Iron-based powder for powder metallurgy and method for producing iron-based powder for powder metallurgy
An iron-based powder for powder metallurgy includes an iron-based powder and a composite oxide powder, and the composite oxide contains, by mass, from 15% to 30% Si, from 9% to 18% Al, from 3% to 6% B, from 0.5% to 3% Mg, from 2% to 6% Ca, from 0.01% to 1% Sr, and from 45% to 55% O.
1. An iron-based powder for powder metallurgy, comprising an iron-based powder and a composite oxide powder,
wherein the composite oxide contains, by mass:
from 15% to 30% Si,
from 9% to 18% Al,
from 3% to 6% B,
from 0.5% to 3% Mg,
from 2% to 6% Ca,
from 0.01% to 1% Sr, and
from 45% to 55% O.
2. The iron-based powder for powder metallurgy according to claim 1 ,
wherein the composite oxide further contains, by mass, at least one element selected from:
from 0.005% to 1% Na,
from 0.005% to 1% K,
from 0.005% to 2% Ti, and
from 0.005% to 5% Ba.
3. The iron-based powder for powder metallurgy according to claim 1 , wherein a content of the composite oxide powder in the iron-based powder for powder metallurgy is from 0.01% by mass to 0.3% by mass.
4. The iron-based powder for powder metallurgy according to claim 1 ,
wherein the composite oxide has a softening point of 780° C. or lower and a viscosity at the softening point of 1×10 7.6 dPa·s or less.
5. The iron-based powder for powder metallurgy according to claim 1 , wherein the composite oxide has a glass transition point of 680° C. or lower.
6. The iron-based powder for powder metallurgy according to claim 1 ,
wherein the composite oxide powder has an average particle diameter of 10 μm or less, the average particle diameter being not more than ⅕ an average particle diameter of the iron-based powder, and a maximum particle diameter of 20 μm or less.
7. The iron-based powder for powder metallurgy according to claim 1 , wherein the composite oxide powder has an average particle diameter of 5 μm or less, the average particle diameter being not more than 1/10 the average particle diameter of the iron-based powder, and a maximum particle diameter of 10 μm or less.
8. The iron-based powder for powder metallurgy according to claim 1 , wherein the composite oxide contains an amorphous component in an amount of 30% by mass or more.
9. The iron-based powder for powder metallurgy according to claim 1 , further comprising at least one of a graphite powder and at least one non-Fe metal powder selected from Cu, Ni, Cr, and Mo powders.
10. The iron-based powder for powder metallurgy according to claim 9 , wherein the graphite powder has an average particle diameter of from 2 μm to 30 μm and is contained in an amount of from 0.2% by mass to 3.0% by mass based on a total amount of the iron-based powder for powder metallurgy.
11. The iron-based powder for powder metallurgy according to claim 9 , wherein the non-Fe metal powder has an average particle diameter of from 10 μm to 100 μm and is contained in an amount of from 0.5% by mass to 6.5% by mass based on the total amount of the iron-based powder for powder metallurgy.
12. A method for producing an iron-based powder for powder metallurgy by mixing an iron-based powder with a composite oxide powder, the method comprising the steps of:
heating a composite oxide containing, by mass:
from 15% to 30% Si,
from 9% to 18% Al,
from 3% to 6% B,
from 0.5% to 3% Mg,
from 2% to 6% Ca,
from 0.01% to 1% Sr, and
from 45% to 55% 0 to a melting point of the composite oxide or higher and then performing cooling or rapid cooling to prepare a composite oxide frit;
coarsely pulverizing the composite oxide frit to an average particle diameter of 20 or less to prepare a coarse powder;
finely pulverizing the coarse powder to a predetermined particle diameter with an airflow pulverizer, which uses no grinding media, to prepare a fine powder; and
mixing the fine powder with the iron-based powder by using a shear force mixer capable of breaking up aggregates of the fine powder.
13. The method for producing an iron-based powder for powder metallurgy according to claim 12 , wherein the airflow pulverizer is a jet mill.
14. The method for producing an iron-based powder for powder metallurgy according to claim 12 , wherein the mixer is a double cone mixer, a stirring mixer, or an eccentric mixer.