For about as long as the parts on both sides of the join stay flat. And therein lies the rub. Permanent cold welding works just fine on small contact areas, but

For about as long as the parts on both sides of the join stay flat. And therein lies the rub. Permanent cold welding works just fine on small contact areas, but on anything large you're at the mercy of thermal movement, etc. How much can that be? Quite a bit, actually [1]. That's just breathing on a braced precision straightedge, and the difference in temperature across the piece is easily measurable. [1]https://youtu.be/UG6LV8v8W-0?t=1922 https://youtu.be/UG6LV8v8W-0?t=1922