molybdenum content combined is between 9% and11%. Although a hardness from 64 to 65 Cone Rockwell is,V common, tools made from preferred composition such as T-'726 and T-72'7 show higherl hardnesses going into the range of 67 to 68 Cone Rockwell and approaching sintered carbide tools in their extreme hardness.

Since all of the foregoing steels were manufactured under laboratory conditions where the size of the ingot and the forging reduction were necessarilyf small and therefore might not be directly representative of heats made on a commercial scale, tWo two-ton heats were made ot the following analyses. In one, the combinedcontent of tungsten and molybdenum was melted for 9%,

and in the other 11.5%.

Steel 282 Steel 283 Carbon .77 .85 Chrome 3.97 4. 18 Molybdenum.- 3. 98 5. 84 Silicon 59 .2l Tungsten 4. 83 5. 57 Vanadium 1. 55 l. 02

These same steels were also made up into twistl drills of various sizes from 1" downto 1%" and tested with 18-4-1 twist drills as a control. Taking the performance of the tools made from steel 282 as a hundred, Table 5 below shows the summary of these tests.

TABLE 5 n Summary of lathe and drill tests (Performance given in percent) No. Type stealasz steel'zsa -1s-4-1 Lubricant v Lathe.-- 100 7s es No.l Drin...l 100 s1 92 Yes.

--.do 100 s0 se D5.

The above tests were conducted under strictly shop conditions; dry cutting in the lathe test` and fully lubricated in the twist' drill tests.. In-many individual cases the performance'of tools madefrom steel 282 exceed` the performance '0f standard 18-4-1 tools in a ratio of 2-to 1.

The results of thecomparative tests of tools made from steels 282 and 283.Were quite unexpected and further tests were run/to determine which of these steels had the greater hardness j When measured in the temperature ranges at whichphigh speed steels often operate. The results which are shown below in Table 6 indicate that the steel containing the lesser quantity of alloy, namely steel 2'82, has'a greater hardness ,than the steel 1283.

l TABLE 6 i Hot Brinell Hardnesses Steel 282 Steel 283 F. tem X p 2320 F. 2320 F. oil, 2320o F. 2320 F. oil,

011 -55 F. air @i1 550 F. au

critical, and that when the combined content of tungsten and molybdenum is maintained well within the limits which I have prescribed, theresults are markedly better thanwhen the total of these elements is close to said limits.

The possibility of increasing the cutting efii-A ciency of the tools with the addition of cobalt in small quantities was investigated by testing tools made from four different `steels allcontaining In Fig. 4 the total cut in inches by tools made from each of these steels and at 3 different speeds is plotted as 'a function ofv the combined'molybdenum and tungsten contents. The life-eiiiciency curves of these cobalt-containing tools shown in Fig. 4 have theirv peak when the combinedy percentage of molybdenum and tungsten is between about 8% and 11%. In other Words, these tools exhibit the same type of life-efficiency curve as the other tools without cobalt. If, however, the combined content of tungsten land/molybdenum is vmaintained Within the above limits, which provides maximum cutting eiiiciency, the addition of higher quantities of cobalt does not improve I the cutting perfomance as will be apparent from a consideration ofthe following tests.

The eiect of cobalt additions above about 2% on the cutting eiliciency of the tools was investigated by making and running tools of each of the 3 analyses given in Table 8 belowat 2 different speeds, is plotted as a function of the percentage of cobalt in the tool.

efliciency curves show that atl the lower cutting speed the efficiency falls rapidly as the cobalt In Fig. 50i. the drawings the cutting eicien'cy,

These lifei quantity is increased. At the higher speeds the eiciency drops as cobalt is added from 2% to 4% and then appears to rise as the cobalt is added up to between 6% and 7%. It would appear,

ytherefore, that cobalt in quantities in excess of. about 2% not only does not improve the eiiciency but seriously detracts therefrom. This result had been observed before but was .diiicult of explanation since it was not known that high speed alloys containing a comparatively low percentage of molybdenum and tungsten had very distinct maxima of cutting eiciency and that if the percentages of. molybdenum and tungsten were raised the cutting eciency of the tools was lowered. The foregoing tests indicate that while cobalt in 'comparatively low percentages does not deleteriousiy affect the cutting efficiency, additions over about 2% seriously detract' from the best cutting performance.

