Large bend production process

TIME：2019-05-25

Manufacturing process of large elbow:

1, the blanking

The plate thickness can be selected according to the wall thickness of the elbow. According to the technical requirements of the bend, a few welds are allowed to come down, usually 90. The bend can allow 3 ~ 4 welds, so the elbow can be divided into 3 ~ 4 sections. In order to ensure the smooth smooth of the welding seam, the edges of each section (the welding seam) will be carried out according to the plane expansion curve.

2, roll bending

After feeding, roll bending, roll bending radius is 1/2 diameter of elbow. Single curvature r= 5OOmm. When rolling, use the straight side as the benchmark to avoid rolling.

3. Weld a closed ring shell

Will roll shell is presented.the welding of closed ring shell, shell in a closed loop on the welding on water and drain mouth, mouth water injection is used to in a closed loop shell filled with liquid medium, and through a pressurized system (hydraulic test pump) to the closed casing internal pressure, drain for unloading pressure surge. Under the action of internal pressure, the shell produces plastic deformation and gradually tends to the ideal form

4. Loop shell bulging process

When bulging, press a certain pressure curve to apply internal pressure load to the ring shell, and after each additional pressure, the pressure will be pressed for a period of time, then the radial displacement data will be tested. The radial displacement in the experiment is obtained by measuring the relative displacement of each point and reference point. When the pressure is zero. After 705MPa, stop the clamping, and after a period of time, the shape and size of the ring-shell are close to the ideal state.

5 a cut,

After the compression molding of the ring shell, the weld is made to ensure the curved surface is smooth, and then cut it according to the bending of the elbow. Such as 30. And 60. , 75. , 90. When the segments are connected with the corresponding flanges, a large stainless steel elbow is made in a different bend.

6. Test results of shell bulging test results

For this experimental ring shell, the initial yield pressure of the ring shell has been calculated according to the formula above. 523MPa, the cracking pressure of the ring shell = 1. 44MPa, the forming pressure in the experiment was 0. The 705MPa is about 35 percent higher than the initial yield pressure. With the increase of internal pressure, the radial displacement of the shell is increasing, and the polyhedron of the shell is approaching to the ring shell. When the internal pressure reaches 0. 705 mpa, the ring size is close to the theoretical value, the size of the ring shell bulging after is obtained by measuring the ring shell dimension, respectively along the forming ring shell outer diameter and the ring diameter measuring axial section. The larger diameter and the smaller diameter of the outer ring of the ring shell are 3006ram and 2997mm respectively, and the larger diameter and smaller diameter of the cross section are lO03mm and lO00mm respectively. As can be seen from the measured data, the multi-surface ring shell is basically close to the ring after the hydraulic bulge, and the size meets the design requirements.