Method for manufacturing steel sheet for rotor core for IPM motor

Patent metadata

Field	Value
Publication number	US-9847168-B2
Application number	US-201314389595-A
Country	US
Kind code	B2
Filing date	Mar 27, 2013
Priority date	Mar 30, 2012
Publication date	Dec 19, 2017
Grant date	Dec 19, 2017

Abstract

The present invention manufactures a steel sheet for a rotor core for an IPM motor, wherein the steel sheet has a magnetic flux density B 8000 of 1.65 T or more as measured when magnetic field strength is 8000 A/m, and a residual magnetic flux density Br of 0.5 T or more as measured at that time, and optionally, a coercivity Hc of 100 A/m or more as measured after magnetization reaches 8000 A/m. By using the steel sheet manufactured according to the present invention for a rotor core of an IPM motor, it is possible to increase further an output torque in a high-speed rotational range and raise further the maximum rotational speed.

First claim

The invention claimed is:

1. A method for manufacturing a steel sheet for a rotor core for an IPM motor, which has a magnetic flux density B 8000 of 1.65 T or more as measured when magnetic field strength is 8000 A/m and a residual magnetic flux density Br of 0.5 T or more as measured at that time, wherein a hot-rolled steel sheet having a composition comprising: C: more than 0.0005% by mass to 0.90% by mass, Si: 0% by mass to 3.0% by mass, Mn: 0% by mass to 0.05% by mass, P: 0.05% by mass or less, S: 0.02% by mass or less, acid-soluble Al: 0.005% by mass to 3.0% by mass, and Si+Al: 5.0% by mass or less, with a balance of Fe and inevitable impurities, is cold rolled, heated to 800° C. or more in a continuous annealing line or continuous quenching line, then cooled down to 450° C. or less at a cooling speed of 10° C./sec or more and held at a temperature range of 200° C. to 450° C. for at least 20 seconds and less than 120 seconds, and then a step of adjusting a flatness defined by a steepness per sheet width to 0.1% or less by performing inline or offline press tempering treatment in a state of being held at said temperature range of 200° C. to 450° C.

2. The method for manufacturing a steel sheet for a rotor core for an IPM motor according to claim 1 , wherein the steel sheet for a rotor core for an IPM motor has a coercivity Hc of 100 A/m or more as measured after magnetization reaches 8000 A/m.

3. The method for manufacturing a steel sheet for a rotor core for an IPM motor according to claim 1 , wherein the metallographic structure of the steel sheet for a rotor core for an IPM motor is composed of a single phase of martensite, a single phase of bainite, or a composite structure including less than 10% by volume of ferrite in addition to martensite.

4. The method for manufacturing a steel sheet for a rotor core for an IPM motor according to claim 1 , wherein the hot-rolled steel sheet further comprises one or more components selected from the group consisting of Ti, Nb, and V at 0.01% by mass to 0.20% by mass in total.

5. The method for manufacturing a steel sheet for a rotor core for an IPM motor according to claim 1 , wherein the hot-rolled steel sheet further comprises one or more components selected from the group consisting of Mo: 0.1% by mass to 0.6% by mass, Cr: 0.1% by mass to 1.0% by mass and B: 0.0005% by mass to 0.005% by mass.

6. The method for manufacturing a steel sheet for a rotor core for an IPM motor according to claim 1 , wherein the hot-rolled steel sheet further comprises one or more components selected from the group consisting of Cu: 0.05% by mass to 1.5% by mass and Ni: 0.05% by mass to 1.0% by mass.

7. The method for manufacturing a steel sheet for a rotor core for an IPM motor according to claim 1 , wherein the content of C in the hot-rolled steel sheet is more than 0.0005% by mass to 0.058% by mass.

8. The method for manufacturing a steel sheet for a rotor core for an IPM motor according to claim 1 , further comprising a step of forming an insulating coating consisting of an organic material, an insulating coating consisting of an inorganic material or an insulating coating consisting of an organic-inorganic composite material on at least one surface of the steel sheet in an inline or offline process.

9. The method for manufacturing a steel sheet for a rotor core for an IPM motor according to claim 1 , wherein a pressure in the inline or offline press tempering treatment is less than 1 kg/cm 2 .

Assignees

• Nisshin Steel Co Ltd

Inventors

• Iwatsu Tomonaga
• Katagiri Yukio
• Fujiwara Susumu
• Kawamoto Akito

Classifications

• C22C38/14

  containing titanium or zirconium · CPC title

• C22C38/32

  with boron · CPC title

• C21D6/005

  containing Mn · CPC title

• C22C38/28

  with titanium or zirconium · CPC title

• C22C38/20

  with copper · CPC title