In order further to demonstrate the extremely narrow and critical ranges of elements within which my invention lies, nine dierent steels were melted having a molybdenum content between 4% and 6% and a tungsten content between 4.26% and 6.50%, the tungsten content in each case being slightly in excess of the molybdenum. The analyses of these steels are shown l in Table 9 below together with the analysis of a standard 18-4-1 steel used as a control. Tools made from each of these steels were tested at a cutting speed of surface feet per minute and the results are shown in Fig. 6 of the drawings. Tools from'these ysteels were alsoy tested at four different cutting speeds, namely, 80, 76, 70 and 67 surface feet per minute and the average performance of each tool is plotted in Fig. 7.

tungsten between 5% and 6%.

and 6%, ,preferably nearer 4% than 6%., with While all the tools in any single' group aboveence among manufacturers of. high speed tools to nd that while'an outstanding record may be made when their tools are used to cut a certain grade or kind of steel, a very poor record may be made when the same tools with the same treatment are used in cutting tests on` a different alloy steel.

For this reason different logs were used in the foregoing tests. The tests shown in Fig. 1 were obtained on a. carbon steel log; the tests shown s in Figs.` 2 and 3 were obtained on a chrome-nickel steel log known for its toughness and hard cutting properties; the tests shown in Figs. 4 and 5 were obtained on a carbon steel log; and the tests shown in Figs. 6 and 7 were obtained on a high carbon-chrome log containing no nickel.

For comparative purposes, three different tools made from 18-4-1 steel were run at three different speeds on a chrome-nickel steel log such as` used for the tests plotted in Figs. 2 and 3, and the raverage life of the three tools at each speed is plotted. These averages are as follows:

TABLE 9 A Vlge S'F'M' inches cut Average n Analysls In. out in. cut at Steel No. at 70 four di- 2'18" o or si Mo W va w-Mo s.F.M. 12.435

. 8,976 7, 539 The apparent inconsistencies that have aps13142 453 sorse als ifgg 1g; gig peared when high speed steels containing rela' V .gg sose 3.56 ms 7,771 tively small proportions of molybdenum and z'u ass 74 sfig 5 LS iof lg fggg tungsten are tested fr cutting ,emciency have 2g 7,324 heretofore been explained as being due to the 344 '7o eoo 615144 12150 nog lgg great diculties encountered in consistently .75 4.20 .37 1s.oo1.25 4,719 3,900 manufacturing tools of uniform quality, such,

It will be noted that the peak of the life-efficiency curve is reached when the combined tungsten and molybdenum content is between 9% and 10% although all ofthe tools which had a combined content of. tungsten andmolybdenum varying from 8.26% to 12.50% are markedly superior v to the 18-4-1` tools.

or more than about 12.0%, the cutting eiilciency of the tool falls rapidly and is not substantially better than the standard 18-4-1 tools. I believe, however, thatthe very best cutting tools are obtained with a molybdenum content between 4% for example, as the dilculty in melting steel to the precise specification desired, giving the tools exactly the same heat treatment or the diiculty in grinding tools exactly alike. All of these difficulties are more or less real but no one, so far as I am aware has discovered that a very high peak of cutting eiiciency existed and could be consistently attained by maintaining the molybdenum and tungsten and the total combined content thereof within the very narrow limits herein disclosed.

The percentage of the various elements stated aboveand in the appended claims is to be understood as meaning percentage by weight.

