Steel for high-strength spring, method for producing same, and high-strength spring

Patent metadata

Field	Value
Publication number	US-9404547-B2
Application number	US-201313886106-A
Country	US
Kind code	B2
Filing date	May 2, 2013
Priority date	Nov 11, 2010
Publication date	Aug 2, 2016
Grant date	Aug 2, 2016

Abstract

A steel for high-strength spring has an Ac 3 transformation temperature as an indicator of the decarburization performance, which is calculated by Equation (1) below, is from 859 to 885° C., a maximum hardened diameter DI as an indicator of the hardening performance, which is calculated by Equation (2) below, is from 70 to 238 mm, and a temper hardness HRC as an indicator of the spring performance, which is calculated by Equation (3) below, is from 50 to 55.

Ac 3 =910−203×√{square root over (C)}−15.2Ni+44.7Si+104V+31.5Mo+13.1W  (1)

DI=D O ×f Si ×f Mn ×f P ×f S ×f Cu ×f Ni ×f Cr   (2)

HRC=38.99+17.48C+2.55Si−2.28Ni+2.37Cr+8.04Ti  (3)

wherein, D 0 =8.65×√{square root over (C)}, f Si =1+0.64×% Si, f Mn =1+4.10×% Mn, f P =1+2.83×% P, f S =1−0.62×% S, f Cu =1+0.27×% Cu, f Ni =1+0.52×% Ni, and f Cr =1+2.33×% Cr.

First claim

What is claimed is:

1. A steel for a spring for a vehicle comprising: C: 0.38 to 0.44%, Si: 2.00 to 2.30%, Mn: 0.99 to 1.25%, Cr: 0.10 to 0.43%, Ni: 0.15 to 0.35%, Cu: 0.15 to 0.35%, Ti: 0.09 to 0.13%, P: 0.02% or less (0% is not included), S: 0.02% or less (0% is not included), Al: 0.003 to 0.10%, N: 0.002 to 0.012%, O: 0.002% or less (0% is not included), by mass %, and the remainder consisting of iron and inevitable impurities, wherein an Ac 3 transformation temperature as an indicator of the decarburization performance, which is calculated by Equation (1) below, is from 859° C. to 885° C., a maximum hardened diameter DI as an indicator of the hardening performance, which is calculated by Equation (2) below, is from 70 to 238 mm, and a temper hardness HRC as an indicator of the spring performance, which is calculated by Equation (3) below, is from 50 to 55,
Ac 3 =910−203×√{square root over (C)}−15.2Ni+44.7Si+104V+31.5Mo+13.1W   (1),

DI=D O ×f Si ×f Mn ×f P ×f S ×f Cu ×f Ni ×f Cr   (2),

HRC=38.99+17.48C+2.55Si−2.28Ni+2.37Cr+8.04Ti   (3),

wherein D O =8.65×√{square root over (C)}, f Si =1+0.64×% Si, f Mn =1+4.10×% Mn, f P =1+2.83×% P, f S =1−0.62×% S, f Cu =1+0.27×% Cu, f Ni =1+0.52×% Ni, and f Cr =1+2.33×% Cr.

2. A method for producing a spring for a vehicle comprising:
hot or cold working a steel which comprises C: 0.38 to 0.44%, Si: 2.00 to 2.30%, Mn: 0.99 to 1.25%, Cr: 0.10 to 0.43%, Ni: 0.15 to 0.35%, Cu: 0.15 to 0.35%, Ti: 0.09 to 0.13%, P: 0.02% or less (0% is not included), S: 0.02% or less (0% is not included), Al: 0.003 to 0.10%, N: 0.002 to 0.012%, O: 0.002% or less (0% is not included), by mass %, and residue consisting of iron and inevitable impurities, wherein an Ac 3 transformation temperature as an indicator of the decarburization performance, which is calculated by Equation (1) below, is from 859° C. to 885° C., a maximum hardened diameter DI as an indicator of the hardening performance, which is calculated by Equation (2) below, is from 70 to 238 mm, and a temper hardness HRC as an indicator of the spring performance, which is calculated by Equation (3) below, is from 50 to 55, into a wire rod;
rolling the wire rod to be formed into a coil spring shape;
subjecting the spring to a heat treatment for hardening and tempering;
hot-setting the spring;
subjecting the spring to hot shot peening; and
pre-setting the spring,
Ac 3 =910−203×√{square root over (C)}−15.2Ni+44.7Si+104V+31.5Mo+13.1W   (1),

