Research on Flower Pattern and Roll Positioning Optimization for Roll Forming Process of TA4 Coiled Tubing

Titanium alloy coiled tubing (CT) has great superiority while operating in deep wells with severe conditions, but it faces serious challenges during roll forming like high springback, edge cracking and surface wearing. In order to utilize the high precision and high efficiency production of titanium alloy CT, it is urgently necessary to develop a detailed process design. Based on the W-forming strategy and the cubic curve of the strip edge projection, the flower pattern and roll design for the 21-pass roll forming process were completed. Different tube dimensions and roll positionings were researched regarding the aspects of contact state, stress-strain distribution and geometry ovality using numerical simulation. The thickness/diameter ratio of the tube that can be formed should be within an effective range: exceeding the range leads to edge cracking, and an insufficient ratio leads to high springback. Roll positioning significantly affects the contact state and stress distribution, but leads to no major differences in the tube geometry. Finally, the trial production of the TA4 titanium CT with a size of Φ50.8 × 4 mm was completed successfully and was consistent with the simulation results.