Why does my weld have undercut?

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Accepted Answer

Undercut is caused by too much heat or too fast travel at the weld toe — the parent metal gets washed away. The fix: reduce current, slow slightly, adjust torch angle to fill the toe. Root causes. Too much heat or too fast travel at the weld toe — the parent metal gets washed away.  The fix sequence.  reduce current, slow slightly, adjust torch angle to fill the toe Change one variable at a time and re-test on scrap Re-inspect the finished bead — chisel, brush, look When to grind it out. Structural or pressure work with visible defects: grind back to sound metal and re-weld — never 'cap over' a defect and hope. For non-critical jobs, judge honestly: a cosmetic defect is a learning note; a fusion or crack defect is a redo.

Root causes

The fix sequence

When to grind it out

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