| 摘要 |
The invention provides for conferring a cup shape to the terminal juncti on segment (2) of pipes that are bi-axially oriented longitudinally and circumferentially and hence very sensitive to diameter and length reduction through heat, by means of passage into a furnace (4) which heats the segment (2) to a differentiated temperature, increasing towards the end of the segment (2), whose inner diameter progressively drops down to a controlled value, as temperature increases (whilst length is simultaneously reduced, with a corresponding increase in thickness). Preferably then, in an appropriate station (33), an additional heating is executed to a plastic deformation temperature suited to obtain a correct preliminary dilation of the terminal segment (2), introducing a rigid element (34) which acts as inner contrast, thereby inhibiting any retraction thereof. Here the segment (2) undergoes a thickening of the dilated wall bot h during the introduction of the rigid element (34), and during its extraction therefrom. Such terminal segment (2), dilated and heated, is then easily and rapidly fitted onto a calibration expander (3), itself also heated to such a temperature as to lim it heat absorption from said segment (2). Here too the terminal end (2) thickens yet again and takes its shape and, afterthe possible additional heating to force the terminal segment (2) to adhere spontaneously and perfectly to the underlying expander (3), at least the outer surface of the terminal segment (2), thus shaped, is cooled.
|
