Technical Requirements of Cast Iron Tee (Part Two)

Taking elbows as an example, if long radius elbows are made, the specifications and materials should be selected at first. It can be calculated by theoretical method, and then cut as per this as the fixed length. Finally, the material is hot pushed. Everyone may have seen the push machine, of which the working principles are very simple. It is a horn-shaped core or core rod, and the core rod changes from thin to thick. The pushing process is a bending process of expanding band. There is a support at the back, which penetrates the blanking pipe section into the core rod. And there is an archway frame at the back to fix the core rod. There is also a trolley in the middle, some of which are driven by hydraulic pressure and some by mechanical drive, that is, screw drive, which then push the trolley forward. The trolley pushes the pipe forward along the mandrel, and there is an induction coil outside the mandrel to heat the pipe. Then the trolley pushes the pipe down, and one pipe is processed. After pushing, the elbow should be shaped in this hot state. The expanding rate, through theoretical calculation, is generally between 33% and 35%. The general expanding rate of short radius 219mm is 50%. After selecting the raw materials, cut the materials according to the elbow specifications, and then consider the radius of curvature, for example, 90° elbow. Through its curvature, you can calculate how long the materials can be processed into 90° elbow.

The process of cast iron tee is basically the same. According to different specifications of cast iron tee fittings. Sand blasting is required after blanking, and iron scale on the surface should be removed before forming. The forming method is hydraulic bulging. There is a mold with a straight bottom and a flange hole on the top. After the pipe is put in, the pipe is fixed with hydraulic cylinder, and both sides are filled with liquid to bulge inward, then the pipe is squeezed into a "convex" shape, and then the bulge is removed from the proper position, which is also made into a groove. It needs to be shot blasted twice. Because there is work hardening during processing, heat treatment is also needed. These are the situations in the production process of cast iron tee fittings.