Composite Tungsten Carbide Insert With Heterogeneous Composition And Structure And Manufacturing Method Thereof

Abstract

A composite tungsten carbide insert (B, I) with heterogeneous composition and structure has a working part (W) and a non-working part (N). The working part (W) is made of a tungsten carbide material consisting of tungsten carbide powder and cobalt powder or nickel. The non-working part (N) is made of a low density tungsten carbide material consisting of titanium carbide powder, tungsten carbide powder, and cobalt powder or nickel powder. During pressing, the tungsten carbide material for the working part (W) and the low density tungsten carbide material for the non-working part (N) are weighed and added to a steel die successively for molding and then sintering. The non-working part (N) which accounts for most of the overall product volume has low density and less material consumption, and can greatly reduce the raw material costs of the product, significantly improving the performance-cost ratio of the insert (B, I).

What is claimed is: 
     
         1 . A composite tungsten carbide insert with heterogeneous composition and structure, comprising:
 the insert consists of a working part and a non-working part;   the working part is made of a tungsten carbide material consisting of uniformly mixed tungsten carbide powder (80-92%) and cobalt powder or nickel powder (8-20%) by weight, with a layer thickness of 5-30 mm;   the non-working part is made of a low density tungsten carbide material consisting of 30-60% of titanium carbide powder (with a density of 4.93 g/cm3), 20-60% of tungsten carbide powder (with a density of 15.79 g/cm3), and 10-20% of cobalt powder or nickel powder (with a density of 8.9 g/cm3) by weight; and   wherein during pressing, the tungsten carbide material for the working part is weighed and added to a steel die, then the low density tungsten carbide material for the non-working part is weighed and added to the die, a pressure is exerted on the two materials for molding, then the molded product is placed in a sintering furnace for sintering, and the resulting sintered product forms two parts, i.e., the composite tungsten carbide insert with homogeneous composition and structure.   
     
     
         2 . The composite tungsten carbide insert with heterogeneous composition according to  claim 1 , wherein the insert is formed such that the working part is spherical in shape. 
     
     
         3 . The composite tungsten carbide insert with heterogeneous composition according to  claim 1 , wherein the insert is formed such that the working part is cylindrical in shape, having an end face. 
     
     
         4 . A method for manufacturing a composite tungsten carbide insert with heterogeneous composition and structure, comprising the following steps:
 A. preparing a first mixture of tungsten carbide material for the working part by:
 (a) uniformly mixing 80-92% of tungsten carbide powder and 8-20% of cobalt powder or nickel powder by weight; 
 (b) placing the first mixture in a ball mill for wet milling at room temperature for 24 h at a ball-to-material ratio of 4:1 and solid-to-liquid ratio of 1 kg/300 ml; 
 (c) recovering alcohol from the milled wet material of the first mixture using a vacuum dryer, and drying in a steam drying oven; and 
 (d) adding a rubber molding agent to a resulting dried powder from the first mixture at the rubber addition rate of 90 ml/1 kg, uniformly stirring for 2 minutes, and then sieving through 60-100 meshes; 
   B. preparing a second mixture of a low density tungsten carbide material for the non-working part by:
 (a) uniformly mixing 30-60% of titanium carbide powder (with a density of 4.93 g/cm3), 20-60% of tungsten carbide powder (with a density of 15.79 g/cm3), and 10-20% of cobalt powder or nickel powder (with a density of 8.9 g/cm3) by weight; 
 (b) placing the second mixture in a ball mill for wet milling at room temperature for 24 h at a ball-to-material ratio of 4:1 and solid-to-liquid ratio of 1 kg/300 ml; 
 (c) recovering alcohol from the milled wet material of the second mixture using a vacuum dryer, and drying in a steam drying oven; and 
 (d) adding a rubber molding agent to a resulting dried powder from the second mixture at the rubber addition rate of 120 ml/1 kg, uniformly stirring for 2 minutes, and then sieving through 60-100 meshes; 
   C. pressing for molding:
 (a) due to some differences in shrinkage of the two mixtures, in order to prevent distortion of the button or insert after sintering affecting dimensional tolerance, and failing to meet the use requirements, prefabricating a convex pressed compact, the crosshead end being used as the working part, with shrinkage coefficient of 1.20-1.25, and the butt end being used as the non-working part, with shrinkage coefficient of 1.26-1.30, and allowing the joint interface between the working part and the non-working part to be in smooth transition; and 
 (b) weighing and adding the first mixture of the tungsten carbide powder and cobalt powder (or nickel powder) for the working part to a steel die, then weighing and adding the second mixture of the titanium carbide powder, tungsten carbide powder and cobalt powder or nickel powder for the non-working part to the steel die, and exerting 60-100 Mpa/cmi pressure for molding; 
   D. sintering by placing the molded product in a sintering furnace for sintering at temperature of 1420-1460° C., and holding for 2-3 h; and   E. machining product surface by grinding the surface of the sintered product to size, and warehousing after satisfactory inspection.   
     
     
         5 . The method for manufacturing a composite tungsten carbide insert with heterogeneous composition and structure according to  claim 4 , wherein the insert is formed such that the working part is spherical in shape. 
     
     
         6 . The method for manufacturing a composite tungsten carbide insert with heterogeneous composition and structure according to  claim 4 , wherein the insert is formed such that the working part is cylindrical in shape, having an end face.