The production and manufacturing method of stainless steel butt-welded pipe fittings, such as the manufacturing method of stainless steel butt-welded tees, involves injecting liquid into a tube blank that has the same diameter as the tee. The tube blank is then extruded by the two horizontal side cylinders of a hydraulic press. As the tube blank is extruded, its volume decreases, causing the pressure of the liquid inside the tube blank to increase. When the pressure reaches the level required for the expansion of the tee branch pipe, the metal material flows along the inner cavity of the mold. Under the combined effects of the side cylinder and the liquid pressure within the tube blank, the branch pipe is expanded.
The hydraulic bulging process of the tee can be completed in one step, resulting in high manufacturing efficiency and an increased wall thickness of the main pipe and shoulder of the tee. However, the hydraulic bulging process for seamless tees requires equipment with large tonnage. Currently, it is primarily used for manufacturing tees with a standard wall thickness of less than DN400. The materials suitable for this process include low-carbon steel, low-alloy steel, and stainless steel with relatively low cold working tendencies, as well as some non-ferrous metals such as copper, aluminum, and titanium. There are two types of production processes: seamless cold-drawn tees and seam-welded tees.
In addition to carbon (C) and a certain amount of silicon (Si) (generally not exceeding 0.40%) and manganese (Mn) (generally not exceeding 0.80%, but can be as high as 1.20%) as alloy elements for deoxidation, steel does not contain other alloy elements (except for residual elements). The distinction between steel and iron lies in their carbon content: steel with a carbon content below 2.11% is classified as steel, while iron with a carbon content above 2.11% is classified as iron. The higher the carbon content in steel, the lower its toughness; conversely, the higher the carbon content in iron, the greater its toughness. In the pure oxygen pipeline, the two larger scales represent the main pipes, while the smaller scale directly emerging from them represents the branch pipe.
