US 3249410 A
Description (OCR text may contain errors)
y 3, 1966 M. P. LORENZO ETAL 3,249,410
PROCESS OF MAKING METAL BONDED DIAMOND ABRASIVE ARTICLES Filed Sept. 28, 1962 2 Sheets-Sheet 1 MIXING EXTRUSION SINTERING ROLLING, HOT
- ROLLING, COLD SHAPING CARBURIZING MI'VENTOR fiwffiwwfiizfi W .23. v -Q- y 3, 1966 M. P. LORENZO ETAL 3, 9, 0
PROCESS OF MAKING METAL BONDED DIAMOND ABRASIVE ARTICLES Filed Sept. 28, 1962 2 Sheets-Sheet 2 United States Patent PROCESS OF MAKING METAL BONDED DIAMOND ABRASIVE ARTICLES Manuel P. Lorenzo, Royersford, and Jesse F. I-Iuusberger,
Pottstown, Pa., assiguors to A. P. de Sanno & Son, Incorporated, 'Phoen'ixville, Pa., a corporation of Pennsylvania Filed Sept. 28, 1962, Ser. No. 226,934
Claims. (Cl. 51-293) The present invention relates to the forming of abrasive objects which have homogeneous or uniform distribution of abrasive and may be used for example as grinding wheels, cutoff wheels, circular saws, band saws, laps or homes, or can be mounted by brazing or cementing to form tool bits, tool points, cutting edges or abrasive facings.
A purpose of the invention is to more uniformly distribute abrasive in an abrasive object.
A further purpose is to provide a tougher, stronger and more impact-resisting abrasive object for use in various grinding applications. v
A further purpose is to incorpoarte diamonds in a tool which will be stronger, harder, and longer-lived.
Further purposes appear in the specification and in the claims.
In the drawings we have chosen to illustrate a few only of the numerous embodiments of the invention and a few only of the steps which are performed in the method.
FIGURE 1 is a flow chart of a procedure which may be followed in the method of the invention in certain of its embodiments.
FIGURE 2 is a diagrammatic central vertical section showing the initial extrusion of the abrasive strip.
FIGURE 3 is a front elevation of FIGURE 2.
FIGURE 4 shows the blanking of the abrasive strip into abrasive objects.
'FIGURE '5 is an axial section of an abrasive wheel produced according to the invention.
FIGURE 6 is an axial section of a modified form of abrasive wheel produced according to the invention.
Abrasive objects such as grinding wheels are commonly produced by means of a vitreous bond or by means of a resin bond.
The present invention is concerned with incorporating abrasive particles in powder metal compacts which are suitable for grinding wheels, cutofi wheels, circular saws, band saws, laps, hones, or tool bits, tool points, cutting edges or abrasive facings.
The invention is concerned particularly with making such abrasve articles which will be relatively strong, hard, and tough and can undergo severe service including impact even at low temperatures.
The invention is particularly concerned with the mounting of such valuable abrasive materials as diamond particles or dust in an abrasive object in such a form that the object will be long-lived and will permit economical use of the diamonds.
In accordance with the invention, metallic particles, preferably iron powder, but permissibly a blend of iron powder with other powders such as nickel powder, copper powder, low carbon steel powder or the like, or consisting entirely! of low carbon steel powder, nickel powder, bronze powder, copper powder or the like, will be used as the base mixture.
Into the metal particles or blend of metal particles is introduced. abrasive particles. In many cases the abrasive particles will be diamond powder, although in other cases other abrasives will be used such as aluminum oxide, silicon carbide, boron carbide or tungsten carbide.
The quantity of abrasive particles by weight in the total mixture will vary, and may be insome cases as little 3,249,410 Patented May .3, 1966 as 0.1% and in other cases as high-as.20%.' In the case of abrasives other than diamonds, 2 to 15% represent good practice.
In the case of diamonds the abrasive mixture should contain sufiicient diamonds to introduce approximately 36 carats of diamonds per cubic inch of the abrasive object. A suitable composition in the preferred range will be about 18 to 72 carats of diamonds per cubic inch.
