US 2270209 A
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Description (OCR text may contain errors)
Jan 13, 1942. E. VAN DER. PYL
ABRASIVE ARTICLE Filed May 20. 1959 1.2 is 27, 2 a 0 1 4/0729 EDWARD VAN DER PYL as I Patented? .Fan l3, i942 ABRASWIE ARTICLE Edward Van der lE'yl, Holden, Mass.,'assignor to Norton Company, Worcester, Mam, a corporation of husett Application May 20, 1939, Serial No. 274,786
I satisfactory combination of bond and backing for wheel to be manufactured with a pressed cold rolled steel center, securing good adhesion'between the abrasive portion and the center. Another object of the invention is to provide a light weight pressed metal diamond grinding wheel. Another object of the invention is to provide a diamond grinding tool of great strength and hardness capable of'withstanding the most severe usage. Other objects will be in part obvious or in part pointed out hereinafter.
The invention accordingly consists in the features of construction, combinations of elements, arrangements of parts, and in the several steps and relation and order of each of said steps to one or more of the others thereof, all as will be illustratively' described herein, and the scope of the application of which will be indicated in the following claims.
In the accompanying drawing illustrating two of many possible embodiments of the mechanical features of this invention,
Figure l is an axial sectional view of a mold which is filled but not closed;
Figure 2 is a view similar to Figure 1, showing the mold closed;
Figure 3 is a face view of the completed wheel made in the mold of Figures 1 and 2;
Figure 4 is an axial sectional view of another mold for a slightly difi'erent wheel, the mold being open;
Figure 5 is a view similar to Figure 4, showing the mold closed Figure 6 is a face view of the grinding wheel produced in the mold of Figures 4 and 5;
figure 7 is an axial sectional view of the wheel of Figure 6 mounted on a spindle.
Referring first to Figure 1, I provide a pressed ferrous metal back it), preferably made of cold rolled steel. This is a cup-shaped wheel having an internal annular flange ll, providing a good cylindrical mounting or bearing surface for the wheel, having a radial portion M in which may be located countersunk holes it, having conical portions I l and i5, the former on the inside and the latter on the outside of the radial portion l2;
having a radial portion i6 upon which the abrasive is to be mounted, and having an outer cylindrical flange IT. The foregoing constitutes a very rigid but light structure which can be pro duced at slight cost. It is rigid because any bending stresses to bend its radial surfaces out of radial planes are resisted by the flange M, the conical portions id and i5, and theflange ll. Stresses tending to collapse this wheel are resisted by reason of the fact that it is practically continuous metal from the central hole to the periphery. Nevertheless this shape can readily be made by die pressing operations so that the article is relatively inexpensive and, furthermore, great uniformity of size and shape is readily attainable. Onto the outer surface of the radial portion I6 I mold an abrasive mix 26, as will now be described in detail.
Still referring to Figure 1, I provide a mold platen 2!, a mold ring 22, a mold bottom plate 23, an inside mold top plate 26, an outside mold top plate 25, a conforming plate 26, a conforming plate 27, and a mold plug 28. All of these parts excepting the platen 2i and the plug 28 are annuluses.
The mold is assembled as shown in Figure l,
placed in position. A mixture of abrasive and bond 20 to be hereinafter described is placed in the cavity between the top plate 26 and the mold ring 22, and a soft aluminum ring 29 is then placed upon the mixture 20. mold plate 25 is then placed in position and the mold is closed to the position shown in Figure 2. The diamonds project from the pressed abrasive. 30 since they are forced-slightly into the aluminum ring 29. The mold 'may be closed in a suitable hydraulic press. Desirably all parts of. the mold are ground to accurate dimensions and smooth surfaces and with a mold so constructed, the mold can be readily closed, reaching a pressure of four thousand pounds to the square inch without any danger of forcing the material 20 between the plates 2 and 26. As the final pressure is applied, the upper platen of the hydraulic press contacts the top plate 24, holding the various parts together firmly. During the pressing operation, the conforming plate 2? supports the thrust against the radial portion it, so
The outer top' there is no chance of the metal back id being collapsed. It is preferable to sandizolast or otherwise roughen the outer surface of the radial por= tion it prior to the pressing operation in order to achieve a good union.
Considering now the nature of the abrasive and bond, as heretofore indicated I use diamonds but so far as certain features of the invention are concerned, other abrasives might be used. However, since the ultimate abrasive is very high in grade hardness, a hard abrasive is also desired and a composite structure as described herein has particular utility as embodied in a diamond grinding wheel. Although a wide range of ratio of abrasive to bond may be adopted. as an illustrative example of a volume percentage which represents the best proportions now known to me, I mention 25% by volume of abrasive with porosity limited to not more than 2%.
For bonding diamonds to a ferrous metal back, particularly a steel back as herein described, E use a hard metal bond obtained by pressing powdered metal and thereafter sintering.
