Cemented carbide for cutting tools, cutting tools, and method for manufacturing cemented carbide for cutting tools

Abstract

The present invention relates to a cemented carbide for cutting tools comprising, by weight %, 4-13% of Co, 1-12% of a compound, and the balance being WC and other unavoidable impurities, characterized in that when the average particle diameter of the compound is 0.4 μm or less and the average particle diameter of WC is 1.2 μm to 2.2 μm, the average particle diameter of the compound and the average particle diameter of WC satisfy the following relational expression 1. [Relational Expression 1] 18≤100 (A/B)≤30 (where A means the average particle diameter of the compound in the cemented carbide for cutting tools, and B means the average particle diameter of WC).

1 . A cemented carbide for cutting tools comprising, by weight %, 4˜13% of Co, 1˜12% of a compound, and the remaining being WC and other unavoidable impurities, wherein an average particle diameter of the compound and an average particle diameter of the WC satisfy Relational expression 1 below,
 wherein [Relational expression 1] 18≤100(A/B)≤30 (in Relational expression 1, A refers to the average particle diameter of a compound in a cemented carbide for cutting tools, and B refers to an average particle diameter of WC). 
 
     
     
         2 . The cemented carbide of  claim 1 , wherein the average particle diameter of the compound is 0.4 μm or less, and the average particle diameter of the WC is 1.2 μm to 2.2 μm. 
     
     
         3 . The cemented carbide of  claim 1 , wherein the compound is provided as a carbide, a nitride, and a carbonitride formed by combining one or more elements selected from a group consisting of elements of group 4a, group 5a, or group 6a with carbon or nitrogen. 
     
     
         4 . The cemented carbide of  claim 3 , wherein the compound is any one metal carbide selected from TiC, NbC, and TaC. 
     
     
         5 . The cemented carbide of  claim 1 , wherein the cemented carbide for cutting tools has crack point A of 25% or less described below,
 wherein crack point A=(the number of interfaces of compounds per unit area)/(the total number of compounds per unit area)×100.   
     
     
         6 . A cutting tool manufactured by using the cemented carbide for cutting tools of  claim 1 . 
     
     
         7 . The cutting tool of  claim 6 , further comprising:
 a hard film formed by one or more methods selected from a chemical vapor deposition (CVD) method and a physical vapor deposition (PVD) method.   
     
     
         8 . A method for manufacturing a cemented carbide for cutting tools, the method comprising:
 a step of manufacturing a mixture by weighing raw material powder consisting of 4˜13% of Co, 1˜12% of a compound by weight % and the remaining being WC, and mixing the raw material powder;   a step of manufacturing a molded body by putting the mixture into a mold and pressing the mixture; and   a step of manufacturing a cemented carbide by sintering the mixture,   wherein the sintering comprises:   a step of dewaxing the molded body at about 200 to 300° C. for one to three hours;   a step of primarily sintering the molded body, which is dewaxed, at 1,000 to 1,250° C. for a predetermined period of time;   a step of secondarily sintering the primarily-sintered molded body at 1,400 to 1,450° C. for a predetermined period of time;   a step of thirdly sintering the secondarily-sintered molded body at 1,500 to 1,600° C. for a predetermined period of time;   a step of primarily cooling the thirdly-sintered molded body down to 1000 to 1300° C.; and   a step of secondarily cooling the primarily-cooled molded body down to a room temperature.   
     
     
         9 . The method of  claim 8 , wherein the primary sintering step is maintained at 1,000 to 1,250° C. for 30 to 120 minutes, and the secondary sintering step is maintained at 1,400 to 1,450° C. for 30 to 120 minutes. 
     
     
         10 . The method of  claim 8 , wherein the third sintering step is maintained at 1,500 to 1,600° C. for 90 to 120 minutes. 
     
     
         11 . The method of  claim 8 , wherein the second cooling step is performed at a cooling rate of 120 to 150° C./min.