DI=D O ×f Si ×f Mn ×f P ×f S ×f Cu ×f Ni ×f Cr   (2),

HRC=38.99+17.48C+2.55Si−2.28Ni+2.37Cr+8.04Ti   (3),

wherein D O =8.65×√{square root over (C)}, f Si =1+0.64×% Si, f Mn =1+4.10×% Mn, f P =1+2.83×% P, f S =1×0.62×% S, f Cu =1+0.27×% Cu, f Ni =1+0.52×% Ni, and f Cr =1+2.33×% Cr.

3. The method according to claim 2 , wherein the wire rod is rolled by hot or cold forming to be formed into the coil spring shape, and the spring is subjected to hot shot peening so as to give a maximum shear stress of 1176 MPa or more.

4. The method according to claim 2 , wherein the hot shot peening is performed at 200° C. to 300° C.

5. A spring for a vehicle comprising a steel which comprises C: 0.38 to 0.44%, Si: 2.00 to 2.30%, Mn: 0.99 to 1.25%, Cr: 0.10 to 0.43%, Ni: 0.15 to 0.35%, Cu: 0.15 to 0.35%, Ti: 0.09 to 0.13%, P: 0.02% or less (0% is not included), S: 0.02% or less (0% is not included), Al: 0.003 to 0.10%, N: 0.002 to 0.012%, O: 0.002% or less (0% is not included), by mass %, and the remainder consisting of iron and inevitable impurities;
the steel being formed into a wire rod by hot or cold working, the wire rod being formed into a coil spring shape by rolling, the coil spring being subjected a heat treatment for hardening and tempering, being subjected a hot-setting, being subjected a hot shot peening, and being subjected a pre-setting;
wherein an Ac 3 transformation temperature as an indicator of the decarburization performance, which is calculated by Equation (1) below, is from 859° C. to 885° C., a maximum hardened diameter DI as an indicator of the hardening performance, which is calculated by Equation (2) below, is from 70 to 238 mm, and a temper hardness HRC as an indicator of the spring performance, which is calculated by Equation (3) below, is from 50 to 55,
Ac 3 =910−203×√{square root over (C)}−15.2Ni+44.7Si+104V+31.5Mo+13.1W   (1),

DI=D O ×f Si ×f Mn ×f P ×f S ×f Cu ×f Ni ×f Cr   (2),

HRC=38.99+17.48C+2.55Si−2.28Ni+2.37Cr+8.04Ti   (3),

wherein D O =8.65×√{square root over (C)}, f Si =1+0.64×% Si, f Mn =1+4.10×% Mn, f P =1+2.83×% P, f S =1−0.62×% S, f Cu =1+0.27×% Cu, f Ni =1+0.52×% Ni, and f Cr =1+2.33×% Cr.

6. The spring according to claim 5 , wherein the wire rod is rolled by hot or cold forming to be formed into the coil spring shape, and the spring is subjected to hot shot peening so as to provide a maximum shear stress of 1176 MPa or more.

7. The spring according to claim 5 , wherein the hot shot peening is performed at 200° C. to 300° C.

Assignees

• Nhk Spring Co Ltd

Inventors

• Okada Hideki
• Tange Akira
• Tango Koichi
• Sumiyoshi Isao

Classifications

• C21D8/06

  during manufacturing of rods or wires · CPC title

• C22C38/42

  with copper · CPC title

• C22C38/001

  containing N · CPC title

• C21D9/02

  for springs · CPC title

• F16F1/02

  made of steel or other material having low internal friction {(characterised by their special construction from fibre-reinforced plastics F16F1/366; spring units consisting of several springs F16F3/02; making springs from wire B21F35/00)}; Wound, torsion, leaf, cup, ring or the like springs, the material of the spring not being relevant · CPC title