Production method of thick-walled titanium welded pipe and forming machine

The invention discloses a production method of a thick-walled titanium welded pipe with the wall-diameter ratio being greater than or equal to 10%. The production method is characterized by comprising the following steps of: uncoiling, cleaning, forming, welding, pre-sizing and on-line annealing. A forming machine comprises a primary forming section (4), a precise forming section (5) and a sizing section (6), and is characterized in that the primary forming section (4) is formed by the alternate arrangement of four forming flat roll racks (1) and three guiding vertical roll racks (2), the precise forming section (5) is formed by the alternate arrangement of at least three forming flat roll racks (1) and at least three guiding vertical roll racks (2), and the sizing section (6) is formed by the arrangement of at least two guiding flat roll racks (3). After trial production, the wall thickness and outer diameter of the titanium welded pipe produced by the production method are uniform, the dimensional accuracy of the titanium welded pipe is higher than that of a seamless pipe, the mechanical performance of the titanium welded pipe can reach the level of a seamless titanium pipe of the same specification, the production cost and environmental pollution are greatly reduced, and the production efficiency is improved.