What jI claim is:

1. A high- 'speed tool having a low alloy conk tent and characterized by its exceptionally long and iicient cutting life; said tool being formed of an alloy steel containing a plurality of ele.- ments of which the following, within the ranges and proportions stated, are the only elements necessary to Aattain said characteristic, carbon from about 0.20% to about 1.20%, tungsten from about 2.0% to 6.5%, molybdenum from about y3.0% to about 7.0%, chromium from about. 2.0%

to about 6.0%, vanadium from about 0.50% to about 3.0% and the balance iron; the tungsten and molybdenum combined constituting from about 7.0% to about 12.0% of the alloy.

2. A. high speed tool having a low alloy content and characterized by its exceptionally long and encient cutting life; said tool being formed of an alloy steel containing a plurality of elements of which the following, within the ranges and proportions stated, are the only elements necessary to attain said characteristic, carbon from about 0.20% to about 1.20%, tungsten from about 2.0% to about 6.5%, molybdenum from about 3.0% to about 7.0%, chromium from about 2.0% to about 6.0%, vanadium from about 0.50% to about 3.0% and the balance iron; the tungsten and molybdenum combined constituting from about 8.5% to about 10.5% of the alloy. f

3. A high speed tool having a low alloy content and characterized by its exceptionally long and efficient cutting life; said tool being formed of an alloy steel containing a plurality of elements of which the following, within the ranges 'and proportions stated, are the only elements necessary to attain said characteristic, carbon from about 0.20% to about 1.20%, tungsten from about 4.5% to about 6.5%, molybdenum from about 3.0% to about 5.5%, chromium from aboutl 20% to about 6.0%, vanadium from about 0.50%

to about 3.0% and the balance iron; the tungsten being in excess of the molybdenum and the tungsten and molybdenum combined constituting from about 9.0% to about 12.0% of the alloy.

4. A high speed tool having a low alloy content and characterized by its exceptionally long and efficient cutting life; said toolv being formed of an alloy steel containing a plurality of elements of which the following, within the ranges and proportions stated, are the` only elements necessary to attain said characteristic, carbon from about 0.20% to about 1.20%, tungsten from about 2.0% to about 4.5%, molybdenum from about 4.0% to about 7.0%,vchromium from about 2.0% to about 6.0%, vanadium from about 0.50%

to about 3.0% and the balance iron; the molybli'lenum. being in excess of the tungsten and the tungsten and molybdenum combined constituting from about 7.0% to about 10.5% of the alloy.

5. A high speed tool having a comparatively low alloy content and characterized by its exceptionally long and efllcient cutting life; said tool being formed of an alloy steel containing a plurality of ingredients of which the following, within the ranges and proportions stated, are the only elements necessary to attain said chaiacteristiccarbon from about 0.60% to about 1.20%, chromium from about 2.0% to about 5.0%, vanadium from about 0.50% to about 3.0.%, tungsten from more than 5.0% to about 6.5%, molybdenum from about 3.0% to about 6.0%, and the balance iron; the combined content of tungsten and molybdenum being from about 8.0% to about 12.0%.

6. A high speed tool having a low alloy content and characterized by its exceptionally long and efcient cutting life; said tool being formed 'of an alloy steel containing a plurality of elements of which the following, within the ranges and proportions stated, are the only elements necessary to attain said characteristic, carbon from about 0.70% to about 0.90%, tungsten from more than 5.0% to about 6.0%, molybdenum from more than 4.0% to less than 5.0%, chromium from about 3.0% to about 4.0%, vanadium between about 1.0% and 2.0%, and the balance iron; the tungsten and molybdenum combined constituting from about 9.0% to about 11.0% of the alloy. 1

7. A high speed tool having a low alloy content and characterized by its exceptionally long and eficient cutting life; said tool being, formed of an alloy steel containing a plurality of elements of which the following, within the ranges and proportions stated, are the only elements necessary to attain said characteristic, carbon from about 0.20% to about 1.20%, tungsten from more than 2.8% to 6.5%, molybdenum from about 3.0% to about 7.0%, chromium from about 2.0% to about 6.0%, vanadium from about 0.50% to about 3.0% and the balance iron; the tungsten and molybdenum combined constituting from about 7.0% to about 12.0% of the alloy.

Y RALPH P. DE VRIES.

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