What are the common defects of pipe fitting bend and how to solve them

　　With the different bend radius, the former four kinds of defects occur in different ways and different parts, and they may not occur at the same time. Let's explain the common defects and methods of pipe fitting bend carefully.

　　1. Bending crack on the outside of the arc of ASME B16.47 Schedule 80 10D Carbon Steel Special Pipe Fitting Bend.

　　In terms of the bending crack on the outside of the bend arc, first of all, it is necessary to ensure that the pipe has outstanding heat treatment conditions, then check whether the pressure of the pressing die is too large, adjust the pressure to make it appropriate, and finally ensure that

　　It is proved that there is outstanding smoothness between the mandrel and the pipe wall to reduce the resistance of the bend and the friction between the inner wall and the mandrel.

　　2. The inside of the arc of pipe fitting bend is wrinkled

　　The corrugation on the inner side of the arc of pipe fitting bend should be carried out according to the corrugation direction.

　　If the front cut point is wrinkled here, the mandrel orientation shall be adjusted forward to support it reasonably when reaching pipe fitting bend. If the back cut point is wrinkled, anti wrinkle block shall be added to make the anti wrinkle block device orientation correct, so that the gap between the mandrel and the pipe wall is too large, perhaps the die pressing force is too small to make the pipe fit well with the bending die and anti wrinkle block in the process of twists and turns. Therefore, the mandrel should be replaced, and the pressing die should be adjusted to make the pressing die force appropriate.

　　3.pipe fitting bend rebound

　　As for the zigzag rebound phenomenon, compensation method and correction method are mainly used to control it.

　　The compensation method is to analyze the influencing factors of zigzag springback, estimate the size of springback in advance according to various conditions and springback trend during zigzag, correct the size and geometry of the working parts of convex and concave dies during the design and manufacturing of dies, and complete the "over positive" zigzag. The correction method is to take measures on the die structure, so that the correction force is concentrated at the corner, trying to eliminate the elastic deformation and overcome the rebound. For example, in the process of stretch bending, the tension is applied at the same time of twists and turns, so that the whole section is under the effect of tensile stress. When unloading, the elastic recovery and deformation direction are the same, which can reduce the amount of rebound.