BAR STEEL FOR NON-HEAT TREATED CONNECTING RODS

摘要

A bar steel for non-heat treated connecting rods which has a chemical composition that contains 0.25 to 0.35% of C, 0.40 to 0.70% of Si, more than 0.65 to 0.90% of Mn, 0.040 to 0.070% of P, 0.040 to 0.130% of S, 0.10 to 0.30% of Cr, 0.05 to 0.40% of Cu, 0.05 to 0.30% of Ni, 0.01 to 0.15% of Mo, 0.12 to 0.20% of V, more than 0.150 to 0.200% of Ti, 0.002 to 0.100% of Al, and up to 0.020% of N, and further contains up to 0.30% of Pb and/or up to 0.30% of Te as necessary, and that satisfies the relationships:[0.60=C+(Si/10)+(Mn/5)+(5Cr/22)+1.65V-(5S/7)+(Cu/33)+(Ni/20)+(Mo/10)=0.80] and [(Mn+Ti)/S=7], and in which at least 90% of the structure is a ferrite/pearlite structure having a ferrite content of 40% or more. The bar steel can be easily cut and hot-forged and is suitable as a material for non-heat treated connecting rods for automobile engines or the like, said material being required to have excellent machinability, fracture crackability and fatigue resistance.