AU427368B2 - Resin bonded abrasive products - Google Patents

Description

32 06 9/71

-This invention relates to abrasive tools, in

particular grinding wheels and coated abrasive belts,

containing the hardest known abrasives, diamond and bubio

boron nitride which, when metal coated diamond grit is the primary 1abrasive are partlouliarly suitable for the

dry grinding of cemented carbide tool material (e.g.

cemented tungsten carbide), and when metal coated boron

nitride grit is the primary abrasive are particularly

suitable for grinding hard tool steels. Improvement of resinoid bonded diamond (or

cubie boron nitride) abrasive tools has been recently achieved by the use of metal clad diamond grit or by the use of metal clad cubic nitride grit. The present

applicants have found that finely divided graphite can

be used in such tools in United States Application Serial

No. 876,655, to improve, significantly the performance in

dry igribding,. The present invention provides further im-

provement in performance through the use of particular

combinations of particulate solid film lubricant fillers

and silver or copper fillers.

The present invention involves modifying the

bond of resinold bonded abrasive tools, containing metal

clad diamond or cubic boron nitride, by inclusion of from

to 60% by volume, preferably 30 to 50% by volume of the total of bond -and fillers (exclusive of the me-tal clad ab- 4-27 368

3 9,06 97 rasive) of silver or copper (or a combination such as

silver coated copper), and from 5 to 30%, preferably 10 to

of a solid dry film lubricant, hereinafter defined.

Known synthetic resins useful in making

coated or bonded abrasives may be employed in the present

invention. Obviously, strength and heat resistance are

necessary properties. The well-known cross linked resins

such as phenol-aldehyde resins, melamine-aldehyde resins,

urea-aldehyde resins, polyester resins, and epoxy resins,

including the epoxy novolacs, may be used and conventional

modifiers and plasticizers may be used. Part of the filler

content may consist of conventional particulate fillers

such as silicon carbide. Fairly recently, new essentially

linear polymers as well as thermoset polymers (such as

thermoset polymers disclosed in French Patent 1,455,514)

have been introduced which have utility in bonding abrasive

grains. These resins, like the cross linked resins dis-

cussed above, are infusible, as opposed to the more common

thermoplastic linear polymers having definite softening

ranges and which are reversibly softenable. Examples of

such resins, having utility in making abrasive tools, are

given in United States Patent 3,329,489 (polybenzimidazole),

and United States Patents 3,295,940 and 3,385,684 (polymides).

Polysulfide resins such as disclosed in United States Patent

3,303,170 and polypyrrones may also be employed. For use in

making coated abrasive discs or belts liquid resin systems

may be preferred, while for bonded abrasives solid powdered

resins can be used.

One of the preferred features of the present

invention is that the abrasive, diamond grit, or cubic boron

3- 427.368

32, 06 9 nitride, has a metal coating encapsulating the abrasive

grit such that the metal is present in the coated particle

in an amount between 10 and 70%, by volume. Uncoated

diamonds can be used, however, .and tools employing them.

are considered part of the present invention. Metal coated

diamonds are disclosed in Soulard French Patent 1,142,688,

aBeSgeian Patents a683,,508 and ~98,28, 'and Frenchl'Patent

1,522,735. Possible metal coatings are copper, silver,

nickel, cobalt, molybdenum and, in general, any metal

melting above about 5000F which is ohemically stable in

the grinding tool. Although, for wet grinding the volume

,per cent of metal coating can be higher, for dry grinding,

to which the tool of the present invention is particularly

directed, the volume per cent of metal coating should be

between 10 to 60%, by volume.

Coated diamonds are commercially :available which

have nickel coatings within the above range of 10 to

by volume, and -copper coatings, within the same range.

TIhese coatings can be produced by electrodeposition on a

thin, -silver coating produced by chemical deposition on the

grits. Thus the coatings need not be a single metal, only,

and a wide variety of metal coatings are possible and use-

ful in the present invention. Alloys of the metals are also

useful.

The grit size of the abrasive is not generally

relevant to the present invention, but grit sizes of

throngh 320 (b:ased on the uncoa-ted .grit) are commonl-y used in diamond wheels. Grinding elements according to the present in- vention may be formed by pressing the mixture -in a mold

427.3,8

.32 06 9 of the desired shape. The mold may be heated and the

resin may be completely or partially cured in the mold.

Figure 1 shows a perspective view of a grinding

element such as produced according to the present invention.

