| 摘要 |
<p>PURPOSE:To increase the straightness of a tube after working and to reduce the number of steps for bend straightening by regulating the tube axis-direction residual stress of a steel tube for machine structural use to a residual stress capable of compensating the work bend at the time when working asymmetrical about the tube axis is applied by regulating heat-treating temp. CONSTITUTION:Before the above steel tube which is previously cold-drawn and has tube axis-direction residual stress is subjected to working such as cutting of racks, etc., asymmetrical about the tube axis at least in a part in the tube-axis direction, heat treatment is applied to the above steel tube at a proper temp. lower than the temp. at which the above residual stress can be perfectly relieved, that is, heat treatment is carried out at a temp. where the above tube axis-direction residual stress can be adjusted to a stress capable of removing the tube-axis bend due to the above working such as cutting. By this method, the dimensional accuracy of the steel tube after working can be increased and stages for bend straightening can be obviated.</p> |
