US2085137A - Abrasive article - Google Patents

Description

Patented June 29, 1937 UNITED STATES PATENT OFFICE 2,085,137 ABRASIVE ARTICLE No Drawing. Application December 8, 1933,

Serial N0. 701,532

, 9 Claims. (01. 51-278 This invention relates to an imprdvement 1nthemanuiacture of abrasive articles and consistsin producing such articles having a' porous 'or'cellular structure.- 5 Abrasive articles, for example, grinding wheels, are, in general, made from graded abrasive grains mixed with bonding materials. This mixture is moistened with water, formed into the desired shape, dried and burned in a kiln. It 10 has been the practice to'control the porosity of the article within a limited range of variation, by varying the grain size of the abrasive material, by varying the percentage of bond used, by the pressure applied during the forming, by the 16 addition of wood fl6ur which. burns out leaving pore spaces, or by other'changes.

The present invention contemplates close control of the porosity and cell structure of finished abrasive articles by adding to the mix of granulated abrasive material and bond, granulated, oxidizable, non-compressible material which will burn away'during'the firing of the article inthe kiln leaving pores of a number and character the oxidiz'able, non-compressible material used.

An object of this invention, therefore, is to provide amethod of making abrasive articles of a predetermined porosity and having pores or interstices of a predetermined size.

Anotherobject is to provide a mix from which abrasive articles having the desired characteristics as to porosity and cell structure may be made.

Other objects of the invention will be apparent from the following description and appended claims.

The granulated material added to the mix as set forth above may be any suitable material which, will not be compressed in the mix by the pressure used to form the abrasive articles and which will-burn away during the firing .of the articles in the kiln for example coke.

The granulated coke used may be mulled or not mulled as found desirable in use. If used directly as crushed and graded it will have very irregular shapes with many sharp points and edges. It mulled, e. g.,- put through a slow revolving ball mill, the sharp corners and edges will be worn ofi and the granules will be more rounded in shape and contour.

Any coke or related material, such as charcoal, may be used in carrying out the present invention, but for best results petroleum coke will be found desirable since it is relatively free from ash which might alter the character of the bond. Depending upon the cellular structure desired depending on the relative quantity and size of in the finished abrasive article the size of the granular coke may be smaller than, larger than,

I or equal to, that of the granular abrasive mate- Y rial used in the mix. For grinding many mate- 'rials it may be necessary to have a highly porous articlehaving a great numberof pores or interstices substantially equal to, or smaller than, the abrasive grains. To produce such an article it is desirable to use in the mix coke grains smaller than or substantially equal to the abrasive grains. in size. -'I'his does not mean, however, that the size of the pores in the finished article is equal to the size of the coke grains used, as the size of the pores is aiiected by other factors such as the nature and quantity oi the bond used and the degree of compression reached in forming the article. By controlling these factors as well as the size of the coke grains the cellular structure of the finished article may be determined in ad:

vance.

When coke smaller than, or substantially the same size as the abrasive material is used, each abrasive grain in the finished article will contact with practically all the adjacent grains as in the present non-porous articles, except that at intervals varying in frequency as the degree of porosity desired, several grains will be so spaced as to provide a void or interstice larger, than those formed by the vitrification of the bond but not substantially larger than each of the adjacent grains of abrasive.

For grinding other material it may' be-necessary to have an abrasive article wherein there are relatively large pores, compared to the size of the abrasive grains. The pores of such an article may be many times the size of the abrasive grains so that the walls of the pores are formed of a large number of abrasive grains. For the production of such articles it is necessary to add to the mix coke particles substantially equal to or larger than the abrasive grains. For. example, to produce an abrasive article having pores many times the size of the abrasive grains it is necessary to use coke grainsmany times the size of the abrasive particles.

