Hollow seamless pipe for high-strength spring

Patent metadata

Field	Value
Publication number	US-9429255-B2
Application number	US-201314389866-A
Country	US
Kind code	B2
Filing date	Apr 2, 2013
Priority date	Apr 2, 2012
Publication date	Aug 30, 2016
Grant date	Aug 30, 2016

Abstract

A hollow seamless pipe for a high-strength spring in the present invention includes a steel material in which chemical component compositions are properly adjusted, wherein a depth of a whole decarburized layer in an inner surface layer part is 100 μm or less, a depth of a flaw which is present in an inner surface is 40 μm or less, a width of the flaw is 60 μm or less, and a number density of a carbide which has a circle equivalent diameter of 500 nm or more and is present in the inner surface layer part is 1.8×10 −2 particles/μm 2 or less.

First claim

The invention claimed is:

1. A hollow seamless pipe suitable for a high-strength spring, comprising a steel material comprising 0.2 mass % to 0.7 mass % of C, 0.5 mass % to 3 mass % of Si, 0.1 mass % to 2 mass % of Mn, more than 0 mass % and 0.1 mass % or less of Al, more than 0 mass % and 3 mass % or less of Cr, more than 0 mass % and 0.02 mass % or less of P, more than 0 mass % and 0.02 mass % or less of S, and more than 0 mass % and 0.02 mass % or less of N, wherein a depth of a whole decarburized layer in an inner surface layer part is 100 μm or less, a depth of a flaw which is present in an inner surface is 40 μm or less, a width of the flaw is 60 μm or less, and a number density of a carbide which has a circle equivalent diameter of 500 nm or more and is present the inner surface layer part is 1.8×10 −2 particles/μm 2 or less.

2. The hollow seamless pipe suitable for a high-strength spring according to claim 1 , wherein the steel material further comprises at leas one of the following groups (a) to (f):
(a) more than 0 mass % and 0.015 mass % or less of B,
(b) one or more kinds selected from the group consisting of: more than 0 mass % and 1 mass % or less of V; more than 0 mass % and 0.3 mass % or less of Ti; and more than 0 mass % and 0.3 mass % or less of Nb,
(c) one or more kinds selected from the group consisting of: more than mass % and 3 mass % or less of Ni; and more than 0 mass % and 3 mass % or less of Cu,
(d) more than 0 mass % and 2 mass % or less of Mo,
(e) one or more kinds selected from the group consisting of: more than 0 mass % and 0.005 mass % or less of Ca; more than 0 mass % and 0.005 mass % or less of Mg; and more than 0 mass % and 0.02 mass % or less of REM, and
(f) one or more kinds selected from the group consisting of: more than 0 mass % and 0.1 mass % or less of Zr; more than 0 mass % and 0.1 mass % or less of Ta; and more than 0 mass % and 0.1 mass % or less of Hf.

3. The hollow seamless pipe suitable for a high-strength spring according to claim 1 , wherein the depth of a flaw which is present in an inner surface is 30 μm or less.

4. The hollow seamless pipe suitable for a high-strength spring according to claim 1 . wherein the depth of a flaw which is present in an inner surface is 20 μm or less.

5. The hollow seamless pipe suitable for a high-strength spring according to claim 1 , wherein the width of the flaw is 40 μm or less.

6. The hollow seamless pipe suitable for a high-strength spring according to claim 1 , wherein the width of the flaw is 20 μm or less.

7. The hollow seamless pipe suitable for a high-strength spring according to claim 1 , wherein the depth of a decarburized layer is 80 μm or less.

8. The hollow seamless pipe suitable for a high-strength spring according to claim 1 , wherein the depth of a decarburized layer is 60 μm or less.

9. The hollow seamless pipe suitable for a high-strength spring according to claim 1 , wherein the number density of a carbide which has a circle equivalent diameter of 500 nm or more and is present in the inner surface layer part is 1.5×10 −2 particles/μm 2 or less.

10. The hollow seamless pipe suitable for a high-strength spring according to claim 1 , wherein the number density of a carbide which has a circle equivalent diameter of 500 nm or more and is present in the inner surface layer part is 1.0×10 −2 particles/μm 2 or less.

11. The hollow seamless pipe suitable for a high-strength spring according to claim 1 , comprising 0.35 mass % to 0.60 mass % of C.

12. The hollow seamless pipe suitable for a high-strength spring according to claim 1 , comprising 1.5 mass % to 2.2 mass % of Si.

13. The hollow seamless pipe suitable for a high-strength spring according to claim 1 , comprising 0.2 mass % to 1.0 mass % of Mn.

14. The hollow seamless pipe suitable for a high-strength spring according to claim 1 , comprising 0.05 mass % or less of Al.

15. The hollow seamless pipe suitable for a high-strength spring according to claim 1 , comprising 1.7 mass % or less of Cr.

16. The hollow seamless pipe suitable for a high-strength spring according to claim 1 , comprising 0.008 mass % or less of P.

17. The hollow seamless pipe suitable for a high-strength spring according to claim I, comprising 0.008 mass % or less of S.

18. The hollow seamless pipe suitable for a high-strength spring according to claim 1 , comprising 0.0050 mass % or less of N.

Assignees

• Kobe Steel Ltd
• Shinko Metal Prod
• Nhk Spring Co Ltd

Inventors

• Kochi Takuya
• Hatano Hitoshi
• Tamura Eiichi
• Toyotake Kotaro
• Yajima Takashi
• Tange Akira

Classifications

• C22C38/54

  with boron · CPC title

• C22C38/50

  with titanium or zirconium · CPC title

• C22C38/20

  with copper · CPC title

• C21D2211/004

  Dispersions; Precipitations · CPC title

• C21D6/008

  containing Si · CPC title