Figures2 and 3 show a perspective view of the

grinding element of Figure 1 mounted for use in two

different mountings;

Figure 1 shows a typical grinding element

Figure 2 shows the grinding element mounted on a core

to produce a straight grinding wheel. Figure 3 shows the element 10 mounted on a cup shaped support to form a grind-

ing wheel commonly referred to as a "cup wheel.". A suitable

material for making the support member is an aluminum-

filled resin as disclosed in United States Patent 2,150,886.

The tool may be molded directly onto the support, the support may be molded onto the tool, or the tool may be

cemented onto the support after fabrication.

For the production of coated abrasive discs or

belts, a liquid phenol-formaldehyde resin can be used. A size coat of liquid resin should be employed after the

maker coat, and at least the size coat should contain the

fillers of this invention. The size should be "high", that

is, it should extend from the maker coat to close to the

tips of the abrasive so that the fillers in the coat contact

the work during grinding.

The required fillers of the present invention

are:

silver or copper or a combination such as silver

coated copper, present in the bond in the amount

of from 10 to 60% by volume, preferably 30

427.368

32 069 /7 a solid dry-film lubricant present in the bond in the amount of from 5 to 30%, by volume, and .preferably from 10 to Silver is significantly better than copper, and silver coated copper is better than copper. Although the exact particle size range is not critical, the finer metal powders are. more effective.. Typical .powder are 325 mesh and'. finer and may measure 1 to 10 microns in size, by conventional microscopic examination. When copper is employed, deoxidized powders should be used. The lubricant filler may be one of the known inorganic materials such as graphite, fluorinated graphite, metal coated graphite (United States Patent 3,402,035) hexagonal boron nitride, tungsten disulfide, molybdenum disulfide, niobium diselenide, and tungsten diselenide, all of which have been effective in the present invention to give a grinding efficiency at least 200% of a standard test wheel containing a silicon carbide filler only. Further the dry film lubricant filler may be an inorganic crystalline material having layer-lattice structure in which the bonding between atoms is an individual layer is by strong covalent or ionic forces, while the bonding force between layers is by relatively weak Van der Waal's forces or an organic polymer. Organic dry-film lubricants are finely divided solid polymeric materials. Suitable materials are extrusion grades of acrylonitride-butadiene-styrene terpolymers, acetal copolymers (polyformaidehyde), chlorinated polyethers, polytetrafluorotrifluoroethylene, fluorinated ethylene propylene, 6 427.368

32, 06 9 i polyvinylidene fluoride, ionomers, nylons, polyphenylene oxides, polyvinyl chloride, polyvinylidene chloride,

polycarbonates, thermoplastic polyesters, flexible polyesters,

polyethylene, polysulfones, styrene butadiene

427,368

32.069/71 copolymers, and urethanes.

In addition to the metal and dry-film lubricant

powder fillers, inert-fillers such as silicon carbide may

be added to improve the strength of the bond or otherwise

control its physical properties. Where lower diamond con-

centrations are employed it may be desirable to add such

fiIlers to reduce the overall bond content of the tool or grinding element.

Normal process steps, conventional in the art,

can be used to fabricate the wheels, discs, or belts accord-

ing to the present invention.

A preferred example of a bond mix for making a

bonded abrasive ring for mounting on a backing element,

such as shown in the drawing is as follows:

PHENOLIC BOND EXAMPLE

Parts by Weight Parts by voluium Powdered Phenol-aldehyde pre-polymer (BRP 59 8 0-available from Union Carbide Corporation 17.3 45.2 which includes 9% hexamethylene tetr*ine and to which 10% by weight of lime Is added

Silver powder (Metz Ref-ning 58.6 Co. C-18)

Polytetrafluoroethylene powder (Liquid Nitrogen Processing Co. 6.0 TL-115) Silicon-Carbide (800 grit) 15.8 17.7

Furfural 2.3 7.1

In making a bonded abrasive tool employing the

'abbve mix, the -abrasive is wet with the'furfural and the

mixture of bond and fillers is added and mixing continued

to form a homogeneous batch. Sufficient of the mix is then

g 427,368

3. 069 71 placed in a mold of the desired shape and the mix is hot-

pressed to shape. Normally, using the above bond, the tool

is then removed from the mold and further cured in an oven.

Typical molding conditions are a pressure of 5 tons per

square inch, a temperature of 160 0 C, and a molding time of

minutes. The final cure can be carried out in an air

atmosphere oven for 24 hours at 175 0 C. Control of the

temperature of the final cure is effective, as is well

known in the art, in controlling the hardness or grade of

the bond which may differ depending upon the specific'

application.

