Forming Process of Titanium Tee Pipe Fittings

For common Titanium Tee pipe fittings, due to their small diameter, thin walls, and the high pressure requirements they must withstand, manufacturing them by casting is challenging and does not ensure quality. If two straight pipes are welded together to form the tee, the spatial intersection of the circular seams makes cutting and welding operations difficult to control. Moreover, the small size of the parts only allows for external welding, making it hard to maintain the internal weld quality. Even if casting and welding could shape the part, the inherent risks of porosity and slag inclusions in these processes make them unsuitable for medium and high-pressure pipelines.

Technicians considered using die forging or radial extrusion processes to first form a T-shaped solid billet, and then drilling horizontal and vertical holes. However, experiments showed that maintaining the quality of the Ti Pipe fittings was difficult. Additionally, this method had disadvantages such as multiple processing steps, large equipment requirements, and low material utilization.

Ultimately, the decision was made to use a backward extrusion forming process for the straight pipe. In this process, the straight pipe blank, filled with an incompressible filler, is placed into the mold cavity. The upper and lower molds are closed tightly, and then two push rods, sized the same as the pipe diameter, are pushed from both sides at the same speed. Under the pressure at both ends, the Titanium Pipe inside the mold cavity undergoes plastic deformation, either upsetting or being extruded through the radial holes of the mold.

Since the pipe is filled with an incompressible filler, upsetting deformation is impossible. Thus, under pressure, the straight pipe and the filler together extrude through the radial holes in the mold. To prevent the extruded radial pipe from bursting under the internal pressure of the filler, a push rod is installed in the mold’s radial hole to apply sufficient compressive stress on the extruded radial branch pipe.

When the extruded branch pipe reaches the required dimensions, the mold is opened, and the part is removed and cleared of the filler, resulting in the desired titanium tee pipe fitting. Practice has shown that the extruded tee pipe fitting has equal wall thickness in all three directions, minimal upsetting deformation, and the height of the extruded section reaches 2 to 3 times the pipe diameter. Additionally, because the filler and the titanium pipe move synchronously in the mold cavity, the inner wall of the pipe fitting is free of mechanical scratches, and both the dimensions and quality meet the drawing requirements.