Microalloyed steel easy to separate by fracture splitting at low temperature and fitting member produced through separation by fracture splitting at low temperature

Abstract

A microalloyed steel easy to separate by fracture splitting at low temperatures, which comprises from 0.15 to 0.35 wt % carbon, from 0.5 to 2.0 wt % silicon, from 0.5 to 1.5 wt % manganese, from 0.03 to 0.15 wt % phosphorus, from 0.01 to 0.15 wt % sulfur, from 0.01 to 0.5 wt % copper, from 0.01 to 0.5 wt % nickel, from 0.01 to 1.0 wt % chromium, from 0.001 to 0.01 wt % soluble aluminium, from 0.005 to 0.035 wt % nitrogen, from 0.001 to 0.01 wt % calcium, and from 0.001 to 0.01 wt % oxyge ough separation by fracture splitting at a low temperature, e.g., a connecting rod for engines.

What is claimed is:  
     
         1 . A microalloyed steel easy to separate by fracture splitting at low temperatures, which comprises from 0.15 to 0.35 wt % carbon, from 0.5 to 2.0 wt % silicon, from 0.5 to 1.5 wt % manganese, from 0.03 to 0.15 wt % phosphorus, from 0.01 to 0.15 wt % sulfur, from 0.01 to 0.5 wt % copper, from 0.01 to 0.5 wt % nickel, from 0.01 to 1.0 wt % chromium, from 0.001 to 0.01 wt % soluble aluminium, from 0.005 to 0.035 wt % nitrogen, from 0.0001 to 0.01 wt % calcium, and from 0.001 to 0.01 wt % oxygen, the remainder comprising iron and inevitable impurities, and which satisfies the following relationships 1 and  2 : 
 Relationship 1    0.6≦Ceq≦0.85    wherein Ceq=C+0.07×Si+0.16×Mn+0.61×P+0.19×Cu+0.17×Ni+0.2×Cr    Relationship 2    0≦T Tr ≦1.5    wherein T Tr =(C+0.8×Si+5×P)−0.5×(Mn+Cr+Cu+Ni).    
     
     
         2 . The microalloyed steel easy to separate by fracture splitting at low temperatures according to  claim 1 , which contains one or both of up to 0.02 wt % titanium and up to 0.02 wt % zirconium in place of part of the iron as the remainder.  
     
     
         3 . The microalloyed steel easy to separate by fracture splitting at low temperatures according to  claim 1  or  2 , which contains one or both of up to 0.3 wt % lead and up to 0.3 wt % bismuth in place of part of the iron as the remainder.  
     
     
         4 . A fitting member produced through separation by fracture splitting at a low temperature, which comprises from 0.15 to 0.35 wt % carbon, from 0.5 to 2.0 wt % silicon, from 0.5 to 1.5 wt % manganese, from 0.03 to 0.15 wt % phosphorus, from 0.01 to 0.15 wt % sulfur, from 0.01 to 0.5 wt % copper, from 0.01 to 0.5 wt % nickel, from 0.01 to 1.0 wt % chromium, from 0.001 to 0.01 wt % soluble aluminium, from 0.005 to 0.035 wt % nitrogen, from 0.001 to 0.01 wt % calcium, and from 0.001 to 0.01 wt % oxygen, the remainder comprising iron and inevitable impurities, and which satisfies the following relationships 1 and 2: 
 Relationship 1    0.6≦Ceq≦0.85    wherein Ceq=C+0.07×Si+0.16×Mn+0.61×P+0.19×Cu+0.17×Ni+0.2×Cr    Relationship 2    0≦T Tr ≦1.5    wherein T Tr =(C+0.8×Si+5×P)−0.5×(Mn+Cr+Cu+Ni).    
     
     
         5 . The fitting member produced through separation by fracture splitting at a low temperature according to  claim 4 , which contains one or both of up to 0.02 wt % titanium and up to 0.02 wt % zirconium in place or part of the iron as the remainder.  
     
     
         6 . The fitting member produced through separation by fracture splitting at a low temperature according to  claim 4  or  5 , which contains one or both of up to 0.3 wt % lead and up to 0.3 wt % bismuth in place of part of the iron as the remainder.  
     
     
         7 . The fitting member produced through separation by fracture splitting at a low temperature according to any one of  claims 4  to  6 , which is a connecting rod for an engine.