Large-Caliber carbon steel butt weld seamless pipe fitting tee welding technolog

　　Large-Caliber carbon steel butt weld seamless pipe fitting tee is used as a pipe fitting at the branch of the pipeline. As for the selection of seamless pipe to manufacture pipe fitting tee, the commonly used technology is hydraulic bulging and hot pressing. Hot-pressing forming: hot-pressing forming is to flatten the tube blank larger than the diameter of the pipe fitting tee to the size of the tee diameter, and make a hole in the part of the drawing branch pipe; the tube blank is heated, put into the forming die, and put the drawing branch pipe into the tube blank; under the effect of pressure, the tube blank is compressed radially, in the process of radial compression The middle metal flows to the branch pipe and forms a branch pipe under the stretching of the die.

　　The whole process is formed through the radial tightening of the billet and the stretching process of the branch. Unlike the hydraulic bulging pipe fitting tee, the metal of the hot-pressed pipe fitting tee branch is compensated by the radial motion of the billet, so it is also called the radial compensation process.

　　Due to the selection of three passes after heating, the tonnage required for data forming is reduced. Hot-pressed tee has wide adaptability to data, and is suitable for low carbon steel, alloy steel and stainless steel materials; especially for tee with large diameter and thick pipe wall, this forming process is generally used.

　　Large-Caliber carbon steel butt weld seamless pipe fitting tee is on the intersection line between main pipe and branch pipe. The shape and position of butt weld are disorderly and the quality of weld is difficult to control. The main disadvantages are incomplete penetration, porosity and slag inclusion. The groove of weld seam on intersecting line is mainly made by cutting or plasma cutting. The machining precision is not high, the view point of groove is small, and the welding parameters are not properly selected, resulting in incomplete penetration. Another primary reason for the quality defect of welded pipe fitting tees is the faulty blanking process, the outer groove of the branch pipe is machined into the inner groove, and the branch pipe is directly lapped on the main pipe for welding. Incomplete penetration reduces the strength of the weld. With regard to the pipeline delivering corrosive medium, the heat affected zone of the weld will be thinned with the addition of production cycle, resulting in leakage of the weld. The reason for porosity and slag inclusion is that the groove before welding and the adjacent oil, rust, moisture and other impurities are not cleaned up, and the skin is not cleaned during welding. In other welding operations, the welding speed is too fast and the welding current is too small, which accelerates the cooling rate of the weld.