High-strength spring steel having excellent corrosion resistance

Abstract

A high-strength spring steel coil spring of a vehicle suspension, having excellent corrosion resistance, may include 0.4 to 0.9 wt % of C, 0.9 to 2.3 wt % of Si, 0.5 to 1.2 wt % of Mn, 0.6 to 1.5 wt % of Cr, 0.01 to 0.5 wt % of Mo, 0.01 to 0.9 wt % of Ni, 0.5 wt % or less (excluding 0 wt %) of V, 0.5 wt % or less (excluding 0 wt %) of Nb, 0.3 wt % or less (excluding 0 wt %) of Ti, 1.0 wt % or less (excluding 0 wt %) of Co, 0.1 wt % or less (excluding 0 wt %) of B, 0.3 wt % or less (excluding 0 wt %) of W, 0.3 wt % or less (excluding 0 wt %) of Cu, 0.3 wt % or less (excluding 0 wt %) of Al, 0.03 wt % or less (excluding 0 wt %) of N, 0.003 wt % or less (excluding 0 wt %) of O, and a remainder of Fe and inevitable impurities.

What is claimed is: 
     
         1 . A high-strength spring steel having excellent corrosion resistance, suitable for use as steel for a coil spring of a vehicle suspension, the high-strength spring steel comprising: 0.4 to 0.9 wt % of Carbon (C), 0.9 to 2.3 wt % of Silicon (Si), 0.5 to 1.2 wt % of Manganese (Mn), 0.6 to 1.5 wt % of Chromium (Cr), 0.01 to 0.5 wt % of Molybdenum (Mo), 0.01 to 0.9 wt % of Nickel (Ni), 0.5 wt % or less (excluding 0 wt %) of Vanadium (V), 0.5 wt % or less (excluding 0 wt %) of Niobium (Nb), 0.3 wt % or less (excluding 0 wt %) of Titanium (Ti), 1.0 wt % or less (excluding 0 wt %) of Cobalt (Co), 0.1 wt % or less (excluding 0 wt %) of Boron (B), 0.3 wt % or less (excluding 0 wt %) of Tungsten (W), 0.3 wt % or less (excluding 0 wt %) of Copper (Cu), 0.3 wt % or less (excluding 0 wt %) of Aluminum (Al), 0.03 wt % or less (excluding 0 wt %) of Nitrogen (N), 0.003 wt % or less (excluding 0 wt %) of Oxygen (O), and a remainder of Iron (Fe) and inevitable impurities. 
     
     
         2 . The high-strength spring steel of  claim 1 , wherein the spring steel has a tensile strength of 2200 MPa or more. 
     
     
         3 . The high-strength spring steel of  claim 1 , wherein the spring steel has a hardness of 700 HV or more. 
     
     
         4 . The high-strength spring steel of  claim 1 , wherein the spring steel has a pit depth of 20 μm or less. 
     
     
         5 . The high-strength spring steel of  claim 1 , wherein the spring steel endures a bending fatigue test at least 320 thousand times. 
     
     
         6 . The high-strength spring steel of  claim 1 , wherein the spring steel endures a component corrosion fatigue life test at least 30 thousand times. 
     
     
         7 . The high-strength spring steel of  claim 1 , wherein the spring steel endures a cyclic corrosion fatigue life test at least 400 thousand times.