Four-way tees have opposing dimensions at their ends; the main tee of the non-standard diameter tees faces the same dimensions, while the branch tee dimensions are ten sizes smaller than the main tee. Stainless steel four-way tees are pipe fittings used at pipe branching points. For four-way tees made of seamless tubes, the current processes commonly used are hydraulic expansion and hot pressing. The hydraulic expansion of four-way tees is a forming process that involves expanding the branch pipe by compensating for the axial deformation of the metal material.

The process involves using a hydraulic press to inject liquid into a billet with the same diameter as the four-way fitting. The billet is then uniformly compressed through simultaneous movement of the press's two horizontal side cylinders. As the billet is compressed, its volume decreases, causing the liquid inside to increase in pressure. When the pressure reaches the level required to expand the four-way fitting's branch pipe, the metal material flows and expands into the branch pipe under the combined pressure of the side cylinder and the liquid pressure inside the billet.

Four-way hydraulic胀形red art can be formed in one go, offering higher production efficiency; the supervisor and shoulder wall thickness of the Four-way have both been increased.