Steel wire for high-strength spring

• Main Authors: KISU TAKAYUKI, DEMACHI HITOSHI, SUZUKI SHOICHI, KAWAGUCHI JUN, SUEHIRO MOTONOBU, MAEKAWA KEIICHI, MURAKAMI ATSUSHI, HASHIMURA MASAYUKI
• Format: Patent
• Language: Chinese; English
• Published: 14.03.2012
• Subjects: ALLOYS; BLASTING; CHEMISTRY; ENGINEERING ELEMENTS AND UNITS; FERROUS OR NON-FERROUS ALLOYS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVEFUNCTIONING OF MACHINES OR INSTALLATIONS; HEATING; LIGHTING; MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS; MEANS FOR DAMPING VIBRATION; MECHANICAL ENGINEERING; METALLURGY; METALLURGY OF IRON; MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; SHOCK-ABSORBERS; SPRINGS; THERMAL INSULATION IN GENERAL; TREATMENT OF ALLOYS OR NON-FERROUS METALS; WEAPONS

Disclosed is a steel wire for a high strength spring. The wire is characterised by including, by mass%, at least 0.67% but less than 0.75% of C, 2.0-2.5% of Si, 0.5-1.2% of Mn, 0.8-1.3% of Cr, 0.03-0.20% of V, 0.05-0.25% of Mo, 0.05-0.30% of W and 0.003-0.007% of N, where the total content of Mn and V is 0.70%Mn+V1.27%, the total content of Mo and W is 0.13%Mo+W0.35%, P is limited to 0.025% or less, S is limited to 0.025% or less, Al is limited to 0.003% or less and the remainder consists of iron and unavoidable impurities. Said steel wire is also characterised in that: the metallographic structure consists of tempered martensite and retained austenite with a volume fraction of more than 6% but not more than 15%; the former austenite grain size number is not smaller than 10; the density of spherical carbides with a circle-equivalent diameter of 0.2-0.5[mu]m is 0.06 particles/[mu]m2 or less; the density of spherical carbides with a circle-equivalent diameter exceeding 0.5[mu]m is 0.01particles/[mu]m2 or less;