Hello, we got a deformation in a 9 mm plate, S-275-J2, of a storage tank, for error some fitters tried to correct the problem applying flame straightening but they heating up 10 cm length directly above the weld, we decided to make it a hardness test and we got 205 and 225 HB in the HAZ, our client says that we got to do a full PWHt in the weld, that have 2,5 m of length but only 10 cm was really affected, in API 582 says that the max hardness it can be 225 HB and 200 in crack-inducing environments (that is our client requirement), API 650 indicates that we can have a max of 22 HRC, It's really need it to do a PWHt?; The weld its in the upper rings ;Its this hardness value a critic indicator that the weld its going to fail?
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Heat Treatment in S-275-J2 STEEL PLATE 1
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So, you performed local heat straightening and in the process formed local spots of increased hardness, which is typical for flame straightening. In this situation, the hardness boarders on the maximum allowed because this hardness is the threshold where stress corrosion cracking can occur.
It makes no difference what I or anyone else recommends because your client has provided a requirement for you to follow. I would perform local stress relief at 1100 to 1150 deg F using a bulls eye approach with electric resistance heating elements to soften (temper) the local hard spots from flame straightening. As this is done, the deformation may come back because of relieving residual stresses from flame straightening.
It makes no difference what I or anyone else recommends because your client has provided a requirement for you to follow. I would perform local stress relief at 1100 to 1150 deg F using a bulls eye approach with electric resistance heating elements to soften (temper) the local hard spots from flame straightening. As this is done, the deformation may come back because of relieving residual stresses from flame straightening.
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Thank you metengr for your answer, about the PWHt if i perform local heating as you said, it doesn't affect the rest of the weld?, that's one of my concerns about the stress relief, altough our client doesn't specified to do a full PWHt in the totally of the weld, they certainly want to do it, i think that bring more problems than solutions, and now i will affect other weld that doesn't have been heated, and the other thing that bother's me is that the area witch have more hardness was the HAZ, the weld bead and the plate do not have out of range hardness.
If performed correctly, your objective is to knock the local hardness where the flame straightening was performed below the maximum for acceptance by heating this location with electric resistance pads. The stress relief temperature I recommended should not effect bulk properties and that includes the weld region.
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