Steel material having excellent corrosion resistance and excellent magnetic properties and production method therefor

Patent metadata

Field	Value
Publication number	US-2016012947-A1
Application number	US-201414771319-A
Country	US
Kind code	A1
Filing date	Mar 26, 2014
Priority date	Mar 29, 2013
Publication date	Jan 14, 2016
Grant date	—

Abstract

The present invention inexpensively provides a steel material having greater corrosion resistance than electromagnetic stainless steel and also having excellent magnetic properties. The steel material comprises, in % by mass, 0.001%-0.025% C, 1.0%-4.0% Si, 0.1%-1.0% Mn, more than 0% but no more than 0.030% P, more than 0% but no more than 0.10% S, more than 0% but less than 4.0% Cr, more than 0% but no more than 0.010% Al, and more than 0% but no more than 0.01% N, with the remainder being iron and unavoidable impurities; and is characterized by having an oxide coating formed on the steel surface material, said oxide coating including either Si or Cr, or both, including a non-crystalline layer, and having a thickness of 50-500 nm.

First claim

1 . A steel material comprising:
0.001 mass %-0.025 mass % C; 1.0 mass %-4.0 mass % Si; 0.1 mass %-1.0 mass % Mn; more than 0 mass % but no more than 0.030 mass % P; more than 0 mass % but no more than 0.10 mass % S; more than 0 mass % but no more than 4.0 mass % Cr; more than 0 mass % but no more than 0.010 mass % Al; and more than 0 mass % but no more than 0.01 mass % N, with the remainder consisting of iron and unavoidable impurities, wherein said steel material comprises an oxide coating on its surface, and wherein the oxide coating comprises either Si or Cr, or both, includes a non-crystalline layer, and has a thickness ranging from 50-500 nm.

2 . The steel material according to claim 1 , further comprising:
more than 0 mass % but no more than 0.5 mass % Cu, more than 0 mass % but no more than 0.5 mass % Ni; and/or more than 0 mass % but no more than 1.0 mass % Pb.

3 . A method for producing the steel material of claim 1 comprising:
producing a steel material comprising:
0.001 mass %-0.025 mass % C;
1.0 mass %-4.0 mass % Si;
0.1 mass %-1.0 mass % Mn;
more than 0 mass % but no more than 0.030 mass % P;
more than 0 mass % but no more than 0.10 mass % S;
more than 0 mass % but no more than 4.0 mass % Cr;
more than 0 mass % but no more than 0.010 mass % Al; and
more than 0 mass % but no more than 0.01 mass % N,
with the remainder consisting of iron and unavoidable impurities; and
annealing the steel material, wherein annealing comprises treating the steel material in an atmosphere containing no more than 1.0 ppm oxygen by volume at a temperature ranging from 800° C. to 1,200° C. for a time ranging from 1 hour to no longer than 20 hours.

4 . The method according to claim 3 , wherein the annealing temperature ranges from 800° C. to 1,100° C.

5 . The method according to claim 3 , wherein the annealing temperature ranges from 800° C. to 1,000° C.

6 . The method according to claim 3 , wherein the annealing time is no longer than 10 hours.

7 . A method for producing the steel material of claim 2 comprising:
producing a steel material comprising:
0.001 mass %-0.025 mass % C;
1.0 mass %-4.0 mass % Si;
0.1 mass %-1.0 mass % Mn;
more than 0 mass % but no more than 0.030 mass % P;
more than 0 mass % but no more than 0.10 mass % S;
more than 0 mass % but no more than 4.0 mass % Cr;
more than 0 mass % but no more than 0.010 mass % Al;
more than 0 mass % but no more than 0.01 mass % N; and
more than 0 mass % but no more than 0.5 mass % Cu, more than 0 mass % but no more than 0.5 mass % Ni; and/or more than 0 mass % but no more than 1.0 mass % Pb;
with the remainder consisting of iron and unavoidable impurities; and

annealing the steel material, wherein annealing comprises treating the steel material in an atmosphere containing no more than 1.0 ppm oxygen by volume at a temperature ranging from 800° C. to 1,200° C. for a time ranging from 1 hour to no longer than 20 hours.

8 . The method according to claim 7 , wherein the annealing temperature ranges from 800° C. to 1,100° C.

9 . The method according to claim 7 , wherein the annealing temperature ranges from 800° C. to 1,000° C.

10 . The method according to claim 7 , wherein the annealing time is no longer than 10 hours.

11 . The steel material according to claim 1 which exhibits a corrosion resistance characterized by a rust area ratio of less than 10% after immersion of a test piece of the steel material having size of 8 mm in diameter×8 mm in length in 1% H 2 SO 4 stirred for 24-36 hours at room temperature.

12 . The steel material according to claim 2 which exhibits a corrosion resistance characterized by a rust area ratio of less than 10% after immersion of a test piece of the steel material having size of 8 mm in diameter×8 mm in length in 1% H 2 SO 4 stirred for 24-36 hours at room temperature.

13 . The steel material according to claim 1 which exhibits a coercive force no more than 80 A/m and a magnetic flux density no less than 1.20 T as determined by JIS C2504 on a ring shaped specimen of the steel material having a size of 18 mm in outer diameter×10 mm inner diameter×3 mm in thickness.

14 . The steel material according to claim 2 which exhibits a coercive force no more than 80 A/m and a magnetic flux density no less than 1.20 T as determined by JIS C2504 on a ring shaped specimen of the steel material having a size of 18 mm in outer diameter×10 mm inner diameter×3 mm in thickness.

15 . An iron core, magnetic shield material, or an actuator member for an electromagnetic valve, solenoid, relay or other electromagnetic component, comprising the steel material according to claim 1 .

16 . An iron core, magnetic shield material, or an actuator member for an electromagnetic valve, solenoid, relay or other electromagnetic component, comprising the steel material according to claim 2 .

Assignees

• Kobe Steel Ltd
• Kaigandori 2 Chome Chuo Ku Kk

Inventors

• Masumoto Kei

Classifications

• C22C38/34

  with more than 1.5% by weight of silicon · CPC title

• C22C38/16

  containing copper · CPC title

• C21D6/001

  containing Ni (C21D6/004 takes precedence) · CPC title

• C22C38/02

  containing silicon · CPC title

• C21D1/26

  Methods of annealing · CPC title