Issues related to welding flaw detection of composite panels
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The question was raised by a friend who works in supervision of manufacturing processes; he was supervising equipment production at a large state-owned factory and there were disputes with the manufacturer: 1. Is surface flaw detection necessary before welding the transition layers of composite panels? The materials are 16MnR + 304, with a thickness of over 70 mm plus an additional 3 mm. As far as I know, it’s good to treat the surface before welding the transition layer; some factories do this as well. The technical requirements for this project specify that the base layer should have its surface prepared before cladding, but the manufacturer in question believes that cladding is different from welding composite plates, and therefore does not need to follow these technical requirements. However, the inspection team holds that it’s based on the same principle and insists on preparing the surface, although there is no standard to support this requirement. 2. How is RT testing generally carried out for composite plates? In the factory where I used to work, after the base layer was welded and passed the RT test, the transition layer and the cladding layer were welded, and then the surface was treated. But in my friend’s factory, the base layer and the cladding layer are welded together first, and then RT testing is conducted. What’s the quality of the RT images for composite panels? Is the negative with two layers of dissimilar steel visible?
Composite plates consist of a composite layer and a base layer; generally, it is a composite structure. Regarding the inspection of the welded joints in composite plates, GB150 provides relevant regulations – surface testing of the composite layer is sufficient (using magnetic particle or penetrant testing)
Sequence of non-destructive testing for composite plates: 1. For ordinary carbon steel, perform MT testing after the base layer welding is completed; if successful, carry out surfacing to form the transition layer, followed by PT testing, and if that is successful, proceed with further surfacing layers. RT+PT testing: For chromium-molybdenum steel, perform MT testing on the groove before welding; once it passes, carry out welding of the base layer, followed by MT testing again. If that is successful, then apply a surfacing layer, and after that conduct PT testing; if successful, apply additional surfacing layers. RT+UT+PT+MT testing after 24 or 36 hours, UT+MT+PT testing after heat treatment. UT+MT+PT testing after hydrostatic testing; in the past, for Monel materials, RT testing was carried out after welding, followed by surfacing. The material is special, with too many cracks. The non-destructive testing of all composite panels will now follow the sequence mentioned above.
For this, one can refer to the standards HG/T20580 to 20585 issued by the Ministry of Chemical Industry, which contain specific requirements regarding the flaw detection of composite steel plates. It involves specifics such as whether the laminated structure is taken into account in the shell strength.