CONTINUOUS HEAT TREATING METHOD FOR OIL TEMPERED STEEL WIRE FOR SPRING HAVING HIGH STRENGTH AND HIGH TOUGHNESS

摘要

PURPOSE:To offer a continuous heat treating method capable of obtaining an oil tempered steel wire for a spring having high strength and high toughness and capable of corresponding to the need for its lightening. CONSTITUTION:At the time of continuously quenching and tempering an oil tempered steel wire for a spring constituted of a medium carbon-low alloy steel in which martensitic transformation is not substantially completed only by oil quenching, at first, this steel wire is subjected to two-stage accelerated quenching of executing quenching by oil quenching and thereafter swiftly executing water quenching and is successively subjected to tempering treatment. As the medium carbon-low alloy steel, a steel having chemical components contg. 0.40 to 0.65% C, furthermore consisting essentially of Si and Mn, moreover contg. at least one kind among Cr, Ni, Mo and V and having =80 deg.C (preferably 10 to 70 deg.C) Mf point is suitably used. After the quenching, oil content stuck to the surface of the steel wire is removed by wiping before the water quenching is executed.