| 摘要 |
<p>PURPOSE:To facilitate the processing and to heighten an improvement effect by providing a hollow ring on the outside surface of a base pipe and supplying a cooling fluid thereto and generating the stress to exceed a yield point close to a welded joint and afterward, stopping the cooling fluid supply. CONSTITUTION:The hollow ring 9 is provided on the outside of the welded joint 7 such as duplex metallic pipes, etc., and a hollow part 10 is connected with a cooling fluid supply system 11. When the cooling fluid is supplied to the inside of the ring 9, the ring 9 contracts thermally and presses an inwall of the base pipe 4 close to the welded joint 7 and projects and deforms it inward. At this time, the stress to exceed the yield point at a point A of an inner pipe 5 is generated and afterward, when the supply of the cooling fluid is stopped and the fluid is eliminated, the compressive stress remains via stress- strain bystersis of the point A. In this way, the residual stress is improved by the simple processing and the accuracy of the improving process is improved. Accordingly, the processing is facilitated and the improvement effect is heightened.</p> |
