Frankly, I'd at least use ND-filters certified for solar photography. Welding plasma is not fun: it emits a brutal amount of high energy UV light. I'd not trust the camera-internal filters to be able to deal with it gracefully. I've seen a guy who thought welding gloves were unnecessary and worked without them for some task. If you think you have seen bad sunburn, think again.
You don't want this shit to make it into your camera: it would probably wreak ruin on non-glass lenses and other parts possibly not 100% impervious to very hard UV light. You also want to definitely protect your eyes from exposure.
While you won't damage them using an electronic viewfinder, a DSLR with an optical viewfinder would be a different matter.