Coarse grain cemented carbide and preparation method thereof

A preparation method of grain cemented carbide, characterized in that comprising following steps;

• S1, pretreating coarse grain tungsten carbide with a Fisher particle size above 30 μm;
• performing a dry ball milling process with a ball to material ratio of 1:2, of which time is 60-120 min;
• sieving the material by a 325-mesh sieve after ball milling;
• the pretreated coarse grain tungsten carbide is on sieve;
• S2, putting a water-soluble cobalt salt, a nano fine grain tungsten carbide and the pretreated coarse grain tungsten carbide in a certain proportion in an agitating vessel;
• adding deionized water;
• stirring it to obtain a mixture;
• spray granulating the mixture to obtain a mixed material;
• wherein the mass ratio of the water-soluble cobalt salt, the nano fine grain tungsten carbide, and the coarse grain tungsten carbide is (5-10):(0.5-1.5):(88.5-94.5), with the amount of cobalt salt calculated on the basis of cobalt content;
• S3, putting the mixed material in a mold;
• sintering it;
• the sintering proceeds in stages;
• S31, putting the mold containing the mixed material in a tube furnace for sintering;
• sintering temperature is 300-450° C.;
• sintering atmosphere is nitrogen;
• sintering time is 120-180 min;
• S32, putting the mold containing the mixed material sintered by S31 in the tube furnace for sintering;
• sintering temperature is 550-650° C.;
• sintering atmosphere is hydrogen;
• sintering time is 150-240 min;
• S33, putting the mold containing the mixed material sintered by S32 in a spark plasma sintering furnace for sintering;
• sintering temperature is 1500-1800° C.;
• sintering pressure is 15-25 MPa;
• sintering time is 3-8 min to obtain the cemented carbide.