The metal particles should be below mesh per linear inch in size, preferably below mesh, although coarser particles can be used, as coarse as 60 mesh or even as coarse as 20 mesh. The abrasive particles will preferably be within the same size range as the metal particles.
Any suitable technique well known in the art may be used to improve bonding to the abrasive particles and this forms no part of the present invention. Thus, in the case of diamonds the surface of the diamonds may have deposited thereon a metal coating such as cobalt or tungsten using well known techniques prior to incorporation with the metal particles, This, however, is not necessary.
The mixture may suitably contain a lubricant as well known in the art such as a fraction of apercent of soap to promote extrusion. This feature forms no part of the present invention.
'The mixture after suitable blending to obtain a homogeneous blend is then extruded continuously into a strip. We illustrate in FIGURE 2 a mixture 20 of metal particles and abrasive particles in a hopper 21 which feeds downward between extrusion rolls 22 to form continuously a green strip 23 which may be of the order of 0.010 inch thick, or 0.015 inch thick, although in some cases it may be much thicker, of the order of A inch or even inch.
A suitable extrusion mill as well known in the art is the Bliss mill.
The green strip 23 after extrusion isnext sintered using any well known sintering technique for the particular powder metal or alloy. Where .the powder metal or alloy is iron or primarily iron, sintering may take place for example at 1900 F. in a furnace containing an atmosphere which excludes oxygen, the suitable atmosphere preferably being hydrogen, although cracked ammonia may be used.
The resulting sintered product is substantially dead soft. The next step in many cases is to form the product further so as to'irnprove its properties and desirably also render it more suitable for use.
In the preferred technique the sintered strip is hot rolled suitably at a temperature of 1850 F. to 2200 F.
The hot rolling is followed by cold rolling in the preferred embodiment. The result is to improve the toughness and hardness and strength of the product and also to densify it. The amount of reduction need not be great, for example, of the order of 5 to 15% in hot rolling and similarly in cold rolling.
A product of the hot rolling or of the hot rolling and cold rolling, or of the cold rolling when only cold rolling is used, or the product of the sintering where only sintering is used,'is next fabricated into useable abrasive objects. In FIGURE 4 we show the strip 23'being blanked into grinding wheels 24 and in FIGURE 5 one of the grinding wheels 24 is shown having a center opening 25 for the spindle and having a generally uniform wall thickness.
In some cases the grinding wheel contour is not flat as shown in FIGURE 5, but may be dished or otherwise shaped, and for this purpose the blanks of FIGURE 4 are cupped into the dished grinding wheel 24' shown in FIGURE 6, which has a flange 26 intended to do the bones and the Where iron or an iron alloy is used as the powdered metal, it is often desirable to increase the strength and hardness of the metallic matrix by carburizing. The finished object, as shown in FIGURES or 6, is suitably placed in a carburizing furnace such as a gas carburizing furnace maintaining a reducing atmosphere and suitably carburizing at a temperature between 1500 F. and 1750 F., the time of carburizing depending of course on the dimensions of the object and the carbon content desired. Normally, carbon contents in the range between 0.25 and 1.25% will be desired in the case, the degree of penetration into the core being controlled by time and temperature as well known in the art.
Pack carburizing can also be used.
Where the abrasive is diamond powder and where iron or steel is the base of the powder metallurgy matrix, care should be taken that the carburizing does not convert the diamonds into carbon. For this purpose the following precautions should be taken:
(1) A lower temperature should be used rather than a higher temperature.
(2) The carburizing condition should be reducing.
(3) The time should be kept at a minimum.
