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911nut 911nut is offline
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Join Date: May 2001
Location: Michigan
Posts: 2,511
Originally Posted by BoxxerSix View Post
ALL performance stainless headers need back purging during the welding process to prevent the molten stainless on the back side of the weld joint from crystalizing in the open atmosphere which makes the joint extremely brittle after it has cooled and prone to cracking with thermal cycles.
Boxxer, all metals are composed of crystalline arrays.
During fusion welding all metals require some sort of shielding from the atmosphere to eliminate the possibility of hydrogen or oxygen embrittlement (depending on the alloy it will be more susceptible to one or the other).
Even if the weld is not a full penetration weld, without shielding there is still the risk of embrittlement.
Paul B.
'91 964 Turbo
Port matched, SC cams, K27/K29 turbo, Roush Performance custom headers w/Tial MV-S dual wastegates, Rarlyl8 muffler, LWFW, GT2 clutch & PP, BL wur, factory RS shifter, RS mounts, FVD timing mod, Big Reds, - 210 lb
Old 12-18-2007, 06:10 PM
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