I used to weld my old plough every year to keep it going. i welded blades of mowers, choppers and self loading hay wagons to it, and also normal construction steel. All with no problems. that kept me ploughing for several years untill last winter we finally bought a 3 furrow 16" reversible.
When looking at bargain ploughs, we found quite a few welded ploughshares on areas with chunks of iron ore in the soil. It's not uncommon to weld ploughshares, so i'd advise to just stop thinking and talking of the metallurgy, weld the plough and hurry it before the rain...
Searching for cheap parts is something i allways delay untill the field work is done..