|Title of Invention||
A PROCESS OF MANUFACTURE OF ABRASIVE GRAINS AT AMBIENT TEMPERATURE FOR PROVIDING A UNIFORM, HARD, SURFACE THEREON
|Abstract||A process of manufacture of abrasive grains for providing a uniform, hard surface thereon comprising the steps of wetting the said grains with phosphorin acid up to 7% by weight of the grains): adding and mixing therewith a solid component containing powdered fines selected from alumina and atumious compounds: and firing the same, thereafter, between 300 deg. c to 700 deg. c for a period up to 2 hours, before sieving the grains to break down lumps, If any.|
This invention relates to a process of manufacture of abrasive grains for providing a uniform, hard, surface thereon^ leading to delayed fracture and, therefore, enhanced life of abrasive wheels made from such qrains-
Coating of abrasive grains with chemicals^ using binders^ is known to the art. US Patent No. 2»527,t:544 of 24th October 1950 disc loses the use of a temporary binder for coating powdered binding material (frit) and the required o>!ide on : to the grain surf ace-However;, this process results in a non-uniform coating which tends to peel off in use. Furthermore^ SiC grains cannot be treated by this process since frit reacts with Sic.
In the process proposed herein ■, abrasive grains are chemically modified to provide a uniform, hard, surface of enhanced service? life. No temporary binder is used s instead, one of the reactants used is in liquid form ensuring better adhesion and uniform coating.
The process of manufacture of abrasive grains for
providing a uniform;, hard surface thereon, according to this invention ^ comprises the steps of wetting the said grains with phosphoric acid (up to 7% by weight of the grains) ; adding and mixing therewith a solid component containing powdered fines selected from alumina and aluminous compounds; and firing the same;, thereafter, between 300 deg- C to 700 deg- C for a period up to 2 hours j, before sieving the grains to break down lumps^, if any.
Any form of phosphoric acid may be used -
The alumina may be finely divided calcined alumina^ fine abrasive alumina grains or other aluminium compounds-
Optionally, the sol id component also contains powdered fines selec ted from o>: ides, such as, i ron OK ide, chromium oxide- The addition of these substances serves as a grinding aid and improves the grinding performance of the ul timate product,, namely, an abrasive wheel.
The pckwder component is sieved through fine mesh to avoid lumps- If two components BrB to be used, they are mixed in the required proportions and sieved into a uniform blend- This powder component is added to the wetted grains in the mixer- The powder component can be used in the proportion 2s1 to 7:1 to the weight of the liquid component depending on the thickness of the coating (more the quantity of the powder, more the thickness of the coatina)-
Dependinq on the type of mixer, assesBment of /fct^e uniformity of mixinq, mixinq time may be increased Sf necessary»
The coated qrains are loaded on trays and fi red in a furnace at 300 deq-C to 700 deq-C preferably at 550 deq.C for 2 hours- After firinq, the qrains are sieved throuqh coarse meshes to break down lumps, if any. The qrains so treated Bve now ready for use-
10 kq. of alumina qrains (Grit 24) of friability 35'/# is charqed into a mixer- 4 % (of 10 kq«) of phosphoric acid is added and mixed- A blend consistinq of iron oxide and alumina abrasive fines in the ratio 60:40 is prepared- 10*/* (of 10 kq) of this blend is charqed into the mixer and allowed to run- The qrain is then discharqed on to tray^ and loaded in an electric furnace for ftrinq at 600 deq- C for 2 hours- After firinq the friability is found to be 18*/* which is a clear indication . of improvement in breakdown
Sreen BiC grit was treated with phosphoric acid
The results show a positive increase in the whee.1 1 ife' by a clear reduction of wheel wear while maintaining the same amount of material removal™
Abrasive grains manufactured by the process proposed herein arB well suited for use in vitrified;, resinoid and rubber wheels-
The terms and ex press iqns in this specification &r^ of^ description and not of limitation, there being no
intention in the use of such terms and expressions of excluding any equivalents of the features illustrated &nd described, but it is understood that various other modes of cs.rTyinf^ out the process proposed herein sre possible without departing from the scope and ambit of this invention-
Our co-pendinci Application No» 2173 MAS 97 relates to a process of manufacture of abrasive grains at ambient temperature for providing a uniform, hard surface thereon-
1.A process of manufacture, of abrasive grains for providing a uniform, hard surface thereon comprising the steps of wetting the said grains with phosphoric acid (up to 77- by weight of the grains) ; adding and mixing therewith a solid component containing powdered fines selected from alumina and aluminous compounds; and firing the same„ thereafter, between 300 deg. C to 700 deg. C for a up to 2 hours, before sieving the grains to break down lumps,, if any-
2.A process as c1 aimed in Claim 1 wherein the sol id component also contains powdered fines selected from oxides, such as, iron co-side, chromium oxide.
3-A process as c1 aimed in CI aim 2 wherein the powdered fines selected from alumina and aluminous compounds and powdered fines selected from oxides, such as, iron oxide;, chromium oxide i;Ar(B in the proportion 2s 1 to 7s 1 by weight of the phosphoric acid _
4-A process of manufacture; of abrasive grains for
providing a uniform, hard surface thereon submtantially as herein described and illustrated by the Examples-Dated this the ist day of October 1997
|Indian Patent Application Number||2171/MAS/1997|
|PG Journal Number||30/2009|
|Date of Filing||01-Oct-1997|
|Name of Patentee||CARBORUNDUM UNIVERSAL LIMITED|
|Applicant Address||TIRUVOTTIYUR, CHENNAI - 600 019|
|PCT International Classification Number||B24D3/16|
|PCT International Application Number||N/A|
|PCT International Filing date|