The cured abrasive element is attached to a core

or holder, as is conventional in the art, to produce a

grinding tool such as shown in Figures 2 and 3 of the

drawing. In the tabulated examples below, cup type wheels

were employed of the dimensions and standard indicated.

All the tests were run dry (no liquid coolant).

Where other resin systems are employed than

the phenolic bond given above, it is known in the art that

different curing or processing temperatures may be required.

For example, in the case of the polymide resins, typical

fabrication conditions would be a pressure of 10 tons per

square inch, and a hold at 270 0 C. for 15 minutes. No post

cure is required. A commercial polymide available from

Rhone-Poulenc, identified as P.I.-M33A, cured under these

conditions, and containing 50% silver filler and 10% poly-

tetrafluoroethylene as fillers, gave a grinding efficiency

of 202%, or 102% above the control wheel, in a test similar.

to that of Table I. A second test with a different polymide

identified as P.I.-M33B, gave a grinding efficiency of 293%

9 427.368

32,069 1 under identical conditions where 40% silver and 10% TFE

fillers were used.

EXAMPLES

The following test was made on wheels made

according to the Phenolic Bond Example given above, the

amounts of fillers" and resin, how'ever, being varied ai i indicated. The wheels were cup wheels, 6A9 type, 4" x 1-3/4

x The diamond was coated with 56 weight per cent

nickel and was 150 grit (Uncoated), and the wheels con-

tained 17% diamond by volume. The work ground on a modified

surface grinder was a cemented tungsten carbide, the unit

infeed was 2.5 mils. Grinding conditions and the work piece

were the same for all the wheels. The first wheel listed

was a standard commercial wheel containing 35% by volume

of silicon carbide in the bond. Table I give the results.

The "wheel no." is for identification purposes, G is the

grinding ratio or grinding efficiency expressed as a ratio

of the volume of carbide iemoved from the workpiece to the

volume bf wheel orn away, P is the average power drawb by

the wheel in wattt, and %G aid %P give the in terms of

the standard comparison wheel. TFE stands for polytetra-

fluoroethylene.

427.368

32, 06 9 pi TABLE I

Fil ler Level of bond) Wheel No. G G Sic A TFE 18617 36.2 1390 100 100 35 0 0* 18577 33.0 950 91 68 25 0 18578 36.9 1085 102 78 37. 7 0 18580 74.5 1215 205 87 5 20 18641 96.6 1180 266 85 17. 7 20 18583 47.2 1350 130 97 20 18584 46.7 1095 129 78 10 15 18593 36.4 1380 100 99 20 15 0* *Compar ative Tests The above results show that the lubricant filler alone, at the 10% level, does not significantly improve the grinding efficiency, although the power is substantial-

ly reduced. Similarly the metal, alone, at the 15% level produces no significant improvement. But combined, at these levels, the efficiency is significantly improved and the power is significantly reduced. Best results, in this test, were shown with 20% silver and 10% polytetra-

fluoroethylene. The results thus show a synergistic effect when the two fillers are employed together in the bond, which would not be expected from the results obtained when only silver or only polytetrafluoroethylene are employed.

The test results given in Table II compare the results for wheels of various levels of fillers with a standard wheel like that of Table I, but containing a

slightly higher level of silicon carbide filler. The diamond was 150 grit, nickel coated, except for the diamond in the last two wheels which was copper coated in the amount of 11 427.368

32 069 fll weight per cent. The infeed was 2.5 mils on cemented tungsten

carbide workpieces. The carbide material and the grinding

conditions were the same for all wheels.

TABLE I.

Filler Level

Wheel No. G P LG SiC A& TFE

18664 47.6 1425 100 100 40 0 0*

18665 78.5 1120 165 79 10 20 18666 89.6 975 188 68 5 20 18667 87.7 1180 184 83 5 25 18668 95.2 1020 200 72 0 25 18669 147.5 1280 312 90 0 30 18670 108.5 1090 228 76 0 30 18671 91 1120 191 79 10 20

18672 75.3 960 158 67 5 20 *Comparative Test

The conclusions drawn from this test are that

the optimum silver content is over 30%, 15% TFE is better

than 10% from the standpoint of power drawn, and nickel

and copper coated diamond are similar in performance when

silver filler is employed.

The followinr results were performed on a dif-

ferent, somewhat more rigid machine than the previous

tests. Otherwise the test conditions were essentially the

same, but a different cemented tungsten carbide sample was

employed in the workpieces. This test evaluated silver con-

tents of 10 to 20% with no lubricants and silver contents

of 10 to 20% combined with 15 to 25% graphite.

