Abstract: The present invention provides, at low cost, a valve spring steel having a tensile strength as high as 210 to 240 kgf/mm.sup.2 after oil tempering. The high strength spring steel comprises, based on weight, 0.65 to 0.85% of C, 1.90 to 2.40% of Si, 0.50 to 1.00% of Mn, 0.70 to 1.30% of Cr, 0.10 to 0.30% of Mo, 0.20 to 0.50% of V, 0.01 to 0.04% of Nb and the balance Fe and unavoidable impurities and is subjected to heating at temperature of 1,050 to 1,250.degree. C. and then to rolling so that carbides in the steel have a size of up to 0.15 .mu.m in terms of equivalent circle. A valve spring having a tensile strength as high as 210 to 240 kgf/mm.sup.2 after oil tempering and stabilized quality can be produced while the material cost is greatly reduced by decreasing costly alloying components as much as possible.

Abstract: A spring steel having a good durability and a good sag-resistance consisting essentially of by weight 0.35-0.55% carbon, 1.80-3.00% silicon, 0.50-1.50% manganese, 0.50-3.00% nickel, 0.10-1.50% chromium, 0.01-0.05% aluminum and 0.010-0.025% nitrogen, the remainder being iron and inevitable impurities.The spring steel has been completed for the purpose of obtaining a spring steel having a high toughness in a high hardness of not less than HRC 55 and having a good sag-resistance, in particular examining the contents of nickel, chromium and nitrogen in addition to the carbon content.

Abstract: A spring steel having a good sag-resistance comprises by weight 0.5-0.8% carbon, 0.5-1.4% silicon, 0.5-1.5% manganese and a member or members selected from a group consisting of 0.05-0.5% vanadium, 0.05-0.5% niobium and 0.05-0.5% molybdenum, the remainder being iron together with impurities. The steel may further contain a member or members selected from a group consisting 0.0005-0.01% boron, 0.2-2.0% nickel and not greater than 0.3% rare-earth elements and/or a member or members selected from a group consisting of 0.02-0.1% titanium and 0.02-0.1% zirconium.

Abstract: A spring steel having a good sag-resistance and a good hardenability comprises by weight 0.5-0.8% carbon, 1.5-2.5% silicon, 1.6-2.5% manganese and a member or members selected from a group consisting of 0.05-0.5% vanadium, 0.05-0.5 niobium and 0.05-0.5% molybdenum, the remainder being iron together with impurities. The steel may further contain a member or members selected from a group consisting 0.0005-0.01% boron, 0.2-1.0% chromium, 0.2-2.0% nickel and not greater than 0.3% rare-earth elements and/or a member or members selected from a group consisting of 0.03-0.1% aluminum, 0.02-0.1% titanium and 0.02-0.1% zirconium.

Abstract: A steel for use in a vehicle suspension spring having a good sag-resistance comprising by weight 0.80% carbon, 1.50-2.50% silicon, 0.50-1.50% manganese, a member or members selected from a group consisting of 0.05-0.50% vanadium, 0.05-0.50% niobium and 0.05-0.50% molybdenum, the remainder being iron together with impurities. The steel may further contain a member or members selected from a group consisting of 0.0001-0.01% 0.20-1.00% chromium, and not greater than 0.0008% nitrogen.

Abstract: A spring steel having a good sag-resistance and a good hardenability comprises by weight 0.5-0.8% carbon, 1.5-2.5% silicon, 1.6-2.5% manganese and a member or members selected from a group consisting of 0.05-0.5% vanadium, 0.05-0.5 niobium and 0.05-0.5% mobybdenum, the remainder being iron together with impurities. The steel may further contain a member or members selected from a group consisting 0.0005-0.01% boron, 0.2-1.0% chromium, 0.2-2.0% nickel and not greater than 0.3% rare-earth elements and/or a member or members selected from a group consisting of 0.03-0.1% aluminum, 0.02-0.1% titanium and 0.02-0.1% zirconium.

Abstract: A steel for use in a vehicle suspension spring having a good sag-resistance comprising by weight 0.50-0.80% carbon, 1.50-2.50% silicon, 0.50-1.50% manganese, a member or members selected from a group consisting of 0.05-0.50% vanadium, 0.05-0.50% niobium and 0.05-0.50% molybdenum, the remainder being iron together with impurities. The steel may further contain a member or members selected from a group consisting of 0.0001-0.01% boron and 0.20-1.00% chromium, and not greater than 0.0008% nitrogen.