EXAMPLE I I N0. 50 concentration strip A mixture was made of the following components in percentage by weight:
' Percent Diamond powder 5.3 Metal powder 94.7
The diamonds were standard industrial diamonds of sizes finer than 100 mesh per linear inch. The metal powder consisted of the following ingredients in percentage by weight and of a size between 100 and 120 mesh per linear inch:
. Percent Iron 80 Nickel 20 EXAMPLE II No. 75 concentration strip The procedure of Example I was carried out except for the following changes:
Instead of diamonds the abrasive was aluminum oxide powder through 100 mesh per linear inch. The mixturre of abrasive and metal powder was in the following concentration by weight:
Percent Aluminum oxide 10.8 Metal powder 89.1
The metal powder composition was as in Example I. After sintering and annealing the strip was carburized in wet illuminating gas at 1650" F. for ten hours.
The finished strip was used as an abrasive wheel and was found to cut very effectively.
EXAMPLE III The procedure of Example I was carried out except that the finished strip is hot rolled at 1900 F. to obtain a reduction of Some increase in compactness is obtained by hot rolling.
4 EXAMPLE IV The procedure of Example III is carried out and hot rolling is followed by 5% reduction by cold rolling at room temperature. Slight increase in strength results.
EXAMPLE V The procedure of Example I is carried out except that the metal powder has the following composition in percentage by weight and is of a mesh size through mesh:
Percent Carbon 1.30 Molybdenum 5.90 Tungsten 5.61 Vanadium 3.75
Sulphur Trace Silicon Trace Phosphorus Trace Balance, iron.
The product has somewhat greater strength than the product of Example I.
EXAMPLE v1 The procedure of Example V is carried out and in addition the strip after sintering and annealing is hot rolled at a temperature between 1900 and 2050 F. to reduce 10%. The strip is then cold rolled at room temperature to reduce 10%. The strip is effectively used for grinding and is appreciably strengthened.
EXAMPLE VII The procedure of Example H is carried out except that the metal powder composition is as follows in percentage by weight:
The metal powder is through 130 mesh per linear inch.
An exceptionally strong and ductile strip is obtained which is effectively used for grinding wheels.
Various variations of the above examples may be employed, including changes in the abrasive. As far as diamonds .are concerned any of the conventional powder grades of industrial diamonds can be used, for example those available from Englehard-Hanovia.
Metal powders of both finer and coarser sizes can be used. Good results are obtained using metal powders of 325 mesh or liner.
If desired lubricants can be added to the powders prior to extrusion. Suitable lubricants are stearic acid and zinc s-tearate. They aid in compacting the metal powders. The concentration of lubricant may be between 0.001% and 3% by weight.
In view of our invention and disclosure, variations and modifications to meet individual whim or particular need will doubtless become evidentto others skilled in the art, to obtain all or part of the benefits of our invention, without copying the Process and Method and we, therefore, claim all such insofar as they fall within the reasonable spirit and scope of our claims.
Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:
11. A method for the continuous production of metal sheet articles having an abrasive incorporated throughout, which comprises mixing together abrasive particles with sinterable metal powder to form a homogeneous blend, extruding the blend consisting essentially of the metal powder and the abrasive particles into a self-sup- 5 porting strip having abrasive particles distributed completely throughout the strip, and sintering the strip in a non-oxidizing atmosphere to obtain a metal bonded abrasive article.
2. The method of claim 1 which includes the step of shaping the metal sheet into an abrasive article.
3. The method of claim 1 which comprises subsequent- 1y hot rolling the strip.
4. The method of claim 1 which comprises cold rolling the strip after hot rolling the strip.
5. A method of producing metal sheets having an abrasive incorporated throughout, which comprises mixing together diamond particles with a sinterable iron powder to form a homogeneous blend, extruding the blend consisting essentially of diamond particles and iron particles into a self-supporting strip having abrasive particles distributed completely throughout the strip, sintering the strip in an atmosphere which excludes oxygen to obtain an iron bonded abrasive article and then carburizing the strip in a reducing atmosphere which protects the diamonds.
References Cited by the Examiner OTHER REFERENCES Treatise on Powder Metallurgy, Geotzel, 1950, vol. II, pages 172 and 173.
ALEXANDER H. BRODMERKEL, Primary Examiner.
LESLIE H. GASTON, Examiner.
D. J. ARNOLD, Assistant Examiner.