SPRING STEEL, PROCEDURE FOR FABRICATION OF SPRING OUT OF THIS STEEL ANS SPRING OUT OF THIS STEEL Russian patent published in 2010 - IPC C22C38/50 C21D9/02 

FIELD: metallurgy.

SUBSTANCE: invention refers to ferrous metallurgy, particularly to fabricating spring steel. In a converter or electric furnace there is melted liquid steel containing the following elements, wt %: carbon 0.45 - 0.70, silicon 1.65 - 2.50, manganese 0.20-0.75, chromium 0.60 - 2, nickel 0.15 - 1, molybdenum (traces) - 1.0, vanadium 0.003 - 0.8, copper 0.10 - 1, titanium 0.020 - 0.2, niobium (traces) - 0.2, aluminium 0.002 - 0.050, phosphorus (traces) - 0.015, sulphur (traces) - 0.015, oxygen (traces) - 0.0020, nitrogen 0.0020 - 0.0110, iron and associated impurities at melting - the rest. Steel is cast and there are produced blooms, ingots or flat bars. During their solidification or after it they are cooled at rate 0.3°C/s within the range 1450 - 1300°C. The said blooms, ingots or flat bars are rolled at temperature 1200 - 800°C per one or two cycles of heating and rolling. Rods, rolled bars, work-pieces or springs made out of them are subject to austenisation within the range 850 - 1000°C and to successive quenching in water, polymer or oil and tempering at 300 - 550°C to strengthen steel to 55 HRC or more and to maximal dimension of nitrides or carbonitrides of titanium at depth 1.5 mm ± 0.5 mm from surface of rod, rolled bar, work-piece or spring with cross section of 100 mm² area constituting 20 mcm or less. Also the said dimension is a value of square root of surface area of the said inclusions, shape of which is taken as square.

EFFECT: steel possesses upgraded tensile strength and durability, fatigue strength in air and in corrosion medium and high resistance to cyclic fatigue softening.

5 cl, 4 tbl, 4 dwg