When coke is granulated the particles or granules formed takevery irregular and diiierent shapes. When these particles are mixed in the abrasive article and subsequently burned out during the firing of the article the voids or interstices will in general take on substantially the shape of the particles of coke previously located therein. r

The proportion of granulated coke used in the mix is determined by the degree of porosity de- 30 abrasive grams:

sired in the finished product. The amount may be as large as is practicable to produce a porous article which is alsq strong enough for the use for which it is intended. In preparing articles for most purposes the proportion of coke used is 5 to 30 percent by weight of the abrasive and bond used.

As an illustration of the invention a mix having the following formula may be prepared and used to produce a porous abrasive article:

' Parts by weight Abrasive grain (80 grit) 85 Vitreous bond (through 109) Calcined coke (40 on 74) 15 Temporary binder 2 Parts by weight Abrasive grain (40 grit) 85 Vitreous bond (through 109) 15 Calcined coke (through 40 on 74) Temporary binder 2 To produce an article having pores smaller than the abrasive grains the following formula could be used:

' Parts by weight Abrasive grain (40 grit) 85 Vitreous bond (through 109) 15 Calcined coke (through 74 on 150) 20 Temporary binder 2 The following formula could be used to produce an article having pores many times the size of the abrasive grains used:

Parts by weight Abrasive grain (150 grit) a0 Vitreous bond (through 109) 20 Calcined coke (through 40 on 74) 20 Temporary binder.. 2

. By means of the .present invention it is possible to economically produce abrasive article's having any practicable number and shape of cells. Articles which are light in weight and yet possess sufiicient' internal strength may be so produced. Because the use of coke increases the porosity and tends to spread out the abrasive grains 9.

relatively large proportion of bond may be used.

maintaining or increasing the internal strength, without increasing the tendency of the article to glaze in use. The use of coke or similar material is advantageous in that it is not compressed by the pressure used to form the articles so that the form to which the mix is pressed will not swell or spring back or otherwise lose its shape when pressure is released. Because the coke or other similar material will not compress and can be accurately graded in advance the cell size can be determined in advance and produced without particularly'skillful handling. This method is easier and more accurate than, .for example, a method employing gas bubbles to produce the voids or cells. Furthermore, a mixture employing coke is stable and does not have to be used immediately. Also, when coke is used to form the cells the cell walls tend to be more solid and less' porous while by the gas method the cell walls tend to be porous due to minute gas bubbles contained therein.

It will be understood that the above description is not intended to limit the scope of the invention herein but that the invention may be otherwise practiced or embodied without departing from the scope of the claims.

We claim: a

1. A mix for making abrasive articles which containsgranular abrasive material, bond, and granulated coke.

2. A mix for making abrasive articles which comprises granular abrasive material and granulated coke having an average particle size at least as great as that of the abrasive material.

3. A mix for making abrasive articles which comprises granular abrasive material and granulated coke having an average particle size smaller than that of the abrasive material.

4. A mix for making abrasive articles which consists of granular abrasive material, a vitreous bond, a temporary bond, water, and granulated coke.

5. A mix for making abrasive articles which comprises granular abrasive material and granulated coke having an average particle size greater than that of the abrasive material.

6. In the process of making a bonded abrasive article the steps of adding to the mix granulated coke, pressing the mixture to the desired shape, and effecting removal of the coke granules by, firing the shaped article.

7. The process of making a bonded abrasive 7 article which comprises intimately mixing granular abrasive material, suitable bondingmaterial, and granulated coke having an average particle size at least equal tothat of the'abrasive material, pressing the mixture to the desired shape, and firing the same to burn away the coke granules and vitrify the bond.

8. The process of making a bonded abrasive article which comprises intimately mixing granular abrasive material, suitable bonding material, and granulated coke, having an average particle size several times as great as that of the abrasive material, pressing the mixture to the desired shape, and firing the same to burn away the said oxidizable material and vitrify'the bond.

9. The process of making'a bonded abrasive article which comprises intimately mixing granular abrasive material, suitable bonding material, and granulated coke having an average particle size smaller than that of the abrasive material, pressing themixture to the desired shape, and firing the same to burn away the said granulated coke and vitrify the bond.

CHARLES E. WOODDELL. JOHN F. BARNES.