| 摘要 |
PROBLEM TO BE SOLVED: To manufacture small diameter flux-cored seamless wire at high productivity by drawing the wire, work-hardened through preceding wire drawing, at a specified temperature after heat treatment at a specified temp. and for a specified duration of time. SOLUTION: The wire work-hardened through preceding wire drawing is heat-treated at 850-950 deg.C for a duration of (wire diameter (mm))×(30-40)sec. A wire of a small diameter of 1.0 to 0.8mmϕis drawn at -80 to 0 deg.C. This heat treatment is on a condition of transformation process in which martensite induced by working disappears and turns into a stable austenite. Under a heat treatment temperature of <850 deg.C, sufficient enough annealing effect is not obtained, and a slight drawing causes work hardening over again leading to breaking of wire. Under a heat treatment temperature over 950 deg.C, the outer skin gets too soft and the tensile strength goes down. A shorter heat treatment time does not bring the outer skin to softening, but a longer time brings it to be too soft. At the time of drawing temperature <-80 deg.C, the tensile strength of wire is improved but the elongation decreases, and at a temperature exceeding 0 deg.C, both the tensile strength and elongation decrease.
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