High strength spring steel having excellent corrosion resistance
Disclosed herein is a steel composition with improvement in tensile strength and fatigue life, which can be used for a vehicle part such as a vehicle suspension system.
1. A spring steel comprising:
a steel composition comprising:
carbon (C) in an amount of about 0.4 to 0.9% by weight;
silicon (Si) in an amount of about 1.3 to 2.3% by weight;
manganese (Mn) in an amount of about 0.5 to 1.2% by weight;
chromium (Cr) in an amount of about 0.6 to 1.2% by weight;
molybdenum (Mo) in an amount of about 0.1 to 0.5% by weight;
nickel (Ni) in an amount of about 0.05 to 0.8% by weight;
vanadium (V) in an amount of about 0.05 to 0.5% by weight;
niobium (Nb) in an amount of about 0.05 to 0.5% by weight;
titanium (Ti) in an amount of about 0.05 to 0.3% by weight;
cobalt (Co) in an amount of about 0.01 to 3% by weight;
zirconium (Zr) in an amount of about 0.001 to 0.2% by weight;
yttrium (Y) in an amount of 0.89 to 1.5% by weight;
copper (Cu) in an amount of about 0.3% by weight or less but greater than 0% by weight;
aluminum (Al) in an amount of about 0.3% by weight or less but greater than 0% by weight;
nitrogen (N) in an amount of about 0.03% by weight or less but greater than 0% by weight;
oxygen (O) in an amount of about 0.003% by weight or less but greater than 0% by weight; and
balance iron (Fe), all the % by weights are based on the total weight of the steel composition,
wherein martensite is formed in the spring steel,
wherein the spring steel has a tensile strength of about 2100 MPa or greater, and
wherein the spring steel has a hardness of about 700 HV or greater.
2. The spring steel of claim 1 , wherein the spring steel has a corrosion pit depth of about 15 μm or less.
3. The spring steel of claim 1 , wherein the spring steel has a fatigue lifetime of about 280,000 cycles or greater as measured by a bending fatigue test.
4. The spring steel of claim 1 , wherein the spring steel has a fatigue lifetime of about 28,000 cycles or greater as measured by a single corrosion fatigue life test.
5. The spring steel of claim 1 , wherein the spring steel has a fatigue lifetime of about 400,000 cycles or greater as measured by a complex corrosion fatigue test.
6. A vehicle part comprising the spring steel of claim 1 .
7. The vehicle part of claim 6 , wherein the spring steel used in a suspension system in a vehicle.