Three methods and processes for forming titanium tricouplers

The titanium three-way fitting is produced by the stamping forming process, which involves a one-time overall forming using a seamless tube blank. The main forming method is extrusion and expansion. The mechanical properties of the resulting component are better than those of the welded three-way fitting. The stamping forming process for making the three-way fitting mainly includes three methods: filling material extrusion forming, hydraulic expansion forming, and hot press forming. The specific processes of each method are as follows:

I. Extrusion forming with filler:
The packing extrusion forming process involves the extrusion forming of a straight tube blank with internal filling of packing. After placing the tube blank into the mold cavity and closing the mold, a convex die with the same diameter as the tube is used to push from both sides at the same speed. Under the pressure from both ends, the tube and the packing are extruded out from the radial holes of the mold to form a three-way fitting. To prevent the branch pipe from bursting under the pressure of the packing, a balancing convex die is installed in the radial hole of the mold, applying sufficient balancing pressure to support the intense bulging of the branch pipe.

The titanium three-way pipe fittings produced by the extrusion process with the filling material being expanded have the same wall thickness in all directions, with very little thickening deformation and the extruded part reaching 2 to 3 times the diameter of the pipe. The filling material and the metal pipe move synchronously in the mold cavity, and there is no mechanical abrasion on the inner wall of the pipe fitting. One of the key technologies of this process is the selection of the expansion medium filling material. The expansion medium mainly includes paraffin, butter, clay, nylon, silicone rubber and polyurethane rubber, etc. For three-way pipe fittings with high inner wall requirements, nylon, polyurethane rubber, and silicone rubber can be used as the medium; for those with less or no inner wall requirements, paraffin can be used as the medium, which is recyclable and has a lower cost.

II. Hydraulic Forming:
Three-way hydraulic expansion is a forming process that involves expanding a branch pipe by axially compensating the metal material. Its working principle is to use a hydraulic press, place a tube blank with the same diameter as the titanium three-way fitting into the mold cavity, close the mold, inject liquid into the tube blank, and then the two horizontal side cylinders of the hydraulic press move synchronously and relatively towards the center to compress the tube blank. After the tube blank is compressed, its volume decreases, and the pressure of the liquid inside the tube blank increases as its volume decreases. Under the dual action of the high-pressure liquid in the tube blank and the squeezing force from the left and right axes, the tube blank flows along the inner cavity of the mold to expand into the shape and size required for the branch pipe. To prevent the branch pipe from breaking, a balancing punch with balancing force needs to be added to support the intense deformation of the branch pipe.

The forming materials applicable for hydraulic bulging titanium tricouplers are those with relatively low cold work hardening tendency, such as carbon steel, alloy steel, stainless steel, and some colored metal materials, including copper, aluminum, titanium, etc.

III. Hot Pressing Forming:
Hot pressing involves pressing into a three-way connection after heating. The equipment required for material shaping has a low tonnage. The process is to flatten a pipe billet larger than the diameter of the titanium three-way connection to the size of the three-way connection, make holes at the branch pipe locations, and heat the pipe billet. During the radial compression process, the metal flows towards the branch pipe direction, and the branch pipes are formed under the stretching of the mold. The entire process of hot forming is through the radial compression of the pipe billet and the drawing of the branch pipes. The difference between hot forming and hydraulic bulging lies in that the metal of the three-way connection's branch pipes compensates for the radial movement of the pipe billet, so it is also called the radial compensation process.

The hot-pressed titanium three-way fitting is suitable for materials such as low-carbon steel, alloy steel, and stainless steel. Especially for three-way fittings with larger diameters and thicker pipe walls, the hot-pressed forming process is often used for manufacturing.