Method for preparing diamond tool bit from pure iron-based matrix

Abstract

The present invention provides use of a pure iron-based matrix for preparing a diamond bit and a method for preparing a diamond bit. The present invention uses the diamond bits prepared from the pure iron-based matrix made of iron powder with an average particle size of 1-25 μm in different scenarios. In the present invention, the iron powder with the average particle size of 1-25 μm is used to shorten a movement distance of iron ions, which greatly enhances activity of the iron powder, is beneficial to improving hardness and strength of the diamond bit, and can increase a holding power and wear resistance to the diamond. In addition, in the present invention, a pressure of hot press sintering of the diamond bit is controlled at 700-860° C., and a temperature of pressureless sintering is controlled at 900-960° C., thereby controlling reaction rate of the iron powder and the diamond, so that the iron powder can form a chemical bond with the diamond, and the diamond is not excessively carbonized to affect the strength of the diamond bit, thereby obtaining the diamond bit with excellent comprehensive performance and low price.

What is claimed is: 
     
         1 . A method for preparing a diamond bit from a pure iron-based matrix, wherein the diamond bit is made by combining the pure iron-based matrix with diamond, the method comprises the following steps:
 step S1: mechanically mixing iron powder and diamond and fully mixing to obtain a mixture, wherein a mass fraction of the iron powder with an average particle size of 1-25 μm is ≥40%, and an oxygen content of the iron powder with the average particle size of 1-25 μm is 2000-7000 ppm; and a volume of the diamond is 25-30% of a volume of the iron powder, and   step S2: hot press sintering the mixture obtained in the step S1 for forming and cooling to obtain the diamond bit; wherein a temperature of the hot press sintering is 700-860° C., a holding time is 90-120 s, and a pressure of the hot press sintering is 200-400 kgf/cm 2 .   
     
     
         2 . The method for preparing a diamond bit from a pure iron-based matrix according to  claim 1 , wherein in the step S1, the diamond is wetted with a wetting agent and then mechanically mixed with the iron powder; and wherein the wetting agent is a motor oil or paraffin. 
     
     
         3 . The method for preparing a diamond bit from a pure iron-based matrix according to  claim 1 , wherein in the step S1, a binder with a mass of 1.2-2.2% of a mass of the iron powder is added to be mechanically mixed with the diamond and the iron powder, and wherein the binder is polyethylene glycol or polyvinyl alcohol. 
     
     
         4 . A method for preparing a diamond bit from a pure iron-based matrix, wherein the diamond bit is made by combining the pure iron-based matrix with diamond, the method comprises the following steps:
 step C1: mechanically mixing iron powder and diamond and fully mixing to obtain a mixture, wherein a mass fraction of the iron powder with an average particle size of 1-25 μm is ≥40%, and an oxygen content of the iron powder with the average particle size of 1-25 μm is 2000-7000 ppm; and a volume of the diamond is 25-30% of a volume of the iron powder;   step C2: preparing the mixture obtained in the step C1 into a body with a density of 3.95-6.29 g/cm 3 ; and   step C3: forming the body obtained in the step C2 by pressureless sintering and cooling to obtain the diamond bit; wherein a temperature of the pressureless sintering is 900-960° C., and a holding time is 30-60 min.   
     
     
         5 . The method for preparing a diamond bit from a pure iron-based matrix according to  claim 4 , wherein in the step C1, the diamond is wetted with a wetting agent and then mechanically mixed with the iron powder; and wherein the wetting agent is a motor oil or paraffin. 
     
     
         6 . The method for preparing a diamond bit from a pure iron-based matrix according to  claim 4 , wherein in the step C1, a binder with a mass of 1.2-2.2% of a mass of the iron powder is added to be mechanically mixed with the diamond and the iron powder; and wherein the binder is polyethylene glycol or polyvinyl alcohol.