What is the reason for cracking that occurs when carbon steel elbows are welded to pipes after pickling?
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The user put the carbon steel elbow into an acid washing tank for acid cleaning, and cracks occurred during welding it to the pipeline after the cleaning was completed. I suspect that during the pickling process, rust was present on the elbows, which led to uneven corrosion – some areas were corroded more than others, resulting in tiny holes. The high temperatures during welding caused cracks in those areas. Is this a possible explanation? The material is 20G, with a diameter of 150 and a wall thickness of 14 mm. The cracks appear in the middle. Does anyone understand this?
I don’t understand this: seamless steel pipes don’t need to be pickled, yet elbows are pickled. Moderator **, I don’t know much about the pickling process, but is my view valid?
I don’t know much about it; I’ve only heard of stainless steel pickling.
Yes, stainless steel pickling creates a passivation protective layer
What is the purpose of pickling carbon steel?
Does it crack just by soaking in acid like this? Then why is carbon steel pipe still used to hold acid? Go and take pictures of the origin of the cracks – did they start cracking from the port? If so, it was during the processing of the elbow that the cracks at the ports were not removed thoroughly. If not, I guess it’s because the seamless tube used for the elbow is cracked itself
Pickling solutions are generally mixtures of sulfuric acid, nitric acid, hydrofluoric acid, etc. I believe pickling will not cause cracks in 20G elbows, and I agree with what was said on floor 7.
It’s not the right time to do acid cleaning either; will it still be usable after this?
Pickling does not cause cracks, but what is the purpose of pickling carbon steel?
It is a problem with the material of the elbow itself; it should be re-inspected to check for defects such as cracks, delamination, and inclusions. It can be used in production and construction only after passing the inspection!