I need something that can weld to mild steel. The seller doesn't know what kind of steel this is. Can you deduce by color? It's a wastegate flange, btw.

 

Looks like it may be mild, but then again its nearly impossible to tell just by looking at it. You can always try a spark test on it. Hit it with a grinder and see the spark pattern/color. It might take a while to figure it out but take a look at this. Spark Testing

 

99% sure that's mile, screws are stainless though.

 

Have you tried asking it?

Seriously though. Most common grades of stainless are non-magnetic, so that's one test. Another is to put a scratch into it, apply some water, and see what happens.

I'm with curly, it does look like regular steel from the pic.

 

you can weld stainless to mild anyway. Just get some 309L electrode and weld that **** up!

 

Indeed! Just be aware that dissimilar metals heat and cool at different rates, therefore expand and contract at different rates and are prone to shearing fractures between the two metals.

Sometimes it's no problem and other times you may have to re-weld a seam 2 or 3 times because it cracks while it's cooling.

Just some food for thought.