Title of Invention

A PROCESS OF MANUFACTURE OF ABRASIVE GRAINS OF ENHANCED ELECTRICAL PROJECTABILITY

Abstract

Abstract A process of manufacture of abrasive grains of enhanced electrical projectability comprising the steps of wetting the said grams with phosphoric add (up to 7% by weight of the said grain) in a suitable mixingh device; preparing a blend of substances selected from aluminous compounds, refractory oxides, electric insulators, rare earths and of fine particles of electrical property altering material selected from electrically conductive material such as SiC2 Iron Oxide and metel, powders in the ratio of 30 : 70 to 70 : 30 ; adding the blend to, and inking it with the wetted grains; and firing the same between 300 deg. C and 850 deg, C for up to 2 hours, before sieving the grains to break down limps, if any.

Full Text

This invention relates to aprocess of manufacture of abrasive grains of enhanced electrical projectability. The said process altera the surface electrical properties of abraidve grains for inp-oving their projectsdility in an electrical field. The use of magnesium chloride on zirconia abrasive graiss is known to the art. However, since magnesium chloride is hygroscopic, processing these grains is a tedious job. Besides, this process can be used only for increasing projectability characteristics, Our co-pending application under Nos.2171 MAS 97 and 2173 MAS 91 relate to aprocess of manufacture of abrasive grains for providing a uniform, hard surface thereon and aprocess of manufacture of abrasive grains at ambient temperature for providing a uniform hard surface thereon. The process proposed herein however does not use hygroscopic material. It can also be used to decrese projectabilily of very active grains such as coarse SiC. In coated abrasive manufacture electrostatic projection is used for uniform and sharp anchoring of the abrasive on the backing. Abrasives are passed on a belt moving just below the backing, in an electrostatic field. Some grains get coated on the backing and the grains remaining on the belt are re-cycled. Some abrasives like zirconia lose their projectability. during recycling- Some grains like coarse SIC i:^rR very conductive resulting in arcing betwesn the grain tip and the backing, consequent to which the grains do not get coated on the backing - ThuB, both reduced projection o-f zirconia and increasti3d projection of SiC resuIt in a poor product of non-uniform co^ting « The grain is wetted with any type of phosphoric scid (up to 77- by weight of the grain) and mixed in a sui table mixing device- A blend of substances se1ec ted f rom a 1 uminouB Compounds , inBU 1 ators ^ rein^c: tory oxides, rai-e earths (for reduction in proj ec tab! 1 i ty ) : and electrical property altering material selected from fine particles of SiC, Iron OxideH ar other electrically conductive material such as metal powders, is prBpar-ed in t.he ratio 30 s 70 to 70 : 30 . This f)I ei")d is added to the wetted grain preferably in the ratio 2:1 to 7:1 of the weight o-f the said acid„ The process of manufacture of abrasive grains of electrical projec tability., according to this invention, comprises the steps of wetting the said grains with phosphoric acid (up to 7% by weight of the said grain) in a BUi tab 1 B mixing device; prE?parinq a blend of substances sBlected from aluminous compounds, refractory ojiides, electric insulators- rs(rB earths and of fine particles of electrical property altering material selected from electrically conductive material sueh as SiC ^ I ron Q>; ide , and meta 1 powders in the ratio of 30:70 to 70:30; adding the blend to, i^nd mixing it withp the wetted grains; and firing the same between 300 deg - C and B^"j0 deg. C for up to 2 hours, before sieving the grains to break down lumps j, if any - Any form of phosphoric acid may be used. EXAMPLE 1 Zirconia grains were wetted with 5X by weight of phosphoric acid s^nd coated with 40:60 blend of alumina and SiC fines in the ratio of 4:1 to the weight of the said acid- The grains were then fired at 700 deg.C for two hours- After firing, the grains B.re sieved through coarse mesh to break 1umps ^ i f any- The gr^ins are now rs^adv -for use-, EXAMPLE II SiC grains (Grit 30) wG?re treated as in E.>!amplB I using a 50:50 blend of alumina powder and yttria powder -While untreated grains caused arcing and non-adhesion at several places^ the treated grains had good (reduced) projectabi1ity without any arcing problem. This gave a good uniform adhesion of the grains on the modes of carring out the process proposed herein are possible without departing from the scope and ambit of this invention. We Claim: 1 -A process of manufacture of abrasive grains of improved electrical projectability comprising the staps of wetting the said grains with phosphoric acid (up to 7% by weight of the said grain) in a suitable mixing devices preparing a blend of substances selected from aluminous compounds, refractory oxides, electric insulators, rare earths and of fine particles of electrical property altering material selected from electrically conductive material such as SiC, Iron Oxide,, and metal powders in the ratio of 30:70 to 70:30; adding the blend to, and mixing it with the wetted grains; and firing the same between 300 deg, C and 850 deg- C for up to 2 hours, before sieving the grains to break down lumps, if any. 2. A process as claimed in Claim 1 wherein the blend is added to the wetted grains in the proportion 2:1 to 7:1 to the weight of the said acid. 3-A process for the manufacture of abrasive grains of improved electrical projectabi1ity substantially as herein described and illustrated by the Example- 4.Abrasive grains of improved electrical projectabi1ity whenever manufactured by a process as claimed in any one of the preceding Claims,

Documents:

2170-mas-1997 abstract-duplicate.pdf

2170-mas-1997 abstract.pdf

2170-mas-1997 claims-duplicate.pdf

2170-mas-1997 claims.pdf

2170-mas-1997 correspondence-others.pdf

2170-mas-1997 correspondence-po.pdf

2170-mas-1997 description (complete)-duplicate.pdf

2170-mas-1997 description (complete).pdf

2170-mas-1997 form-1.pdf

2170-mas-1997 form-19.pdf

2170-mas-1997 form-26.pdf