Martensitic free cutting stainless steel

Abstract

The present invention relates to a martensitic free cutting stainless steel, comprising: by weight percent, C: 0.10 to 1.20%, Si: 0.10 to 2.00%, Mn: 0.80 to 2.00%, S: 0.10 to 0.30%, Cr: 10.5 to 18.0%, Pb: 0.03 to 0.30%, Te: 0.01 to 0.10%, B: 0.0005 to 0.010%, and O: 0.005 to 0.030%, with the reminder being substantially Fe and inevitable impurities; wherein, among the inevitable impurities, contents of P and N are, P: 0.005 to 0.10%, and N: ≦0.050%; wherein respective formulae of 3.0≦[Mn]/[S]≦15.0, 0.10≦[Te]/[S], and 10≦[S]/[O]≦40 are satisfied; and wherein a sulfide having a circle equivalent diameter of 2.0 μm or more and an aspect ratio of 10 or less is present in a total amount of 0.50 to 10% by area ratio.

1 . A martensitic free cutting stainless steel, comprising:  
       by weight percent, 
 C: 0.10 to 1.20%,  
 Si: 0.10 to 2.00%,  
 Mn: 0.80 to 2.00%,  
 S: 0.10 to 0.30%,  
 Cr: 10.5 to 18.0%,  
 Pb: 0.03 to 0.30%,  
 Te: 0.01 to 0.10%,  
 B: 0.0005 to 0.010%, and  
 O: 0.005 to 0.030%, with the remainder being substantially Fe and inevitable impurities;  
 wherein, among the inevitable impurities, contents of P and N are:  
 P: 0.005 to 0.10%, and  
 N: ≦0.050%;  
 wherein respective formulae of  
 3.0≦[Mn]/[S]≦15.0,  
 0.10≦[Te]/[S], and  
 10≦[S]/[O]≦40 are satisfied; and  
 wherein a sulfide having a circle equivalent diameter of 2.0 mm or more and an aspect ratio of 10 or less is present in a total amount of 0.50 to 10% by area ratio.  
 
     
     
         2 . The martensitic free cutting stainless steel according to  claim 1 , which further comprises: 
 by weight percent,    at least one element selected from the group consisting of    Cu: 0.01 to 2.0%,    Ni: 0.01 to 2.0%, and    Mo: 0.01 to 1.0%.    
     
     
         3 . The martensitic free cutting stainless steel according to  claim 1 , which further comprises: 
 by weight percent,    Bi: 0.01 to 0.30%.    
     
     
         4 . The martensitic free cutting stainless steel according to  claim 2 , which further comprises: 
 by weight percent,    Bi: 0.01 to 0.30%.    
     
     
         5 . The martensitic free cutting stainless steel according to  claim 1 , which further comprises: 
 by weight percent,    at least one element selected from the group consisting of    Ca: 0.0001 to 0.05%,    Mg: 0.0001 to 0.02%, and    REM: 0.0001 to 0.02%.    
     
     
         6 . The martensitic free cutting stainless steel according to  claim 2 , which further comprises: 
 by weight percent,    at least one element selected from the group consisting of    Ca: 0.0001 to 0.05%,    Mg: 0.0001 to 0.02%, and    REM: 0.0001 to 0.02%.    
     
     
         7 . The martensitic free cutting stainless steel according to  claim 3 , which further comprises: 
 by weight percent,    at least one element selected from the group consisting of    Ca: 0.0001 to 0.05%,    Mg: 0.0001 to 0.02%, and    REM: 0.0001 to 0.02%.    
     
     
         8 . The martensitic free cutting stainless steel according to  claim 4 , which further comprises: 
 by weight percent,    at least one element selected from the group consisting of    Ca: 0.0001 to 0.05%,    Mg: 0.0001 to 0.02%, and    REM: 0.0001 to 0.02%.    
     
     
         9 . The martensitic free cutting stainless steel according to  claim 1 , further comprising, by weight percent, at least one element selected from the group consisting of: 
 W: 0.01 to 2.0%.    Nb: 0.01 to 0.50%    Ta: 0.01 to 0.50%, and    V: 0.01 to 0.5%.    
     
     
         10 . The martensitic free cutting stainless steel according to  claim 2 , further comprising, by weight percent, at least one element selected from the group consisting of: 
 W: 0.01 to 2.0%,    Nb: 0.01 to 0.50%    Ta: 0.01 to 0.50%, and    V: 0.01 to 0.5%.    
     
     
         11 . The martensitic free cutting stainless steel according to  claim 3 , further comprising, by weight percent, at least one element selected from the group consisting of: 
 W: 0.01 to 2.0%.    Nb: 0.01 to 0.50%    Ta: 0.01 to 0.50%, and    V: 0.01 to 0.5%.    
     
     
         12 . The martensitic free cutting stainless steel according to  claim 4 , further comprising, by weight percent, at least one element selected from the group consisting of: 
 W: 0.01 to 2.0%,    Nb: 0.01 to 0.50%    Ta: 0.01 to 0.50%, and    V: 0.01 to 0.5%.    
     
     
         13 . The martensitic free cutting stainless steel according to  claim 5 , further comprising, by weight percent, at least one element selected from the group consisting of: 
 W: 0.01 to 2.0%.    Nb: 0.01 to 0.50%    Ta: 0.01 to 0.50%, and    V: 0.01 to 0.5%.    
     
     
         14 . The martensitic free cutting stainless steel according to  claim 6 , further comprising, by weight percent, at least one element selected from the group consisting of: 
 W: 0.01 to 2.0%,    Nb: 0.01 to 0.50%    Ta: 0.01 to 0.50%, and    V: 0.01 to 0.5%.    
     
     
         15 . The martensitic free cutting stainless steel according to  claim 7 , further comprising, by weight percent, at least one element selected from the group consisting of: 
 W: 0.01 to 2.0%.    Nb: 0.01 to 0.50%    Ta: 0.01 to 0.50%, and    V: 0.01 to 0.5%.    
     
     
         16 . The martensitic free cutting stainless steel according to  claim 8 , further comprising, by weight percent, at least one element selected from the group consisting of: 
 W: 0.01 to 2.0%,    Nb: 0.01 to 0.50%    Ta: 0.01 to 0.50%, and    V: 0.01 to 0.5%.    
     
     
         17 - 32 . (canceled)