Quote:
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Originally Posted by Cuog
Quote:
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Originally Posted by Andrew Blair
I was under the impression that, with the exception of the fact that you're adding extra metal around that joint, a weld is actually far weaker in a heat treated alloy. For example, with 6061 T6, the weld is reduced to T0, and therefore, the weld was at a disadvatage to the rest of the material. The only way to restore the strength is to reduce everything to T0, and re-heat treat.
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I think(again not sure) that this is only true for heat treated metals and not standard metals |
Andrew is mostly correct. the -T6 represents a heat treatment called "solution heat treatment and artificial aging". When you weld it, you're removing the heat treatment, but not to -T0 (that doesn't really exist); it's actually the -F "as fabricated" temper, which means that no control of the heat treatment was employed during fabrication. There's more
here, and even more in MIL-HDBK-5. It's possible for a weld to be stronger or weaker than the surrounding metal—there's no universal rule. The suggestion to take everything to the -O temper (that's "annealing"), and re-harden to -T6 is good in principle, but probably bad in practice because of the difficulty finding a suitable hardening oven (to fit an entire frame), and the difficulty of dealing with deformation and uneven heating. In industry, it's (very) occasionally necessary to do this, but stiffening jigs and distributed heat sources will be employed if there's any worry about deformation and uneven application of the heat treatment. More often, though, wrought aluminum alloys and similar metals come hardened from the factory to their highest strength level.