Following the mixing of the diamonds with the bond, which is in comminuted form and con sists of a mixture of powders, and following the I pressing operation described, the article is first stripped from the mold and then placed in a furnace and heated. The furnace is provided with hydrogen flame curtains at its entrance and exit ends in order to exclude oxygen therefrom. Under such conditions the diamonds are not burned, the metal bond is not oxidized, and the back is uninjured.
The final article shown in Figure 3 is rigid and z the abrasive portion 3% is attached so firmly to the back It that it cannot be dislodged therefrom under ordinary conditions of use and even abuse. The abrasive is hard and the bond is also so hard that wear is reduced to a minimum; wherefor the wheel is particularly advantageous for grinding cemented carbides and other very.
it may be used for hard materials. In fact, faceting diamonds themselves and also other gem stones. Of course, the type of finish obtained will depend upon the grit size of the diamonds used, and I prefer fine grit sizes of the order of from 100 to 600 grit size and even finer. The wheel is sharpcuttlng from the start by reason of the fact that the diamonds project slightly from the abrasive portion" on account of the use of the aluminum ring 29.
I am not. limited to use of any particular bond I providedit is a hard'brittle ferrous metal bond.
I may use electrolytic iron particles, as described in the patent to Gauthier No. 1,625,463, with added elements to make the bond hard and brittle. the bond (not described by Gauthier), heating the pressed diamond-iron mixture to around 1000 C. upwards in a furnace from which oxygen is excluded. In order to make this ferrous metal bond sufliciently hard, I add suitable amounts of comminuted carbon to produce a cementlte or illustrative examples pearlite. The following are thereof: I
Example 1 Percent Fe 94 C 3. 5 Si 3. 5
Example 2 Percent Fe 97 C 3 amazon Example 3 Percent Fe 95 C a P 2 In each of the formulae, the ferrous metal consists of pearlite and cementite. Example 1 is the formula for gray cast iron. Example 2 is the formula for white cast iron. Example 3 is a special formula. which I term phosphorous iron.
Preferably my bond, while very hard, is also somewhat brittle or friable and Examples 1, 2 and S are examples of such bonds. The sintering temperature employed is sufllciently high to cause the formation of true pearlite and cementite in the bond, at least so far as I am able to determine. At all events, the bond has the char acteristics indicated, namely itis hard, it is also pacity of making iron very brittle and friable.
. but in figuring the proportion of abrasive to- Howevento obtain a hard abrasive, I sinter Ordinarily precautions are taken to remove phosphorus from ferrous metals and alloys. Phosphorus can be .used in any amount short of that point where the iron completely lacks strength, that is to say; it can be used up to about 5% of the total bond content. 'In the above examples, the proportions are by weight bond,- the volume content is referred to.
I have given a range of from 1000" C. upwards. However, it is preferable to use somewhat lower temperatures and some results can be obtained by heating to 10001 C. provided the mixture is maintained at this temperature for a longer time, say half an hour or more. When carbon additions are used, it is preferred to use an inert gas in the furnace, such as helium. But nitrogen may also be used with satisfactory results in most cases.
I can also make wheels having a peripheral diamond abrasive portion, as illustrated in Figures 4 to '1 inclusive. As shown in Figure 4,
. mold bottom plate 40 inside of a mold ring ll and top mold plates 42 and 43 are provided in the upper part inside of the mold ring 4|. The mold is completed by a mold platen H and a plug 4, and spacers 48 are used while filling, the mold. The exact shapes of all these parts I will not describe because the same are adequately shown in the drawing. The mold is shown filled, with abrasive material 20a in Figure 4 and it is then taken to a hydraulic press, the spacers 40 are removed, and the mold is then closed to the position shown in Figure 5. This compacts the material 20a against the cylindrical flange 31- and thereafter the article is heat treated, as already described. It will be noted that the flange 31 extends beyond the abrasive portion "a in Figure 5; this flange may be turned over inwardly. as
,pleted wheel is shown in Figures 8 and 7, it being shown mounted on a. spindle I! in Figure .7, being held in place by a collar 48 and a nut 49 screwed onto a reduced portion 50 of the spindle 41. However, countersunk holes like the holes I 3 might be provided for mounting.
It will thus be seen that there has been provided by this invention an article and a method in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to-be understood that all matter hereinbefore set forth or shown in the accompanying drawing is to be interpreted as illustrative and not in a limiting sense.
I claim: a
1. An abrasive article comprising a preformed relatively soft ferrous metal backing and an abrasive portion comprising a sintered hard brittle ferrous metal bond and diamond abrasive particles, the whole being merely sintered together into an integral piece.
2. An abrasive article comprising a relatively soft pressed steel backing and an abrasive portion integrally sintered thereto made out of diamonds bonded with a hard brittle ferrous metal bond sintered to a unitary mass.
3. An abrasive article comprising a relatively soft pressed metal backing made out of cold rolled steel and a diamond abrasive portion comprising diamonds embedded in a hardbrittle ferrous metal bond integrally attached to the cold rolled steel, the metal bond being sintered and the abrasive portion being sintered to the metal backing.
EDWARD VAN nan PYL.