# US 11,028,468 B2 · Soft magnetic alloy optimized for metal injection molding

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- Number: US 11,028,468 B2
- Document ID: US11028468B2
- Status: Granted
- Kind: B2
- Application number: 16/273,761
- Filed: 2019-02-12
- Published: 2020-04-02
- Granted: 2021-06-08
- Earliest claimed: 2018-09-28
- Assignees: Apple Inc.
- Applicants: Apple Inc.
- Inventors: John C. DiFonzo; Abhijeet Misra; Charles J. Kuehmann; Daniel T. McDonald
- Web page: https://patentgrep.com/patent/US11028468B2

## CPC

- C22C 38/10: containing cobalt
- C22C 33/0285: {with Cr, Co, or Ni having a minimum content higher than 5%}
- H01F 1/147: Alloys characterised by their composition {(treatment thereof for enhancing their electromagnetic properties C21D8/12)}
- H01F 1/22: pressed, sintered, or bound together
- H01F 41/0246: {Manufacturing of magnetic circuits by moulding or by pressing powder (magnetic cores made by moulding or by pressing powder H01F27/255; soft magnetic particles H01F1/20, H01F1/36)}
- H01F 1/20: in the form of particles, e.g. powder (H01F1/147 takes precedence)
- H04R 1/1016: {Earpieces of the intra-aural type}
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K)

## Abstract

A component for an electronic device can include a metal alloy formed by a metal injection molding process. The metal alloy can have a composition of about 32 wt % to about 38 wt % cobalt and about 62 wt % to about 68 wt % iron.

## Claims

### Claim 1

A sintered magnetic component for an electronic device, comprising:
a metal alloy in a body-centered cubic phase and comprising about 32 weight percent (wt %) to about 38 wt % cobalt and about 62 wt % to about 68% wt % iron;
the sintered magnetic component having a porosity between 2% and 10% and an average pore size of 2 microns to 5 microns.

### Claim 2 (depends on 1)

The component of claim 1, wherein the metal alloy has an average grain size of about 60 microns to about 100 microns.

### Claim 3 (depends on 1)

The component of claim 1, wherein the metal alloy includes less than about 60 parts per million (ppm) of each of oxygen, phosphorus, and sulphur.

### Claim 4 (depends on 1)

The component of claim 1, wherein the metal alloy is in an ordered body-centered cubic phase.

### Claim 5 (depends on 1)

The component of claim 1, wherein the magnetic component is a magnetic shunt.

### Claim 6 (depends on 1)

The component of claim 1, wherein the magnetic component is a magnetic retention component.

### Claim 7

A magnetic article, comprising:
sintered particles comprising a magnetic alloy, the magnetic alloy comprising about 34 weight percent (wt %) to about 36 wt % cobalt and about 64 wt % to about 66 wt % iron;
the magnetic article in an ordered body-centered cubic phase and having an average pore size of 2 microns to 5 microns.

### Claim 8 (depends on 7)

The magnetic article of claim 7, wherein the alloy includes about 35 wt % cobalt and about 65 wt % iron.

### Claim 9 (depends on 7)

The magnetic article of claim 7, wherein the magnetic article has a porosity less than about 10%.

### Claim 10 (depends on 7)

The magnetic article of claim 7, wherein the magnetic article has an average grain size of about 60 microns to about 100 microns.

### Claim 11 (depends on 7)

The magnetic article of claim 7, wherein the alloy has a saturation magnetization (Bsat) of about 2 tesla (T) to about 2.3 T.

### Claim 12 (depends on 11)

The magnetic article of claim 11, wherein the article is a magnetic shunt.

### Claim 13

A method of forming a sintered article from a feedstock, comprising:
heating a binder and the feedstock, the feedstock having about 34 weight percent (wt %) to about 36 wt % cobalt and about 64 wt % to about 66 wt % iron;
injecting the heated binder and feedstock into a mold; and
cooling the heated binder and feedstock; and
sintering the feedstock to form the sintered article, the sintered article comprising about 34 weight percent (wt %) to about 36 wt % cobalt and about 64 wt % to about 66 wt % iron and in an ordered body-centered cubic phase and having an average pore size of 2 microns to 5 microns.

### Claim 14 (depends on 13)

The method of claim 13, wherein:
the feedstock comprises a powder; and
90% of the particles of the powder have a maximum diameter of less than about 16 microns.

### Claim 15 (depends on 13)

The method of claim 13, further comprising:
sintering the article at a temperature between about 600° C. to about 800° C.; and
cooling the sintered article at a rate so that the article is in an ordered body-centered cubic phase.