| 摘要 |
<p>A metal tubing joint to connect lengths of pipe is made either by forcibly drawing a ductile sleeve over ends of pipe in telescopingly engaged overlapped relation, the sleeve being plastically strained and enlarged permanently in diameter by from 1% to 7% by the drawing operation, or by forcibly drawing an enlarged end of another pipe over the pipe end to plastically strain the enlarged end further by at least 1%, and the heat developed in distending the metal and in frictional work during rubbing contact is controlled so that the members, when cooled to ambient temperature, have relative diameters at their engaged surfaces such that the remanent circumferential tensile stress is the wall of the outer member is considerably reduced below the peak stress at maximum distention, and the members act as opposed tension and compression springs within their elastic limits. The joint allows repeated application of rated fluid pressures without risk of plastically straining the outer member. The pipe may be warmed prior to assembly so that a temperature gradient exists, decreasing to the entry end, or the leading ends of the sleeve is coned to develop friction heating of the pipe surface as a constricting zone of the sleeve end is forced over it, or both means used to attain the condition that the pipe is warmer by from 12.degree.C to 100.degree. than the sleeve at the conclusion of the drawing step. A heat sink may be used on the exterior of the outer member to lower its peak temperature at the leading end, or along its whole length.</p> |
