Ductile iron composition and process of forming a ductile iron component

Patent metadata

Field	Value
Publication number	US-10787726-B2
Application number	US-201615142323-A
Country	US
Kind code	B2
Filing date	Apr 29, 2016
Priority date	Apr 29, 2016
Publication date	Sep 29, 2020
Grant date	Sep 29, 2020

Abstract

A ductile iron composition including, by weight:
about 3.4% to about 4.0% Si; about 3.0% to about 3.5% C; about 0.5% to about 1.0% Cr; about 0.02% to about 0.05% Mo; up to about 0.01% S; up to about 0.5% Mn; and balance iron and incidental impurities.

The composition has a a ferritic body center cubic microstructure and has a graphite nodule density of greater than 100 per mm 2 . A method for forming a ductile iron composition is also disclosed.

First claim

What is claimed is:

1. A ductile iron composition, consisting of, by weight:
about 3.4% to about 4.0% Si;
about 3.0% to about 3.5% C;
about 0.5% to about 1.0% Cr;
about 0.02% to about 0.05% Mo;
up to about 0.01% S;
about 0.3% to about 0.5% Mn; and
balance iron and incidental impurities;
wherein the ductile iron composition includes a ferritic body center cubic microstructure and has a graphite nodule density of greater than 100 per mm 2 ; and
wherein the ductile iron composition is devoid of Ni.

2. The ductile iron composition of claim 1 , wherein the ductile iron composition consists of, by weight:
about 3.5% to about 3.9% Si;
about 3.1% to about 3.4% C;
about 0.6% to about 0.9% Cr;
about 0.03% to about 0.04% Mo;
up to about 0.01% S;
about 0.3% to about 0.4% Mn; and
balance iron and incidental impurities.

3. The ductile iron composition of claim 1 , wherein the ductile iron composition includes microstructure containing less than 15 areal % pearlite.

4. The ductile iron composition of claim 1 , wherein the ductile iron composition includes microstructure containing less than 5 areal % pearlite.

5. The ductile iron composition of claim 1 , wherein the ductile iron composition includes microstructure containing carbide volumetric percentage between about 5% and about 20%.

6. The ductile iron composition of claim 1 , wherein the graphite nodule density is greater than 125 per mm 2 .

7. The ductile iron composition of claim 1 , wherein the graphite nodule density is greater than 150 per mm 2 .

8. A component comprising the ductile iron composition, according to claim 1 .

9. The component of claim 8 , comprising a component selected from the group consisting of gearbox components, ring gears, planetary gears, and mining equipment.

10. A method of forming a ductile iron component, the process comprising:
forming a melt of a charge alloy;
nodularizing the melt with a nodularizing alloy;
inoculating the melt with an inoculating composition to nucleate graphite nodules and form the component comprising a ductile iron composition consisting of, by weight:
about 3.4% to about 4.0% Si;
about 3.0% to about 3.5% C;
about 0.5% to about 1.0% Cr;
about 0.02% to about 0.05% Mo;
up to about 0.01% S;
about 0.3% to about 0.5% Mn; and
balance iron and incidental impurities;

wherein the ductile iron composition includes a ferritic body center cubic microstructure and has a graphite nodule density of greater than 100 per mm 2 ; and
wherein the ductile iron composition is devoid of Ni.

11. The method of claim 10 , wherein the nodularizing composition comprises, by weight:
a first portion comprising, by weight, of the first portion:
about 0.2 to about 2.0% Al;
about 0.2 to about 2.0% Ca;
about 0.2 to about 2.0% rare earth elements;
2.0 to about 4.0% Mg; and
balance essentially FeSi and incidental impurities; and

second portion comprising, by weight:
about 0.2 to about 2.0% Al;
about 0.2 to about 2.0% Ca;
less than about 0.1% rare earth elements;
2.0 to about 4.0% Mg; and
balance essentially FeSi and incidental impurities.

12. The method of claim 11 , wherein the nodularizing composition comprises, by weight, from about 1.0% to about 1.4% of the charge alloy and nodularizing composition.

13. The method of claim 10 , wherein the inoculating composition includes a ferrosilicon composition comprising, by weight, about 0.2 to about 2.0% Al, about 0.2 to about 2.0% Ca, and about 1.0 to about 2.0% Ce.

14. The method of claim 10 , further comprising heat treating the component at a temperature and for time sufficient to induce formation of carbides in the ductile iron composition.

15. The method of claim 14 , further comprising heat treating the component at a temperature between about 400° C. and 600° C.

16. The method of claim 14 , wherein the ductile iron composition includes microstructure containing carbide volumetric percentage between about 5% and about 20%.

17. The method of claim 10 , wherein the ductile iron composition includes microstructure containing less than 15 areal % pearlite.

Assignees

• Gen Electric

Inventors

• Park Junyoung
• Ucok Ibrahim

Classifications

• C21D5/14

  Graphitising · CPC title

• C21C1/105

  Nodularising additive agents · CPC title

• C21D9/32

  for gear wheels, worm wheels, or the like · CPC title

• C21D5/00

  Heat treatments of cast-iron · CPC title

• C21D2211/009

  Pearlite · CPC title