Steel material

Abstract

The present invention relates to a steel material containing, in terms of mass %: 0.30%≤C≤0.45%, 0.10%≤Si≤1.00%, 0.60%≤Mn≤1.20%, 0.20%≤Cr≤0.70%, 0.30%≤V≤0.47%, Ti≤0.015%, P≤0.100%, and S≤0.080%, with the balance being Fe and inevitable impurities, and has a P0 value defined by P0=P0′×V/P1, satisfying P0≥0.30, here, P0′=Mn+0.49Cu+0.89Ni+0.40Cr−0.30Si, and P1=C+0.07Si+0.16Mn+0.61P+0.19Cu+0.17Ni+0.2Cr+V, in the formulae, each element symbol indicates a content of each element in units of mass %.

What is claimed is: 
     
         1 . A steel material,
 comprising, in terms of mass %:
 0.30%≤C≤0.45%, 
 0.10%≤Si≤1.00%, 
 0.60%≤Mn≤1.20%, 
 0.20%≤Cr≤0.70%, 
 0.30%≤V≤0.47%, 
 Ti≤0.015%, 
 P≤0.100%, 
 S≤0.080%, 
 Cu≤0.50%, 
 Ni≤0.50%, 
 Nb≤0.010%, 
 Ti≤0.015%, 
 Pb≤0.30%, 
 Bi≤0.20%, 
 Ca≤0.0100%, 
 Zr≤0.010%, 
 Mg≤0.010%, 
 Te 5 0.010%. 
 Mo≤0.10%, 
 Al≤0.050%, and 
 N≤0.030%, 
 with the balance being Fe and inevitable impurities, and 
   having a P0 value defined by the following formula (1), satisfying P0≥0.30:
   P0=P0′×V/P1  (1)
 
   here, 
   P0′=Mn+0.49Cu4−0.89Ni+0.40Cr−0.30Si  (2)
 
   P1C+0.07Si+0.16Mn+0.61P+0.19Cu+0.17Ni+0.2Cr+V  (3)
 
 in the formulae (1) to (3), each element symbol indicates a content of each element in units of mass %. 
   
     
     
         2 . The steel material according to  claim 1 , wherein the steel material is used in a state where heat treatment is not performed. 
     
     
         3 . The steel material according to  claim 1 ,
 comprising, in terms of mass %, at least one selected from:
 0%≤Cu≤0.50%, 
 0%≤Ni≤0.50%, 
 0%≤Nb≤0.010%, 
 0%≤Ti≤0.015%, 
 0%≤Pb≤0.30%, 
 0%≤Bi≤0.20%, 
 0%≤Ca 0.0100%, 
 0%≤Zr≤0.010%, 
 0%≤Mg≤0.010%, and 
 0%≤Te≤0.010%. 
   
     
     
         4 . The steel material according to  claim 1 , wherein the P1 value defined by the formula (3) satisfies 1.04≤P1≤1.15. 
     
     
         5 . The steel material according to  claim 1 , having a P2 value defined by the following formula (4) and a P3 value defined by the following formula (5), satisfying P2/P3≥1.4:
   P2=417−242C+30Si−25Mn−17Cu−22Ni−14Cr−35Mo  (4)
 
   P3=10∧(1.35−0.54C+0.02Si+0.77Mn+0.47Cu+0.42Ni+0.52Cr−4.84Mo)   (5)
 
 
       in the formulae (4) and (5), each element symbol indicates a content of each element in units of mass %. 
     
     
         6 . The steel material according to  claim 4 , having a P2 value defined by the following formula (4) and a P3 value defined by the following formula (5), satisfying P2/P3≥1.4:
   P2=417−242C+30Si−25Mn−17Cu−22Ni−14Cr−35Mo  (4)
 
   P3=10∧(1.35−0.54C+0.02Si+0.77Mn+0.47Cu±0.42Ni+0.52Cr+4.84Mo)   (5)
 
 in the formulae (4) and (5), each element symbol indicates a content of each element in units of mass %. 
 
     
     
         7 . The steel material according to  claim 1 , wherein
 in a cross section of the steel material in a state after hot forging,   the number of precipitates satisfying (V+Ti)≥30% and having an area of 1 μm 2  or more is 10 or less per 1 mm 2 .   
     
     
         8 . The steel material according to  claim 4 , wherein
 in a cross section of the steel material in a state after hot forging,   the number of precipitates satisfying (V+Ti)≥30% and having an area of 1 μm 2  or more is 10 or less per 1 mm 2 .   
     
     
         9 . The steel material according to  claim 5 , wherein
 in a cross section of the steel material in a state after hot forging,   the number of precipitates satisfying (V+Ti)≥30% and having an area of 1 μm2 or more is 10 or less per 1 mm2.   
     
     
         10 . The steel material according to  claim 6 , wherein
 in a cross section of the steel material in a state after hot forging,   the number of precipitates satisfying (V+Ti)≥30% and having an area of 1 μm 2  or more is 10 or less per 1 mm 2 .   
     
     
         11 . The steel material according to  claim 1 , having, in a state after hot forging:
 a yield point of 900 MPa or more, and   a yield ratio of 0.80 or more.