Filler component for investment casting slurries

Abstract

A filler component for making an investment casting slurry, which comprises: a major portion of finely divided silica, aluminum silicate, alumina, zircon, or mixtures thereof; and a minor portion of one or more finely divided materials having particles in which, on average, at least one dimension of the particle is at least about four times greater than at least one other dimension of the particle. Typically, the particles are of generally plate-like or needle-like shape.

1 . A filler component for making an investment casting slurry, which comprises: 
 a major portion which comprises at least one finely divided material selected from the group consisting of silica, aluminum silicate, alumina, and zircon, comprising particles having, on average, a generally similar extent in their three dimensions; and    a minor portion of one or more finely divided materials comprising particles having plate-like, needle-like, or tubular structure, in a concentration sufficient to reduce drainage time of a slurry containing said filler component after application to an investment casting pattern, when compared with a similar slurry without said minor portion.    
   
   
       2 . The filler component of  claim 1  which is essentially free of organic fibers.  
   
   
       3 . The filler component of  claim 1 , in which said major portion consists essentially of silica.  
   
   
       4 . The filler component of  claim 1  in which said minor portion is present in an amount of 0.1 to 15 weight percent.  
   
   
       5 . The filler component of  claim 1  in which said minor portion consists essentially of kaolin.  
   
   
       6 . The filler component of  claim 5  in which from 0.25 to 5 weight percent of kaolin is present.  
   
   
       7 . The filler component of  claim 1 , in which said major portion consists essentially of aluminum silicate.  
   
   
       8 . The filler component of  claim 1 , in which said major portion consists essentially of a blend of fused silica and aluminum silicate.  
   
   
       9 . The filler component of  claim 1 , in which said major portion consists essentially of fused silica.  
   
   
       10 . An investment casting slurry which comprises a mixture of the filler component of  claim 1 , and a lesser amount of a binder component comprising binder materials in water.  
   
   
       11 . The slurry of  claim 10  in which said binder materials comprise colloidal silica and an organic polymer.  
   
   
       12 . The slurry of  claim 10  which carries from 55 to 85 weight percent of said filler component.  
   
   
       13 . The slurry of  claim 10 , which has a viscosity of 8 to 30 seconds, using a Gardco/ISO Mini Dip Viscosity Cup with a 6 mm orifice.  
   
   
       14 . The filler component of  claim 1  in which said minor portion of finely divided materials has a melting point of at least about 1000° F.  
   
   
       15 . The filler component of  claim 1  in which said minor portion of finely divided materials have a plate-like particle shape.  
   
   
       16 . The filler component of  claim 15  in which the finely divided materials consist essentially of at least one material selected from the group consisting of kaolin and other clays mica, talc, vermiculite, boehmite, titanium dioxide, gibbsite, diaspore, pyrophyllite, and laponite.  
   
   
       17 . The filler component of  claim 1  in which said minor portion of finely divided materials have a needlelike particle shape.  
   
   
       18 . The filler component of  claim 17  in which the finely divided materials consist essentially of at least one material selected from the group consisting of mullite, kyanite, wollastonite, sillimanite, magnesium silicate, amphibole, asbestos and magnesium aluminosilicate.  
   
   
       19 . The investment casting slurry of  claim 10  in which said major portion of the filler component comprises fused silica, and said minor portion of the filler component comprises kaolin.  
   
   
       20 . The investment casting slurry of  claim 19  in which from 0.25 to 5 weight percent of kaolin is present.  
   
   
       21 . The slurry of  claim 19  which has a viscosity of 13 to 26 seconds using a Gardco/ISO Mini Dip Viscosity Cup with a 6 mm orifice.  
   
   
       22 . The slurry of  claim 21  which carries from 55 to 85 weight percent of said filler component.  
   
   
       23 . A filler component for making an investment casting slurry, which comprises: 
 a major portion which comprises at least one finely divided material comprising particles selected from the group consisting of silica, aluminum silicate, alumina, and zircon, said particles having, on average, a generally similar extent in their three dimensions; and    a minor portion of from 0.1 to 15 weight percent of one or more finely divided materials comprising particles in which, on average, at least one dimension of the particle is at least about four times greater than at least one other dimension of the particle.    
   
   
       24 . The filler component of  claim 23  which, when formed into a slurry having a viscosity of 8 to 30 seconds, using a Gardco/ISO Mini Dip Viscosity Cup with a 6 mm orifice, and applied to an investment casting pattern, exhibits a reduced drainage time when compared with a similar slurry without said minor portion.  
   
   
       25 . The filler component of  claim 24  in which said slurry also produces shells with more uniform cross section, where edge thickness is closer to face thickness than investment casting shells made by corresponding slurries which do not contain said minor portion.  
   
   
       26 . The filler component of  claim 23  which is essentially free of organic fibers.  
   
   
       27 . The filler component of  claim 23  in which said major portion consists essentially of silica.  
   
   
       28 . The filler component of  claim 23  in which said minor portion is present in an amount of 0.25 to 5 weight percent.  
   
   
       29 . The filler component of  claim 23  in which said minor portion consists essentially of kaolin.  
   
   
       30 . The filler component of  claim 27  in which from 0.25 to 5 weight percent of kaolin is present.  
   
   
       31 . An investment casting slurry which comprises an intimate mixture of the filler component of  claim 23  and a relatively smaller portion of a binder component comprising binder materials in water.  
   
   
       32 . The slurry of  claim 31  in which said binder materials comprise colloidal silica and an organic polymer.  
   
   
       33 . The slurry of  claim 31  which has from 60 to 90 weight percent of solids.  
   
   
       34 . The slurry of  claim 31  which has a viscosity of 13 to 26 seconds, using a Gardco/ISO Mini Dip Viscosity Cup with a 6 mm orifice.  
   
   
       35 . The slurry of  claim 31  in which said minor portion of finely divided materials has a melting point of at least about 1,000° F.  
   
   
       36 . The filler of  claim 31  in which said minor portion of finely divided materials has a plate-like particle shape.  
   
   
       37 . The filler of  claim 23  in which said minor portion of finely divided materials has a needle-like particle shape.  
   
   
       38 . The slurry of  claim 31  in which said finely divided materials of the minor portion of the filler component comprise a clay mineral selected from the group consisting of kaolinite, montmorillinite/smectite, illite, and chlorite.  
   
   
       39 . The slurry of  claim 10 , which has a viscosity of 13 to 26 seconds, using a Gardco/ISO Mini Dip Viscosity Cup with a 6 mm orifice.  
   
   
       40 . The slurry of  claim 19  which has a viscosity of 8 to 30 seconds using a Gardco/ISO Mini Dip Viscosity Cup with a 6 mm orifice.  
   
   
       41 . The slurry of  claim 31  which has a viscosity of 8 to 30 seconds, using a Gardco/ISO Mini Dip Viscosity Cup with a 6 mm orifice.  
   
   
       42 . The filler component of  claim 23  which, when formed into a slurry having a viscosity of 13 to 26 seconds, using a Gardco/ISO Mini Dip Viscosity Cup with a 6 mm orifice, and applied to an investment casting pattern, exhibits a reduced drainage time when compared with a similar slurry without said minor portion.  
   
   
       43 . The filler component of  claim 42  in which said slurry also produces shells with more uniform cross section, where edge thickness is closer to face thickness than investment casting shells made by corresponding slurries which do not contain said minor portion.