| 摘要 |
PURPOSE:To manufacture an excellent auto-fretting double tube that heightens grade of fit and prevents stress corrosion cracking by expanding an inner tube at a temperature above Md point, reducing after plastic deformation, cooling at a temperature below Ms point and expanding with martensitic transformation. CONSTITUTION:A material that generates work induced martensite is selected for an inner tube, and the inner tube is inserted into an outer tube. Under this condition, the outer tube is expanded through expanding of the inner tube causing yielding by hydraulic expanding at a temperature above Md temperature. At a specified diameter expanding stress is released and the tube is reduced preventing occurrence of martensitic transformation. Next, under this condition, the inner tube is cooled at a temperature below Ms point and expanded giving rise to martensitic transformation in the inner tube. Thus, an auto-fretting double tube having high grade of fit due to difference in diameter between inner and outer tubes can be obtained. |
