Only after welding can the joints be polished. The following specifications can be selected for pipes: outer diameters 42, 48, 5 1, 57 and 60. Not much money. Such a product. This is not a difficult product. 1, the tensile stress distance of the outer arm wall of the neutral layer of the pipeline under the action of external force m & amp； 1 thinning, internal compressive stress. The resultant forces N 1 and N2 change the cross section of the tube. Based on this factor, the main reasons for the decline of elbow quality are RX and SX. Therefore, in GBJ 235-82, the value of RX and the amount of external thinning under various pressure levels are clearly defined to control the values of RX and SX and ensure the quality.

2. The last article mentioned that when the material is stretched outside, the position of the neutral axis of the material is different from that of the bending method. In top bending (press bending) operation, the outer wall of neutral wheelbase is about 1/3, and in rotary bending (back bending) operation, the outer wall of neutral wheelbase is about 2/3. Therefore, it is beneficial to bend thin-walled tubes by rotary bending method.