Mixed powder for powder metallurgy, method of manufacturing same, and method of manufacturing iron-based powder sintered body

Abstract

A mixed powder for powder metallurgy includes a machinability improvement powder that is crystalline layered alkaline silicate heat-treated at 400° C. to 1100° C. and whose mix proportion is in an amount of 0.01% to 1.0% by mass in terms of total content of an iron-based powder, an alloying powder, and the machinability improvement powder. Such a mixed powder not only enables a compact to be sintered without adversely affecting the environment in a sintering furnace, but also enables a sintered body having excellent lathe machinability and excellent drill machinability to be obtained.

1 .- 17 . (canceled) 
     
     
         18 . A mixed powder for powder metallurgy obtained by mixing an iron-based powder, an alloying powder, a machinability improvement powder, and a lubricant, wherein the machinability improvement powder comprises crystalline layered alkaline silicate heat-treated at 400° C. to 1100° C., and a mix proportion of the machinability improvement powder is 0.01% to 1.0% by mass in terms of total content of the iron-based powder, the alloying powder, and the machinability improvement powder. 
     
     
         19 . The mixed powder according to  claim 18 , wherein the machinability improvement powder further comprises at least one selected from the group consisting of an enstatite powder, a talc powder, a kaolin powder, a mica powder, a granulated slag powder, a levigated clay powder, a magnesium oxide (MgO) powder, and a powder mixture of silica (SiO 2 ) and magnesium oxide (MgO), in an amount of 10% to 80% by mass in terms of total content of the machinability improvement powder. 
     
     
         20 . The mixed powder according to  claim 19 , wherein the machinability improvement powder further comprises an alkali metal salt powder in an amount of 10% to 80% by mass in terms of total content of the machinability improvement powder. 
     
     
         21 . The mixed powder according to  claim 20 , wherein the alkali metal salt powder is one or two selected from the group consisting of an alkali carbonate powder and an alkali metal soap. 
     
     
         22 . The mixed powder according to  claim 18 , wherein the machinability improvement powder further comprises a calcium fluoride powder. 
     
     
         23 . The mixed powder according to  claim 18 , wherein the machinability improvement powder further comprises one or two selected from the group consisting of a metal boride powder and a metal nitride powder. 
     
     
         24 . The mixed powder according to  claim 23 , wherein the metal boride powder consists of at least one selected from the group consisting of TiB 2 , ZrB 2 , and NbB 2 , and the metal nitride powder consists of at least one selected from the group consisting of TiN, AlN, and Si 3 N 4 . 
     
     
         25 . The mixed powder according to  claim 18 , wherein the machinability improvement powder further comprises at least one selected from the group consisting of an alkali metal sulfate and an alkaline earth metal sulfate, in an amount of 10% to 80% by mass in terms of total content of the machinability improvement powder. 
     
     
         26 . A method of manufacturing a mixed powder for powder metallurgy by preparing and then mixing an iron-based powder, an alloying powder, a machinability improvement powder, and a lubricant to obtain a mixed powder,
 wherein the machinability improvement powder comprises crystalline layered alkaline silicate heat-treated at 400° C. to 1100° C., and a mix proportion of the machinability improvement powder is 0.01% to 1.0% by mass in terms of total content of the iron-based powder, the alloying powder, and the machinability improvement powder, and   the mixing includes:   primary mixing in which a part or whole of the machinability improvement powder and a part of the lubricant are added, as a primary mixture material, to the iron-based powder and the alloying powder and heated to perform mixing while melting at least one type of the lubricant, and a resulting mixture is cooled for solidification; and   secondary mixing in which a remaining powder of the machinability improvement powder and the lubricant is added, as a secondary mixture material, to the mixture to perform mixing.   
     
     
         27 . The method according to  claim 26 , wherein the machinability improvement powder further comprises at least one selected from the group consisting of an enstatite powder, a talc powder, a kaolin powder, a mica powder, a granulated slag powder, a levigated clay powder, a magnesium oxide (MgO) powder, and a powder mixture of silica (SiO 2 ) and magnesium oxide (MgO), in an amount of 10% to 80% by mass in terms of total content of the machinability improvement powder. 
     
     
         28 . The method according to  claim 27 , wherein the machinability improvement powder further comprises an alkali metal salt powder in an amount of 10% to 80% by mass in terms of total content of the machinability improvement powder. 
     
     
         29 . The method according to  claim 28 , wherein the alkali metal salt powder is one or two selected from the group consisting of an alkali carbonate powder and an alkali metal soap. 
     
     
         30 . The method according to  claim 26 , wherein the machinability improvement powder further comprises a calcium fluoride powder. 
     
     
         31 . The method according to  claim 26 , wherein the machinability improvement powder further comprises one or two selected from the group consisting of a metal boride powder and a metal nitride powder. 
     
     
         32 . The method according to  claim 31 , wherein the metal boride powder consists of at least one selected from the group consisting of TiB 2 , ZrB 2 , and NbB 2 , and the metal nitride powder consists of at least one selected from the group consisting of TiN, AlN, and Si 3 N 4 . 
     
     
         33 . The method according to  claim 26 , wherein the machinability improvement powder further comprises at least one selected from the group consisting of an alkali metal sulfate and an alkaline earth metal sulfate, in an amount of 10% to 80% by mass in terms of total content of the machinability improvement powder. 
     
     
         34 . A method of manufacturing an iron-based powder sintered body, by filling a die with a mixed powder for powder metallurgy manufactured by the method according to  claim 26 , compression-forming the mixed powder into a compact, and subjecting the compact to a sintering process to obtain a sintered body.