Making an industrial style desk lamp (part 1)

A while back I got my hands on a couple of unique pieces of steel from a factory that was about to scrap them. After taking them home I immediately knew what I wanted to make them in to, an industrial style desk lamp!

Fitting them together was easy since the finish on the corners was excellent.

I used TIG to weld the four pieces together. At first I thought it was regular carbon-steel but I noticed strange bubbling of my weld pool as if it was cast iron. I haven't figured out the cause.

Now i need to decide what kind of lamp shade would best fit, any suggestions?

Don't forget to follow for part 2!