Not contesting the chemistry involved...
Metallurgy aside, welders do tend to practice the fine art of 'structural overkill'.
They are not concerned about shaving a few extra pounds or a couple bucks worth of steel from the bottom line, like an auto manufacturer is.
A couple of well-placed 'gussets' (for example) would more than make up for any structural integrity lost from heating.
1986 300E 5-Speed 240k mi.