| 摘要 |
PURPOSE: To provide a method for manufacturing high strength bolts, the method for extending strength and life of bolts formed by heat treatment or cold rolling working, preventing the bolts from easily being cracked during forming and manufacturing bolts having excellent processing efficiency. CONSTITUTION: The method comprises a step of cutting a carbon steel or alloy steel wire rod on which heat treatment or cold rolling working is performed to a plurality of wire rods in a certain size; a step of partially heating portions(8) of the cut wire rods corresponding to a bolt head part and a screw front part to a temperature of 400 deg.C to A1 transformation temperature; and a step of forming the partially heated wire rods in a bolt shape in the temperature of 400 deg.C to A1 transformation temperature, wherein the heating step is performed by using a small capacity heating equipment such as a high frequency heating coil.
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