Al2O3 and ZrO2 based abrasive grain, method for the production and use thereof

Abstract

An Al 2 O 3 and ZrO 2 based abrasive grain containing titanium compounds in a reduced form, especially in the form of oxides and/or suboxides and/or carbides and/or oxycarbides and/or oxycarbonitrides and/or silicides, corresponding to a proportion of 0.510 wt %, expressed as TiO 2 , containing 20-50 wt % ZrO 2 , wherein more than 75 wt. % of the ZrO 2 is present in a tetragonal crystal form, having an overall carbon content of 0.03-0.5 wt. %, a proportion of impurities caused by raw materials of less than 3.0 wt %, wherein the rare earth content calculated in the form of oxides is less than 0.1 wt %, having an Si-compound content of 0.05-1.0 wt %, expressed as SiO 2 , and an Al 2 O 3 content of 50-80 wt. %, obtained by melting a mixture required for a corresponding abrasive grain composition, said mixture corresponding to Al 2 O 3 , ZrO 2 , TiO 2 and TiO 2 , and/or raw materials containing the latter in the presence of a surplus of a reducing agent and quenched in such a way that the melt is fully solidified in less than 10 seconds. The invention also relates to a method for the production thereof and the use thereof in abrasives.

1 .- 16 . (canceled)  
   
   
       17 . An alumina-zirconia abrasive grain product prepared by a process comprising: 
 forming a melt from a mixture of source materials containing aluminum oxide, zirconium oxide, titanium oxide and silicon oxide in the presence of excess carbon as a reducing agent, wherein the amount of silicon oxide is from 2.0 to 5.7 wt % relative to all of the source materials; and    quenching the melt to produce the abrasive grain product comprising:    (a) aluminum oxide;    (b) zirconium oxide with at least 85 wt. % thereof being in tetragonal crystal form;    (c) titanium compounds in reduced form of oxide, suboxides, carbides, oxycarbides, oxycarbonitrides, suicides or mixtures thereof present from 2-5 wt. %; and    (d) silicon compounds content, expressed as silicon oxide, between 0.2 and 0.7 wt. %.    
   
   
       18 . The abrasive grain product of  claim 17  further comprising a carbon content between 0.03 and 0.5 wt. %.  
   
   
       19 . The abrasive grain product of  claim 17  further comprising a eutectic composition that accounts for 35 to 45 wt. % of the ZrO 2  and 55 to 65 wt. % of the Al 2 O 3  in the abrasive grain product.  
   
   
       20 . The abrasive grain product of  claim 19  wherein the eutectic composition comprises dentritic eutectic domains of aluminum oxide and zirconium oxide with a median cross section of less than 15 microns.  
   
   
       21 . The abrasive grain product of  claim 17  further comprising a rare earths content, expressed as oxides, of less than 0.1 wt. %.  
   
   
       22 . The abrasive grain product of  claim 17  wherein the quenching of the melt to solid form occurs in gaps that exist between cooling plates and is complete within 5 seconds.  
   
   
       23 . The abrasive grain product of  claim 17  wherein the tetragonal crystal structure of the zirconium oxide content is at least 90 wt. %.  
   
   
       24 . The abrasive grain product of  claim 17  wherein the silicon compounds content, expressed as silicon oxide is between 0.2 and 0.49 wt. %.  
   
   
       25 . The abrasive grain product of  claim 17  wherein the amount of silicon compounds, expressed as silicon oxide, is between 0.32 and 0.49 wt.-%.  
   
   
       26 . An alumina-zirconia abrasive grain product prepared by a process comprising: 
 providing a mixture of source materials comprising Al 2 O 3 , ZrO 2 , TiO 2  and SiO 2 , wherein the amount of SiO 2  relative to the amount of TiO 2  in the mixture as defined by a ratio SiO 2  wt. %/TiO 2  wt. % is from 0.41 to 1.62, and wherein the amount of silicon oxide is from 2.0 to 5.7 wt % relative to all of the source materials;    heating the mixture to form a melt and exposing the melt to reducing conditions; and    quenching the melt to a solid form, wherein the amount of ZrO 2  in the abrasive grain is between 20 and 50 wt-% with at least 85 wt. % of the ZrO 2  in tetragonal crystal form, and the amount of silicon compounds in the abrasive grain, expressed as silicon oxide, is between 0.2 and 0.7 wt. %.    
   
   
       27 . The abrasive grain product of  claim 26  wherein the ratio SiO 2  wt. %/TiO 2  wt. % is from 0.59 to 1.18.  
   
   
       28 . The abrasive grain product of  claim 26  wherein the quenching of the melt to solid form occurs in gaps that exist between cooling plates and is complete within 5 seconds.  
   
   
       29 . The abrasive grain product of  claim 28  wherein the gaps of the cooling plates are from 3 mm to 5 mm.  
   
   
       30 . The abrasive grain product of  claim 26  wherein the amount of silicon compounds, expressed as silicon oxide, is between 0.32 and 0.49 wt.-%.  
   
   
       31 . An abrasive grain comprising: 
 aluminum oxide and zirconium oxide with at least 85 wt.-% thereof being in tetragonal crystal form;    silicon compounds, expressed as silicon oxide, between 0.2 and 0.7 wt.-%; wherein the abrasive grain has an extremely fine structure with dentritic eutectic domains of aluminum oxide and zirconium oxide with a median cross section of less than 15 microns.    
   
   
       32 . An abrasive grain according to  claim 31  wherein the amount of silicon compounds, expressed as silicon oxide, is between 0.2 and 0.49 wt.-%.  
   
   
       33 . An abrasive grain according to  claim 31  wherein the amount of silicon compounds, expressed as silicon oxide, is between 0.32 and 0.49 wt.-%.