12 427.368

32 069 i TABLE III

Filler Level Wheel No. P LG P %sic %Ag %Graphite 18713 (control) 10775 loo 1oo 40 0 0* 18714 79;0 146 70 15 10 18715 62 ?5 150 58 5 10 18716. 77 75 123 72 10 "15 18721 77 r5 112 72 0 20 18722 75 107, 89 10 30 10 0* 18723 975 73 68 25 15 o* i 18724 lOC0 85 93 20 20 0* *Comparative Test Table givees the results of a test wherein silver contents 30 to 50%, with a solid film lubricant filler, were compared to a standard wheel and to a wheel containing graphite only. As in the previous tests, the wheels were all-run on the same sample of carbide and un-

der the same test oonditions. The infeed was 2.0 mil. The diamond was present in the amount of 11% by volume in the

wheels, instead of 17% as in the previous tests, and was

nickel clad, except for the diamond in wheel 84 which was

copper clad.

TABLE IV Filler Levels Wheel No.: G P %G %P Ag TFE Graphite SiC

47 (control) 17.4 1025 100 100 0 0 0 51 22.6 765 130 75 0 10 20 82 63.6 1135 365 11 40 10 0 0 83 79.8 1190 459 116 50 10 0" 0 84 67.8 925 390 '90 50 0 1i 0 0 44.0 840 253 82 30 0 20 0 86 43.1 840 248 82 40 0 20 0 *Comparative Test 421.368

32.069 n7 At 2.5 mil. infeed the relative results were

similar except that wheels 84 and 86 were unsatisfactory

under the higher infeed in that they loaded, chipped, and

drew high power. Wheel 82 appeared best for general use.

In the following test silver filler was compared

with silver coated copper. The wheels all contained 11%

by volume of diamond, and the diamond was nickel clad.

The unit infeed was 2.0 mils. The results were as follows:

TABLE V

Wheel No. G P %G %P A_ TFE Ag on Cu SiC

Control 17.8 875 100 100 0 0 0

28.9 825 162 94 50 15 0 0 950 29.6 800 166 91 45 15 0 0 951

956 29.2 750 164 86 0 15 45 0

Although this test showed that Ag and Ag coated

Cu are equivalent, more sensitive testing has indicated

the superiority of Ag over Ag coated Cu.

In the grinding of high-speed steels, wheels em-

ploying metal clad 150 grit cubic boron nitride were com-

pared with various filler contents. The unit infeed was

mils. and the wheels were the same shape and dimensions

as in the tests reported above.

The filler content of the wheels was as follows:

TABLE VI

Wheel Fo SiC Al203 A TFE Graphite

20 20- 0 0 0 Com 81B 35 0 0 0 0 par a- tiv e 82B 15 0 0 0 20 Tes ts

83B 28 0 0 0

w f 0 0 40 0 427.368 14.

32,069I The test results on M3, M43, and Tl5 high-speed

steel workpieces were as follows:

TABLE VII

Wheel M3~ 43 Tl _Mo. VP 0G-P G 0 P 50 AP G P %G %T

21.8 625 100 100 39.2 500 100 100 3.0 675 100 100

81B 32.8 5o00 10 83 15. 1 475 39 995 5.4 450 180 78 821 22.7 425 1i 71 19.6 350 50 o70 8.8 400 293

8.3B 38.7 425 177 71 32.7 400 83 80 12.1 450 403 78

58.6 i50 269 75 57.3 .425 1W7 85 22.9 425" 765 74

Based on the most reproduceable testing methods,

gained from the above tests, a variety of metal and solid

lubricant combinations were employed. Grinding efficiencies

of at least 40% above the standard were achieved with the

metal silver, copper, or silver coated copper with various

fillers, as listed below in table VIII and grinding ef-

ficiencies lower than the standard control wheel were

achieved with nickel, molybdenum, iron, tin, and aluminum

fillers.

