Method for manufacturing atomized metal powder

Abstract

[Object] Provided is a method for manufacturing atomized metal powder having a high amorphous material fraction by using a water atomizing method. [Solution] A method for manufacturing atomized metal powder in which atomized metal powder having an amorphous material fraction of 90% or more is obtained, the method including ejecting high-pressure water so as to collide with a molten metal stream flowing vertically downward, separating the molten metal stream into metal powder, and cooling the metal powder, in which the high-pressure water collides with the molten metal with a collision pressure of 20 MPa or higher, and in which a temperature of the molten metal and/or a temperature of the high-pressure water are controlled so that the high-pressure water is in a subcritical state or a supercritical state on a collision surface with the molten metal.

1 . A method for manufacturing atomized metal powder in which atomized metal powder having an amorphous material fraction of 90% or more is obtained, the method comprising ejecting high-pressure water so as to collide with a molten metal stream flowing vertically downward, separating the molten metal stream into metal powder, and cooling the metal powder,
 wherein the high-pressure water collides with the molten metal with a collision pressure of 20 MPa or higher, and   wherein a temperature of the molten metal and/or a temperature of the high-pressure water are controlled so that the high-pressure water is in a subcritical state or a supercritical state on a collision surface with the molten metal.   
     
     
         2 . The method for manufacturing atomized metal powder according to  claim 1 , wherein an average temperature of the molten metal and the high-pressure water is 374° C. or higher at a time of collision between the high-pressure water and the molten metal. 
     
     
         3 . The method for manufacturing atomized metal powder according to  claim 1 , wherein, when a flow rate of the molten metal stream per unit time is defined as Qm (kg/min) and an ejection rate of the high-pressure water per unit time is defined as Qaq (kg/min), a mass ratio (Qaq/Qm) is 35 or more. 
     
     
         4 . The method for manufacturing atomized metal powder according to  claim 2  wherein, when a flow rate of the molten metal stream per unit time is defined as Qm (kg/min) and an ejection rate of the high-pressure water per unit time is defined as Qaq (kg/min), a mass ratio (Qaq/Qm) is 35 or more. 
     
     
         5 . The method for manufacturing atomized metal powder according to  claim 1 , wherein the atomized metal powder contains iron-group constituents (Fe, Ni, and Co) in a total amount of 76.0 at % or more in terms of atomic fraction and Cu in an amount of 0.1 at % or more and 2.0 at % or less in terms of atomic fraction. 
     
     
         6 . The method for manufacturing atomized metal powder according to  claim 2 , wherein the atomized metal powder contains iron-group constituents (Fe, Ni, and Co) in a total amount of 76.0 at % or more in terms of atomic fraction and Cu in an amount of 0.1 at % or more and 2.0 at % or less in terms of atomic fraction. 
     
     
         7 . The method for manufacturing atomized metal powder according to  claim 3 , wherein the atomized metal powder contains iron-group constituents (Fe, Ni, and Co) in a total amount of 76.0 at % or more in terms of atomic fraction and Cu in an amount of 0.1 at % or more and 2.0 at % or less in terms of atomic fraction. 
     
     
         8 . The method for manufacturing atomized metal powder according to  claim 4 , wherein the atomized metal powder contains iron-group constituents (Fe, Ni, and Co) in a total amount of 76.0 at % or more in terms of atomic fraction and Cu in an amount of 0.1 at % or more and 2.0 at % or less in terms of atomic fraction. 
     
     
         9 . The method for manufacturing atomized metal powder according to  claim 1 , wherein the atomized metal powder contains iron-group constituents (Fe, Ni, and Co) in a total amount of more than 82.5 at % and less than 86.0 at % in terms of atomic fraction, at least two selected from Si, P, and B, and Cu and has an average particle size of 5 μm or more. 
     
     
         10 . The method for manufacturing atomized metal powder according to  claim 2 , wherein the atomized metal powder contains iron-group constituents (Fe, Ni, and Co) in a total amount of more than 82.5 at % and less than 86.0 at % in terms of atomic fraction, at least two selected from Si, P, and B, and Cu and has an average particle size of 5 μm or more. 
     
     
         11 . The method for manufacturing atomized metal powder according to  claim 3 , wherein the atomized metal powder contains iron-group constituents (Fe, Ni, and Co) in a total amount of more than 82.5 at % and less than 86.0 at % in terms of atomic fraction, at least two selected from Si, P, and B, and Cu and has an average particle size of 5 μm or more. 
     
     
         12 . The method for manufacturing atomized metal powder according to  claim 4 , wherein the atomized metal powder contains iron-group constituents (Fe, Ni, and Co) in a total amount of more than 82.5 at % and less than 86.0 at % in terms of atomic fraction, at least two selected from Si, P, and B, and Cu and has an average particle size of 5 μm or more. 
     
     
         13 . The method for manufacturing atomized metal powder according to  claim 1 ,
 wherein the subcritical state is represented by a pressure of 0.5 MPa to 22 MPa and a water temperature of higher than 150° C. and lower than 374° C., and   wherein the supercritical state is represented by a pressure of 22 MPa or higher and a water temperature of 374° C. or higher.   
     
     
         14 . The method for manufacturing atomized metal powder according to  claim 2 ,
 wherein the subcritical state is represented by a pressure of 0.5 MPa to 22 MPa and a water temperature of higher than 150° C. and lower than 374° C., and   wherein the supercritical state is represented by a pressure of 22 MPa or higher and a water temperature of 374° C. or higher.   
     
     
         15 . The method for manufacturing atomized metal powder according to  claim 3 ,
 wherein the subcritical state is represented by a pressure of 0.5 MPa to 22 MPa and a water temperature of higher than 150° C. and lower than 374° C., and   wherein the supercritical state is represented by a pressure of 22 MPa or higher and a water temperature of 374° C. or higher.   
     
     
         16 . The method for manufacturing atomized metal powder according to  claim 4 ,
 wherein the subcritical state is represented by a pressure of 0.5 MPa to 22 MPa and a water temperature of higher than 150° C. and lower than 374° C., and   wherein the supercritical state is represented by a pressure of 22 MPa or higher and a water temperature of 374° C. or higher.   
     
     
         17 . The method for manufacturing atomized metal powder according to  claim 5 ,
 wherein the subcritical state is represented by a pressure of 0.5 MPa to 22 MPa and a water temperature of higher than 150° C. and lower than 374° C., and   wherein the supercritical state is represented by a pressure of 22 MPa or higher and a water temperature of 374° C. or higher.   
     
     
         18 . The method for manufacturing atomized metal powder according to  claim 6 ,
 wherein the subcritical state is represented by a pressure of 0.5 MPa to 22 MPa and a water temperature of higher than 150° C. and lower than 374° C., and   wherein the supercritical state is represented by a pressure of 22 MPa or higher and a water temperature of 374° C. or higher.   
     
     
         19 . The method for manufacturing atomized metal powder according to  claim 9 ,
 wherein the subcritical state is represented by a pressure of 0.5 MPa to 22 MPa and a water temperature of higher than 150° C. and lower than 374° C., and   wherein the supercritical state is represented by a pressure of 22 MPa or higher and a water temperature of 374° C. or higher.   
     
     
         20 . The method for manufacturing atomized metal powder according to  claim 10 ,
 wherein the subcritical state is represented by a pressure of 0.5 MPa to 22 MPa and a water temperature of higher than 150° C. and lower than 374° C., and   wherein the supercritical state is represented by a pressure of 22 MPa or higher and a water temperature of 374° C. or higher.