FYI, if you need to strip it before welding it, a great method is to put in your oven and run a self clean cycle if your oven has it. When it comes out, the black seasoning will be turned to grey ash and will brush right off. Just be sure to avoid water on the bare cast iron as it will rust in a hurry.
Also, there are several very informative posts here about how to care for cast iron if you use the search function.