Method for manufacturing fine free carbon dispersion type cemented carbide, cutting tip with exchangeable cutting edge, machined product formed from alloy, and method for manufacturing same

Abstract

The present invention relates to a cemented carbide and coated cemented carbide which contain free carbons, and provides a cemented carbide which enables to remove or reduce the disadvantages of the free carbons even if the cemented carbide contains the free carbons, specifically to decrease in the strength is reduced by finely dispersing the free carbons even if the cemented carbide contains the free carbons and to obtain a beautiful mirror surface on a mirror-finished surface by finely dispersing free carbons in the cemented carbide. The present invention is a cemented carbide composed of tungsten carbide (WC) and cobalt (Co), which contains carbon in such an amount range that no solid carbon is contained in a liquid phase while the liquid phase is present at a high temperature, characterized in that the maximum diameter of the pores resulting from the free carbons is 20 μm or smaller.

1 - 7 . (canceled) 
     
     
         8 . A method for manufacturing a cemented carbide composed of tungsten carbide (WC) and cobalt (Co), wherein:
 the cemented carbide contains 0.02 mass % or more to 0.15 mass % or less of free carbons;   free carbons are finely dispersed in the cemented carbide;   shrinkage during sintering occurs evenly;   the cemented carbide in which a maximum diameter of pores resulting from the free carbons is 20 μm or smaller is defined as Cemented carbide A;   the cemented carbide in which a maximum diameter of pores resulting from the free carbons is 15 μm or smaller is defined as Cemented carbide B;   the cemented carbide in which a maximum diameter of pores resulting from the free carbons is 10 μm or smaller is defined as Cemented carbide C;   the Cemented carbide A, B or C to which chromium carbide or chromium nitride is added in an amount of 2 to 18 mass % based on cobalt (Co) content is defined as Cemented carbide D;   the Cemented carbide A, B, C or D in which a part of tungsten carbide (WC) is replaced by any one or combinations of: a carbide, a nitride or a carbonitride of transition metal of groups 4 and 5 in the periodic table; and a double carbide or a double carbonitride of tungsten (W) with the carbide, the nitride or the carbonitride of the transition metal is defined as Cemented carbide E; and   the Cemented carbide E in which a β-free layer is formed on a surface of the cemented carbide and the β-free layer has a thickness of 1 to 30 μm is defined as Cemented carbide F,   the Cemented carbide A, B, C, D, E or F in which a lattice constant of an fcc in a binder phase (Co phase) of the cemented carbide is 3.560 Å or higher is defined as Cemented carbide G,   the method is characterized in that, when manufacturing any of the Cemented carbides A, B, C, D, E, F and G, after sintering a mixed powder for producing the cemented carbide at a sintering temperature not lower than a liquid-phase appearance temperature, the method comprises:   a step of rapidly cooling from the temperature not lower than the liquid-phase appearance temperature; or   a step of reheating to the temperature not lower than the liquid-phase appearance temperature and then rapidly cooling.   
     
     
         9 . The method for manufacturing the cemented carbide according to  claim 8 , wherein, in the step of rapidly cooling and the step of reheating and rapidly cooling, a cooling rate from the temperature not lower than the liquid-phase appearance temperature to 800° C. is set to 30° C./min or higher. 
     
     
         10 . A method for manufacturing a coated cemented carbide, wherein the cemented carbide manufactured by the method for manufacturing the cemented carbide according to  claim 8  is used as a base material when manufacturing the coated cemented carbide. 
     
     
         11 . An edge replacement-type cutting tip formed of a cemented carbide composed of tungsten carbide (WC) and cobalt (Co), wherein:
 the cemented carbide contains 0.02 mass % or more to 0.15 mass % or less of free carbons;   free carbons are finely dispersed in the cemented carbide;   shrinkage during sintering occurs evenly;   dimensional accuracy is improved;   the cemented carbide in which a maximum diameter of pores resulting from the free carbons is 20 μm or smaller is defined as Cemented carbide A;   the cemented carbide in which a maximum diameter of pores resulting from the free carbons is 15 μm or smaller is defined as Cemented carbide B;   the cemented carbide in which a maximum diameter of pores resulting from the free carbons is 10 μm or smaller is defined as Cemented carbide C;   the Cemented carbide A, B or C to which chromium carbide or chromium nitride is added in an amount of 2 to 18 mass % based on cobalt (Co) content is defined as Cemented carbide D;   the Cemented carbide A, B, C or D in which a part of tungsten carbide (WC) is replaced by any one or combinations of: a carbide, a nitride or a carbonitride of transition metal of groups 4 and 5 in the periodic table; and a double carbide or a double carbonitride of tungsten (W) with the carbide, the nitride or the carbonitride of the transition metal is defined as Cemented carbide E;   the Cemented carbide E in which a β-free layer is formed on a surface of the cemented carbide, and the β-free layer has a thickness of 1 to 30 μm is defined as Cemented carbide F; and   the Cemented carbide A, B, C, D, E or F in which a lattice constant of an fcc in a binder phase (Co phase) of the cemented carbide is 3.560 Å or higher is defined as Cemented carbide G,   the edge replacement-type cutting tip is characterized in that the edge replacement-type cutting tip is formed of any of the Cemented carbides A, B, C, D, E, F and G, or any of coated cemented carbides using the Cemented carbide A, B, C, D, E, F or G as a base material.   
     
     
         12 . A cemented carbide machined product such as tools, molds and parts formed of a cemented carbide composed of tungsten carbide (WC) and cobalt (Co), wherein:
 the cemented carbide contains 0.02 mass % or more to 0.15 mass % or less of free carbons;   free carbons are finely dispersed in the cemented carbide;   shrinkage during sintering occurs evenly;   dimensional accuracy and/or machinability is improved;   the cemented carbide in which a maximum diameter of pores resulting from the free carbons is 20 μm or smaller is defined as Cemented carbide A;   the cemented carbide in which a maximum diameter of pores resulting from the free carbons is 15 μm or smaller is defined as Cemented carbide B;   the cemented carbide in which a maximum diameter of pores resulting from the free carbons is 10 μm or smaller is defined as Cemented carbide C;   the Cemented carbide A, B or C to which chromium carbide or chromium nitride is added in an amount of 2 to 18 mass % based on cobalt (Co) content is defined as Cemented carbide D;   the Cemented carbide A, B, C or D in which a part of tungsten carbide (WC) is replaced by any one or combinations of: a carbide, a nitride or a carbonitride of transition metal of groups 4 and 5 in the periodic table; and a double carbide or a double carbonitride of tungsten (W) with the carbide, the nitride or the carbonitride of the transition metal is defined as Cemented carbide E;   the Cemented carbide E in which a β-free layer is formed on a surface of the cemented carbide, and the β-free layer has a thickness of 1 to 30 μm is defined as Cemented carbide F; and   the Cemented carbide A, B, C, D, E or F in which a lattice constant of an fcc in a binder phase (Co phase) of the cemented carbide is 3.560 Å or higher is defined as Cemented carbide G,   the cemented carbide machined product is characterized in that any of the Cemented carbides A, B, C, D, E, F and G is machined by one or combinations of following machining methods: an electric discharging, grinding/polishing or cutting.