Stone Stone hot forming is greater than the diameter of the tube, flattened to Stone diameter approximately the size of the branch pipe portion in the drawing to open a hole; tube by heating, into a mold, and in the tube loaded in the branch pipe stretching die; the tube under pressure to be radially compressed, the compression process in the radial direction in the direction of flow of metal into the branch pipe under tension in a die forming a branched pipe. The whole process is accomplished by radial compression tube and pipe branches and forming part of the stretching process. Stone with different hydraulic bulging, the hot metal pipe four-way branch tube is made to compensate for radial movement, it is also known as radial compensation processes.