Problems occurred after the composite layer was welded on
Thread Content
The last edit to this post was made by 515133307 on 2017-1-6 at 16:54. As shown in the diagram, the manhole flanges and blind plates are made of Q345 with a S31603 surfacing; the weld layer has a thickness of 6 mm. PT testing was conducted after each layer was applied during the surfacing process, and PT testing was also carried out after machining was completed – yet problems still occurred. What’s the reason? For those in the center of the flange cover, they can be repaired by welding followed by grinding. So, does the sealing surface need to have the defect cut out first, then welded and machined?
Use a grinder to remove defects, perform weld repairs, re-machine, and then conduct surface inspection.
Why isn’t a stainless steel plate welded onto the surface of the flange cover as a substitute for surfacing welding?
That is, a weld layer this thick is not as good as one with a lining ring
It seems to be defects such as inclusions; although PT testing was performed during welding, the surfacing surface is not smooth, and there is overlapping between the weld seams. PT testing requires that the weld surface be polished smoothly, otherwise defects may go unnoticed. This was certainly not achieved during the inter-layer testing.
The surfacing PT can only detect surface defects; if there are inclusions or pores inside the deposited metal, these defects will become visible after machining. The gasket structure can be modified or plug welding can be used.
What was said upstairs is correct, but there are also principles behind surfacing welding, right? Weld overlay porosity is basically inevitable, but slag inclusions can definitely be avoided
The main concern is that with the gasket ring in place, it’s more difficult to ensure welding quality, and RT or UT cannot be applied to those fillet welds. Additionally, this device is designed for high temperatures and pressures. Considering issues such as thermal deformation and the creation of signal holes in the backing plates, weld cladding was chosen for this application. Subsequent analysis suggested that the problem might lie in the manual welding process; could the quality be improved if automatic welding using a welding positioner were employed?
Hello, what is the difference between surfacing welding and lining rings?
Cladding is definitely better than linings, offering better resistance to high temperatures and pressures. Gland rings generally have limitations on pressure and temperature.
1. Although PT is performed on each layer during the surfacing process, and PT is also carried out after machining is completed, as mentioned on floor 5, there is a risk of missed inspections in this case, as the surface is not machined before testing. 2. An angle grinder can be used to remove spot and strip defects; after cleaning, cracks are checked for, followed by welding repairs and machining, and finally surface inspection. 3. During the surfacing process, the base layer is submerged in a water tank or other cooling measures are employed to allow heat from the surfaced layer to dissipate rapidly, thereby reducing the likelihood of cracks forming. 4. The composite structure type shall be in accordance with the design drawings; if changes are necessary during manufacturing, a design change notice or application form shall be submitted for design review and approval.