Major causes of deterioration of bend quality

　　1. In pure bending, under the action of external force distance, the outer arm wall of the neutral layer is thinned by tension stress, while the inner arm wall is under compression stress. Thickening due to action, combined force changes the cross section of the pipe. Based on this factor, the main reason for the decline of bend quality is that the value under various pressure levels and the outer thinning are clearly defined, so as to ensure the quality.

　　2. When 4 inch carbon steel 45 degree 5D large radius bend, the material is pulled on the outside and the neutral axis under internal pressure is different from the bending method. When bending the pipe, the neutral axis is about 1/3 away from the outer wall. When bending the pipe, the neutral axis is about 2/3 away from the outer wall. Therefore, it is beneficial to use rotary bending method for thin-walled pipe bend.

　　3. The precision of bend is also one of the factors affecting the quality of pipe bend. In the manufacture of bending tyres, besides the requirement of specifications and sizes to be controlled within a certain tolerance range, users are also required to select the corresponding bending tyres according to the diameter of the bend pipe.

　　4. The bendability and surface corrosion of the pipe itself may also affect the quality of the bend. In site construction, operators also need to know the material of the pipe bend processed, the processing performance and the production judgment of the surface corrosion.