Steel material

Abstract

A steel material which is excellent in machinability, in which occurrence of cracks during hot working and melting cracks during induction hardening can be suppressed, and which has excellent fatigue strength when formed into a component for machine structural use is provided. A steel material of the present embodiment contains, in percent by mass, C: 0.05 to 0.30%, Si: 0.05 to 0.45%, Mn: 0.30 to 2.00%, P: 0.030% or less, S: 0.010 to 0.095%, Cr: 0.01 to 2.00%, Bi: 0.0051 to 0.1500%, and N: 0.0030 to 0.0250%, and satisfies the following Formula (1). In the steel material, a number density of fine Bi particles is 80 to 8000 pieces/mm2 and a number density of coarse Bi particles is 10 pieces/mm2 or less.0.25≤C+(Si/10)+(Mn/5)-(5⁢S/7)+(5⁢Cr/22)+1.65V≤1.(1)

1 - 7 . (canceled) 
     
     
         8 . A steel material comprising of, in percent by mass,
 C: 0.05 to 0.30%,   Si: 0.05 to 0.45%,   Mn: 0.30 to 2.00%,   P: 0.030% or less,   S: 0.010 to 0.095%,   Cr: 0.01 to 2.00%,   Bi: 0.0051 to 0.1500%,   N: 0.0030 to 0.0250%,   Al: 0 to 0.060%,   Mg: 0 to 0.0100%,   Ti: 0 to 0.1500%,   Nb: 0 to 0.0800%,   W: 0 to 0.4000%,   Zr: 0 to 0.2000%,   Ca: 0 to 0.0100%,   Te: 0 to 0.0100%,   B: 0 to 0.0050%,   Sn: 0 to 0.0100%,   rare earth metal: 0 to 0.0100%,   Co: 0 to 0.0100%,   Se: 0 to 0.0100%,   Sb: 0 to 0.0100%,   In: 0 to 0.0100%,   V: 0 to 0.200%,   Mo: 0 to 1.00%,   Cu: 0 to 0.20%,   Ni: 0 to 0.20%, and   with the balance comprising Fe and impurities,   and satisfying Formula (1),   wherein, in the steel material,   a number density of fine Bi particles having an equivalent circular diameter of 0.1 to 1.0 μm is 80 to 8000 pieces/mm 2 , and   a number density of coarse Bi particles having an equivalent circular diameter of 10.0 μm or more is 10 pieces/mm 2  or less;
   0.25≤C+(Si/10)+(Mn/5)−(5S/7)+(5Cr/22)+1.65V≤1.00  (1)
 
   where, a content in percent by mass of a corresponding element is substituted for each symbol of an element in the formula, and if an element is not contained, “0” is substituted for the corresponding symbol of an element.   
     
     
         9 . The steel material according to  claim 8 , wherein:
 the steel material contains containing one or more kinds of element selected from a group consisting of a first group to a fifth group,   [first group]   one or more kinds of element selected from a group consisting of:   Al: 0.001 to 0.060%, and   Mg: 0.0001 to 0.0100%;   [second group]   one or more kinds of element selected from a group consisting of:   Ti: 0.0001 to 0.1500%,   Nb: 0.0001 to 0.0800%,   W: 0.0001 to 0.4000%, and   Zr: 0.0001 to 0.2000%;   [third group]   one or more kinds of element selected from a group consisting of:   Ca: 0.0001 to 0.0100%,   Te: 0.0001 to 0.0100%,   B: 0.0001 to 0.0050%,   Sn: 0.0001 to 0.0100%, and   rare earth metal: 0.0001 to 0.0100%;   [fourth group]   one or more kinds of element selected from a group consisting of:   Co: 0.0001 to 0.0100%,   Se: 0.0001 to 0.0100%,   Sb: 0.0001 to 0.0100%, and   In: 0.0001 to 0.0100%;   [fifth group]   one or more kinds of element selected from a group consisting of:   V: 0.001 to 0.200%,   Mo: 0.01 to 1.00%,   Cu: 0.01 to 0.20%, and   Ni: 0.01 to 0.20%.   
     
     
         10 . The steel material according to  claim 9 , wherein:
 the steel material contains the first group.   
     
     
         11 . The steel material according to  claim 9 , wherein:
 the steel material contains the second group.   
     
     
         12 . The steel material according to  claim 9 , wherein:
 the steel material contains the third group.   
     
     
         13 . The steel material according to  claim 9 , wherein:
 the steel material contains the fourth group.   
     
     
         14 . The steel material according to  claim 9 , wherein:
 the steel material contains the fifth group.