| 摘要 |
720,278. Diamond tools. WHEEL TRUEING TOOL CO. July 31, 1951, No. 18091/51. Class 124. A drill bit or like tool comprises a coherent sintered body portion including a inner layer of tungsten and diamonds embedded in and exposed at the surface of an outer layer of tungstentungsten carbide, the diamonds being surrounded by a layer of massive tungsten carbide. In the form shown, there is placed in a carbon mould 10 a number of diamonds or discrete diamond particles 13 kept in upright position by a setting matrix 14, a layer 15 of a mixture of powdered tungsten and tungsten carbide, and then a layer 16 of tungsten particles, these layers then being cold compacted under a pressure of 400-600 p.s.i. The diamonds may be set in a single horizontal plane or in a set of inclined planes or steps. The tungsten powder is of less than 200 mesh and the tungsten carbide varies between 30 and 200 mesh. German silver, bronze or other brazing metal 21 is then added, and the compact heated for at least 1 hour at a temperature of 1700-2100‹F. but below the melting point of the brazing metal. This forms massive tungsten carbide in the layer 18 including the diamonds by interaction of the tungsten-tungsten carbide mixture and the carbon of the mould, a layer of tungsten carbide at the junction of the tungsten and the carbon wall of the mould, and a relatively soft solid tungsten inner mass 19. Further heating to above 2100‹F. causes the brazing metal to infiltrate the compact. The resulting mass is then compressed at 400-600 p.s.i. before cooling.
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