427.368

32069 71 TABLE VIII

Wheel No. G %G P Metal Lubricant

19083 42 410 1200 120 Ag Bn

19076 39.5 383 1150 115 Ag. TFE

19086 35.9 348 1250 125 Ag WS2

19229 30.8 299 1350 135 Ag BN Nickel Coated

19089 30.5 296 1400 140 Ag Graphite

19085 27.9 271 110 115 Ag MoS 2

19088 27.8 270 1150 115 Ag Polyethylene

19084 26.3 255 1350 135 Ag NbSe 2

19087 20.2 196 1100 110 Ag WSe 2

19077 1~.4 140 1150 115 Ca TFE

19231 11.9 116 1000 100 Mo MoS 2

19257 10.7 104 850 85 Graphite

19252 10.3 104 1000 100 Control Wheel 35% SiC

19078 9.3 90 950 95 Ni TFE

19082 7.5 73 800 80 Mo TFE

19228 6.1 62 850 85 Mo TFE

19081 5.8 56 850 85 Fe TFE

19079 5.4 52 900 90 Al TFE

19080 4.4 43 800 80 Sn TFE 19230 3.2 31 750 75 Al TFE

A large variety of organio fillers, in the form

of a finely divided powder were prepared and tested at the

and 15% levels in the bond, in combination with 40% of

fine silver in the bond. The following gave improvement in

G of from 2-1/2 to 5 or more times that of a similar wheel

omitting the organic filler, but including 40% silver:

styrene butadiene ("56B" Pliolite from Goodyear Company, from

styrene by weight and 15% butadiene): acrylonitrile-but-

.16 427.368

32, 0 9 [7 adiene-styrene (Lustran 1-410-1000 supplied by Monsanto)

styrene-acrylonitrile (Lustran A-21-2020 from Monsanto,

71% styrene, 21% acrylonitrile); polyurethane (Estane Type

58105 from Goodrich): polyvinil chloride (Geon 92 from

Goodrich) acetal (Delirin from DuPont): polysulfone (Union

Carbide -TXRP 2044); polyurethane (made from 83% Adiprene

L-167-, and -17% by -weight of methylenebis (2 chloro-

aniline), Adiprebe being a -liquid difiabcyanate react-ion ro-

duct with a polyalkylene ether glycol, available from DuPont):

ny on (DuPont Zytel), and polycarbonate (General Eleotfio

Lexan) i'

To show the improvement obtained using non-metal

clad diamond phenolic bonded wheels were compared in dry.

carbide grinding as follows, employing uncoated diamond:

Filler G Power

Control Wheel 35% SiC 21 1200 watts

Test Wheel 40% Ag., 10% PTFE 97 1100 watts

Thus, in comparing with wheels employing un-

coated diamond the invention wheel is almost S times as

efficienit, with a lower power draw.

Although instances have been found of solid pow-

dered organic polymers, which do not improve wheel performance,

that is do not function as solid -lubricants, when employed

according to this invention, this selection of an operative

polymer-from one of those disclosed generically or specifi-

cally herein, or an obvious equivalent., is a simple matter

'f6rohe -skilled in the art, involving at most, in the case

of equivalent materials, the manufacture and testing of a

wheel containing such material.

17 427.368

32 069 71 Throughout the specification the volume of

fillers in he bond means the parts of filler per hundred

parts of total bond solids, including fillers, but not

including abrasive particles and not including the metal

cladding on the abrasive.

427.368

Claims (1)

31 06 9 f7 The.claims defining the invention are as follows:

1. An abrasive tool in which abrasive grits are bonded' by an organic .polymer bond, the abrasive grits are'diamohd.or

metal clad cubic boron nitride particles or both, and the bond

contains from 10 to 60%, by volume, of finely divided

metal filler which is silver, silver coated copper, or copper,

or a combination thereof, in the presence of from 5 to

of a particulate dry film lubricant filler.

2. An abrasive tool according to claim 1, in which

the metal filler is present in an amount of from 30 to

by volume, and the dry film lubricant filler is present in

an amount of from 10 to 20%, by volume.

3. An-abrasive tool according to either of claims

1 and 2, in which the dry film lubrican n inorgani

crystalline material having a layer-lattice structure in

which the bonding between atoms in an individual layer is

by strong covalent or ionic forces, while the bonding force

between layers is by relatively weak Van der Waal's forces

or an organic polymer.

4. An abrasive tool accordin to any one of claims

1 to 3, in which the dry film lubricant/is MoS WS 2 WSe 2 2

NbSe 2 graphite, fluorinated graphite, hexagonal boron nitride,

polytetrafluoroethylene, polyethylene, polychlortrifluoro-

ethylene, fluorinated ethylene-propylene, nylon, polycarbonate,

polysulfone, styrene-butadiene, acrylonitrile-butadiene-styrene, 427.368

3 q 069 r7i styrene-acrylonitrile, polyurethane, polyvinylehioride,

pol-yformaldehyde, or polyester polymers.

-An abrasive tool according to any one of claims

1 to substantially as hereinbefore described in the Examples.

DATED this FOURTH day of AUGUST. 1971

NORTON COMPANY

Patent Attorneys for the Applicant SPRUSON FERGUSON

-4.27.369&

3Z~ 06 9 i

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F710. 2

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F7B~.3 224 427.368