High Strength Spring Steel, High Strength Springs and Manufacturing Method Thereof

Abstract

A high strength spring steel of this invention is characterized in containing, in percent of mass, of C: 0.36-0.48%; Si: 1.80-2.80%; Mn: 0.20-1.40%; P: 0.015% or less; S: 0.010% or less; Cu: 0.10-0.50%; Ni: 0.10-2.00%; Cr: 0.05-1.20%; s-Al: 0.005-0.040%; N: 0.002-0.012%; O: 0.002% or less, while the remainder is constituted of Fe and inevitable impurities and the quantity of inclusions of 10 μm or larger in diameter per field of vision of 100 mm 2 is 10 or less. A manufacturing method of high strength spring of this invention is characterized in that the high strength spring steel which is tempered to HRC52 or higher is formed into a spring shape by hot forming or cold forming and warm shot peening is carried out so as to produce a high strength spring of 1176 MPa or higher in maximum shearing stress.

1 . A high strength spring steel containing in percent of mass: C: 0.36-0.48%; Si: 1.80-2.80%; Mn: 0.20-1.40%; P: 0.015% or less; S: 0.010% or less; Cu: 0.10-0.50%; Ni: 0.10-2.00%; Cr: 0.05-1.20%; s-Al: 0.005-0.040%; N: 0.002-0.012%; O: 0.002% or less, while the remainder is constituted of Fe and inevitable impurities, wherein following equations (1), (2), (3) are satisfied and the quantity of inclusions of 10 μm or larger in diameter per field of vision of 100 mm 2  is 10 or less:  
       1.2%≦C(%)+Mn(%)+Cr(%)≦2.0%  equation (1)  1.4%≦Si(%)/3+Cr(%)/2+Mn(%)≦2.4%  equation (2)  0.4%≦Cu(%)+Ni(%)  equation (3)  
   
   
       2 . A high strength spring steel containing in percent of mass: C: 0.36-0.48%; Si: 1.80-2.80%; Mn: 0.20-1.40%; P: 0.015% or less; S: 0.010% or less; Cu: 0.10-0.50%; Ni: 0.10-2.00%; Cr: 0.05-1.20%; s-Al: 0.005-0.040%; N: 0.002-0.012%; O: 0.002% or less, while further one or more of Ti: 0.020-0.070%, Nb: 0.020-0.050%, B: 0.0005-0.0030% are contained and the remainder is constituted of Fe and inevitable impurities, wherein following equations (1), (2)′, (3) are satisfied and the quantity of inclusions of 10 μm or larger in diameter per field of vision of 100 mm 2  is 10 or less:  
       1.2%≦C(%)+Mn(%)+Cr(%)≦2.0%  equation (1)  1.4%≦Si(%)/3+Cr(%)/2+Mn(%)+170B(%)≦2.4%  equation (2)′ 0.4%≦Cu(%)+Ni(%)  equation (3).  
   
   
       3 . The high strength spring steel according to  claim 1  further containing one or two of Mo: 0.01-0.50% and V: 0.05-0.30% as steel component.  
   
   
       4 . A manufacturing method of high strength spring wherein the high strength spring steel according to  claim 1 , which is tempered to HRC52 or higher, is formed into a spring shape by hot forming or cold forming and warm shot peening is carried out so as to produce a high strength spring of 1176 MPa or higher in maximum shearing stress.  
   
   
       5 . The manufacturing method of high strength spring according to  claim 4  wherein the warm shot peening is executed in a temperature range of 200-350° C.  
   
   
       6 . A high strength spring using the high strength spring steel according to  claim 1  wherein the hardness is tempered to HRC52 or higher and the maximum shearing stress is 1176 MPa or higher.  
   
   
       7 . The high strength spring steel according to  claim 2  further containing one or two of Mo: 0.01-0.50% and V: 0.05-0.30% as steel component.  
   
   
       8 . A manufacturing method of high strength spring wherein the high strength spring steel according to  claim 2 , which is tempered to HRC52 or higher, is formed into a spring shape by hot forming or cold forming and warm shot peening is carried out so as to produce a high strength spring of 1176 MPa or higher in maximum shearing stress.  
   
   
       9 . A manufacturing method of high strength spring wherein the high strength spring steel according to  claim 3 , which is tempered to HRC52 or higher, is formed into a spring shape by hot forming or cold forming and warm shot peening is carried out so as to produce a high strength spring of 1176 MPa or higher in maximum shearing stress.  
   
   
       10 . A manufacturing method of high strength spring wherein the high strength spring steel according to  claim 7 , which is tempered to HRC52 or higher, is formed into a spring shape by hot forming or cold forming and warm shot peening is carried out so as to produce a high strength spring of 1176 MPa or higher in maximum shearing stress.  
   
   
       11 . The manufacturing method of high strength spring according to  claim 8  wherein the warm shot peening is executed in a temperature range of 200-350° C.  
   
   
       12 . The manufacturing method of high strength spring according to  claim 9  wherein the warm shot peening is executed in a temperature range of 200-350° C.  
   
   
       13 . The manufacturing method of high strength spring according to  claim 10  wherein the warm shot peening is executed in a temperature range of 200-350° C.  
   
   
       14 . A high strength spring using the high strength spring steel according to  claim 2  wherein the hardness is tempered to HRC52 or higher and the maximum shearing stress is 1176 MPa or higher.  
   
   
       15 . A high strength spring using the high strength spring steel according to  claim 3  wherein the hardness is tempered to HRC52 or higher and the maximum shearing stress is 1176 MPa or higher.  
   
   
       16 . A high strength spring using the high strength spring steel according to  claim 7  wherein the hardness is tempered to HRC52 or higher and the maximum shearing stress is 1176 MPa or higher.