| 摘要 |
PURPOSE:To obtain a screw product having a high accuracy, which is excellent in its tensile strength and durability, and has no strain, by heating instantaneously the surface of the outside periphery of the lower diameter of a screw to a specified temperature prior to rolling working of an object to be worked, and executing a screw rolling. CONSTITUTION:A heat treatment of a conventional method is performed in advance to a work 1, the surface of a screw working part 2 of this work 1 is heated instantaneously to 330-350 deg.C, and thereafter, a screw rolling of a conventional method is executed. In this case, by the instantaneous heating, the surface hardness and the tensile strength drop, but this defect is dissolved due to a fact that the tensile strength is raised by a residual stress caused by a compression generated by a warm screw rolling, and a screw product having an excellent durability is obtained.
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