High carbon steel wire rod excellent in drawability and fatigue characteristics after wire drawing

Abstract

High performance high carbon wire with refined inclusions after wire rolling, extremely low wire breakage rates at the time of drawing even in tough applications, and excellent in fatigue characteristics after wire drawing, characterized by having a predetermined composition of ingredients and in that the number ratio of inclusions satisfying (% SiO 2 )=40 to 95%, (% CaO)=0.5 to 30%, (% Al 2 O 3 )=0.5 to 30%, (% MgO)=0.5 to 20%, and (% MnO)=0.5 to 10% and further satisfying (% Na)=0.2 to 7% and (% F)=0.17 to 8% (below, referred to as “inclusions covered due to composition”) in the oxide-based nonmetallic inclusions of a short axis of 0.5 μm or more, a long axis of 1.0 μm or more, and a circle equivalent diameter (area converted to diameter) of 1 μm or more which are seen in the L direction cross-section of the wire (below, referred to as “inclusions covered due to size”), that is, the number of inclusions covered due to composition/number of inclusions covered due to size×100, is 80% or more.

1 . High carbon steel wire rod excellent in drawability and the fatigue characteristics after wire drawing which contains, by mass %,
 C: 0.5 to 1.2%,   Si: 0.15 to 2.5%,   Mn: 0.20 to 0.9%,   P≦0.025%   S: 0.004 to 0.025%,   Al: 0.000005 to 0.002%,   Ca: 0.00001 to 0.002%,   Mg: 0.00001 to 0.001%,   Na: 0.000005 to 0.001%, and   F: 0.000003 to 0.001%,   has a total oxygen amount of 16 to 30 ppm, and which has a balance of Fe and unavoidable impurities,   the high carbon steel wire characterized in that the number ratio of inclusions satisfying (% SiO 2 )=40 to 95%, (% CaO)=0.5 to 30%, (% Al 2 O 3 )=0.5 to 30%, (% MgO)=0.5 to 20%, and (% MnO)=0.5 to 10% and further satisfying (% Na)=0.2 to 7% and (% F)=0.17 to 8% (below, referred to as “inclusions covered due to composition”) in the oxide-based nonmetallic inclusions of a short axis of 0.5 μm or more, a long axis of 1.0 μm or more, and a circle equivalent diameter (area converted to diameter) of 1 μm or more which are seen in the L direction cross-section of the wire (below, referred to as “inclusions covered due to size”), that is, the number of inclusions covered due to composition/number of inclusions covered due to size×100, is 80% or more: where (% SiO 2 ), (% CaO), (% Al 2 O 3 ), (% MgO), (% MnO), (% Na), and (% F) respectively are the contents of SiO 2 , CaO, Al 2 O 3 , MgO, MnO, Na, and F in the inclusions (mass %).   
     
     
         2 . The high carbon steel wire excellent in drawability and the fatigue characteristics after wire drawing as set forth in  claim 1  characterized by further including REM:
 0.000005 to 0.001%, said inclusions covered due to composition satisfying, by average concentration, furthermore (% T.REM)=0.3 to 1.0% and (% S)=0.05 to 0.2%, 
 where, (% T.REM) and (% S) respectively include the total of rare earth elements in the inclusions and the content of S (mass %). 
 
     
     
         3 . The high carbon steel wire excellent in drawability and the fatigue characteristics after wire drawing as set forth in  claim 1  characterized by further including B: 0.0005 to 0.002%. 
     
     
         4 . The high carbon steel wire excellent in drawability and the fatigue characteristics after wire drawing as set forth in  claim 1  characterized by further including one or more of:
 Cr: 0.05 to 1.0%, 
 Ni: 0.05 to 1.0%, 
 Cu: 0.05 to 1.0%, 
 Ti: 0.001 to 0.25%, 
 Nb: 0.001 to 0.25%, 
 V: 0.001 to 0.25%, 
 Mo: 0.05 to 1.0%, and 
 Co: 0.1 to 2%. 
 
     
     
         5 . The high carbon steel wire excellent in drawability and the fatigue characteristics after wire drawing as set forth in  claim 3  characterized by further containing one or more of
 Cr: 0.05 to 1.0%, 
 Ni: 0.05 to 1.0%, 
 Cu: 0.05 to 1.0%, 
 Ti: 0.001 to 0.25%, 
 Nb: 0.001 to 0.25%, 
 V: 0.001 to 0.25%, 
 Mo: 0.05 to 1.0%, and 
 Co: 0.1 to 2%. 
 
     
     
         6 . The high carbon steel wire excellent in drawability and the fatigue characteristics after wire drawing as set forth in  claim 2  characterized by further including B: 0.0005 to 0.002%. 
     
     
         7 . The high carbon steel wire excellent in drawability and the fatigue characteristics after wire drawing as set forth in  claim 2  characterized by further including one or more of:
 Cr: 0.05 to 1.0%, 
 Ni: 0.05 to 1.0%, 
 Cu: 0.05 to 1.0%, 
 Ti: 0.001 to 0.25%, 
 Nb: 0.001 to 0.25%, 
 V: 0.001 to 0.25%, 
 Mo: 0.05 to 1.0%, and 
 Co: 0.1 to 2%. 
 
     
     
         8 . The high carbon steel wire excellent in drawability and the fatigue characteristics after wire drawing as set forth in  claim 6  characterized by further containing one or more of
 Cr: 0.05 to 1.0%, 
 Ni: 0.05 to 1.0%, 
 Cu: 0.05 to 1.0%, 
 Ti: 0.001 to 0.25%, 
 Nb: 0.001 to 0.25%, 
 V: 0.001 to 0.25%, 
 Mo: 0.05 to 1.0%, and 
 Co: 0.1 to 2%.