Issues regarding surface inspection of weld surfaces that require metalworking after welding
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This post was last edited by chun_ing on 2010-11-22 at 15:15. After a weld is completed, the drawings specify that metalworking is required; the sheet metal is thickened by 2 mm during cutting, and this excess thickness is removed using a planer after manufacturing (the amount of material to be removed is determined according to the specifications in the drawings)； However, the drawings also require 100% magnetic particle testing on this weld; it’s not clear whether this testing is to be carried out before or after metal machining ； If it’s done before finishing, I feel like magnetic particle testing is pointless, isn’t it? Surface inspection using magnetic powder – it’s not clear what the depth of detection is. If it’s a shallow surface, will it still be effective even after metal machining has removed some material from that area? What effect could it have if it is done after gold processing? The drawing does not specify the timing for selecting flaw detection. But the specified methods for flaw detection. Could anyone with experience give some advice?
Finishing is done after flaw detection. Additionally, color flaw detection can also be used in this case.
I think magnetic particle testing should be carried out before final machining. Firstly, magnetic particle testing can detect near-surface defects on its own. Secondly, if 100% magnetic particle testing is required for welds, this represents an important requirement for welding quality, or rather a quality standard; therefore, process engineers need to take into account both the manufacturing processes and the welders prior to welding. If inspection is carried out after finishing machining, and defects are found, the excess height and deformation resulting from patch welding require further finishing machining; at this point, however, no machining allowance is left.
Reply to 3# xsj1972: Haha, I also think it was done before； However, there is one issue that isn’t clear: since magnetic particle testing is a surface-based inspection (it’s not known whether the detection depth can reach 2 mm), and metal machining involves removing 2 mm of material, does that mean that the entire area to be inspected is removed as well? In other words, whether this inspection is carried out or not, the result will be the same – no internal defects in the welds can be detected.
I think it’s a bit more guaranteed in terms of quality after finishing processing
The depth that magnetic particle testing can reach is quite significant; I have carried out magnetic particle testing on depths of around 20 mm with no issues.
Can magnetic powder detect internal defects in welds? It’s not that it can only detect cracks on the shallow surface; it’s supposed to be able to detect internal defects as well, right? I’m confused. . . . . . For example, if the required thickness after machining is 18 mm, an additional 2 mm must be taken into account when cutting the material; thus, 20 mm of material is cut, and then 2 mm is removed after manufacturing to meet the specifications outlined in the drawings. I still think that magnetic particle testing can only detect surface defects, and the areas detected will be removed with a planer, which means the testing is pointless. Hey, never mind; just do it according to the blueprint requirements. . . In confusion. . .
Hehe. . . I’ll answer regarding the testing: 1: It’s done according to the standard procedures; the client will definitely approve it. :) It will indeed be scraped off. But it was also done before: lol. 2: The detection depth of MT is about 3 mm more. 3: MT detects surface and near-surface defects. 4: The magnetic suspension used in MT can cause corrosion to the finish surface.